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Dave wrote: I recently hooked up a thirty-six foot (plus or minus a couple of feet) piece of four-stranded wire with alligator clip to the internal "whip" antenna of my portable shortwave receiver, for the extra performance such a device offered. It works so well that I now cannot usually use my "DX" setting because of all the background noise (sounds like hundreds of other broadcasts vying for attention.) I don't know the frequency source of all this background noise, but would like to filter out as much of it as I can. One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? What receiver? It sounds like it's being overloaded. |
"N8KDV" wrote in message ... Dave wrote: I recently hooked up a thirty-six foot (plus or minus a couple of feet) piece of four-stranded wire with alligator clip to the internal "whip" antenna of my portable shortwave receiver, for the extra performance such a device offered. It works so well that I now cannot usually use my "DX" setting because of all the background noise (sounds like hundreds of other broadcasts vying for attention.) I don't know the frequency source of all this background noise, but would like to filter out as much of it as I can. One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? What receiver? It sounds like it's being overloaded. Sorry, forgot to include that information. I am using a DX-402 (aka Sangean ATS-505). I honestly wondered about that, but hesitated to shorten the wire because I would (obvioiusly) lose some sensitivity, and really like being able to pick up VOK's English broadcasts to Central America. Only problem is the noise that makes it difficult to single out. Thanks, Dave |
Is it ALL frequencies that have the " overload" or just a few??
- try Unclipping the antenna wire & moving it 1/4 inch away from the antenna ( use a string to move it around) & see if that helps.. Dan In article , "Dave" writes: Subject: Shortwave random-wire antenna question From: "Dave" Date: Sat, 3 Apr 2004 13:41:21 -0600 I recently hooked up a thirty-six foot (plus or minus a couple of feet) piece of four-stranded wire with alligator clip to the internal "whip" antenna of my portable shortwave receiver, for the extra performance such a device offered. It works so well that I now cannot usually use my "DX" setting because of all the background noise (sounds like hundreds of other broadcasts vying for attention.) I don't know the frequency source of all this background noise, but would like to filter out as much of it as I can. One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? TIA Cross-posted between sci.electronics.basics and rec.radio.shortwave Dave |
"Dave" ) writes:
I recently hooked up a thirty-six foot (plus or minus a couple of feet) piece of four-stranded wire with alligator clip to the internal "whip" antenna of my portable shortwave receiver, for the extra performance such a device offered. It works so well that I now cannot usually use my "DX" setting because of all the background noise (sounds like hundreds of other broadcasts vying for attention.) I don't know the frequency source of all this background noise, but would like to filter out as much of it as I can. One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? TIA Cross-posted between sci.electronics.basics and rec.radio.shortwave Dave It's probably designed for use with the whip, note the absence of an antenna jack. It needs to be sensitive because it's using that small whip, and when you add something longer, it overloads. In other words, it's not one single signal, but all the strong local signals, that are overloading it. TV and AM and FM broadcast stations can put out pretty strong signals locally, and they can get around any filtering in the radio, and still be strong, and then overload the active stages in the receiver. Michael |
Do you have some filtering built in to your radio? Some of the better rigs
have noise blanking, AGC, extra RF amplification (which can be bypassed), frequency shift/width, etc. |
"Dave" wrote in message If I were going to
try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? Bring it down? You mean bring it up. It's resonant about 6 mhz or so. To tune it for 30 mhz, you would need to cut about 28 ft or so off of it. If you are severely overloading, cutting off a few ft would be a good place to start anyway.. You probably can't handle more than 5-10 ft by the sound of it... MK TIA Cross-posted between sci.electronics.basics and rec.radio.shortwave Not no mo... I dumped s.e.b. ...MK |
In article ,
"Dave" wrote: I recently hooked up a thirty-six foot (plus or minus a couple of feet) piece of four-stranded wire with alligator clip to the internal "whip" antenna of my portable shortwave receiver, for the extra performance such a device offered. It works so well that I now cannot usually use my "DX" setting because of all the background noise (sounds like hundreds of other broadcasts vying for attention.) I don't know the frequency source of all this background noise, but would like to filter out as much of it as I can. One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? Since you have cross posted to sci.electronics.basics lets try to look at this logically and as non technically as possible. The are two things that you need to accomplish to hear a station on your radio in the way of signal strength. 1. The signal must large enough for the radio to amplify it and reproduce it at the speaker. 2. The signal must be stronger than the noise floor of the radio and any external noise the antenna picks up by some margin over the station you want to hear. Usually this is something like 10 dB. You can't do anything about the noise floor of the radio unless you want to modify it. The basic sensitivity of the radio is a decision you made when you bought it. That leaves the antenna. What you did was to put up the most basic type, which is called a Marconi or common mode antenna. For a simple antenna it is about as non-selective as you can make hence the noise level is high on the radio. Worse you might be over loading the radio and the radio itself may be generating some of the noise. Portables are designed to be sensitive and simple so they can't handle much signal. A strong signal out or in band could be causing you additional trouble. Whether 36 feet of wire is to much or not depends on where you live but for most radios generally won't cause the overload problem it's just that it is picking up everything well including lots of locally generated noise. That is the basically where you are at. What can you do about this. You want to pick up more of the signals (stations) you want to hear without hearing noise from other electrical appliances or stuff out of band. You need a more complex antenna design that will not pick up as much noise as the signal you want to hear. Noise is on all frequencies and comes from all directions. A more complex antenna design can do things like: 1. Limit the direction it picks up signal or noise. You can benefit from this by pointing the antenna at the signal you want or conversely attenuating a noise source. 2. Changing the type of energy the antenna picks up. The antenna type determines whether it picks up common mode or differential mode. 3. The antenna type also determines whether it is sensitive to the electric, magnetic fields or both. 4. The antenna type also determines the band or bands of frequencies it will pick up well. All the above will limit the total amount of noise energy it will present to the radio so it has less to deal with. Basically you use the antenna design to preselect the signals you want to pick up. The downside of this is short wave covers a wide range of frequencies so you will need more than one antenna. For some type of resonant antenna the smallest number of antennas you need are two and better would be three. To get started with a more complex antenna and to see if you are really improving your reception start with a weak signal using just the radios whip antenna. Use a station on a high band (smaller antenna) during the daytime. Make a simple resonant antenna like a dipole cut for that frequency connected to a coax and determine how to connect the coax to your radio. If it is a portable radio try operating on the batteries as some of the wall wart power supplies are noisy or noise on the house wiring is being conducted to your radio through the power cord. Now to test the antenna to see if it really helping you can disconnect it from the radio and extend the radios whip antenna and collapse it again reconnecting the external antenna to see which works the best. You can put the external antenna outside away from noise generating electrical equipment or switch them off. Once you have a dipole making an improvement on weak signals you can make other antenna types and antennas for other frequencies. There are plenty of antenna sites on the web and ideas on finding local noise sources. -- Telamon Ventura, California |
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Howard wrote:
Here's an idea: Instead of alligator clipping the wire to the antenna, loosely wrap about 6 - 8 turns of the wire around the whip so it inductively couples to the antenna. If the radio is indeed overloading this could solve the problem; not as much signal is transferred to the whip as with a direct connection. I've done this with portables and have had success, your mileage may vary. HK Good idea. You can adjust the number of turns of the coil which are over the whip by slowly moving it up or down to see how much signal the radio can handle. Do this with the whip fully down. The coil must have insulation on the wire. One of the symptoms of overloading is hearing many strong stations *outside* the international bands where they don't belong. Tune to a frequency range that is not an international band and see if you can still hear those stations. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Here's an idea: Instead of alligator clipping the wire to the antenna, loosely wrap about 6 - 8 turns of the wire around the whip so it inductively couples to the antenna. If the radio is indeed overloading this could solve the problem; not as much signal is transferred to the whip as with a direct connection. I've done this with portables and have had success, your mileage may vary. HK The above idea has worked for me in the past. These radios are very sensitive so they can be used with the whip, I might be wrong but I dont think it has anything to do with the resonance frequency of the wire, I would say its more the length of the wire that is the problem when it comes to the smaller portable radios. |
"Dave" wrote in message ...
I recently hooked up a thirty-six foot (plus or minus a couple of feet) piece of four-stranded wire with alligator clip to the internal "whip" antenna of my portable shortwave receiver, for the extra performance such a device offered. It works so well that I now cannot usually use my "DX" setting because of all the background noise (sounds like hundreds of other broadcasts vying for attention.) I don't know the frequency source of all this background noise, but would like to filter out as much of it as I can. One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? TIA Cross-posted between sci.electronics.basics and rec.radio.shortwave Dave Antenna basics with formulas http://www.electronics-tutorials.com...nna-basics.htm you may also want to do a search on "antenna tuners" |
"Dave" wrote in message ... One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? This isn't likely to help your basic problem, which appears to be a lack of selectivity in the radio (in other words, it is accepting signals over too wide a bandwidth, so you hear not only the station you're interested in, but those "to either side" as well. Having the passband too wide also makes for more noise in general. There are filters that can be added (within the receiver) to improve this, but your best bet may be to simply look for a better receiver. Bob M. |
"Bob Myers" wrote in message news:M7Dcc.2397
"Dave" wrote in message One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? This isn't likely to help your basic problem, which appears to be a lack of selectivity in the radio (in other words, it is accepting signals over too wide a bandwidth, so you hear not only the station you're interested in, but those "to either side" as well. Having the passband too wide also makes for more noise in general. There are filters that can be added (within the receiver) to improve this, but your best bet may be to simply look for a better receiver. Not necessary at all. With a little studying of how antennas work, Dave could build an antenna tuner and preselector all rolled into one, with only a few parts. For specifics, that's a homework problem and I'm personally currently engaged in a project much like this; I'll post when I have something a little more concrete. Cheers! Rich |
"-=jd=-" wrote in message
On Wed 07 Apr 2004 07:18:56a, "Dave" wrote in message : "Rich Grise" wrote in message Thank you, Rich. That is just what I have decided I need. Where are you finding your information on building such a device? I've no interest re-inventing the wheel, so if you come up with a design or have links to the design(s) you've settled on - and if you are agreeable to it - please share. Well, I was just basically thinking of an ordinary antenna tuner, which can be as simple as one capacitor or one inductor, or various combinations, depending on what kind of impedance you're seeing at the feed point. The seat-of-the-pants way to do it is get a variable cap and variable inductor in a range appropriate for the freq, and just stick them in various arrangements and play with the tuning until you get the best signal. If you want to be scientific aboutg it, you might find something he http://www.google.com/search?hl=en&l...tenna+tuner%22 Have Fun! Rich |
Dave,
I have been in a very similar situation. I used almost an identical antenna and had fantastic results. The radio likely does not have sufficent filtering in this case (Antenna is likely working great). I would start by ensuring the antenna has a good ground connection to the radio. An antenna tuner/preselector would defantely help. Purchasing a new or used amateur radio tuner (i.e. MFJ) 1.8Mhz-30Mhz would be the easiest option. Adding capacitors separetely could work, but from experience is a challenge to achive an workable solution for all frequencies. Homac "Dave" wrote in message ... I recently hooked up a thirty-six foot (plus or minus a couple of feet) piece of four-stranded wire with alligator clip to the internal "whip" antenna of my portable shortwave receiver, for the extra performance such a device offered. It works so well that I now cannot usually use my "DX" setting because of all the background noise (sounds like hundreds of other broadcasts vying for attention.) I don't know the frequency source of all this background noise, but would like to filter out as much of it as I can. One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? TIA Cross-posted between sci.electronics.basics and rec.radio.shortwave Dave |
The antenna does indeed seem to be working great, and the radio is not
operating too shabily either as it is only the "background noise" I am trying to reduce. I hooked a 100 mH RF choke up to it with good results, and am planning on adding another one or two similar devices in an effort to cut down on higher frequency interference. Question: how would I ground this antenna? I have a grounding rod right outside the window, but don't know what to hook it too. The negative battery terminal? This radio does have an external antenna input, but that has a plastic ring around the outside. Open to suggestions. And thanks for the input RE purchasing a new/used tuner. dave "Private" wrote in message om... Dave, I have been in a very similar situation. I used almost an identical antenna and had fantastic results. The radio likely does not have sufficent filtering in this case (Antenna is likely working great). I would start by ensuring the antenna has a good ground connection to the radio. An antenna tuner/preselector would defantely help. Purchasing a new or used amateur radio tuner (i.e. MFJ) 1.8Mhz-30Mhz would be the easiest option. Adding capacitors separetely could work, but from experience is a challenge to achive an workable solution for all frequencies. Homac "Dave" wrote in message ... I recently hooked up a thirty-six foot (plus or minus a couple of feet) piece of four-stranded wire with alligator clip to the internal "whip" antenna of my portable shortwave receiver, for the extra performance such a device offered. It works so well that I now cannot usually use my "DX" setting because of all the background noise (sounds like hundreds of other broadcasts vying for attention.) I don't know the frequency source of all this background noise, but would like to filter out as much of it as I can. One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? TIA Cross-posted between sci.electronics.basics and rec.radio.shortwave Dave |
"Bob Myers" wrote in message ... "Dave" wrote in message ... One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? This isn't likely to help your basic problem, which appears to be a lack of selectivity in the radio (in other words, it is accepting signals over too wide a bandwidth, so you hear not only the station you're interested in, but those "to either side" as well. Having the passband too wide also makes for more noise in general. There are filters that can be added (within the receiver) to improve this, but your best bet may be to simply look for a better receiver. Bob M. Hello Bob, The selectivity doesn't actually seem to be too bad, as it is only the weaker signals that I have trouble digging out of the hash and trash. It does seem to be picking up some out-of-band signals, but they are very, very weak. As I posted in another message, a 100 microhenry RF choke cut that stuff out considerably, and I am planning on adding another 100 or 200 microhenry RF choke to see if that helps make the slightly stronger signals a little more discernable. Next on the worksheet is an antenna tuner of some sort. Thanks all, Dave |
"Michael Black" wrote in message ... "Dave" ) writes: I recently hooked up a thirty-six foot (plus or minus a couple of feet) piece of four-stranded wire with alligator clip to the internal "whip" antenna of my portable shortwave receiver, for the extra performance such a device offered. It works so well that I now cannot usually use my "DX" setting because of all the background noise (sounds like hundreds of other broadcasts vying for attention.) I don't know the frequency source of all this background noise, but would like to filter out as much of it as I can. One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? TIA Cross-posted between sci.electronics.basics and rec.radio.shortwave Dave It's probably designed for use with the whip, note the absence of an antenna jack. It needs to be sensitive because it's using that small whip, and when you add something longer, it overloads. In other words, it's not one single signal, but all the strong local signals, that are overloading it. TV and AM and FM broadcast stations can put out pretty strong signals locally, and they can get around any filtering in the radio, and still be strong, and then overload the active stages in the receiver. Michael Just a quick note: it actually does have an external antenna input, I just don't know what type of plug to stick into it. Plastic ring with metal contact inside, looks like 1/8" mono would do it, but how would I ground it? Negative battery term? Thanks, Dave |
DAVE : Wind yer coil of at least a hundred turns of magnet "war"
around a 1" PVC pipe segment (when I was a KID I used a lacquered toilet paper core) and take taps off it every 2-5 turns (arbitrary) and use the selector switch to derive signal from the taps that give you the best performance (it will vary per band) The capacitors are from old garage sale radios and may not even be needed This accomlishes what you have already proven with your work, that certain frequencies can be canceled out by selection of signal inductor-load.in series with your antenna The capacitors merely help you tune it in more making a tank circuit that resonates with the frequency you're "working" I did perhaps the same thing by winding 100 turns of magnet war on a salvaice ring torid core from a ttransistor powwer supply off a dead computer...The antenna went to 1 end of this 100 turns and the other end was grounded. On top this hundred turns I wound 25-40 turns and ran on end of THAT winding to my radio's antenna IN connector and the other end to the radio's ground You have just made a 4:1 balun...which all in one almost does what the couple above does...no adjustment tho Or you can do the quick and dirty trick with a TV 300 ohm to 75 ohm coupler, connecting the 300 ohm end to the antenna and ground as above, and the 75 ohm connectors to your radio's antenna and ground You wont notice the difference Yodar Dave wrote: The antenna does indeed seem to be working great, and the radio is not operating too shabily either as it is only the "background noise" I am trying to reduce. I hooked a 100 mH RF choke up to it with good results, and am planning on adding another one or two similar devices in an effort to cut down on higher frequency interference. Question: how would I ground this antenna? I have a grounding rod right outside the window, but don't know what to hook it too. The negative battery terminal? This radio does have an external antenna input, but that has a plastic ring around the outside. Open to suggestions. And thanks for the input RE purchasing a new/used tuner. dave ... Private wrote: Dave, I have been in a very similar situation. I used almost an identical antenna and had fantastic results. The radio likely does not have sufficent filtering in this case (Antenna is likely working great). I would start by ensuring the antenna has a good ground connection to the radio. An antenna tuner/preselector would defantely help. Purchasing a new or used amateur radio tuner (i.e. MFJ) 1.8Mhz-30Mhz would be the easiest option. Adding capacitors separetely could work, but from experience is a challenge to achive an workable solution for all frequencies. Homac "Dave" wrote in message ... I recently hooked up a thirty-six foot (plus or minus a couple of feet) piece of four-stranded wire with alligator clip to the internal "whip" antenna of my portable shortwave receiver, for the extra performance such a device offered. It works so well that I now cannot usually use my "DX" setting because of all the background noise (sounds like hundreds of other broadcasts vying for attention.) I don't know the frequency source of all this background noise, but would like to filter out as much of it as I can. One manufacturer of a similar "wind-up" antenna adds a capacitor to the wire in order to lower the resonance frequency of the wire. If I were going to try something similar (adding a capacitor, in series) in an attempt to bring the resonance of the wire down into the 30 MHz range, what size (roughly) capacitor should I use? Should I just try a few with different ranges, or does anyone here have any suggestions? TIA Cross-posted between sci.electronics.basics and rec.radio.shortwave Dave |
For many years, it was common practice to use a lead and aligator clip in
place of a roller inductor. Continuously variable and cheap. "-=jd=-" wrote in message The variable inductor is my stumbling block. I want that continuously variable functionality, but without dropping $100 - $200 for a new/used inductor. I'm thinking about trying to build one - but that's all I'm doing... just thinking... -=jd=- -- My Current Disposable Email: (Remove YOUR HAT to reply directly) |
Take the batteries out. Put your (unconnected) plug into the socket. Check
for continuity between its outer contact (barrel) and the negative battery terminal. Many radios have jacks with plastic external rings but there is a ground terminal inside. "Dave" wrote in message ... Just a quick note: it actually does have an external antenna input, I just don't know what type of plug to stick into it. Plastic ring with metal contact inside, looks like 1/8" mono would do it, but how would I ground it? Negative battery term? Thanks, Dave |
You don't in this newsgroup (shortwave). This is a text only group.
"Yodar" wrote in message m... I just tried to send a post with a schematic for a simple antenna tuner and the diagram was cut out...how do I add it? |
"-=jd=-" wrote in message . .. I'm thinking a bead (say, 1/2") threaded on a rod (brass for both bead and rod?), positioned so that the bead can be lifted just slightly, then slid along the coil - but when you release the bead, there's a bit of tension pressing it against the coil. I thought about the gator clip method, but I'm thinking it might be easier to fool with if I had something I could adjust without taking my focus off the radio. Then again, alligator clips and leads are a more widely available than the pseudo roller inductor parts rattling around in my head... -=jd=- I'll suggest you try the alligator clip and wire first. It will be alot easier to do any modifications. Also, you might find the whole experiment isn't particularly helpful in your situation. If so, you might as well find out right away. Frank Dresser |
The bead on a wire idea works. It has been used frequently in crystal
radios. "-=jd=-" wrote in message . .. On Fri 09 Apr 2004 12:40:57p, "CW" wrote in message : For many years, it was common practice to use a lead and aligator clip in place of a roller inductor. Continuously variable and cheap. I'm thinking a bead (say, 1/2") threaded on a rod (brass for both bead and rod?), positioned so that the bead can be lifted just slightly, then slid along the coil - but when you release the bead, there's a bit of tension pressing it against the coil. I thought about the gator clip method, but I'm thinking it might be easier to fool with if I had something I could adjust without taking my focus off the radio. Then again, alligator clips and leads are a more widely available than the pseudo roller inductor parts rattling around in my head... -=jd=- -- My Current Disposable Email: (Remove YOUR HAT to reply directly) |
Good advice. No need to over design something if your not sure it will work.
"Frank Dresser" wrote in message news:NTBdc.1512$K_.34795@bgtnsc05- I'll suggest you try the alligator clip and wire first. It will be alot easier to do any modifications. Also, you might find the whole experiment isn't particularly helpful in your situation. If so, you might as well find out right away. Frank Dresser |
"Dave" wrote in message
... The antenna does indeed seem to be working great, and the radio is not operating too shabily either as it is only the "background noise" I am trying to reduce. I hooked a 100 mH RF choke up to it with good results, and am planning on adding another one or two similar devices in an effort to cut down on higher frequency interference. Question: how would I ground this antenna? Uh, you don't ground the antenna. You ground ground. :-) The ground is like a "return" path for the current induced in the antenna by the radio wave. I have a grounding rod right outside the window, but don't know what to hook it too. The negative battery terminal? Probably. Any handy chassis ground will be fine. This radio does have an external antenna input, but that has a plastic ring around the outside. Open to suggestions. The radio might be grounded through the power cord, if it's a 3-prong. Otherwise, just a wire from the radio's chassis to the ground rod, or even to one of the mounting screws of a grounded outlet. And thanks for the input RE purchasing a new/used tuner. dave As you seem to have mentioned, you have lots & lots of signal strenth, so you actually might want to make your antenna even _less_ sensitive. What it sounds like you're looking for is selectivity, and you do that with tuned circuits. Or you did back when I was learning this stuff. ;-) Hope This Helps! Rich |
"Dave" wrote in message
... As you seem to have mentioned, you have lots & lots of signal strenth, so you actually might want to make your antenna even _less_ sensitive. What it sounds like you're looking for is selectivity, and you do that with tuned circuits. Or you did back when I was learning this stuff. ;-) Hope This Helps! Rich Yes, a tuned circuit, I am thinking. There is currently much more signal than I need. Is an antenna tuner what I am looking for? I hooked up 300 microhenries worth of RF choke, which reduces the entire signal just a hair, but that is enough to knock the noise level down considerably. I am not yet sure, but this *may* be all I need. BTW, did some fiddling withe the anchor of the random wire, and decided it is more like 45 - 50 feet total. I am planning on moving it, however, and placing it under the eaves and off to the side of the aluminum rain gutter, which may deflate it some. Right now I have signal to waste. That may change. Thanks for the input. Working with RF is new to me. Actually, if you've got good electrical conductivity, the aluminum rain gutters themselves might make a passable antenna. Ground _one_ of the downspouts at the bottom end, and experiment with different pickoff points along the length of the gutter. An antenna has different impedances at different points along its length, based on the wavelength of interest. And you'd add inductance and capacitance as needed to make the whole thing resonant at the freq. you want. (that's the philosophy of an "antenna tuner.") It really wouldn't do any harm to look up some books on antennas and stuff, like "The ARRL Antenna Book", and talk with practically any radio amateur - those guys do this stuff all day long. Cheers! Rich |
i have that receiver. the amp connected to the whip is hot as a
firecracker and it overloads very easily. (the external ant jack isnt much different!) use the antenna jack instead of the whip for a connection. even then it wont handle that much wire. try laying your wire right on the ground. i use a "snake" antenna with several sangean radios with excellent results. even the low gain properties of an on ground antenna is too much for this radio if its too long. |
Dave wrote:
"starman" wrote in message It sounds like you need a passive preselector rather than an antenna tuner, if your receiver can't handle the strong signals on the antenna. Are you hearing stations outside the bands where they are actually located? Is there a lot of noise from many stations all over the shortwave range. I am picking up a few very weak signals out-of-band, and there is only background noise on the DX setting. The RF choke seems to have done a nice job of cleaning up most of the hash and trash in the background. I would like to enhance the signal I am actually looking for, however. During periods of good propogation I have ocassionally picked up Voice of Korea transmissions aimed at Central and South America, and I would like to load the dice in my favor if I can. I really think you should try a passive preselector. It will reject the strong out of band signals which cause intermodulation products while peaking the weak stations. The choke helps but it also reduces the receivers sensitivity to the signals you want to hear. The preselector does the opposite. I used a preselector with my Sony-2010 and an inverted-L antenna. It worked great. Without the preselector the 2010 would overload and produce a lot of spurious signals throughout the shortwave spectrum. It's pretty easy to build a passive preselector that will cover the range of 3-30 Mhz with two coils. The larger coil will tune the range of about 3-7 Mhz and the smaller one 7-30 Mhz. It's best to use ferrite cores in the coils for the best selectivity or 'Q'. Of course you'll also need an air variable capacitor like 10-365/pf and a simple rotary switch to select the coils. The circuit is a parallel (tank) design which is connected between the antenna input of the radio and ground, along with the antenna itself. If you're not into building, you can buy a passive preselector at: http://www.grove-ent.com/MFJ1046.html Here's an interesting article on antenna tuners: http://www.nyx.net/~dgrunber/tuner.ssi -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
"-=jd=-" wrote in message ... On Sun 11 Apr 2004 01:39:04a, "Dave" wrote in message : She absolutely hates having a piece of wife laying across the roof, and can't wait until I fix it in place underneath the eaves. There's a few different ways I could interpret that!! -=jd=- -- LOL! I meant to say "a piece of WIRE..." Guess I was thinking something else. Dave |
"starman" wrote in message ... Dave wrote: "starman" wrote in message It sounds like you need a passive preselector rather than an antenna tuner, if your receiver can't handle the strong signals on the antenna. Are you hearing stations outside the bands where they are actually located? Is there a lot of noise from many stations all over the shortwave range. I am picking up a few very weak signals out-of-band, and there is only background noise on the DX setting. The RF choke seems to have done a nice job of cleaning up most of the hash and trash in the background. I would like to enhance the signal I am actually looking for, however. During periods of good propogation I have ocassionally picked up Voice of Korea transmissions aimed at Central and South America, and I would like to load the dice in my favor if I can. I really think you should try a passive preselector. It will reject the strong out of band signals which cause intermodulation products while peaking the weak stations. The choke helps but it also reduces the receivers sensitivity to the signals you want to hear. The preselector does the opposite. I used a preselector with my Sony-2010 and an inverted-L antenna. It worked great. Without the preselector the 2010 would overload and produce a lot of spurious signals throughout the shortwave spectrum. It's pretty easy to build a passive preselector that will cover the range of 3-30 Mhz with two coils. The larger coil will tune the range of about 3-7 Mhz and the smaller one 7-30 Mhz. It's best to use ferrite cores in the coils for the best selectivity or 'Q'. Of course you'll also need an air variable capacitor like 10-365/pf and a simple rotary switch to select the coils. The circuit is a parallel (tank) design which is connected between the antenna input of the radio and ground, along with the antenna itself. If you're not into building, you can buy a passive preselector at: http://www.grove-ent.com/MFJ1046.html Here's an interesting article on antenna tuners: http://www.nyx.net/~dgrunber/tuner.ssi Hmmm. A tank circuit between the antenna input and ground, to improve reception? I believe you, but I don't understand how it works. Could you enlighten me a little? Does it resonate at the selected frequency (chosen by adjusting the variable cap) and thereby "select" that signal for the input to the radio? (This is all I can figure.) I could do that real easy. I have several variable caps of that general size, and can pick up whatever size inductor I need. I even have the charts and formulas for calculating the appropriate value of inductance, just have to sit down with them. Thanks for the suggestion. PS: Haven't checked out the links yet, but will do so asap. Dave |
Dave wrote:
"starman" wrote in message ... Dave wrote: "starman" wrote in message It sounds like you need a passive preselector rather than an antenna tuner, if your receiver can't handle the strong signals on the antenna. Are you hearing stations outside the bands where they are actually located? Is there a lot of noise from many stations all over the shortwave range. I am picking up a few very weak signals out-of-band, and there is only background noise on the DX setting. The RF choke seems to have done a nice job of cleaning up most of the hash and trash in the background. I would like to enhance the signal I am actually looking for, however. During periods of good propogation I have ocassionally picked up Voice of Korea transmissions aimed at Central and South America, and I would like to load the dice in my favor if I can. I really think you should try a passive preselector. It will reject the strong out of band signals which cause intermodulation products while peaking the weak stations. The choke helps but it also reduces the receivers sensitivity to the signals you want to hear. The preselector does the opposite. I used a preselector with my Sony-2010 and an inverted-L antenna. It worked great. Without the preselector the 2010 would overload and produce a lot of spurious signals throughout the shortwave spectrum. It's pretty easy to build a passive preselector that will cover the range of 3-30 Mhz with two coils. The larger coil will tune the range of about 3-7 Mhz and the smaller one 7-30 Mhz. It's best to use ferrite cores in the coils for the best selectivity or 'Q'. Of course you'll also need an air variable capacitor like 10-365/pf and a simple rotary switch to select the coils. The circuit is a parallel (tank) design which is connected between the antenna input of the radio and ground, along with the antenna itself. If you're not into building, you can buy a passive preselector at: http://www.grove-ent.com/MFJ1046.html Here's an interesting article on antenna tuners: http://www.nyx.net/~dgrunber/tuner.ssi Hmmm. A tank circuit between the antenna input and ground, to improve reception? I believe you, but I don't understand how it works. Could you enlighten me a little? Does it resonate at the selected frequency (chosen by adjusting the variable cap) and thereby "select" that signal for the input to the radio? (This is all I can figure.) I could do that real easy. I have several variable caps of that general size, and can pick up whatever size inductor I need. I even have the charts and formulas for calculating the appropriate value of inductance, just have to sit down with them. Thanks for the suggestion. PS: Haven't checked out the links yet, but will do so asap. Dave The parallel tuned (tank) circuit causes all frequencies above and below the tuned one, to be shunted to ground while passing the desired frequency range to the radio's antenna input. It makes up for the lack of good preselection in the receivers front-end. This is the main problem when connecting a good antenna to a portable radio. Be sure to use coils with ferrite cores for good selectivity. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
"starman" wrote in message ... Dave wrote: "starman" wrote in message ... Dave wrote: "starman" wrote in message It sounds like you need a passive preselector rather than an antenna tuner, if your receiver can't handle the strong signals on the antenna. Are you hearing stations outside the bands where they are actually located? Is there a lot of noise from many stations all over the shortwave range. I am picking up a few very weak signals out-of-band, and there is only background noise on the DX setting. The RF choke seems to have done a nice job of cleaning up most of the hash and trash in the background. I would like to enhance the signal I am actually looking for, however. During periods of good propogation I have ocassionally picked up Voice of Korea transmissions aimed at Central and South America, and I would like to load the dice in my favor if I can. I really think you should try a passive preselector. It will reject the strong out of band signals which cause intermodulation products while peaking the weak stations. The choke helps but it also reduces the receivers sensitivity to the signals you want to hear. The preselector does the opposite. I used a preselector with my Sony-2010 and an inverted-L antenna. It worked great. Without the preselector the 2010 would overload and produce a lot of spurious signals throughout the shortwave spectrum. It's pretty easy to build a passive preselector that will cover the range of 3-30 Mhz with two coils. The larger coil will tune the range of about 3-7 Mhz and the smaller one 7-30 Mhz. It's best to use ferrite cores in the coils for the best selectivity or 'Q'. Of course you'll also need an air variable capacitor like 10-365/pf and a simple rotary switch to select the coils. The circuit is a parallel (tank) design which is connected between the antenna input of the radio and ground, along with the antenna itself. If you're not into building, you can buy a passive preselector at: http://www.grove-ent.com/MFJ1046.html Here's an interesting article on antenna tuners: http://www.nyx.net/~dgrunber/tuner.ssi Hmmm. A tank circuit between the antenna input and ground, to improve reception? I believe you, but I don't understand how it works. Could you enlighten me a little? Does it resonate at the selected frequency (chosen by adjusting the variable cap) and thereby "select" that signal for the input to the radio? (This is all I can figure.) I could do that real easy. I have several variable caps of that general size, and can pick up whatever size inductor I need. I even have the charts and formulas for calculating the appropriate value of inductance, just have to sit down with them. Thanks for the suggestion. PS: Haven't checked out the links yet, but will do so asap. Dave The parallel tuned (tank) circuit causes all frequencies above and below the tuned one, to be shunted to ground while passing the desired frequency range to the radio's antenna input. It makes up for the lack of good preselection in the receivers front-end. This is the main problem when connecting a good antenna to a portable radio. Be sure to use coils with ferrite cores for good selectivity. Gotcha. That was the only way I could figure it. I saw something almost similar (is that like almost pregnant?) in my Practical Antenna Hanbook (Joe Carr) last night, but suspect it is a printing error. It was an series inductor following behind a capacitor shunt to ground. Only that would (I think) choke off RF and shunt it to ground. (Am I wrong?) Have been trying to figure that one out all day. Last night I fixed my big solder gun, and can now solder a ground wire to the grounding rod outside my bedroom window. Hope to do that tomorrow. I am definetly going to set this up. Have already tested several of my small capacitors, but they do not appear stable enough for anything serious. Just to familiarize myself with the mathematics, I have already calculated the inductors I would need for the first one I tested. Just finished removing a better variable cap from an old junk shortwave radio (a Luke, I think) and am going to try to use it. May have a problem with my meter though. May have to take the variable cap to the shop and have it tested on a known good LCR meter (gotta get one of those. I a currently using a DMM with limited capacitance capability.) If I do that I'll take my calculator and notepad with me, so I can figure out and write down the values of inductance I need. Damn I'm having fun. :) Thank you very much for this suggestion. It is much appreciated. Dave |
"Dave" wrote in message ... What you saw in the antenna book was not a misprint. It was an L network tuner. It is an impedance matcher, not a preselector. Gotcha. That was the only way I could figure it. I saw something almost similar (is that like almost pregnant?) in my Practical Antenna Hanbook (Joe Carr) last night, but suspect it is a printing error. It was an series inductor following behind a capacitor shunt to ground. Only that would (I think) choke off RF and shunt it to ground. (Am I wrong?) Have been trying to figure that one out all day. Last night I fixed my big solder gun, and can now solder a ground wire to the grounding rod outside my bedroom window. Hope to do that tomorrow. I am definetly going to set this up. Have already tested several of my small capacitors, but they do not appear stable enough for anything serious. Just to familiarize myself with the mathematics, I have already calculated the inductors I would need for the first one I tested. Just finished removing a better variable cap from an old junk shortwave radio (a Luke, I think) and am going to try to use it. May have a problem with my meter though. May have to take the variable cap to the shop and have it tested on a known good LCR meter (gotta get one of those. I a currently using a DMM with limited capacitance capability.) If I do that I'll take my calculator and notepad with me, so I can figure out and write down the values of inductance I need. Damn I'm having fun. :) Thank you very much for this suggestion. It is much appreciated. Dave |
Oh. An impedance matcher. Never was much good with those... Does this
match the impedance of the random wire to that of the radio input? That would be good too... Yes, an L network, that was what it was called I think. I marked it, to go back to it. Thanks, Dave "CW" wrote in message ... "Dave" wrote in message ... What you saw in the antenna book was not a misprint. It was an L network tuner. It is an impedance matcher, not a preselector. Gotcha. That was the only way I could figure it. I saw something almost similar (is that like almost pregnant?) in my Practical Antenna Hanbook (Joe Carr) last night, but suspect it is a printing error. It was an series inductor following behind a capacitor shunt to ground. Only that would (I think) choke off RF and shunt it to ground. (Am I wrong?) Have been trying to figure that one out all day. Last night I fixed my big solder gun, and can now solder a ground wire to the grounding rod outside my bedroom window. Hope to do that tomorrow. I am definetly going to set this up. Have already tested several of my small capacitors, but they do not appear stable enough for anything serious. Just to familiarize myself with the mathematics, I have already calculated the inductors I would need for the first one I tested. Just finished removing a better variable cap from an old junk shortwave radio (a Luke, I think) and am going to try to use it. May have a problem with my meter though. May have to take the variable cap to the shop and have it tested on a known good LCR meter (gotta get one of those. I a currently using a DMM with limited capacitance capability.) If I do that I'll take my calculator and notepad with me, so I can figure out and write down the values of inductance I need. Damn I'm having fun. :) Thank you very much for this suggestion. It is much appreciated. Dave |
Thank you for this. I will check this out.
Dave "CW" wrote in message ... Take the batteries out. Put your (unconnected) plug into the socket. Check for continuity between its outer contact (barrel) and the negative battery terminal. Many radios have jacks with plastic external rings but there is a ground terminal inside. "Dave" wrote in message ... Just a quick note: it actually does have an external antenna input, I just don't know what type of plug to stick into it. Plastic ring with metal contact inside, looks like 1/8" mono would do it, but how would I ground it? Negative battery term? Thanks, Dave |
Impedance matching on a random wire antenna may or may not do much good. It
is considerably more helpful with short wires. The most useful impedance match you are likely to get is that obtained with a 9:1 transformer at the base of your antenna before the coax. Take a look at my website (long overdue for an update). www.kc7nod.20m.com "Dave" wrote in message ... Oh. An impedance matcher. Never was much good with those... Does this match the impedance of the random wire to that of the radio input? That would be good too... Yes, an L network, that was what it was called I think. I marked it, to go back to it. Thanks, Dave "CW" wrote in message ... "Dave" wrote in message ... What you saw in the antenna book was not a misprint. It was an L network tuner. It is an impedance matcher, not a preselector. Gotcha. That was the only way I could figure it. I saw something almost similar (is that like almost pregnant?) in my Practical Antenna Hanbook (Joe Carr) last night, but suspect it is a printing error. It was an series inductor following behind a capacitor shunt to ground. Only that would (I think) choke off RF and shunt it to ground. (Am I wrong?) Have been trying to figure that one out all day. Last night I fixed my big solder gun, and can now solder a ground wire to the grounding rod outside my bedroom window. Hope to do that tomorrow. I am definetly going to set this up. Have already tested several of my small capacitors, but they do not appear stable enough for anything serious. Just to familiarize myself with the mathematics, I have already calculated the inductors I would need for the first one I tested. Just finished removing a better variable cap from an old junk shortwave radio (a Luke, I think) and am going to try to use it. May have a problem with my meter though. May have to take the variable cap to the shop and have it tested on a known good LCR meter (gotta get one of those. I a currently using a DMM with limited capacitance capability.) If I do that I'll take my calculator and notepad with me, so I can figure out and write down the values of inductance I need. Damn I'm having fun. :) Thank you very much for this suggestion. It is much appreciated. Dave |
Dave wrote:
"starman" wrote in message Hmmm. A tank circuit between the antenna input and ground, to improve reception? I believe you, but I don't understand how it works. Could you enlighten me a little? Does it resonate at the selected frequency (chosen by adjusting the variable cap) and thereby "select" that signal for the input to the radio? (This is all I can figure.) I could do that real easy. I have several variable caps of that general size, and can pick up whatever size inductor I need. I even have the charts and formulas for calculating the appropriate value of inductance, just have to sit down with them. Thanks for the suggestion. PS: Haven't checked out the links yet, but will do so asap. Dave The parallel tuned (tank) circuit causes all frequencies above and below the tuned one, to be shunted to ground while passing the desired frequency range to the radio's antenna input. It makes up for the lack of good preselection in the receivers front-end. This is the main problem when connecting a good antenna to a portable radio. Be sure to use coils with ferrite cores for good selectivity. Gotcha. That was the only way I could figure it. I saw something almost similar (is that like almost pregnant?) in my Practical Antenna Hanbook (Joe Carr) last night, but suspect it is a printing error. It was an series inductor following behind a capacitor shunt to ground. Only that would (I think) choke off RF and shunt it to ground. (Am I wrong?) Have been trying to figure that one out all day. Last night I fixed my big solder gun, and can now solder a ground wire to the grounding rod outside my bedroom window. Hope to do that tomorrow. I am definetly going to set this up. Have already tested several of my small capacitors, but they do not appear stable enough for anything serious. Just to familiarize myself with the mathematics, I have already calculated the inductors I would need for the first one I tested. Just finished removing a better variable cap from an old junk shortwave radio (a Luke, I think) and am going to try to use it. May have a problem with my meter though. May have to take the variable cap to the shop and have it tested on a known good LCR meter (gotta get one of those. I a currently using a DMM with limited capacitance capability.) If I do that I'll take my calculator and notepad with me, so I can figure out and write down the values of inductance I need. Damn I'm having fun. :) Thank you very much for this suggestion. It is much appreciated. Dave If you can find a large enough variable capacitor, like 10-600 pf, you can tune the entire shortwave spectrum (3-30 Mhz) with one coil. One way to do this is to connect the individual gangs of a multi ganged capacitor together in parallel. However there is a practical limit to this because the high end (fully opened) range of the cap' will also get larger and this will prevent the circuit from tuning all the way up to 30-Mhz. That's why it's usually easier to use a standard capacitor like 10-365 pf with at least two coils and a switch. It's also best to use coils with an adjustable ferrite core (slug) so you can fine tune the circuit's tracking on the low end of the range. You can buy such coils from suppliers like Amidon and Miller. They come either wound for a particular value of inductance or without any windings, if you want to wind your own. The ferrite core material should be the type made for HF use, such as T-43. I used to get my coil forms from old televisions that used vacuum tubes. These sets had several coils in the I.F. and chroma circuits which worked well for shortwave purposes. I would remove the windings and rewind them for the value I needed in the preselector. Let us know how your project goes. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Dave,
Here is the Radio Netherlands 'review' of the Sangean ATS-505. http://www.rnw.nl/realradio/ats505.html The Shortwave "External Antenna" Jack appears to be a 1/8" Mono-Jack. The Outer-Barrel is Ground and the Tip-End is the Antenna. Using a 1/8" Mono-Plug 'wire' the External Antenna to the Tip-End of the plug and the Ground Wire 'connection' to the Outer-Barrel of the plug. iane ~ RHF .. .. = = = "Dave" wrote in message = = = ... - - - - S N I P - - - - - Just a quick note: it actually does have an external antenna input, I just don't know what type of plug to stick into it. Plastic ring with metal contact inside, looks like 1/8" mono would do it, but how would I ground it? Negative battery term? Thanks, Dave .. |
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