Home |
Search |
Today's Posts |
#1
![]() |
|||
|
|||
![]()
Thanks to the generosity of a fellow radio club member I now have the
use of a Yaesu FT-1000 (no Suffix). Since it has a built in antenna tuner, that I'm hoping to use, I need to ask what the best way is to couple the window line that feeds my folded dipole antenna into a short; say twenty feet; coaxial feeder from the radio. I used an Icom AH4 antenna coupler with my FT-857D on this antenna with very good results. I would guess that I need a balun but which type is a mystery to me. So is a balun a good solution to this challenge or should I resort to the two pieces of coax in parallel that I have read of elsewhere? When you use the two parallel coax leads do you ground and/or bond the two shields at the transceiver end? Further since the FT-1000 does not have obvious balanced feed line terminals would I connect a balanced feed line to the ground terminal and the the center pin of the SO239 connector by using say a banana plug. Since I really am asking questions I hope there is already a consensus answer as I would not be able to sort out the various sides of any debate. Thank you in advance to all who choose to tackle this question. Tom Horne W3TDH |
#2
![]() |
|||
|
|||
![]()
"Tom Horne" wrote
Thanks to the generosity of a fellow radio club member I now have the use of a Yaesu FT-1000 (no Suffix). Since it has a built in antenna tuner, that I'm hoping to use, I need to ask what the best way is to couple the window line that feeds my folded dipole antenna into a short; say twenty feet; coaxial feeder from the radio. I used an Icom AH4 antenna coupler with my FT-857D on this antenna with very good results. I would guess that I need a balun but which type is a mystery to me. So is a balun a good solution to this challenge or should I resort to the two pieces of coax in parallel that I have read of elsewhere? When you use the two parallel coax leads do you ground and/or bond the two shields at the transceiver end? Further since the FT-1000 does not have obvious balanced feed line terminals would I connect a balanced feed line to the ground terminal and the the center pin of the SO239 connector by using say a banana plug. Tom, I looked up the AH-4. It appears it is to be used only with a random-length single wire antenna. You cannot feed a ladderline transmission line to it. So as you already may know, that's out. And you cannot connect the referenced two pieces of coax directly to the FT-1000. What you must do is use a transmatch (erroneously called an "antenna tuner") such as any of the various MFJ "tuners," or those from Palstar, etc., between your ladderline and your FT-1000. The transmatch you use must accommodate a balanced line. It can have coax inputs, too, but it must have balanced line terminals as an available option. The ladderline is fed through your wall (more on that later) to the transmatch; a length of coax connects the transmatch to the FT-1000. I run 100 watts and use RG-8X from my transmatch to my FT-950. The other way is to use a balun outside your shack. (I think DX Engineering sells some of these. You would normally find a 4:1 balun, in a weatherproof container, for this purpose.) The ladderline connects to the balun, and from the balun you run a SHORT LENGTH of RG-8 type coax (any RG-8 size coax will do -- but definitely not anything smaller) through the wall to your transmatch. The swr's can be very high on various bands at the balun, so you have to use one rated for many thousands of volts to be sure it can handle the heat. And because the swr's can be high, you want the coax lead through the wall to be as short as possible -- maybe five feet or less, or try to keep it under ten to reduce losses as much as possible. By the way, I tried this method 20 years ago using a Radio Works 4 KV "current" balun to work with my then MFJ-948 transmatch. Running just 100 watts, that balun heated up so badly that it was destroyed. So I do not recommend this method. In any case, you *have* to use a transmatch because your FT-1000 tuner can handle swr's of only up to 3:1, and, unless you're really lucky, your transmission line is going to present swr's far higher than that. Thus the need for the transmatch. If you want to run the ladderline through the wall, the way I did mine was to cut a 3" diameter hole in the side of my house, through the vinyl siding and all that, and insert a 3" PVC tube. I made holes in 3" PVC end caps to tightly accommodate two lengths of RG-8/U coax of *identical* length (five feet each, in my case). Outside the house, the ladderline is soldered to the center conductors of the two lengths of coax. Inside the house, the center conductors of the other ends of the coax connect to the balanced line terminals of the transmatch. For good measure, I inserted fiberglass insulation into the PVC tube. On each end of the PVC, the end caps are secured, and bugs can't get through. (Also note I attached a 45 degree PVC elbow to the tube on the outside of the house, pointing it down. That way, any water that gets on the coax will drip DOWN away from the 3" tube itself.) OK, what to do with the coax shields? Solder them together at both ends. Now you have "ladderline" running through the wall, but shielded from any electrical influences that might be inside the wall. Finally, attach a length of coax from the transmatch to the FT-1000, and you're all set. For lightning "protection" I installed, within the ladderline outside, male and female pairs of banana connectors. One housing contains two plugs, the other housing contains two jacks. That makes for a nice and quick connect and disconnect. I think I got them from Mouser Electronics. The width is just right for 450 ohm line. This makes it easy to disconnect the ladderline outside the house when I know a storm is approaching, or for times I go away overnight. Howard N7SO |
#3
![]() |
|||
|
|||
![]()
In article
, Tom Horne wrote: Thanks to the generosity of a fellow radio club member I now have the use of a Yaesu FT-1000 (no Suffix). Since it has a built in antenna tuner, that I'm hoping to use, I need to ask what the best way is to couple the window line that feeds my folded dipole antenna into a short; say twenty feet; coaxial feeder from the radio. I used an Icom AH4 antenna coupler with my FT-857D on this antenna with very good results. I would guess that I need a balun but which type is a mystery to me. So is a balun a good solution to this challenge or should I resort to the two pieces of coax in parallel that I have read of elsewhere? When you use the two parallel coax leads do you ground and/or bond the two shields at the transceiver end? Further since the FT-1000 does not have obvious balanced feed line terminals would I connect a balanced feed line to the ground terminal and the the center pin of the SO239 connector by using say a banana plug. Since I really am asking questions I hope there is already a consensus answer as I would not be able to sort out the various sides of any debate. Thank you in advance to all who choose to tackle this question. Tom- My first choice would be to adapt the AH4 to the FT-1000. If that was not practical, I'd go for a 4 to 1 BALUN to start. My choice of 4 to 1 is based on an assumption that the antenna/feedline will look like a balanced impedance around 200 Ohms. On some bands that may not be the case, and your built-in tuner may not have the range to tune it. If that happens, you may be able to use a 1 to 1 BALUN. If you wind your own, you can rewire it as needed. Fred K4DII |
#4
![]() |
|||
|
|||
![]()
On 11/25/2012 12:21 PM, Tom Horne wrote:
Thanks to the generosity of a fellow radio club member I now have the use of a Yaesu FT-1000 (no Suffix). Since it has a built in antenna tuner, that I'm hoping to use, I need to ask what the best way is to couple the window line that feeds my folded dipole antenna into a short; say twenty feet; coaxial feeder from the radio. ... So is a balun a good solution to this challenge or should I resort to the two pieces of coax in parallel that I have read of elsewhere? IIRC, your antenna is about 90 feet long: that makes it a "natural" for the 60 meter band, so I suggest you try using a 6:1 or a 4:1 balun, and see if the built-in tuner will work with it. If 60 meters is OK, try it on 20 and 10 meters, but 15, 40, and 80 are going to be iffy. I don't like the "choke" baluns that use toroid cores over the coax, since I've had problems with them overheating, but you can make a balun with a short length of PVC pipe: just wind one layer on the pipe, cover it with some Mylar, and wind the other side over that. The ARRL handbook has the formulas, which I can't recall offhand, since they are buried back in the mists of time and/or my misspent youth. ;-) When your balun is tested, and the turns ratio adjusted as needed, you can cover it in plastic to keep moisture out, and leave it outside so that you can keep using Coax for your feedline. HTH. Bill -- Bill, W1AC |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
![]() |
||||
Thread | Forum | |||
Convert DISH TV antenna for WIFI use. USB or RF FEED? | Antenna | |||
A better way to feed a random wire antenna. | Shortwave | |||
how to feed a planar monopole antenna using ie3d | Antenna | |||
How do you get the external antenna feed in? | Scanner | |||
Antenna feed wire question | Antenna |