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DrYattz · August 9th 11, 01:14 AM posted to rec.radio.amateur.antenna

My 15 year old son is exploring shortwave radio, and has purchased a
Realistic DX-394a. We're experimenting with various antenna
configurations, now trying an inverted L. The layout so far can be
seen at:

http://i258.photobucket.com/albums/h...t/antenna2.jpg

So, a single strand wire crosses the yard at a height of about 14-18
feet, stretched east-west, insulated at each end, and another length
of wire connected to it drops to below a window, then passes through
the wall and to the Hi-Z antenna input. (The diagram shows a
lightning arrestor, but that isn't attached yet.)

But it seems to offer little or no advantage over the little
telescoping antenna. In fact, the best reception is when we touch the
antenna lead wire to the telescoping antenna. Do you suggest:

1) an antenna tuner?

2) coaxial cable running from the radio (Lo-Z input) to the end of the
75 foot run?

3) a north-south run?

4) a completely different configuration?

5) anything else?

Rees Chapman
winwinsit at gmail period com

Richard Clark · August 9th 11, 11:02 PM posted to rec.radio.amateur.antenna

On Mon, 8 Aug 2011 16:14:57 -0700 (PDT), DrYattz
wrote:

In fact, the best reception is when we touch the
antenna lead wire to the telescoping antenna.

I would suspect that if you simply touched the same place with your
finger (no antenna then either) you would get "the best reception."

Do you suggest:

1) an antenna tuner?

Very much suggested, yes.

2) coaxial cable running from the radio (Lo-Z input) to the end of the
75 foot run?

A move in this direction would foster more options when you experiment
with other antennas.

Also, use the LO-Z input, even if you don't choose to go with coax
cable right now.

3) a north-south run?

Sure, but that isn't the answer to your immediate problem.

Hi Rees,

The advantage found in using a tuner is that it can cure "deafness"
induced by nearby strong transmitters overloading your receiver's
front end (the first stages of amplification). Such a problem is
rarely obvious aside from the general sense of lack of sensitivity -
and yet this symptom is often the most definite cue. Many who choose
to ignore this necessity proudly proclaim how good their set is, not
knowing that it could be vastly better.

Even though you may not be tuned to the local AM transmitter a couple
of miles away, its strength can be 100,000 times stronger than what
you are attempting to tune in. This signal will force its way into
your radio and develop a voltage called AGC which lowers your radio's
sensitivity - by design.

The solution here is to exclude that signal before it gets in, and to
include that signal that you want to hear so it can get in. This is
the function of a tuner. This function used to be part and parcel to
older non-computerized receivers (read tube-sets and expensive solid
state models). You can add it back in quite simply. Shop for the
cheapest amateur radio antenna tuner that has two variable capacitors,
and a switched inductor - and WITHOUT a meter. You can buy one with a
meter, but the meter will not be functional for reception, it will
probably cost more, but it will still suit the required function of
tuning. There are sure to be SW specific tuners out there. They
don't bring anything extra to the table except for smaller size,
perhaps - and they could be expensive for no real advantage.

If you read this last paragraph closely, it gives a clue to a project
you and your son could engage in: constructing a tuner from parts.
Here's the simple list:
1. Box (any material, but metal is best);
2. Input connector;
3. Input capacitor with knob;
4. Switch with knob for coil inductor;
5. Coil inductor with taps for switch;
6. Output capacitor with knob;
7. Output connector.
That's it. Values for the components, how to arrange them, and where
to find them can be left to investigation on the Web.

73's
Richard Clark, KB7QHC

DrYattz · August 10th 11, 11:39 AM posted to rec.radio.amateur.antenna

THANKS, everyone, for the very thoughtful and thorough responses!
________________________________

John KD5YI wrote:

Check for a slide switch on the back that switches from internal to external antenna.

Would that be the ATT 0dB - 20dB switch? They show it in a figure,
but don't say what it's for. I'll try it.

Sal wrote:

Feedback to me would be nice. A Nobel Prize would be a bonus.

Your detailed suggestions of the antenna connections and
troubleshooting are quite helpful. I will return to them if the new
configuration doesn't work.

Jim Higgins wrote:

Why aren't you connecting the antenna to the Lo-Z SO-239 connector
instead of the Hi-Z Motorola type connector? (Other than the manual
telling you to use the Hi-Z.)

Right. Apparently, Radio Shack improved the DX-394, but kept the
crappy manual. Getting the antenna higher would help, I'm sure, but
for now I'm stuck with what I've got.

Richard Clark KB7QHC wrote:

If you read this last paragraph closely, it gives a clue to a project
you and your son could engage in: constructing a tuner from parts.

I appreciate the suggestions. But I'm going to take the easy way for
now.
_________________________________

These have led me to try another configuration; what I'm imagining is
at http://i258.photobucket.com/albums/h...antenna2-1.jpg

The lightning arrestor I'm considering is at http://ba-electronics.com/a28.htm.

I'm wondering:

1) if this new configuration makes sense.

2) if I should use coaxial cable at A (between the tuner and the
lightning arrestor) since the connectors are SO-239 and PL-259? Or
should I just run more of the insulated wire?

3) about coaxial cable at B (from the arrestor to the antenna wire)?

4) if this antenna tuner would be adequate? MFJ-16010 at
http://www.universal-radio.com/catal...amps/1329.html. If not, any
other recommendations?

Thanks again!

Rees

DrYattz · August 10th 11, 01:15 PM posted to rec.radio.amateur.antenna

For some reason, the photobucket image of the new configuration
doesn't seem to appear. Try this?

http://i258.photobucket.com/albums/h...g?t=1312974756

Rees

On Aug 10, 5:39*am, DrYattz wrote:
THANKS, everyone, for the very thoughtful and thorough responses!
________________________________

John KD5YI wrote:
Check for a slide switch on the back that switches from internal to external antenna.

Would that be the ATT 0dB - 20dB switch? *They show it in a figure,
but don't say what it's for. *I'll try it.

Sal wrote:
Feedback to me would be nice. *A Nobel Prize would be a bonus.

Your detailed suggestions of the antenna connections and
troubleshooting are quite helpful. *I will return to them if the new
configuration doesn't work.

Jim Higgins wrote:

* Why aren't you connecting the antenna to the Lo-Z SO-239 connector
instead of the Hi-Z Motorola type connector? *(Other than the manual
telling you to use the Hi-Z.)

Right. *Apparently, Radio Shack improved the DX-394, but kept the
crappy manual. *Getting the antenna higher would help, I'm sure, but
for now I'm stuck with what I've got.

Richard Clark KB7QHC wrote:
If you read this last paragraph closely, it gives a clue to a project

you and your son could engage in: constructing a tuner from parts.

I appreciate the suggestions. *But I'm going to take the easy way for
now.
_________________________________

These have led me to try another configuration; what I'm imagining is
athttp://i258.photobucket.com/albums/hh242/winwinsit/antenna2-1.jpg

The lightning arrestor I'm considering is athttp://ba-electronics.com/a28..htm.

I'm wondering:

1) if this new configuration makes sense.

2) if I should use coaxial cable at A (between the tuner and the
lightning arrestor) since the connectors are SO-239 and PL-259? *Or
should I just run more of the insulated wire?

3) about coaxial cable at B (from the arrestor to the antenna wire)?

4) if this antenna tuner would be adequate? *MFJ-16010 athttp://www.universal-radio.com/catalog/preamps/1329.html. *If not, any
other recommendations?

Thanks again!

Rees

Wimpie[_2_] · August 16th 11, 08:01 PM posted to rec.radio.amateur.antenna

El 09-08-11 1:14, DrYattz escribió:
My 15 year old son is exploring shortwave radio, and has purchased a
Realistic DX-394a. We're experimenting with various antenna
configurations, now trying an inverted L. The layout so far can be
seen at:

http://i258.photobucket.com/albums/h...t/antenna2.jpg

So, a single strand wire crosses the yard at a height of about 14-18
feet, stretched east-west, insulated at each end, and another length
of wire connected to it drops to below a window, then passes through
the wall and to the Hi-Z antenna input. (The diagram shows a
lightning arrestor, but that isn't attached yet.)

But it seems to offer little or no advantage over the little
telescoping antenna. In fact, the best reception is when we touch the
antenna lead wire to the telescoping antenna. Do you suggest:

1) an antenna tuner?

2) coaxial cable running from the radio (Lo-Z input) to the end of the
75 foot run?

3) a north-south run?

4) a completely different configuration?

5) anything else?

Rees Chapman
winwinsit at gmail period com

Hello Rees,

Mostly it isn't the problem to get sufficient signal, but to get
sufficient signal to noise ratio. If you can operate it outside the
house (with a seperate 12V battery), try this and see whether the
reception improves. Move around to find sweet spots. You may have
interference from indoor electronic equipment and this will be less
when you are outside. Don't run an extension cord to feed the receiver
as this may carry interference from inside towards the receiver.

As this receiver is rather sensitive, a large antenna may result in
worse reception due to overloading the input circuitry. Here a so
called preselector can help, expecially when you have some strong
nearby transmitters. If you like constructing, building such equipment
can be a nice project.

If outside reception is better, you may need coaxial cable to
"transport" the antenna signal to receiver without picking up
interference from indoor equipment.

Don't hesitate to come back with other questions or suggestions.

Wim
PA3DJS
www.tetech.nl
Please remove abc first in case of PM

Sal[_3_] · August 17th 11, 03:24 AM posted to rec.radio.amateur.antenna

"Jim Higgins" wrote in message
...
On Wed, 10 Aug 2011 02:39:47 -0700 (PDT), DrYattz
wrote:

THANKS, everyone, for the very thoughtful and thorough responses!
________________________________

John KD5YI wrote:

Check for a slide switch on the back that switches from internal to
external antenna.

Would that be the ATT 0dB - 20dB switch? They show it in a figure,
but don't say what it's for. I'll try it.

No, that's an attenuator. 0dB gives full signal strength and 20dB
reduces it by 20dB. Very basically it's used when signals are too
strong. Play with it as you receive signals of various strengths and
with various strength signals interfering and you'll discover where it
can help.

On the schematic diagram that I retreived, the attenuator is only in the
path of the LO-Z antenna, the SO-239 jack -- the one with the threads on it.

The telescoping whip and the High-Z jack are electically almost the same
place, separated only by a single capacitor which couples signals from the
HI-Z jack into the path from the telescoping whip. No attenuator in that
path.

Channel Jumper · August 17th 11, 11:30 PM

Quote:

Originally Posted by DrYattz

My 15 year old son is exploring shortwave radio, and has purchased a
Realistic DX-394a. We're experimenting with various antenna
configurations, now trying an inverted L. The layout so far can be
seen at:

http://i258.photobucket.com/albums/h...t/antenna2.jpg

So, a single strand wire crosses the yard at a height of about 14-18
feet, stretched east-west, insulated at each end, and another length
of wire connected to it drops to below a window, then passes through
the wall and to the Hi-Z antenna input. (The diagram shows a
lightning arrestor, but that isn't attached yet.)

But it seems to offer little or no advantage over the little
telescoping antenna. In fact, the best reception is when we touch the
antenna lead wire to the telescoping antenna. Do you suggest:

Buy a good verticle antenna.

1) an antenna tuner? Antenna tuners only adjusts the resistance of the line, the line resistance is important if you are transmitting, but not really all that important when you are in the receive mode.

2) coaxial cable running from the radio (Lo-Z input) to the end of the
75 foot run?
Coaxial cable - has more loss at higher frequencies then lower frequencies.
Some antenna tuners has the capability of converting ladder line - 450 ohm to the appropriate load necessary for your receiver.

You need to build or buy a antenna for the frequency you wish to receive.
You also need to build or buy a antenna rotor - if you wish to receive in more then one direction.

3) a north-south run?
If you point your antenna north - you can use short path propagation to recieive signals out of Europe.

Basically what Short Path Propogation is - is a way to circumnavagate the earth by using the shortest route.
If you take a piece of string and measure from England ( UK ) to Long Island NY - you could get two completely different measurements by just putting the string across the globe as opposed to looping it around the upper portion of the globe and back down to the destination. The long path is the direct route - west to east.

The short path would be up towards Nova Scotia and back down towards
All the great navagators - including Chris Columbus understood how to get from point A to point B in the shortest amount of time.

That is also probably the reason why the Pilgrims landed on Plymouth Rock - because they ran out of BEER and needed to stop and brew a couple of kegs before they could continue south to Virginia to set up their new colony. - It was because New England was right along the way to Virginia by short path navigation.

4) a completely different configuration?

5) anything else?

Rees Chapman
winwinsit at gmail period com

Go back to what I wrote about what I said about your receiver.

A good receiver will receive in all directions with the used of a dipole antenna such as a G5RV - long.
The key is to get it up as high as you can get it in the middle and ends.

The book says to put it 1/2 a wavelength or higher for the frequency you desire to receive.
That is pretty easy for 10 meters - because the 10 meter band is only like 36 feet long.

160 meters would be almost impossible.
The FCC and the FAA limits tower height to 200 feet - for a licensed amateur, even at that, they might require you to use blinking strobe lights and there is rules - if you are in a flight path or closer then 5000 yards from a public use airport.

It all goes back to what I wrote the first time, get yourself the ARRL handbook for the TEchnician Class License and the ARRL Antenna handbook and start reading and attend some club meetings at the local ham club in your area and see what you can learn from the more experienced hams in your area.

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