Copper wire for external AM/SW Antenna

Submitted: Wednesday, Apr 02, 2008 at 13:40
ThreadID: 56188 Views:3897 Replies:6 FollowUps:2
This Thread has been Archived
Hi all,
I have a grundig S350 AM/FM/SW radio that has external 'spring sockets' for antenna for AM and SW. One is colour coded red for antenna and one black for 'ground'. I have found that for best performance I should use a long copper wire 30m long...optimally 500ohms ????. And Non-conductive insulators on both ends of the wire to prevent signal loss. The use of the ground wire is good to do...the same length as the antenna wire, but not necessary (maybe..?).

Have a few questions for anyone who may have interest in this area.

1. What diameter of copper wire would give me 500 ohms?.
2. A good place to find and buy 30 m of wire?.
3. What are Non-conductive insulators?.
4. If I was to use the ground sprocket....does it have to be copper?.

Back Expand Un-Read 0 Moderator

Reply By: splits - Wednesday, Apr 02, 2008 at 16:52

Wednesday, Apr 02, 2008 at 16:52
Years ago I lived for a few years in the Snowy Mountains and had one of those basic General Electric long range raidios. I used a roll of galvanised tie wire from a hardware store for an aerial and earthed the radio with a short length of automotive wire to the earth point of the house.

The insulators were little ceramic cotton reel style things from the hardware store. They are just a connector designed to join two wires without letting them touch each other. I put one at each end of the aerial then ran another short wire from each insulator to the facia boards on the house and as high up a tree as I could get. Another length of automotive wire connected the aerial to the radio.

The whole thing might sound primitive but it picked up Sydney stations perfectly day and night.


AnswerID: 296153

Follow Up By: Pyalong - Wednesday, Apr 02, 2008 at 17:35

Wednesday, Apr 02, 2008 at 17:35
Thanks Brian....very interesting set up. Automotive wire?. I would be using it it out my imagination right that the antenna was shaped like a 'T' coming out of the back of the radio, with a insulator at each end?.

FollowupID: 562230

Follow Up By: splits - Wednesday, Apr 02, 2008 at 19:44

Wednesday, Apr 02, 2008 at 19:44
Yes that is right Mick. The wire from the aerial (tie wire ) to the radio was soldered on a few inches from the house end. This made it look like a sort of a T with the vertical section close to one end of the horozontal part.

This whole system was recommended by the salesman in Retravision in Wagga Wagga. I transferred down to the mountains with my job and found the old radio from home would not pick up anything and had no provision for an external aerial. When I walked into the shop and said I wanted a radio, the first thing he asked was where do I live. When I told him he said the GE one was the only one he had that would work in that area.

It picked up Wagga ok with its internal aerial but needed the old tie wire strung up in the poplar tree trick to go any further.

FollowupID: 562280

Reply By: Mal58 - Wednesday, Apr 02, 2008 at 17:30

Wednesday, Apr 02, 2008 at 17:30
Hi Mick,
A lot depends on whether you are talking about a permanent (at home) or a temporary (out bush) installation.

However, a few comments about the requirements. I know that these are in the user manual, but I agree that they are a bit confusing.

1 & 2) "Optimally 500 Ohms" and a Good Place to Buy
What this means is that the antenna impedance (sort of like resistance) needs to be "high". In radio terms, this impedance is actually measured between the antenna and the ground.

In a temporary installation, to meet this requirement, all you need is some hookup wire connected to just the antenna socket.

I have a roll of hookup wire that I bought from Jaycar. It's
13 x 0.12 tinned hook-up wire. Look at catalog item WH3001 as an example. I know it's only 25 meters, but that is fine.

Dick Smith will have similar wire, but DS tends to be a bit more pricey than Jaycar.

When out and about, I just throw one end up a tree, or if no trees across the top of the tent on the camper.

At home I have a similar arrangement, but is has been broken a number of times in strong winds. For a more permanent installation, something heavier duty is required. Jaycar has plenty of choice, but don't go overboard with expensive wire (Don't use Coax cable, it's not needed).

3) Non Conductive insulators
All these are is something that insulates the antenna wire where it is tied to any supporting structures.

If it is insulated wire, nothing extra is required, except if it is subject to wear, in which case something like a loop of nylon rope where the wire is supported / tied will be sufficient.

4) Ground Socket and Ground Rod.
The "Earth" connection actually provides the other "half" of the antenna.

If out and about, often I don't use anything, but the advise to use another length of wire laid on the ground will do the job.

If at home, just connect to a metal water pipe with the same time as wire as the antenna, this should be fine .

Cheers and Happy listening,


AnswerID: 296163

Reply By: Member - Footloose - Wednesday, Apr 02, 2008 at 17:34

Wednesday, Apr 02, 2008 at 17:34
1. The nominal impedance for any end fed wire is a function of the frequency. A wire a quarter wavelength long will have an impedance of between 38 and 60 ohms.
2. No idea apart from a trade electrical outlet.
3. Ones made from non conducting material (glass, bakelite, PVC)
4. No.
AnswerID: 296165

Reply By: Pyalong - Wednesday, Apr 02, 2008 at 17:39

Wednesday, Apr 02, 2008 at 17:39
Thanks Mal and footloose....very helpful info there...Mal, the use for me would very most probably be always 'temporary'...mainly for use out and again at home.

Thanks again...great answers.

AnswerID: 296167

Reply By: Member - Olcoolone (S.A) - Wednesday, Apr 02, 2008 at 18:45

Wednesday, Apr 02, 2008 at 18:45
Why not go to a auto parts place and buy a 30m roll of 3 or 4mm insulated can even get it in a choice of colours too.

I would not worry to much about resistance as most general coverage recievers have a strong front endand will recieve with a piece of wet string.

Forget signal lose on your general coverage reciever.

If these thing really concern you get rid of the Grundig and get a real reciever like a Icom 8500 or something good.

Regards Richard
AnswerID: 296179

Reply By: Pyalong - Thursday, Apr 03, 2008 at 11:21

Thursday, Apr 03, 2008 at 11:21
Thanks for the input all...!!!. Have a very confident starting point now. I will try the jaycar wire bizzo first Mal, Do i just put one end in the radio the other end up one tree vertical...or is it important to try and get the wire to go horizontal as well (across 2 trees)?.

Ill also try brians snowyriver thing to fartass around.

Have no idea what you mean by 'strong front end' Richard...but will not worry too much about signal lose.

The main reason I want to try and improve signal is when out and about at places over the last few years, I use radio to try and listen to the footy on AM (or SW if cant get signal on AM), most time I get it....BUT always keep losing the signal or very weak and scratchy....especially some places around cape york, kimberley, any of the deserts...etc....etc.

Thanks again, cheers,
AnswerID: 296340

Sponsored Links