- December 23, 2006 at 3:42 am #6781T.ALLREDParticipant
Total posts : 47
I have a 20′ antenna pole I am considering to use for my SSTRAN antenna. Would my tx get as much range using a metal pole instead of copper?December 23, 2006 at 2:27 pm #1436712vmanGuest
Total posts : 45366
[quote=T.ALLRED]I have a 20′ antenna pole I am considering to use for my SSTRAN antenna. Would my tx get as much range using a metal pole instead of copper?[/quote]
The type of metal that the pole is made of isn’t going to make any difference. (The copper could bend easier..)
If you get it high into the air, Tuning is going to be tough unless you have a bucket truck or a ladder. Even at that, Everytime you move the tuning changes..
Put your efforts into some ground radials and keep it close to the ground where you can reach it. I suggest just high enough to reach the tuning part of the antenna. (The copper pipe area) That puts the coil around chest height. Now you can put the VOM in there and adjust for peak voltage. Just remember to move away from the antenna 4-6 feet everytime after each adjustment to get a more accurate reading. You’ll see what I mean…(LOL) A field strength meter sure helps also..
As for the ground area, The best results that I’ve had was with some chicken wire at the base. I bought a 50′ roll, Cut it in half and made an “X” at the center of the base. Soldered it togather at several places where the pieces overlaped and connected it to the mounting pole which was around 5′ tall. (The SStran was grounded to the pole) The near field ground makes tuning a lot easier and you will achieve the 15 volt target voltage closer than anything else that I’ve tried..
Remember your goal.. Get as much resonance going on in the antenna system as possible. The loss in height isn’t going to compare to the loss of resonance in a far field ground. Better resonance, better match to the xmtr, more output..December 23, 2006 at 2:29 pm #14368scwisGuest
Total posts : 45366
The direct answer to your question is “yes.” There is very little difference between “copper” and “metal,” which I’m guessing is cold rolled steel. We use copper for reasons that don’t have a great deal to do with the electrical properties of the element or alloy on question, it’s just easy to find, buy and work with.
The “depends” part comes from the fact that the vertical element, or “antenna pole,” is only part of a properly tuned antenna system. Any short (less than 150 feet for the AM broadcast band) antenna pole will need a loading coil to match the antenna radiator (the pole) to the transmitter.
The accurate answer to your question is “probably not much” because from the perspective of what needs to be accomplished the 20 foot element isn’t really any bigger than a 10 foot element when the ideal is around 150 feet. You would need a slightly smaller loading coil, which would slightly reduce resistance, but at the end of the day you probably wouldn’t notice much difference.
The other issue, one several regular contributors are probably waiting to see if I address, is that by using an antenna pole longer than 9 feet 8 inches you are abandoning rote system description metric compliance for Part 15.
A little discussed aspect of Part 15 compliance in the 510 to 1710 KHz band is that you may certainly use an antenna of any size but if you do, you lose the protection of assumed compliance by system configuration, namely, 100 mW DC input the the final RF output section and a 3 meter non-directional radiator.
Using any other configuration means Part 15 compliance will be determined by the field strength of your emissions, just like FM, and that’s always less favorable to the broadcaster than assumed compliance by system configuration. If anybody really cared about the AM Broadcast band that assumed compliance by configuration would probably have been taken out by now, but I don’t think anyone in the broadcast industry really does care, so it doesn’t get much attention.
Ernie Wilson of Pan Axis Productions sells a $7.50 booklet called ANTSAM about building non-compliant AM broadcast antennas that you might enjoy, but only if you like math. Ernie’s plans start with 50 foot antenna poles and he provides information about loading and tuning for all sizes of antennas.
PS – it looks like 12vman and I were posting at almost EXACTLY the same time 🙂
Experimental broadcasting for a better tomorrow!
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