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Neil, in a recent thread you discussed some of your experiences with the AM 25. Can you say more about adjusting bias with a 3 meter base loaded antenna say at 100 and 500 mw, and also any tips about tuning to the antenna. Did you make your own loading coil, use variable capacitor, etc. My main transmitter is now the SSTRAN which I love, yet still would like to get some use of the AM 25 at a different location if possible.
Neil, in a recent thread you discussed some of your experiences with the AM 25. Can you say more about adjusting bias with a 3 meter base loaded antenna say at 100 and 500 mw, and also any tips about tuning to the antenna. Did you make your own loading coil, use variable capacitor, etc. My main transmitter is now the SSTRAN which I love, yet still would like to get some use of the AM 25 at a different location if possible. I spent much time trying to work the AM 25 with the 3 meter base loaded antenna with no success and haven’t heard of any other real successes with this transmitter. Many thanks, Jim B
Total posts : 45366Hi Jim,
I need to dig some stuff out of my files….will get back to you regarding the power measurements. For a description of my antenna, see my post on this board titled “Glad this site is back on the air again. Now back to business, antennas.”
Neil
Total posts : 45366Jim,
I found the measurements I made. I also repeat here my antenna description.
I built an antenna from about 10 feet of 1/2 inch copper pipe. It is suspended from the rafters in my basement. At one end, the antenna connects to a coil wound with #12 wire on a 2″ PVC form. In parallel is a 20 to 400 pf variable cap. The cold end of the coil is connected directly to a copper water pipe for ground. The AM transmitter is coupled through a 7 turn coil to the loading coil (79 turns) and is wound around the grounded end of the antenna coil.
My scope monitoring setup is a dipole of total length 6 feet with a nonresonant inductor in the center. The dipole is oriented perpendicular to the transmitting antenna 8 feet away. The scope is connected across the inductor. I adjust the antenna coil tuning cap for maximum voltage on the scope.
The antenna works well with the Ramsey, but if you look at my other post, it does not do well with the SSTRAN. I got decent field strength but bad audio. I think the Q is too high and haven’t had time to experiment. The SSTRAN unit audio is great when I use a 3 meter #24 wire in place of the pipe.
With this setup using the #24 wire, I did OK on range with the Ramsey. I get about 200 to 300 feet from the house and about 100 to 200 feet with the SSTRAN, but remember my antenna is underground. When I adjusted the AM25 bias for the best audio the input power was 222 mW. Adjusting by the book gave distortion.
The SSTRAN power input was 97 mW. This probably explains the difference in range.
I will be posting a detailed analysis of this later.
To sum it up and I hope answer one of your questions, the range for the AM25 is greater than the range of the AMT3000, but not by much. I have never run either one with an outdoor antenna, but I would expect the ranges to greatly improved.
Neil
Total posts : 45366Neil, Thanks very much. Jim B
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