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Hi all,
I was wondering if everyone here who uses a Part 15 AM broadcast transmitter could post what their useful transmitting range is, and what they legally did, if anything, to improve it.
I have Part 15 AM transmitter that I want to try in anopther location, and would like to try all the tips and tricks that others did to get the maximum range. I made the loaded antenna with the large coil-form and copper pipe, and the transmitter works fine. I just have trouble getting down the block with it, even when grounded to a 8′ ground rod. I could lay down many 1/4 wave radials at the base of the vertical antenna, but that is not feasible for me, due to cost and space. Would short radials make any difference? If so, how many and should they be bare wire, and how deep in the ground should they be?Hi all,
I was wondering if everyone here who uses a Part 15 AM broadcast transmitter could post what their useful transmitting range is, and what they legally did, if anything, to improve it.
I have Part 15 AM transmitter that I want to try in anopther location, and would like to try all the tips and tricks that others did to get the maximum range. I made the loaded antenna with the large coil-form and copper pipe, and the transmitter works fine. I just have trouble getting down the block with it, even when grounded to a 8′ ground rod. I could lay down many 1/4 wave radials at the base of the vertical antenna, but that is not feasible for me, due to cost and space. Would short radials make any difference? If so, how many and should they be bare wire, and how deep in the ground should they be?
I hear reports of 1-2 mile AM Part 15 broadcast ranges, but is this realistic?
Thanks for any help!
Jeff KP3FT
Total posts : 45366I think that would be possible with the Rangemaster or the SSTRAN, if set up right.
Talking House-II/InfoMax? I highly doubt it. Not designed for that.
I’ve yet to make a loaded coil antenna. I’m told that a mile is the maximum CLEAR reception…after that it gets noisier and noisier…
Hope that helps!
Doug
Total posts : 45366I have a Talking House transmitter and it meets or slightly exceeds the allowed 100 mW input power as tested on a commercial station monitor into a 50 ohm load. So as far as the carrier field strength, it should be very close to any other Part 15 compliant transmitter designed to work into a 50 ohm load.
Where it may be lacking is in the modulation, where the audio power is. So even though the dead carrier may be the same or better, the audio may sound weaker resulting in reduced “useable” range.
My Talking House transmitter was connected to a roof-top antenna. The antenna is a 3 meter radiator connected to an “L” network (lossy) tuner at the base of the antenna. My usable range was about a 4/10 mile radius and could be heard in isolated spots over a mile away.
Recently I did a little story about an antenna project. This new antenna, ground mounted, made quite a difference almost doubling the range.
My point? Tinker, tinker, tinker with the antennas as that’s your best point to improve your signal (all other things staying reasonably legal.) You mentioned using an 8 foot ground rod. For my ground mounted antenna my experience has been that a few wire radials on the ground work better. This was observed using both a field strength meter and driving away from the antenna listening on the car radio.
Since probably 99% of us don’t have the money or space to put 120 radials, 1/4 wavelength long under our antenna, do put whatever you can. Just try to make the radials equal and opposite each other, i.e. 4 radials 90 degrees apart, 6 radials 60 degrees apart, etc. Make them at least as long as the antenna, longer better.
Take a look at this POWERPLANE GROUND SYSTEM marketed by ISS. The drawing gives an excellent description of a ground plane system you could build. I’m not endorsing their products but I was recently involved with installing one of their low power AM stations for our city. I operate and maintain the system and with 2.5 watts into what looks like a Part 15 compliant antenna on the roof, the station can be heard within a 5 mile radius with no problem. I lowered the output power to 100 mW and could still hear it well enough within a 3 mile radius. That says alot about the antenna system.
Total posts : 45366I have an SSTRAN transmitter I aquired and built in December after reading about the unit at this site. I live in the woods near the Olympic mountain range near Quilcene Washington and after assembling the unit and using the 9 foot wire indoors my range was about 400 feet to a good car radio. I then built the SSTRAN base loaded antenna and at ground level outside I added about 200 feet for a total of about 600 feet.
This is going somewhere…. I next rounded up all of the extension cords I had 25 to 150 feet long and laid them out as best I could radially, about 12 total with a few extra wires and my good range jumped to about 1/2 mile in some directions up to a mile+ in others. The next operation was to clamp the station to a 25′ Rohn 25 tower alongside of the house. The range went down a bit but was about the same overall distance.
I rigged 6 shorted duplex recepticles to the base of the tower, plugged in my extension cords/ground radials and the range went back to what the ground mounted unit was. I retuned the antenna after each iteration. A 6 volt reading was as good as I could get but the range was OK. What a pain to adjust on the tower!
Next I connected a spare twisted pair in the audio cable to the meter points and then could meter the rf in the shack/studio. It just so happens that my 40 meter G5RV antenna passes over the part 15 antenna and clears the top by about 5 feet. Connecting a coil and variable capacitor in parallel and placing the combination in series with the G5RV and ground I can now effect the part 15 antenna tuning from in my shack but not as you might expect.
There is a tuning point on my inside capacitor where the SSTRAN meter dips to about 2.8 volts and at this point my range increases some but the signal is very strong in the 1 mile contour. I hope this is making sense, the wire I am tuning is not attached to the part 15 antenna. The next step when the weather improves is to suspend a wire to ground a few feet above a ground mounted vertical and tune it to see if that improves range.
Anyway if nothing else extension cords make great temporary radials and if you give radials a try you will see why everyone makes such a big deal about it.. I hope I dont have to explain that they are NOT connected to 120 volts AC!!! They are just copper borrowed from wherever you can. Good luck and have fun.
Total posts : 45366[quote=Dave]…Anyway if nothing else extension cords make great temporary radials and if you give radials a try you will see why everyone makes such a big deal about it.. I hope I dont have to explain that they are NOT connected to 120 volts AC!!! They are just copper borrowed from wherever you can. Good luck and have fun.[/quote]
Howdy Quilcene – that’s some beautiful county!.
What a great use for all those old extension cords I have in the junk box.
Also made me think of other possible cheap sources of radials, like the almost useless new extension cords sold at many so-called “Dollar” stores in metro areas.
Great contribution
Experimental broadcasting for a better tomorrow!
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