With all the talk (once again) of compliant Part 15 installations, I thought I'd share some information about what might be good alternatives to radials for ground-mounted installations.
Over the weekend, I was doing some research on getting a good ground (or at the very least, some kind of ground) for a balcony mounted amateur radio HF antenna. By necessity, such an antenna has a very short physical length. I read over the usual suggestions, including not requiring radials much longer than the length of your antenna. But I also ran across several actual installations using some interesting approaches, which might be applicable to Part 15.
One installation used aluminum attic insulation foil, cut into rectangles and held together with aluminum tape - the antenna was mounted on top of the foil and grounded to it. It appeared that the foil covered a square of around 15-20 feet.
Another used pieces of sheet metal, screwed together to again form a relatively small square (if you made a rectangle, you might get some directionality, if that's a word).
Both owners of these installations claimed that they were achieving marginal results with small numbers of radials and/or ground stakes with their 'screwdriver' antennas - but when they moved to their respective solutions, the signals started to pour in, and they started to get their signal out.
While both are obviously compromises compared to using a large number of quarter wavelength radials, most people don't have the space for that, and a solid metallic ground will always be better than large numbers of short radials (and easier to install as well).
I'm going to try out the aluminum attic foil, myself.
I tried chicken wire spread out in
different directions for a ground
system for my Part 15.219 set-up.
I may have done something wrong,
but it didn't even work as well as
just 4 ground radials.
I know a window screen can make a
good receiving antenna, but the above
didn't work.
Many times I have mentioned a Part 15
station in CT that operated out of the
back of a truck. The transmitting antenna
was mounted on the rear of the truck. The
ground system was the truck and a bunch of
solid metal strips (I think) went out of
the back on the ground. (I don't know how far.)
It was said that this set-up got out 1/3 of a mile.
But I don't know what that means - there were
no details on receiving aparatus on the other end.
Still, I think it was a good Part 15 effort.
Bruce
FCC Open Area Test Sites (OATS) often use 1/2 inch hardware cloth soldered together. Works jest fine as frog hair.
Frog hair???
It will be wonderful fun to try the alternatives to radials one day in the future, but first I need to play some more with radials.
My AMT3000 transmitter at 1550 kHz does not have radials, it is grounded to the steel I-beam under the floor, which contacts the copper wire to the electrical earth ground and the water pipe ground, using a resonant coil and metal (Wintenna) window frame plus wire as an antenna. In effect, the antenna serves indoors and outdoors, but ranks mostly as an indoor antenna.
At noon I took the TECSUN PL-310 and gathered dBu (signal strength) and S/N (signal-to-noise) readings at key spots around the yard.
Just as PhilB predicted, the best strength was in the house and outside along the powerline.
Uphill at the far end of the rear yard the reception is useless, and today I wanted to work up there, so I powered on the AMT5000 which has two-radials, one north one south, putting a solid signal up the top of the hill.
The broken trees that I worked at cleaning up are part of making way for an outdoor antenna with radials. After that, other kinds of ground planes.
ON FROG HAIR:
John WDCX must be a violinist. Here's what Wikipedia says...
"The bow frog is the end part of a stringed musical instrument 's bow ... mechanism responsible for tightening and holding the bow hair ribbon. ."
I spent an entire summer experimenting with an SStran and a Rangemaster. The best, easiest results was a ground mounted unit above an "X" of chicken fence..
I purchased a 50' roll, unrolled it and cut it in half, made an "X" on the ground and soldered it together in numerous spots where the wires were close enough to solder. Laid rocks, firewood, anything on it to keep the wire flat.. LOL
I didn't bury it but after a while the grass grew up through it and I could mow over it with no issue. It lasted ~3 yrs. before it disappeared..
No ground rod. Didn't need one. It already had contact to the earth well enough, at least I thought so. It just needed to drain static if any developed on the system. Them RF's wanted the fencing, not the earth..
Quick, easy, and it worked just as well as a whole bunch of radials that I spread out in a field 50+ feet long (120 of 'um) which consumed a large spool of electric fence wire and a week of "After the Daytime Job" labor setting it up..
I did my testing with my car radio. I fired it up and went for a ride. Played wth both set ups for over 2 weeks each. (Rangemaster and the SStran on both ground planes, same central "Mount" area)
My observation and conclusion of both xmtrs is ~3/4 mi. with decent coverage in a car, much less in other situations, and the SStran won!! (By a slight margin) I built the copper pipe/coil antenna and modded the SStran. Used a CB whip on the Rangemaster..
I fed both units exactly the same. I used Cat-5 cable at a distance of ~400 ft. Same audio source and power. (12 volts D.C. converted to 24 volts D.C., fed with all 4 pairs of the Cat-5 combined to help with losses. 2 pair positive and 2 pairs for the negative) Audio was sent to the xmtrs. via an FM xmtr. to a rcvr. locally at the AM xmtr. area. Fed earphone level to the Am xmtrs. from the FM rcvr. Adjusted to proper levels, Yada, Yada.. (Hillbilly STL) Got the power from the 24 volt source via a LM7809 regulator to run the FM rcvr. Both units, the SStran and the Rangemaster, will handle 24 V.D.C. They both have regulators on board..
With the AM xmtr on and the FM rcvr.on, no noticable voltage drop from the 24 volt source. Both units together drew ~125 mA. at the business end..
Totally solar powered, BTW.. 😉
Both of my AM xmtrs. are in storage now. I'm off in a different direction.. Building speakers.. LOL
My FM xmtr. is in my car rebroadcasting XM radio to anyone that finds it while I'm on the road. (FM 25B connected to a magnet mount antenna) I provide an alternative to the junk radio stations for ~1/2 mi. radius. (I Know, I Know, Rich.. LOL) Had one fella figure it out and he followed me into the parking lot of my job! He thanked me and said he tunes in every day on his way to work..