Clutter Free wrote: ↑Fri Jan 13, 2023 2:34 pm

Albert H wrote: ↑Tue Apr 05, 2022 12:17 am One MW installation I've done recently uses a loop aerial - 9m up, 16m across the garden, 9m down and a return at (just above) head height back to the starting point. The part of the vertical near to the house is RG8 coax, and the rig feeds the inner, with the rest of the loop connected to the outer - basically making a long, thin transformer! It matches at about 18Ω, and the rig output stage is dimensioned to match into this directly. Radiation efficiency is surprisingly good, and for a peak DC input power of about 140 Watts, (suggesting a carrier power of around 30 Watts with the kind of efficiency I normally get out of Class E stages), I got daytime coverage that would be the envy of many FM stations!

The antenna design was suggested in a Practical Wireless article "Looping Over The Lawn", back in the '80s. In that case, it was used for "Top Band" - 160m / 1.8 MHz. I was pleasantly surprised how easy it was to get some radiation from this makeshift aerial, and experimenting with a chicken-wire groundplane didn't significantly add to the radiation.

The rig itself is a very simple CMOS synthesiser driving a couple of paralleled FETs for the PA, and modulated by (effectively) a power Op-Amp (LM3886). The most expensive parts of the rig are the mains transformer, the 19" rack box it's built in, and the heatsinks!

I finally got to lash this antenna together last weekend. WOW!! Amazing results. 30 watts into this antenna was clearly heard 10 miles away, with more tests to come this weekend, and, all with no wire radials on the ground, which keeps her happy

Thanks for the heads up on this Albert.

Antenna Practical Wireless article "Looping Over The Lawn" MMANA-GAL

EFR wrote: ↑Sat Oct 26, 2024 8:29 am Use MMANA-GAL software for windows.

http://gal-ana.de/basicmm/en/