Try to get hold of a copy of the original Mk1 LF Source Book - I covered
transmitting loops in there in some detail - before realising they are
not the way to go on LF ! Unless you can erect a loop with a huge area
(100s of m^2 at these frequencies) you will always do better with an E
field antenna than an H loop. Radiation resistance / efficeincy is
proportional to the fourth power of loop dimensions (square of loop
area)
What do you mean by small - my garden is just 14m long x 6 wide and have
a 7m high tee antenna with a radiation efficiency around -36dB and feed
impedance 100 - 130 ohms - although being on heavy clay of good
conductivity this is rather better than may otherwise be achieved.
On a receiving loop , why is there such a fuss about preamps ? A tuned
1m square loop with several turns of wire, coupled with one turn (or any
other suitable matching network) to a 50 ohm input provides more than
enough signal for most receivers except perhaps the very deafest
operating outside their specified frequency range.
Andy G4JNT
1) Does anyone have any pointers to or formula for a loop aerial for
transmitting on 136?. Or other ideas on radiating out of a
very small back
yard?
and
2) Having built an RX loop based upon the G3LNP design I am
interested in
receiving recent posts regarding the fet input pre-amp /
modifications. Is
there any reason not to use an op-amp?
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