Topband: No ears

[Greg - ZL3IX]

Continuing with the ideas put forward by Herb, one trick I pulled as ZS5K,
was to make a remote up converter, which took the Topband signals from the
end of my Beverage in a nearby school, and converted them up to a rarely
used part of the 10m band.  I wouldn't suggest for one minute that this
should be done in highly populated areas of the world such as the US and Eu.
In Africa, however, where, spectrum usage is orders of magnitude lower,
no-one cares, or even knows.

My up converter consisted of an input bandpass filter, with a bandwidth of a
few tens of kHz, a stage of amplification, SBL-1 mixer driven by a crystal
osc on about 27 MHz, and an output filter and amp.  In my case, the distance
to be covered was only 100 m or so to get me across a road, so I only needed
100 uW or so.  If you need to push the signal further, its surprising how
far you can get on a few mW.  I had a sense loop that detected my transmit
signal, and I used to send a couple of dits to switch the up converter on.
The whole affair was powered from a 1.2 Ah 12 V rechargeable battery which I
used to swap out once a week for re-charging.

73 Greg, ZL3IX