[Lowfer] Re: LF "Repeater"/Variometers/Mobile

[James Moritz]

Dear Lowfers,

At 04:01 22/04/2003 -0400, you wrote:
>Wow, so a repeater created such changes. And what may be the fate for
>the U.S. 136?

The MB7LF Remote Receiver is actually operated by the Crawley amateur radio 
club - it receives the band 135.7 - 137.8kHz, and translates and 
re-transmits it on 144.9857 - 144.9878MHz, like a satellite transponder. 
The CARC had to negotiate with the regulators to get a special licence for 
it. The idea is to allow amateurs with no LF gear to listen on the band, 
and also to take advantage of the relatively low QRM level at the 
out-of-town club site so that local LF operators with noise problems can 
benefit. I have used it when operating from the RSGB conventions over the 
past couple of years (the  venues had awful noise problems and were quite 
close to Crawley) - the simultaneous transmit/receive facility it gave when 
operating CW was great! I don't understand why GW4ALG got so upset about it 
- after all, it only transmits on VHF, and so has no noticeable impact for 
the "non-repeater" operator.

For my motor driven variometer, I used a slipping shaft coupler to avoid 
damage - a geared motor drives the variometer via the coupling, which is 
made from a small block of nylon. A hole is drilled lengthways through the 
block to match the shafts. The motor end is secured with a grub screw. To 
provide controlled "slip", the variometer end of the coupler is slit 
lengthways with a saw, and compressed onto the shaft by a couple of bolts 
passing through the block at right angles to the shaft. Tightening the 
bolts by the right amount gives enough grip to turn the variometer, but 
when it reaches the end stop, the shaft spins in the nylon block without 
breaking anything. It has been working fine for a few years now.

As far as mobile LF operation goes, there have been at least 1 or 2 
successful LF /M contacts to my knowledge... have a look at 
http://www.wireless.org.uk/moblf.htm

Cheers, Jim Moritz
73 de M0BMU