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Message-ID: <5.1.0.14.0.20011218144613.00a88f00@gemini.herts.ac.uk>
Date: Tue, 18 Dec 2001 15:55:28 +0000
To: rsgb_lf_group@blacksheep.org
From: "James Moritz" <j.r.moritz@herts.ac.uk>
Subject: Re: LF: Re: long haul QSO's
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At 12:42 18/12/2001 +0100, you wrote:
>Hello James and the group,
>    what you all think about the best method of generating multiple, 
> sequential
>frequencies from an LF transmitter?


It depends what your starting point is... There seems to be essentially 3 
types of 136kHz TX exciter around:

1) Oscillator/Synthesiser/DDS etc generating output direct on 136kHz - in 
this case a simple hardware interface makes it easy to home-brew a suitable 
modulator.

2) Some people have linear transverter systems, eg. using an existing HF 
SSB rig with or without an external frequency conversion - in which case 
generating the multiple FSK tones at some convenient audio frequency using 
the sound card would be the simplest implementation.

3)Several people use the HF rig as an LF VFO by dividing the output 
frequency digitally from say 13.6MHz to 136k. In this case, the sound card 
could again be used; to get 0.1Hz spacing at LF, the spacing between tones 
fed into the mic input would then be increased to 10Hz.

Personally, I would be biased towards 1 - since I don't have a synthesised 
HF transceiver, and am happy to build the necessary hardware, which 
experience shows will probably give the best possible performance with the 
minimum overall cost and complexity. The hardware interface gives the 
maximum flexibility to the radio equipment designer - if you wanted to make 
your own LF synthesiser, it would be easy to use, while trying to do 
something with some audio tones coming from a sound card would be difficult 
and messy. It also avoids all the headaches of trying to calibrate out 
frequency errors caused by sound card and HF rig, which has been such a 
hassle for many people with WOLF. However, I'm sure those who are happily 
using the HF rigs they already have as LF exciters will see it differently. 
I'm sure both methods would be used.

>P.S.  Which is more correct in English : "thanks for any 
>reply"  or  "thanks for
>any replies"  ??  The two forms seem to be both used...

I'm not sure, but I think "replies" is better, since you would be hoping 
for more than one reply!

Cheers, Jim Moritz
73 de M0BMU

P.S. While on this subject, can anybody suggest PSK31 software that has the 
phase keying signal as a hardware output? I'd quite like to try this with 
my TX in BPSK mode.