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From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
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Date: Fri, 25 Jul 2008 14:07:34 +0100
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Subject: Re: LF: RE: 600m Info
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Steve

I think you will find 50 to  100 watts will give good comms over the first 
60 or so  miles  and with 'arq' over  a couple of hundred the deep fade 
pattern and high noise level , really prevent the simple broadcast operation 
of the newer multi tone systems,

 , Gary g4wgt  and my self  g0nbd have run various tests over the year , in 
normal rtty  85 hz shift gave very good results local and over distance. The 
85 hz shift was the result of a selective fading test , where 200 Hz 
separation looked to  increase the  possibility of loosing one (the hf) tone 
before the lower one, 23 hz shift also  gave good results but benefitted 
from  a reduction in baud rate.

 psk31 was a magnitude better over any path, good results can be obtained at 
range with the mulit tone systems , eg Olivia , but in qsb the long out 
times result in quite high  data loss due to  re-lock time

I would think, but have not been able to  try it yet  , as not found any 
other station with a pk232  , the original  amtor system would provide quite 
a robust link over distance due to  its very short tx/rx cycle time and 
data frame of only 3 letters  , but at a loss of noise immunity compared to 
the psk  systems.

the mail handling arq psk systems fail due to  the length of the 
transmitted data word and the reliance on  a statistically 'high' level of 
confidence in the reception of the 'echo' pulse, which cannot be archived on 
500, then end result usually a lock up !


Amplifier , As you are nearly fixed tuned, its quite possible to  modify a 
set that works on 160  mtrs by discreet lumped inductance and capacity , 
with the original power level of some 25/30 watts , I used a simple parallel 
tuned atu , not out of palce on 160 mtrs , the 4 gang 1000 pf capacitor was 
a spare for a Marconi cr100  rx , the coil a ww2 bc640  2 mhz tank coil , i 
also  found my weltz sp220 swr bridge worked fine on 500 khz as well .... no 
more than 25 watts or it heats up ..

with the increase of power the atu flashes over , I had to  construct a 
variometer , and oddly , I found the coaxial dynamics  8200G  2/30 mhz  250 
watt bird insert  gave reliable results on 500 , it reads a bit low 170 for 
220 ish , but it doesn't produce a phantom reflected reading and once i had 
made a calibration chart , proved quite usable , notably none of the 'bird' 
slugs in the hf range , 50, 100, 500, 1000 w, worked without giving a false 
return reading ,


Good luck with the system

G ..




> I will begin construction shortly on something basic that will give me
> around 100W for starters and then begin transverter construction in order 
> to
> run some fsk modes.

>Our experimental licences will be geared towards
> fleshing out 600m for regional emergency networks reliability over various
> paths and conditions. It is also looking as if we will be able to work 
> other
> stations within the amateur service, either directly on 600m or via
> crossband but nothing has yet been written in stone.