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From: G0MRF@aol.com
Message-ID: <c8a.d8fdf99.33cd4d8a@aol.com>
Date: Mon, 16 Jul 2007 18:39:06 EDT
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: [500] - G0MRF testing 503.70
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Hello Dave / Brian.
 
Thanks both for the report. Particually for the detailed Argo  screenshot.
 
Equipment is fairly basic.  TX
A trifilar transformer with 2 diodes forming a PSK modulator ( A DBM  really) 
driven from a DDS. Then 4 stages of linear amplification with 6 Watts  out.
 
Antenna: 9m base loaded vertical.   apx radiation resistance 0.08  ohms
Antenna current. barely moving the meter.  apx 100mA
So about a milliwatt ERP !
 
Modulation is the aspect of this that has kept me busy. All modulation is  on 
a PIC chip. The psk data is filtered by a 15Hz low pass built around an  
op-amp. No computer in use.
 
Having seen the spectrum from your argo shot, it appears it's the PSK  
synchronising signal just before the PSK31 message that is responsible for the  
widest bandwidth. The sync signal is a series of phase changes at 15.625Hz (+/-  
my timing errors) it appears to put all the energy from the TX at points  
seperated by 15Hz from the carrier. The PSK31 data however seems to fit  reasonably 
well into its expected 32Hz B/W.
 
Will leave it on overnight.
 
Thanks
 
David G0MRF
 
 
In a message dated 16/07/2007 19:57:56 GMT Standard Time,  
ganymede444@btopenworld.com writes:

Dear LF,  David,

Copied G0MRF PSK beacon this evening on 503.7 kHz.

Beacon  text as follows:-
" PSK31 beacon de G0MRF
QTH West London  IO91TK
g0mrf@aol.com "

Screenshot attached.

73, Dave G3WCB  IO91RM


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<DIV>
<DIV>Hello Dave / Brian.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Thanks both for the report. Particually for the detailed Argo=20
screenshot.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Equipment is fairly basic.&nbsp; TX</DIV>
<DIV>A&nbsp;trifilar transformer with 2 diodes forming a PSK modulator ( A D=
BM=20
really) driven from a DDS. Then 4 stages of linear amplification with 6 Watt=
s=20
out.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Antenna: 9m base loaded vertical.&nbsp;&nbsp; apx radiation resistance=20=
0.08=20
ohms</DIV>
<DIV>Antenna current. barely moving the meter.&nbsp; apx 100mA</DIV>
<DIV>So about a milliwatt ERP !</DIV>
<DIV>&nbsp;</DIV>
<DIV>Modulation is the aspect of this that has kept me busy. All modulation=20=
is=20
on a PIC chip. The psk data is filtered by a 15Hz low pass built around an=20
op-amp. No computer in use.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Having seen the spectrum from your argo shot, it appears it's the PSK=20
synchronising signal just before the PSK31 message that is responsible for t=
he=20
widest bandwidth. The sync signal is a series of phase changes at 15.625Hz (=
+/-=20
my timing errors) it appears to put all the energy from the TX at points=20
seperated by 15Hz from the carrier. The PSK31 data however seems to fit=20
reasonably well into its expected 32Hz B/W.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Will leave it on overnight.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Thanks</DIV>
<DIV>&nbsp;</DIV>
<DIV>David G0MRF</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>In a message dated 16/07/2007 19:57:56 GMT Standard Time,=20
ganymede444@btopenworld.com writes:</DIV>
<BLOCKQUOTE style=3D"PADDING-LEFT: 0px; MARGIN-LEFT: 0px"><FONT=20
  style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>Dear LF,=20
  David,<BR><BR>Copied G0MRF PSK beacon this evening on 503.7 kHz.<BR><BR>Be=
acon=20
  text as follows:-<BR>" PSK31 beacon de G0MRF<BR>QTH West London=20
  IO91TK<BR>g0mrf@aol.com "<BR><BR>Screenshot attached.<BR><BR>73, Dave G3WC=
B=20
  IO91RM<BR></FONT></BLOCKQUOTE></DIV>
<DIV></DIV>
<DIV>&nbsp;</DIV></FONT>   </BODY></HTML>

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