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Date: Fri, 23 Sep 2011 18:46:45 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: VE7TIL long integration grabber online...
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Hi Scott, LF,

Am 23.09.2011 04:10, schrieb Scott Tilley:
> Hi Stefan
>
> In the past three years since I began prolonged 'low noise' listening 
> November has traditionally been the beginning of good opportunities 
> for EU/VE7 DX.  However,  DCF39 has surprised me this year with decent 
> showings already!  A couple of nights ago it reached audible levels!
OK so we will go on trying. But let me stay at QRSS-60 first, until the 
signal was seen at any active RX station in US/CA (east and middle). IF 
DCF39 is audible i think it must have about almost 40 dB S/N in a 22 mHz 
window? And DCF 39 is about 50 dB above a 1 W ERP signal, so not many 
dBs are missed!?! That sounds as if a "6000-test" must be successful 
these days, as long as QSB and phase changes are reasonably low!?

BTW today i collected a 1.2 m long and 0.3m diameter glass tube (got it 
for free, it was a rest of a 1.5m 400 EUR tube! ;-) ). This will be for 
my new loading coil! :-)

> I'd tweek out that system of yours and be ready to lobe some RF over 
> this way as I have a feeling that we may get some good opportunities 
> this season...  Timing is key...!  You need to be ahead of the curve 
> here.
And timing is focused on my local sunrise, thus not to complicated.
>
> My personal goal is to see if it is possible to detect an amateur EU 
> station in VE7.  I have no concerns about the usability of the signal 
> until we demonstrate that its even possible.
Yes, a doubtless detection is always the first goal, just like on VLF. 
Does not need to be a full call to be received, as VE2IQ luckily got.
>
> As a suggestion on how to get QRO with 100% keydown, consider using 
> many smaller stages combined to produce lots of power rather than one 
> stage pushed to the edge of meltdown.
Actually i tried the PA at 1.4 kW key down (longer than all thermal time 
constants) on a 50 Ohm dummy load and it was not much more than hand 
warm after the test. The limiting factor is my variometer and the 
loading coil. I can see the antenna current decreasing a bit during a 
QRSS-120 dash ;-) I'll wind a new one out of HF litz wire soon.

> Since then I've logged hundreds of hours on the same transistors.
Oh, on that H bridge PA is already lost about 10 FETs (in contrast to 
the 120W class E PA) but this is not due to thermal reasons...

> Just make sure you use one LO path and only ONE digital division 
> device to drive the driver ICs.  The reason for only one digital 
> division device is based on the fact a Type D flip flop (or otherwise) 
> can start in any one of four phases on power up.
Understood, yes. Since a few weeks i use a IQ TX-converter that adds 
SL's 11.172 kHz signal from the soundcard to a 125 kHz LO. That a 
circuit based on the design of G4JNT. It works excellent and due to 
locking the LO and soundcard, the signal accuracy seems to be below 1 
mHz, apart from some seldom phase glitches (about 1 to 3 per hour).


Looking forward to the season. We're in the beginning of that! :-) The 
detections at W1VD last night were very promising!

Best 73, Stefan/DK7FC