Re: LF: 817 drift

[Stefan Schäfer <Stefan.Schaefer@iup.uni-heidelberg.de>]

The best is not to use a HF TRX for the MF/LF stuff but to use a simple downconverter, at least for the TX side. A simple NE612 mixer and a xtal (e.g. 1.8432 MHz / 4 by using a CD4013) and a reasonable filter is what i'm using here. Takes 50 mA (ish) at 12V, is compact, is stable, is cheap, is /p...

73, Stefan/DK7FC

Am 03.02.2013 21:38, schrieb Roger Lapthorn:

Thanks for the tip Lawrence. I will try a lower supply voltage first.

73s

Roger G3XBM

On 3 February 2013 19:45, Laurence KL1 X <hellozerohellozero@hotmail.com> wrote:

Roger - I had the same drift issue and added the txco with little improvement - best was when unit was powered driven by lower voltage - think mine is set around 9.6V at the moment and less heat..it also sits in the cool garage...think Dex also found the same

Laurence KL 1 X

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Date: Sun, 3 Feb 2013 19:23:35 +0000
From: rogerlapthorn@gmail.com
To: rsgb_lf_group@blacksheep.org; rsgb_lf_group@yahoogroups.co.uk
Subject: LF: WSPR15 - sort of success

After several attempts Tom G8HUH managed to decode my WSPR15 transmission on 137.607kHz this evening. As the FT817 was drifting around 4Hz in the 15 minute TX slot with the FT817 on 1837.607kHz (I was using a stabilised sig gen for the LO at 1.7MHz), I think this was messing up the decodes as Tom only gave me -32 and -34dB S/N whereas I have been getting some 6dB BETTER than this with the WSPR2 transmissions.

If WSPR15 is going to succeed for me I need a more stable rig (or a 0.5ppm TXCO fitted to the FT817) or a fan to force cool the FT817 - even when running 500mW!

I'll leave the rig on for a little while longer, but will probably revert to WSPR2 for the rest of the evening.

Thank you Tom G8HUH, and Trevor G0KTN, for working with me for the last couple of hours to get this as good as I could.

73s

Roger G3XBM