Re: LF: 500khz WSPR drift

[Andy Talbot <andy.g4jnt@googlemail.com>]

Yes, I did :-)

 

The FT817 block diagram shows two oscillators in the chain  a master at 22.625 and 'another' at 22.7785 - so that idea gets knocked out straightaway.  They done it on the cheap :-( 

 

SO you probably wouldn't even get a drift advantage by moving to a lower RF to transvert from.  I was going to suggest mixing from topband to effect some frequency drift reduction.

Andy
www.g4jnt.com

2010/1/14 Roger Lapthorn <rogerlapthorn@gmail.com>

You mean derive it from the transceiver's master oscilllator. Yes, a good idea, but the MO is not available on an unmodified FT817 but may well be on "grown up" radios.

73s
Roger G3XBM

2010/1/14 Andy Talbot <andy.g4jnt@googlemail.com>

If you are able to derive the transverter LO from the transverter's master oscillator do so.  That way errors will be cancelled out and any frequency drift will be now be in direct proportion to the final output frequency, rather than being that associated with any arbitrarily high IF.

 

Just an example:

The master oscillator in the IC746 is at 30MHz, so transverting from 30.5MHz would be an option in this case.  But one could just as easily divide this by 2 first and transvert from 15.5MHz.

 

Andy
www.g4jnt.com

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2010/1/14 Roger Lapthorn <rogerlapthorn@gmail.com>

My own QRP transverter goes from 28MHz down to 500kHz and this drifts about 40Hz before settling as the oscillator warms, so I have to be on-hand to adjust the dial setting in the first 30 minutes. I should leave the oscillator running all the time or have this on for 30 minutes before I start TXing.

At 50MHz drift would be worse. Also, I'm not sure what ambient temperature LA3EQ has got, but I bet it is cold, so his drift might be even greater as his transverter (higher power than mine) warms up more over a larger temperature range.

73s
Roger G3XBM

2010/1/14 Gary - G4WGT <g4wgt@tiscali.co.uk>

Hi guys,

Yes it was LA3EQ,  started getting decodes as the drift flattened out. 50 MHz to 500 kHz is a long way to transvert, I use 4 MHz & as far as I am aware no drift problems after half an hour or so warm up.

Thanks all the comments.

Gary - G4WGT.

2010/1/13 James Moritz <james.moritz@btopenworld.com>

Dear LF Group,

...The perils of having a 50MHz -> 500kHz transverter! 3.5MHz would be a better IF frequency from the drift point of view.

Cheers, Jim Moritz
73 de M0BMU

----- Original Message ----- From: "Rik Strobbe" <Rik.Strobbe@fys.kuleuven.be>
To: <rsgb_lf_group@blacksheep.org>
Sent: Wednesday, January 13, 2010 10:24 PM
Subject: Re: LF: 500khz WSPR drift

over the past 12 hours I had 51 spots of LA3EQ, frequency ranging from 503848 to 503885

73, Rik

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G3XBM    GQRP 1678      ISWL G11088

--

http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/G3XBM
G3XBM    GQRP 1678      ISWL G11088