[600MRG] Bad news / help request

[Brian, WA1ZMS]

Murray makes an excellent point.....the freq errors being additive for rig +
transverter.  Murphey's Law has always dictated to me that everything drifts
in the same direction so nothing ever cancels out for me. :-)

The best solution is a master freq ref in the shack such as a locked GPS
standard feeding everything.  Or at the very least, you can track your
errors against the standard.

HNY to all as well!


-Brian, WA1ZMS


-----Original Message-----
From: 600mrg-bounces at mailman.qth.net [mailto:600mrg-bounces at mailman.qth.net]
On Behalf Of Murray Greenman
Sent: Monday, December 31, 2018 12:40
To: paul at n1bug.com; rsgb_lf_group at blacksheep.org; rsgb-lf-group at groups.io;
Discussion of the Lowfer (US, European, & UK) and MedFer bands
<lowfer at mailman.qth.net>; 600MRG at mailman.qth.net
Subject: Re: [600MRG] Bad news / help request

Paul,
Here's what I use:

     
https://www.qsl.net/z/zl1bpu/PROJ/MF%20Transmitter/MF%20Transverter.htm

This describes a simple transverter and 100 W power amp for 630 metres (but
could equally be for 2200 metres). At present I use a TCXO at 10 MHz to
convert down from an old marine transceiver with an OCXO reference (Kenwood
TKM-707), running on 30 metres.

For extreme stability you could use a transverter like this with a GPSDO as
the 10 MHz source, or perhaps a rubidium source such as the Frequency
Electronics FE-5680A. But you'd also need to lock the transceiver.

For transmit only, it's also possible to use a DDS synthesiser directly,
with just a power amplifier (such as the one described above). You would
need to write some code to control it in JT9, but that's not impossible. 
I've already done it for WSPR and other modes for a serial programmed
FE-5680A. You would need to lock the DDS synthesiser to a GPSDO or RB
source. Serially programmed FE-5680s are now really hard to find, but can be
programmed to within 10 milliHz and quite fast enough to send JT9. Never
worry about drift again!

If your strengths are in software rather than hardware, commercial DDS
synthesisers such as the Novatek 409B can be serially programmed AND locked
to a 10 MHz source.

The problem with transverters is that the errors ADD even when the
frequencies subtract, so two 0.1 ppm sources at ~10 MHz result in a 630
metre signal that's just 4 ppm! You need both the mix down source and the
transceiver to be 1 ppb stable. Direct generation on 630 metres using an Rb
or GPS referenced synthesiser is much the easiest solution.

73,
Murray ZL1BPU

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