[600MRG] Bad news / help request

[Edward R Cole]

At 630m an OCXO ought to suffice.  My OCXO is +/- 5 E-12.

Used as 10-MHz reference with K3EXREF for the 49.380 MHz internal 
TCXO, that results in about 0.1 ppm or 0.047 Hz at 630m.
At 10-MHz I have 1-Hz short-term stability (0.1 ppm).  I measure 
28-MHz +/- 2-Hz (or so) using EIP538 counter with Rb reference (+/-5 E-11).
Long-term drift amounts to about 1-Hz drift in six months so periodic 
calib is required using my counter.

The K3 with updated Synthesizer board (or a new K3s) operates down to 
about 100-KHz in transmit at 1mw.  Receive sensitivity drops off 
below 630m.  But I run parallel with my SDR-IQ with -132 dBm noise 
floor which is 20-dB below 630m sky noise on average.

I removed the xosc in an old NDB beacon transmitter and drive thru a 
0.1 uF capacitor with my K3. Output is 1.4 A at 50-ohms (100w). That 
provides about 3-4 w EIRP.

73, Ed - KL7uW

At 09:03 AM 12/31/2018, Brian, WA1ZMS wrote:
>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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73, Ed - KL7UW
   http://www.kl7uw.com
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