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Hi Keith

What I found in my testing was that if the calibration takes place before the FSKCW starts, it is successful. But once the FSKCW has started, the GPS frequency calibration doesn't happen, because the RF output never stops (the lower frequency). So you somehow need to use the Frame and Start parameters to make sure that FSKCW transmissions don't start immediately on switch-on, then it should get in a calibration before the FSKCW takes over.

73 Hans G0UPL

On Sat, Jun 1, 2013 at 11:37 PM, Keith Maton <nentecular@...> wrote:

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Now I appreciate that there's a new version of the firmware on the way that fixes the issue described below but something else has just happened.

Earlier today I switched from QRSS to WSPR. ?I've just gone back to FSKCW and there is no stabilisation taking place whatsoever. ?I can tell by cycling through the menus that the calibration figure isn't changing and I'm transmitting around 55Hz away from where I'd expect to be.

I've tried everything I can think of to get it to kick back in again, disabling the GPS, renabling it, inverting the signal, changing modes etc but nothing is working. ?It's not correcting it whatsoever.

If I put my original calibration figure back in (the one I worked out before I had a GPS), it's on roughly the right frequency.

It's very odd that it was working OK previously when first starting in FSKCW mode but now it's not even doing that.

73 Keith.

On 30 May 2013, at 23:09, Keith Maton <nentecular@...> wrote:

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All (specifically Hans),

I've found what I think is a problem with the frequency stabilisation routine in the U2.

The manual says:

"When using the connected GPS module for frequency stabilisation, you must choose a non-zero Frame parameter. This is because the frequency stabilisation must take place when there is no transmission from the kit, i.e. during a pause between transmissions. The frequency stabilisation takes 12 seconds and occurs just before the start of a transmission. Therefore you need to ensure that the Frame parameter is sufficiently large that there is a minimum gap of 12 seconds between the completion of your message transmission and the start of the next one."

This is all great in WSPR because there is a period of non transmission between each frame but it's not possible to do this when running FSKCW (and probably other QRSS modes, I've not checked them all).

I have my kit all working well and when I first start it, the frequency is absolutely spot on because it's calibrated. However, when starting from cold, there's always an initial drift as it all warms up.

My callsign takes 9 minutes and 40 seconds to send, leaving a period of 20 seconds or so before the next frame starts but the kit continues to transmit the lower tone for those 20 seconds and so it doesn't calibrate.

With the kit built into a box which works well as an oven, I've just watched it start transmitting on the correct frequency and then drift 20Hz upwards. When the next frame started, it carried on drifting so I simply cycled through all the menus and after the next frame had completed, I pushed the right button and when it started transmitting a few seconds later, it had run the stabilisation and was back on the correct frequency. It still hadn't reached the stable temperature in the box so it continued to drift upwards.

So as it stands, when running FSKCW (and possibly other modes), there's no stabilisation apart from the initial routine, no matter how long the callsign is because there isn't a pause between transmissions.

I don't think the transmitter should be switched off between frames because that will cause a temperature change of the overall unit, especially if it's built into a sealed enclosure and it will drift again once the transmitter comes back on.

I think a fix would be to force the transmitter off automatically for fifteen seconds prior to the end of the frame to allow stabilisation to take place.

Has anyone else noticed this?

I've uploaded a screenshot of what happens when I cycle through the menus at the end of the frame here - You can see that it's dropped back down to the correct frequency but I'll need to do it again at the end of this cycle as it's still not quite warmed up fully yet.

The automatic stabilisation routine is fantastic but it needs to work every frame to be worthwhile.

Or have I got something wrong in the menus that's stopping this from working? I have my frame length set to 10 and the start set to 1.

73, Keith.