10MHz lock only after power cycle

DF1LON Lars · January 2020

My Flex-6700 with SmartSDR 3.1.8 does not lock on the 10MHz reference after power on. Only after a power cycle it is locked to the external 10MHz.

I purchased a 10MHz GPS-lock frequency reference from Leo Bodnar. It is up an running and I can see the 10MHz signal in the Flex-6700 receiver. My Flex is powered up via the "remote-on" feature. After the first power on I can see the 10MHz reference signal 40Hz above 10MHz. This means the Flex did not lock on the 10MHz reference. I need to switch off/on the Flex and now it is excactly on the 10MHz reference. If I now power off the Flex and the power supply and leave it off for an hour, I have the same issue again. After the first boot of my Flex, the 10MHz signal is 40Hz off. On the second boot my Flex is excactly on the 10MHz reference.

Any idea why my Flex does not lock on the 10MHz signal on the first attempt?

I already checked the 10MHz reference with a handheld RX to make sure that it is present.

73 de Lars
DF1LON

Martin AA6E · January 2020

This behavior is mentioned in the manual. So you could say that's "why". On a deeper level, I guess they are thinking they don't want to switch references during normal operation. Perhaps they are worried about a glitch that might freeze the radio or otherwise upset operation. I've wondered about this myself.

Cal N3CAL · January 2020

Lars, if you have an o-scope check the peak to peak amplitude of your external 10mhz signal. Make sure it's no more than 3.3 volts peak to peak. I had a similar issue where my 6600 would not always lock with a external 10 mhz signal sitting just over the upper limit (3.33 volts peak to peak). I padded mine down to around 2 volts peak to peak and no further issues.

If I recall there may also be an option in the Leo Bodnar software to adjust the signal level. You might try that as well.

73 de Cal/N3CAL

WX7Y · January 2020

Mine has done this from day one with my external GPS 10MHz source, I have had no success in finding a external fix for it.
My 6600 stays locked to the same source and does not have this anomaly.

73
Bret
WX7Y

DF1LON Lars · April 2020

Just a short update. I did send my Flex-6700 to the German Flex Support and they could not find any issue. They think that the issue is caused by my external 10MHz reference. The strange thing is, that the external 10MHz reference is recognized after a reboot.

So the workaround is:
- Power on the Flex-6700
- Power off the Flex-6700 immediately (after aprox. 1sec)
- Power on the Flex-6700 and the external 10MHz reference is recognized as expected

73 de Lars
DF1LON

10MHz lock only after power cycle

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