Frequency stability ANAN100D

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Conrad_PA5Y
Posts: 60
Joined: Fri Jan 19, 2018 8:11 pm

Frequency stability ANAN100D

Postby Conrad_PA5Y » Tue Jun 12, 2018 2:09 pm

To add to my ANAN-100D 'issues' I have noticed something else.

Last night I was listening to the output of a single tone from the transverter TX output socket on a receiver and noticed that every now and then the audio pitch would wander a few tens of Hz then recover with 1 second. I do not know what is causing it. Because this was a single tone generated in the FPGA and that VAC was not active we can forget anything to do with audio.

I actually first noticed it on receive a few months when listening to a strong beacon, I was experimenting with the audio peak filter and assumed that it was caused by some PLL in the audio. The events are quite fleeting in nature and if the frequency goes back to the exact same place it was then I am not so sure that it matters much on the air. I will have to do more to confirm this.

Please do not talk about RF feedback or supply decoupling, these are not likely as the HF PA was disabled and I had around 0dBm coming from the transverter socket.

So has anyone else observed this? I was using a GPSDO locked receiver for monitoring. I will try to quantify the problem and then see if locking to 10 MHz makes the problem go away.

I am not having much luck with my second hand ANAN-100D.

Regards

Conrad PA5Y
n1gp
Posts: 8
Joined: Sun Apr 09, 2017 6:34 pm

Re: Frequency stability ANAN100D

Postby n1gp » Tue Jun 12, 2018 7:42 pm

Conrad,

I remember there was some issue with the internal 10mhz oscillator on the Hermes board
being discussed a while back.

I wonder if this may have something to do with the anomoly your seeing.

Check out this thread:

http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/2013-May/092459.html

73's

-Rick / N1GP
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Conrad_PA5Y
Posts: 60
Joined: Fri Jan 19, 2018 8:11 pm

Re: Frequency stability ANAN100D

Postby Conrad_PA5Y » Thu Jun 14, 2018 11:23 am

Hello Rick thanks for taking the time to answer me. I have not yet had time to do further investigations. I think that the next step needs to be locking to an external 10 MHz clock. However before I do that I need to get 10 MHz distribution to the test bench and during the move to my new shack/house the distribution amplifier has gone missing.

I'll report back.

73

Conrad PA5Y

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