OpenSpot Frequency Correction and/or demodulation weirdness

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N0PKT
Posts: 17
Joined: Thu Apr 13, 2017 5:45 pm

OpenSpot Frequency Correction and/or demodulation weirdness

Post by N0PKT » Wed Nov 22, 2017 1:03 am

After troubleshooting for a considerable amount of time I have finally determined that the openspot seems to be just enough off frequency to cause some headaches. After monkeying with all demodulation types and various advanced settings on the openspot I finally decided to adjust frequency to make the openspot work better with my GD-77 and FT2D radios. Note that when I have the radios set to use 436.000 then I must have the openspot setup for 436.000475 (and Demod Mode D for DMR) or the openspot receives a very lossy signal and the range is substantially negatively impacted. So that is to say that these negative things happen if the openspot is set to 436.000000. Has anyone else seen this? Attached is also a screenshot just for good old fashioned reference.
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Screen Shot 2017-11-20 at 6.52.28 PM.png

K9IUQ
Posts: 54
Joined: Mon Oct 16, 2017 2:05 pm

Re: OpenSpot Frequency Correction and/or demodulation weirdness

Post by K9IUQ » Wed Nov 22, 2017 2:12 am

Before blaming the Openspot I would check the frequency of your radios and the Openspot xmitter with a frequency counter. The GD-77 radio is a cheapo China radio and could very well be off freq. OTOH the FT-2Dr is a much better radio, but of course does not do DMR directly.

I have a Ft-2DR which I used for a couple weeks with my Openspot. Mostly I did C4FM to DMR Brandmiester. Never had a frequency problem, Now I also have a MD-380 DMR which is fine also.

Without a frequency counter it would be hard to tell if the problem is Openspot or your Radio(s).

N0PKT
Posts: 17
Joined: Thu Apr 13, 2017 5:45 pm

Re: OpenSpot Frequency Correction and/or demodulation weirdness

Post by N0PKT » Mon Nov 27, 2017 1:23 am

The issue is persistent on C4FM as well as DMR, and I am well aware of the GD77 cost and source this is why I also noted the FT2D... but if I have to hook it up to a service monitor so be it :roll:

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