Tuning steps

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ChrisABQ

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I just recently noticed that Whistler has true narrow band tuning steps as follows: 2.5, 3.125, 5, 6.25, 7.5, 8.33, 10, 12.5 ad 25 kHz.

I'm wondering when Uniden might implement these more narrow (2.5 & 3.125 kHz) steps into an update for all their firmwares.
 

buddrousa

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I think those were for NXDN 4800 on the Whistlers if I remember correct.
 

jhampton2000

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I think those were for NXDN 4800 on the Whistlers if I remember correct.
I think you're right. However, with the way that Whistler have implemented a fixed bandplan (eg 3.125khz is only used on 700MHz range, 2.5khz isn't used at all), you can't really take advantage of having all these step sizes. The wide selectivity of both the Uniden and the Whistler means you rarely lose out on anything by not having it. But it would be useful to have, to be able to properly program in channels around their true center frequencies, especially for pulling in weak signals.
 

Ubbe

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Hmm, what's the narrowest filter in those scanners? I beleive you do not get outside of the filter bandwidth if you are 2.5 or even 3.125KHz offset.

/Ubbe
 

jhampton2000

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Hmm, what's the narrowest filter in those scanners? I beleive you do not get outside of the filter bandwidth if you are 2.5 or even 3.125KHz offset.
/Ubbe
Good question Ubbe......not sure if there's an official figure, but I did a bit more basic testing:

- On the TRX1, it looks like it's about 5khz (ie to correctly decode, you must be tuned to between + and - 5khz of the center frequency of the transmitter to decode it)

- On the BCDx36HP however, it looks like it's about 2.5khz (ie to correctly decode, you must be tuned to between + and - 2.5khz of the center frequency of the transmitter to decode it)

All tests undertaken on UHF, using 12.5khz bandwidth DMR signals (for the Whistler and Uniden), 12.5khz NXDN for the Whistler only, and 6.25khz signals for the Whistler only (where the testing actually suggested the bandwidth was slightly wider than 5khz).

So maybe I was wrong with the assumption on the Uniden, and that there is an essential need to have 3.125khz steps added - that's IF we ever see NXDN decoding being added (????)

The other thing to remember is that you will likely get some frequency deviation across such a wide band of the frequencies that most scanners operate: on my Yupi for example, it varies from about 1khz at VHF up to 4khz at UHF. I think the filter on the Yupi is at least +/- 5khz and is likely to be wider. On DMR simplex for example, this deviation alone (using my Yupi and DSD+) makes a massive difference and requires precise tuning (which you can do with 1khz tuning steps).

I've no idea what if any deviation I may be getting on the Uniden and Whistler listed above. Might the less-narrow filter bandwidth (partially) explain why the Whistler seems to decode DMR simplex so much better than the Uniden?
 
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