3.125 channel center custom search?

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kd7kdc

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While the firmware coders have 1.15.x in the shop could you have them put in 3.125 kHz step size for the custm search or allow the custom search to start on a 3.125 kc frequency and use 6.25 kHz steps to go from one to the next. Just tried this in my 436 on 1.14.0 with 450.00312 with 6.25 steps and hit search then manual to stop it and started clicking through and it has reverted to 6.25 centers.
I would really like to not rely on dsdplus for accurate frequency centers.

Steve
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Voyager

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That may or may not be possible with the hardware.

6.25 kHz steps means it will use the standard 6.25 kHz steps just as 12.5 kHz will use the 12.5 kHz channels. What you need is 3.125 kHz steps.

Or you can just make a FL with the frequencies you want.
 

kd7kdc

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Check it out 450.003125 + .00625 = 450.009375 Hey look its another 3.125 channel center.
It’s not like im asking for a narrower baseband filter.
#WhistlerDidIt
#LiberalsDon’tLikeMath
 

Ubbe

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Uniden, and Whistler, have always used a fixed frequency raster so it have never made any difference if you state a start frequency that doesn't match the raster. I only know of Icom scanners, or actually receivers, that can do that. Maybe also AOR could do that, It was a long time ago I did search with an AOR.

You specify 420.00625 with a 12,5KHz step size and it will actually add 12,5KHz to get to the next frequency. The usually slow search rate In Icom receivers are then actually doubled in speed, compared to the competitors that have to search in 6,25KHz steps and their channel speed are then half of their actual specified speed.

/Ubbe
 
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DaveNF2G

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While the firmware coders have 1.15.x in the shop could you have them put in 3.125 kHz step size for the custm search or allow the custom search to start on a 3.125 kc frequency and use 6.25 kHz steps to go from one to the next. Just tried this in my 436 on 1.14.0 with 450.00312 with 6.25 steps and hit search then manual to stop it and started clicking through and it has reverted to 6.25 centers.
I would really like to not rely on dsdplus for accurate frequency centers.

Steve
WA/OR/ID/MT DB Admin

DSDPlus does not specify frequencies. That would be the task of the SDR software and a presumably properly calibrated receiver.

Why would we need a step size that is not specified in the FCC (or other entity) regulations?
 

kevino

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Why would we need a step size that is not specified in the FCC (or other entity) regulations?

Because the 3.125 kHz splits are being used in the real world! There is a wide-area NXDN trunked system in the Midwest that uses a good deal of them - regardless of the FCC (or other entity) regulations.
 

kd7kdc

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DSDPlus does not specify frequencies. That would be the task of the SDR software and a presumably properly calibrated receiver.

Why would we need a step size that is not specified in the FCC (or other entity) regulations?


I feel like i’m being trolled in this post....
 

ka3jjz

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There's another issue with such narrow band searches. It's highly unlikely today's scanners have a 3 khz filter so that you can properly tune a 3.125 khz signal without having adjacent channel issues using a 6 khz (or whatever it is these days) bandwidth. Until that happens, such a search is likely to get a lot of false hits.

Mike
 

kd7kdc

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There's another issue with such narrow band searches. It's highly unlikely today's scanners have a 3 khz filter so that you can properly tune a 3.125 khz signal without having adjacent channel issues using a 6 khz (or whatever it is these days) bandwidth. Until that happens, such a search is likely to get a lot of false hits.
Mike

Ummmm do you want to rethink your thesis.......?
Maybe stick to something you’re good at like wiki coding.
This moronic dribble of supposed knowledge is why two way radio shops don’t hire hams that thier only accomplishments are getting a no code ticket.
 

ka3jjz

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Nope, I won't rethink anything - and such manners...

I have seen 2 somewhat different block diagrams of a FM receiver - one with a filter in between the mixer and 1st IF (which is likely more common in professional gear) and, more commonly, one without (which I'm willing to bet is in consumer grade scanners)

With no filter, yes you will have a deviation of 3.125 khz, but with no filtering, I'm willing to bet you will hear it within a 6 khz bandwidth. So will a search using 3 khz steps work well? Maybe not in all situations, especially if the range you're tuning in has a lot of strong signals. Capture effect might lock onto a stronger signal and that might not be what you are interested in

Mike.
 

jonwienke

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We're not talking about deviation, we're talking about 3.125KHz frequency steps, so that one can actually tune to the correct frequency on systems that use such.

There's also the consideration that deliberately tuning slightly off-frequency can reduce adjacent-channel interference if it's only on one side of the desired frequency. A 3.125KHz tuning step can better balance between eliminating the adjacent-channel interference and still receiving the intended signal.
 

kd7kdc

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You’re giving me a 4 point infraction for INSULTS....INSULTS? Really??? Quack
I didn't realize the radioreference forums have become a safe space for like minded idiots.
Thats the problem with modern day America everyone is a ****ing ***** and can’t handle harsh talk anymore the ball up into the fetal position and cry to the governing body to ban “hate speech”.

I love making radio system operators loose their sanity by making the database the most acurate resource out there. I have been threatened personally by the ceo of a large utility company for posting thier new “unmonitorable” MPT1327 220 system complete with talkgroups. Yes I know utility companies are small potatoes to us.

Anyway If you all can’t handle tough talk from time to time, I’m out and will take my expertice elseware.

Steve


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Voyager

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Why would we need a step size that is not specified in the FCC (or other entity) regulations?

Because the FCC allows (or so it seems) FDMA operation. Some system operators are putting two 3.125 kHz channels in a single 6.25 kHz allocation.

I first ran into this with two 6.25 kHz channels in a single 12.5 kHz channel on DMR.

The FCC is pushing equivalent channel capacity and using FDMA is one way to accomplish that. Using 3.125 kHz channels is an effective loading of double the talk paths in a 6.25 kHz channel.

So, if you are licensed for a 12.5 kHz channel, you can use it for one analog signal, a 2-talkpath TDMA channel, or a 4-talkpath FDMA channel using 3.125 kHz channels.

So far, only NXDN is narrow enough to allow that. That will likely change in the future. We might even have 1.5625 kHz channel spacing at some point to allow 8 FDMA talkpaths in a single 12.5 kHz allocation.
 
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wa8pyr

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You’re giving me a 4 point infraction for INSULTS....INSULTS? Really???

All,

This individual is no longer a RadioReference administrator. This kind of behavior is not tolerated, and he has been removed from the staff.
 

mikewazowski

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Anyway If you all can’t handle tough talk from time to time, I’m out and will take my expertice elseware.

Steve

Hopefully wherever Steve ends up, they have a dictionary or spell checker he can borrow.
 
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