narrowband FM vs. FM

[Voyager]

Looks like you missed the addendum. Yes, the owner's manual is wrong, at least the old one is. There isn't room on the filter for the whole part number but the selectivity is usually marked by a letter. F is +/-6 kHz and D is +/-10 kHz. I don't have a PRO-96 to look but the filter may be visible if you take the rear cover off.

OK. You made me curious enough. ;->

I see FY on the filter. So, why am I getting so much adjacent channel interference. I'll have to check the frequency on my unit and the transmitter in question.

BTW, first week PRO-96, so I guess they all do have them.

Joe M.

 

[brianm]

I still haven't put my mind around this narrowband/step stuff. It confuses me to no end, because I didn't know much about steps before hand. Until I get some time to do so...could someone tell me a few things?

On my Uniden 785,

New VHF-HI NB Freqs: Mode NFM Step 7.5?
Old VHF-HI Freqs: Mode FM Step????

Low-band Freqs: Mode FM Step???

UHF Freqs - were already NFM? Step 12.5?


Also, will getting the settings right eliminate reception of an old VHF on an new adjacent NB (say 158.805 on 158.7975?) or would that depend on proximty to the tower and its power?

Thanks

 

[Voyager]

I still haven't put my mind around this narrowband/step stuff. It confuses me to no end, because I didn't know much about steps before hand. Until I get some time to do so...could someone tell me a few things?

On my Uniden 785,

New VHF-HI NB Freqs: Mode NFM Step 7.5?
Old VHF-HI Freqs: Mode FM Step????

Low-band Freqs: Mode FM Step???

UHF Freqs - were already NFM? Step 12.5?


Also, will getting the settings right eliminate reception of an old VHF on an new adjacent NB (say 158.805 on 158.7975?) or would that depend on proximty to the tower and its power?

Thanks

First, see the other thread for which is likely the correct mode.
http://www.radioreference.com/modules.php?name=Forums&file=viewtopic&t=19202

The 7.5 kHz step is correct for VHF NFM.
Old high band step is typically 15 kHz.
Low band is 20 kHz.
UHF were NOT NFM (SNFM), but splinter channels (xxx.xxx5 MHz) were only for low power use. Again, see the other thread to help determine which is the correct mode for UHF systems.

Joe M.

 

[brianm]

hmm


the Uniden 785 only has steps of 5, 7.5, 10, 12.5, 25, 50, and 100.

 

[Voyager]

hmm


the Uniden 785 only has steps of 5, 7.5, 10, 12.5, 25, 50, and 100.

Use 5 or 7.5 for the 15s, and 5 or 10 for the 20s. You will only hit a 'channel' every other step or so, but it will work.

Joe M.

 

[poltergeisty]

I have a question to this fm stuff. Could one be able to hear a frequency hoping spread spectrum using wfm? I was thinking that if the hop was within 200 kHz or so you will be able to hear the audio better. I have always thought that some cordless phones use a frequency hoping spread spectrum. I am not talking about the DSS kind. Is this why when I tune to wfm it sounds like it is right in the room or is this just a wfm mode for the phone?

 

[INDY72]

OK firstly to make sure we cover the legal standpoint- Monitoring any form of telephone conversation except for radio patched phone is illegal.

There thats out of the way...

Now: Spread Spectrum technology's key is in the speed of the frequency changes, not in the actual variance of the frequency, or the spacing....

There isn't a scanner made that can keep up with SS's speeds. To even come close youd need at least two scanners on all the freqs in the set up.

The freq spacing if I am correct is NFM. (800/900 MHz) Then you have the second gen which adds digital to the SS, thus DSS.