246T and VHF conventional Freqs.

[mikext]

It seems that my 246T does not want to pick up VHF Freqs very well. I was wondering if the setting of NFM Vs. FM had any bearing on how well VHF Freqs. are received? Also what is the difference between narrow FM and FM? Thanks, Mike

 

[Voyager]

It seems that my 246T does not want to pick up VHF Freqs very well. I was wondering if the setting of NFM Vs. FM had any bearing on how well VHF Freqs. are received? Also what is the difference between narrow FM and FM? Thanks, Mike

The sensitivity is the same on both, although the squelch setting may be a little more sensitive to NFM.

The difference is that FM sets the bandwidth of the receiver to approximately 16 kHz, and NFM sets it to approximately 11 kHz.

How do you tell the difference and know which to set it to? Read on.

There is no real hardfast rule, but...

If it's low band, it's likely FM (NBFM). There is some Military AM there, too.

If it's high band (150 MHz) and ends in xxx.xxx5, it's likely NFM (SNFM). If it ends in xxx.xxx0, it's likely FM (NBFM), but could be NFM (SNFM).

If it's UHF (below 470 MHz) and ends in xxx.xxx0, it's likely FM (NBFM). If it ends in xxx.xxx5, it's about 50/50 as to which it is. Older portable-only licenses will likely be FM (NBFM). Newer high power repeaters will likely be NFM (SNFM).

If it's 470-512 and ends in xxx.xxx0, it should be NFM (SNFM). If it
ends in xxx.xxx5, it's likely FM (NBFM) but could be NFM (SNFM).

800 is likely FM (NBFM)

900 should be NFM (SNFM)

That said, you can sometimes tell be the license emission designator. If
it starts with 11, it should be NFM (SNFM). If it starts with 16 (or higher), it will likely be FM (NBFM) but could be either.

If all above fails, program it as FM (NBFM). IF the audio sounds low compared with other users on other frequencies, you likely have the
setting wrong - change it to NFM (SNFM) and see if they sound better
balanced. If they do sound better balanced, NFM (SNFM) is likely the
correct setting.

Joe M.

 

[scanfan03]

Or, you can just put the modulation on auto.

 

[Voyager]

Or, you can just put the modulation on auto.

The auto doesn't select the correct modulation - it programs it based on the BANDPLAN programmed in the scanner. It's somewhat misleading to call it 'auto'. In most cases, the scanner will select NFM even though most users are still FM.

I don't use auto at all in my scanner. I use the correct mode so the audio level is equal on all users.

Joe M.

 

[mikext]

Vhf for 246T

Thanks Joe manually adjusting the modulation has improved my problem.