[MilCom] Re: Army low VHF FM question

[Dan Wanchic]

Just for fun I did some tone squelch experimentation
with my BC785D.

Using an IFR 2947 test set, I set up
Channel freq: 41.4 MHz FM
two modulating freq's: 1 Khz @ 1.5 KHz deviation
and CTSS 151.4 Hz @ 500 Hz deviation

Set tone squelch on, freq 151.4 Hz
Squelch break just fine @ -119.8 dBm; .23 uV

Then I adjusted the subaudible tone freq until 
the squelch closed and then readjusted until it 
opened again- limits: 149.2 Hz & 153.8 Hz

This made sure that the PLL decoder dropped 
out of lock range. This is because PLL decoders
will typically stay locked over a wider freq
range than they will capture over. 

Since Larry had reported receiving some milcom with 
the 146.2 Hz CTSS, I was hoping that perhaps I could
get both 150 Hz and 146.2 Hz with the same setting.

So I repeated the same experiment with the 785D set
for 146.2 CTSS freq.

Limits: 144.0 Hz & 148.3 Hz 

Results: shows that the as reported the scanner will
succesfully decode 150 Hz CTSS when set to 151.4 Hz.

Also shows that it isn't possible to find a CTSS
setting that will decode both 146.2 Hz and 150 Hz.

Nixes that grand idea! 

Dan


__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com