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[TenTec] Narrow FM

To: <tentec@contesting.com>
Subject: [TenTec] Narrow FM
From: aa8ve@juno.com (JEFF S JOHNSON)
Date: Mon, 4 Oct 1999 12:57:03 -0400
Thanks Perry,
They never tought me this in kindergarden! I'll have to play around with
it. I've never heard of a 15Khz wide filter for TT that sounds like it
may come for a Paragon or something trying to be an AM rig.
73 Jeff AA8VE

On Mon, 04 Oct 1999 11:40:10 -0400 w8au@sssnet.com writes:
> Jeff:
> Yes, they are correct.   NBFM was established as +/- 3kHz deviation 
> (total
> BW=6kHz), so as to be compatible with existing AM transmissions on 
> any
> band.  It's not very effective (for noise reduction) at that low 
> deviation,
> but it can be copied on any AM receiver by tuning off to the side of 
> the
> signal, thereby allowing the FM signal to slide up and down one side 
> of the
> receiver selectivity curve, causing amplitude variations which are 
> copied
> as AM in your receiver.  This is called, "slope detection."
> The FM restrictions you see in the rules (only above 29.0 mHz) apply 
> to the
> standard commercial deviation of +/- 5kHz.  (or greater)  Copying 5 
> kHz
> (total BW=10kHz) deviation signals on ten meters with your OMNI-V 
> 2.4 kHz
> filter will cause distortion as the sidebands move out beyond the 
> filter
> skirts.  If you have the optional 15 kHz filter installed you will 
> have no
> problems.
> A few years back I excercised my old Hallicrafters HT-19 on 75 
> meters by
> running NBFM on the AM spot freqs.  (The HT-19 did not have AM, only 
> NFM)
> Some caught on, some did not.  I had to set my frequency slightly 
> high or
> low so they would all be copying via "slope detection."
> Now you know how to make more use of your NBFM....if you want to!
> 73,
> Perry    w8au


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