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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