[NLRS] Deafness on 6M

Sun, 05 Jan 2003 17:15:11 -0600

An interesting problem You will get a +/- product on everything (all
modulation) but it is suppressed LSB . Since the audible subcarrier is about
10 dB down from the big video carrier it is very strong +/- 4.5 MHZ from the
video subcarrier. You need to null out the video carrier at least as it will
be the dominant overload creator.

I don't know what you can expect from a filter but you need to provide the
highest Q cavity possible (BIG) because of the small difference in
frequency. A notch cavity with series stub will probably be better than a
BPF but you will have to try to see what is best. (I can explain more later)
Forget using any external preamps. Using Vertical polarization may help
alot. I am not sure polarity is all that important on this DC band (hi!) &
based on experience 40 years ago.

Good Luck

Barry VE4MA
----- Original Message -----
From: "John Oehlenschlager" <[email protected]>
To: <[email protected]>; "Nlrs posting (E-mail)"
<[email protected]>
Sent: Sunday, January 05, 2003 4:47 PM
Subject: Re: [NLRS] Deafness on 6M

> The channel 2 video carrier is 55.25 and sound carrier is 4.500 higher at
> 59.75.  The problem is probably an intermod created at the TV transmitter
> causing a carrier at 50.75.  Although I am about 140 miles from KTCA, on
> very good mornings I am able to receive a weak carrier intermod at times.
>
> The same thing occurs with the Colour subcarrier  55.25+3.58.  An intermod
> appears at 55.25-3.58.  This will be even louder than the sound one.
>
>  John O.  K0JO
>
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