Posted by
Joe Subich, W4TV-3 on
Jun 29, 2008; 6:02pm
URL: http://elecraft.85.s1.nabble.com/Transmit-AM-through-FM-Filter-tp365954p365957.html
> What do most radios with only 15kHz roofing filters do on AM?
It's not a matter for the filter bandwidth. The first IF filter
is a significant factor in controlling image rejection. With a
2nd IF at 15 KHz, the image only 30 away from the desired signal.
Still, the FM filer response SHOULD be down some 70 or 80 dB
+/- 30 KHz from the center. That would be more than enough for
most purposes - nobody is going to be trying to work AM stations
at the noise floor <G>. With 70 dB of image rejection in the
filter, even if the K3 were driving a 1500 W PEP amplifier the
transmitted image would be less than .0005 milliwatts of carrier!
73,
... Joe, W4TV
> -----Original Message-----
> From:
[hidden email]
> [mailto:
[hidden email]] On Behalf Of AD6XY - Mike
> Sent: Sunday, June 29, 2008 1:06 PM
> To:
[hidden email]
> Subject: Re: [K3] [Elecraft] Transmit AM through FM Filter?
>
>
>
>
>
> Dan Atchison wrote:
> >
> >
> >
> > Yeah, I know, it's only $125, but I'm a cheapskate.
> >
> > 73,
> > Dan -- N3ND
> >
> >
>
> It is not only $125. It is $125. This is a lot of money for
> something essentially unnecessary to you. That $125 could be
> much more usefully spent on a better CW filter or if you do
> not need a CW filter, $125 donated to charity would go a long
> way to making you feel good compared to knowing your
> rarely sent AM signal is exceptionally clean.
>
> What do most radios with only 15kHz roofing filters do on AM?
>
> 73 Mike
>
>
> --
> View this message in context:
>
http://www.nabble.com/Transmit-AM-through-FM-Filter--tp18161074p18183029.html
Sent from the [K3] mailing list archive at Nabble.com.
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