Posted by
Joe Subich, W4TV-3 on
Jun 28, 2008; 7:35pm
URL: http://elecraft.85.s1.nabble.com/Transmit-AM-through-FM-Filter-tp365954p365960.html
Since the AM transmit function is implemented in DSP, it should
be clean and band limited anyway. I don't see why it would not
be possible to enable the 13 KHz filter for AM transmit.
As far as image rejection goes ... even if the FM filter has a
shape factor of 2 (and it should be 1.5 or so) the image response
would be down more than 60 dB unless there is a lot of circuit
leakage (filter blow-by).
73,
... Joe, W4TV
> -----Original Message-----
> From:
[hidden email]
> [mailto:
[hidden email]] On Behalf Of Dan Atchison
> Sent: Saturday, June 28, 2008 7:51 AM
> To:
[hidden email]
> Subject: [Elecraft] Re: [K3] Transmit AM through FM Filter?
>
>
> Thanks for all the answers. To set the story straight, the reasoning
> behind the question was not to determine if I could transmit "hi-fi"
> AM, it's simply a matter of cost. At $125 a clip for an AM filter and
> the fact that I may only transmit AM once or twice in a lifetime, I
> couldn't see the extra cost to add the AM filter if TX through the FM
> filter worked.
>
> Since others have already identified that a filter can be
> "fooled" into
> thinking it's a different bandwidth, I do have a plan that I'll try
> somewhere down the road. Looking at the schematics it appears
> to be an
> easy solution that I can use an empty filter spot and diode
> switch (add
> two diodes) that position into an FM filter consumed location. That
> empty spot would be designated as the AM filter spot.
>
> Yeah, I know, it's only $125, but I'm a cheapskate.
>
> 73,
> Dan -- N3ND
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