[Elecraft] Re: [K3] Transmit AM through FM Filter?

[Joe Subich, W4TV]

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: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Dan Atchison
> Sent: Saturday, June 28, 2008 7:51 AM
> To: elecraft at mailman.qth.net
> 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
> _______________________________________________
> Elecraft mailing list
> Post to: Elecraft at mailman.qth.net
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft    
> 
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com