[Elecraft] Use FM filter for AM listening??

[Joe Subich, W4TV]

> When I try to use the FM filter for AM listening, the results 
> are very poor.  Specifically, poor bass and significant 
> ringing, even when adjusted for max bandwidth, which shows as 
> 5 khz on the display.
> 
> If I turn the FM filter off, and use the 2.7 khz 5-pole 
> filter for AM listening, the results are much better--no 
> ringing and a more open sound with better bass.
> 
> The FM filter bandwidth is set for 13 khz in the config menu.
> 
> Did I make an error in judgment when I purchased the FM 
> filter for AM listening, or am I experiencing a technical problem?

Your results are contrary to what I experience.  Results on AM 
(standard and international broadcast) are very good with the 
FM filter with audio response running from 100 - 4200 Hz (the 
current DSP limits of the receiver).  

Results with the 2.8 KHz filter are disappointing, with audio 
limited to about 1500 Hz unless the K3 is tuned to "one side." 
For the offset tuned case, audio is limited to 3 KHz or less 
due to the need to keep the carrier sufficiently high on the 
filter skirt to maintain enough carrier for demodulation.  Due 
to its broader skirts, the 2.7 KHz filter may give somewhat 
better AM performance than the 2.8 KHz filter but the difference 
should not be dramatic. 

Sounds to me like a configuration issue but that's only a guess. 

73, 

   ... Joe, W4TV 
  





> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Dan
> Sent: Sunday, September 20, 2009 9:55 PM
> To: Elecraft at mailman.qth.net
> Subject: [Elecraft] Use FM filter for AM listening??
> 
> 
> I have K3 s/n 3020 with firmware 3.11.
> I'm planning to upgrade firmware at the next release--I 
> didn't see 3.14 as important for me.
> 
> I've been using the K3 on 80 through 20 mostly, with great 
> success and satisfaction--I love this radio.
> 
> I have in filter locations 1-4
> 1 - 13 khz, 0 gain, 0 offset
> 2 - 2.7 khz 5-pole, 0 gain, -.85 offset
> 3 - 1.8 khz 8-pole, 0 gain, 0 offset
> 4 - .4 khz 8-pole, 2 gain, 0 offset
> 
> I did NOT get the AM filter because I did not plan on transmitting AM.
> 
> I DID get the FM filter because I want to listen to AM 
> (broadcast band and SW), and possibly operate on 10 meter FM.
> 
> When I try to use the FM filter for AM listening, the results 
> are very poor.  Specifically, poor bass and significant 
> ringing, even when adjusted for max bandwidth, which shows as 
> 5 khz on the display.
> 
> If I turn the FM filter off, and use the 2.7 khz 5-pole 
> filter for AM listening, the results are much better--no 
> ringing and a more open sound with better bass.
> 
> The FM filter bandwidth is set for 13 khz in the config menu.
> 
> Did I make an error in judgment when I purchased the FM 
> filter for AM listening, or am I experiencing a technical problem?
> 
> I have not tried to use the FM filter for 10 meter FM because 
> I haven't heard any detectable signals at my location.
> 
> Thanks,
> Dan - W4TQ 
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