[Elecraft] K3 Filter question - SSB

[N2TK, Tony]

Down at WP2Z for CQWW SSB Test we sometimes on 20M opened up the bandwidth
to 2.4KHZ. Even with strong adjacent signals (as always the case on 20M) we
could keep our run rate higher than with narrower bandwidth. It was just
easier to copy calls even with all that adjacent QRM.

73,
N2TK, Tony

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bill W4ZV
Sent: Thursday, November 10, 2011 2:21 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3 Filter question - SSB


Barry N1EU wrote:
> 
> 
> Bill W4ZV wrote:
>> 
>> 1. It *WILL* keep your AGC from pumping if there's another strong 
>> station within the 1.8 kHz passband. However, do you really think you 
>> could copy a weak signal while a S9+30 interfering signal is inside 
>> your 1.8k bandwidth? I don't think so. With any typical SSB filter 
>> bandwidth, AGC pumping is not a practical issue (it IS a big deal for 
>> CW however).
>> 
> 
> Bill, I'm confused by that first sentence.  How can a signal within 
> the passband NOT pump the AGC?
> 
> Normally when AGC pumping is discussed, it's a negative reference to 
> an adjacent signal that's outside of the passband.
> 
> Barry N1EU
> 

You're correct Barry.  I meant to say just outside your passband.  However,
given that most SSB signals generate 3rd garbage (spurs, phase noise, etc)
in the area of -35 dBc, an S9+30 signal just outside your 1.8k passband will
easily obliterate a weak signal inside the passband.

I found my ears to be the best tool for copying weak signals in the presence
of strong adjacent splatter.  For whatever reason they heard better using
the stock 5-pole 2.7k set to a DSP BW of 2.0-2.1k than the 8-pole 1.8k set
to actuate at DSP = 1.9k.  I tried many times to use the 1.8k but simply
just found the 2.7k worked better for me.  Of course that's just my
experience which wouldn't necessarily apply to everyone.

73,  Bill


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