[Elecraft] K3s Notch Filter

[Rick Bates (WA6NHC)]

1). The design of the K3 notch filter predates most digital modes currently used (excluding RTTY).   Earlier digital modes, were wider.  It may be possible to change the behavior.  

2). The use of legal limit or not isn’t the issue; as it may be needed to make the DESIRED contact, typically often required on the lower bands.  Your ability to hear such a strong signal has many factors, including band conditions and proximity. 

3). I defy anyone to determine without going to the other station or asking, if the ‘offending’ station is using a 10 dB amp or 10 dB gain antenna.   Gain=gain, the means isn’t important.   Use what is needed to complete the contact. 

Without an amp, I would not have been able to work enough stations this past winter, for a 160 M DXCC (inverted L, 600 watts, 108 worked).  It would have been simpler has most of those I worked, also had more signal.  Full legal limit is very common there. 

I don’t listen to the digital modes but enjoy the quiet, volume down, ears safe (too late now).  I also run with AGC off, which doesn’t stop the audio system from using its AGC and causing blocking. 

However, FT4 and FT8 are very adept at hearing around the very strong, to hear the very weak. 

Rick WA6NHC

Smell Czech correction happen

> On May 12, 2019, at 3:47 PM, Bob McGraw K4TAX <rmcgraw at blomand.net> wrote:
> 
> It appears from my measurements that the manual notch is about 200 Hz wide at the 6 dB points.  That's the width of only 2 FT-8 signals and the depth of the notch is about 40 dB.  Certainly will take out 1 or 2 signals and not affect others in the 2.7 kHz BW of the normal FT-8 receiver bandwidth.
> 
> As to the bleeding ears, turn the volume down.   I don't find it necessary to hear any FT-8 data.   Also, correct attention to AGC parameters does a lot to deal with strong signals in the midst of weaker signals.   Also the use of ATTN and RF Gain reduction is a big advantage, specially on 160M - 40M and to some extent on 20M.
> 
> As to those running "legal limit", that depends on band and conditions, thus one may find legal limit is necessary to make contacts.   It is a weak signal mode not a low power mode. {Flame shields up.}
> 
> 73
> 
> Bob, K4TAX
> 
> 
>> On 5/12/2019 5:27 PM, HB wrote:
>> Unfortunately you can’t.  I miss that feature from several other lesser radios.  You could target a particular audio frequency and set the width of the notch filter and make the offending sound go away!
>> 
>> Hank
>> K4HYJ
>> 
>> From: Richard
>> Sent: Sunday, May 12, 2019 6:24 PM
>> To: Elecraft Reflector
>> Subject: [Elecraft] K3s Notch Filter
>> 
>> Is there any way to make the manual notch filter really narrow to keep morons running legal limit on FT8 from wiping out my waterfall and making my ears bleed?
>> 
>> Don’t like what AGC does.
>> 
>> Cheers!
>> Richard Kunc - W4KBX
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