[Elecraft] Manual notch In K3

[Johnny Siu]

Hello Arie,

Good, at least my observation is correct.

It is essential for a modern transceiver having the ability to notch a strong 
unwanted carrier right at the front.  Upon 'notch' of the offending carrier, the 
'wanted' weak signal should prominently pop out from the noise.  The effect of 
the de-sensed AGC by the strong carrier should, by then,  be greatly reduced.

I would consider 'AGC off' is a solution of the last resort.  A high end radio 
should not reply on this very last weapon.

73

Johnny VR2XMC



----- 郵件原件 ----
寄件人﹕ Arie Kleingeld PA3A <pa3a at xs4all.nl>
收件人﹕ elecraft at mailman.qth.net
傳送日期﹕ 2010/11/10 (三) 9:26:35 PM
主題： Re: [Elecraft] Manual notch In K3

Johnny,

This is correct. Same experience here.

Although I would like that the notch would take the carrier out like a 
conventional IF notch.

It has been said several times in the reflector that taking out the 
carrier and increasing the gain again would degrade performance, 
especially the dynamic range.  If I do not reproduce this right, please 
anyone in the group, please correct me.

What I think of this? I disagree strongly. Not on the IMD thing, I 
cannot measure such things here anyway. I disagree because I feel the 
performance has already degraded. There is a great reduction in 
sensitivity because of something that I cannot hear  (the notched carrier).
Why care about dynamic range in this case? Signals must be very strong 
to even bring up a spurious on the noise level of the K3. Now I have 
something I donot hear and dont want to hear that messes up the sensitivity.

There must be enough spare performance in the K3 to reduce ( I donot say 
eliminate) the effect of the notched carrier?
Say up to the level of what the DSP filtering normally does if working 
with a wide roofing filter.

I plee for a solution.

73
Arie PA3A


Op 10-11-2010 5:18, Johnny Siu schreef:
> I attempted to manual notch a strong carrier adjacent to a weak station. 
> Although I was able to notch out the strong carrier (from the audio), there 
was
> no reduction in S meter level caused by that strong carrier.  In other words,
> the weak station did not pop out from the noise because the stronger
> carrier de-sensed the K3 AGC.
>
> Johnny VR2XMC
>
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