For me, the best noise blanker was on my old Drake R4C. That thing
worked GREAT!
Bob, WG9L
On 12/15/2021 1:14 PM, Fred Jensen wrote:
I find both the NB and NR on my K3 to be moderately underwhelming, not
sure why. Ignition noise used to predominate in urban and suburban
areas and blankers like the one in the 75A4 were very effective. I
don't know what Detroit did, but I haven't heard ignition noise in
years. A general rule of thumb has always been to use blanking in
wider bandwidths which sort of makes sense I guess ... the blanking
pulses consume a smaller fraction of the overall signal passband. My
understanding of the K3 NR is that the DSP processor tries to build a
matched filter around the signal on the fly. It may be a bit too much
for the algorithms, I've never had much success with it on broader
noise such as power mains hash. Backing off the RF gain seems to be
more effective.
The best noise reduction I've ever encountered was on the receivers in
the transportable AN/TRC-96 2.5 KW HF ISB system back in the 60's. 3
voice channels and 16 TTY channels on the 4th. Don't remember the mfr
and don't know how they did it but you could literally make noise
disappear with minimal effects on the signals.
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
Jim Brown wrote on 12/15/2021 10:16 AM:
Lots of good advice here. A major problem with the K3 NB is the way
it is described on screen and in the manual. There are two blankers,
one ahead of the crystal roofing filters, one after them. Each has
multiple tweaks. In contest conditions, I've found good noise
reduction from using the one AFTER the roofing filter, and set for
the greatest depth and shortest time. I THINK it's called the DSP
Blanker.
Yes, by their nature, NBs will modulate signals by the noise.
Let's hope the NB in the K4 is better.
73, Jim K9YC
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