And to this end, there are many different types of pulse noise. Some pulse
noise is repetitive, meaning the timing interval between pulses is equal,
and some is non repetitive which means the pulses are not of equal spacing.
Each requires a notably different approach to blanking. Then there is the
broad band type noise, more related to atmospheric noise, i.e. static
crashes, which of course has different pulse widths and rates. Again,
another approach is required.
In some systems the blanking is ahead of the AGC control and some is after
AGC receiver control. Each of these yields different results. Tentec has
recently addressed this point with firmware updates for the Eagle and the
Argonaut VI. It may have been applied to an Orion release although I can't
confirm this. And then the shape of the pulse in the receiver is modified
by the filter system used for bandwidth control.
Although the simple term "Noise Blanker" is the descriptive, there are many
requirements largely depending on the anticipated noise that is to be dealt
with. There are both hardware noise blanker systems and firmware/software
based noise blanker systems. It seems the hardware systems augmented by
computer based systems seem to be the more effective approach. In other
words, "no single shoe fits all".
73
Bob, K4TAX
----- Original Message -----
From: "Rick - DJ0IP / NJ0IP" <Rick@DJ0IP.de>
To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Sent: Friday, March 28, 2014 9:31 AM
Subject: Re: [TenTec] Corsair II noise blanker
* Why anyone would change a good design is a mystery. *
The requirements changed.
When the Triton was designed, about the only need for a noise blanker was
for ignition noise.
The noise blanker was often optional because if you didn't work mobile,
you
didn't need it.
About the same time, The Woodpecker (terrestrial radar) hit the bands and
was a huge disturbance.
Manufacturers began modifying the NBs in an attempt to fight that
disturbance.
Some helped a little, some helped a lot.
Then rigs changed technology.
Radios with upward conversion were totally different and that required a
fundamental re-design, including the NB.
Now most radios are back to downward conversion.
Requires another re-design.
If we had always only had radios with just one single conversion and all
on
9 MHz, then your question would certainly be a good one. But things have
changed many times since then.
It seems that recently software NBs were tried but didn't work so well.
With the Eagle they have returned to a hardware NB and it seems to be
better.
When judging these NBs, you have to be careful.
In the presence of very short pulses, most DSP radios 'had' huge AGC
problems.
These are things like static crashes or electrical fences.
Flex and Elecraft successfully addressed this but others did not.
If you turned on an NB and find you still have problems, it may very well
have been that the problem was in the AGC and the NB doesn't help.
However
that has finally been improved (for OR and OM7) in recent firmware
releases.
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Doug Reid
Why anyone would change a good design is a mystery.
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