Re: [TenTec] Corsair II noise blanker

["Bob McGraw - K4TAX" <RMcGraw@Blomand.net>]

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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