Topband: noise

[Tree]

On Sun, Jan 14, 2007 at 01:12:34PM -0500, W7lr at aol.com wrote:

> I have two TS-850's, which have an 8.83 MHz IF output.  I wonder about  the 
> comparator circuit and what circuitry to use beyond that, or whether to try  
> and insert that back somewhere into the 850?
>  
> This system may be one used by Motorola in some of their equipment.   It 
> requires finding a "clear" noise frequency near the desired signal  frequency.  It 
> is a lot more effective than a noise blanker which tries to  blank out noise 
> pulses.  

I have two things I can offer.  I have brought out the signal that gets 
asserted when a noise pulse is detected on a TS850.  It essentially acts
like a wired-OR circuit.  I tuned one radio up out of the band to let its
noise blanker work without any signals in its passband - and the other 
radio would essentially mute its receiver when the noise blanker in the 
first radio triggered.

It worked exactly as it should have...  until I started having loud signals
around in the second receiver.  I suspect the edges of the output of the
noise blanker were too square and it was essentially generating key clicks
on all of the signals (clicking with the noise - not the code they were 
sending).  I had to apologize to KI7Y - who was the first to show up on
the band and I thought his radio had problems.  

Perhaps by rounding out the edges of the logic signal - this could be 
improved.  

However, this isn't what Bob was talking about.  I don't know if the 
system Bob outlines is similar to what happens when you use something
like the MFJ-1026 - where you get a sense antenna that has N and 
hopefully not much S.

Speaking of noise - the strange howling sound that was heard during the
Stew was back for a bit last night.  I made a good recording of it here:

http://www.kkn.net/~tree/160/Noise_14Jan07_DF2PY.mp3

The signal in there is DF2PY.

Wolf shifted frequency at one point.  You can sort of hear the noise 
changing tone - which gives it the sound I think is like a Jet passing
overhead.  

Earlier in the evening, I recorded this sound:

http://www.kkn.net/~tree/160/160_Noise_14Jan07_0921UTC.mp3

I think was being heard by other people, so it wasn't a local noise.  It 
turns off at distinct times - on this recording right during a burst of 
static.  This could be some kind of parasitic from some transmitter 
somewhere?  Not sure if that noise can happen in nature.

Had several question marks from the XT2C last night - but then he said 
QRT instead of hanging in there.  I was fit to be tied.  Hopefully, we 
will get another shot tonight.  They were 579 when they QRT'd.  I asked
the 80 meter op to let the 160 op know (they were 599 on 80), but I am
not sure the message was received.

73 Tree N6TR
tree at kkn.net