[NLRS] 6m and up noise

[Chris Elmquist]

On Tuesday (02/28/2006 at 07:31PM -0600), John Oehlenschlager wrote:
> 
> >From "UP NORTH" in EN26oo I see a very strong noise increase when pointed 
> directly at the Twin Cities.  On 6M the noise is typically 2 S-units above 
> the ambient when pointed other directions.  On 2M it is about an S-unit 
> higher.  Don't seem to see any significant noise on 222 or 432.  So much 
> for a quiet spectrum!   K0JO 

One noise issue we have battled for years is at the Shoreview towers
and has to do with the elevator cables arcing between each other and
the tower structure when they blow in the wind.

This not a continuous noise floor increase but instead a crackling,
periodic noise burst like you would expect from an arc.  When the wind
is up around Shoreview, I can get S9 to 10 or 20 dB over S9 noise bursts
on 2m from this situation.  The noise blanker in my FT736 will knock it
down somewhat but not completely.

The cables arc because they are so hot with RF where they run past the FM
broadcast antennas part way down from the top of the tower.  It became
more of a problem when the tower owners stopped parking the elevator
some distance up the tower and instead now keep it on the ground... as
I understand it.

I once discussed the issue with the engineer in charge at KMSP, which
owns the tower, and he said they would investigate if we were able to
produce spectragrams of the noise in action.  I don't think anything
has been done past that point.

I also don't think they are licensed for spark gap transmitter operation
with a 1500' vertical antenna... in any case.

I am not sure if this is the noise you are hearing.  I know there are
other issues with the TV channel 2 transmitter that goes back years
to when they upgraded to a Harris transmitter from whatever they used
to have.  I know some folks here in the Cities worked that issue pretty
hard when the transmitter went online but I think it ended when someone
ruled that it was in compliance and the hams were too "sensitive".

Chris N0JCF

-- 
Chris Elmquist
mailto:chrise at pobox.com
http://www.pobox.com/~chrise