[NLRS] 6m and up noise

[Chris Elmquist]

Hi Tom,

It sure sounds to me like you were hearing the same noise and I know
that the problem has existed since at least that period of time.

I lost the will to fight this fight but could probably be convinced to
rearm if some others want to join the battle.  I think what we need are
some recordings and spectral analysis that shows what the signal looks
like and when it appears.  That is at least what the KMSP people asked
for when I talked to them a couple years ago.

Everyone was quite certain it was the elevator cables arcing but nobody
could agree on who's problem that would be.  The KMSP people seemed to
want to make it the problem of the guys who built the elevator... and
suggested that some new kind of bushings would have to be developed to
keep the cable farther away from the structure.  In any case, it seems
NOTHING gets done on those towers in the winter, which isn't unreasonable
I suppose but now that we are heading into spring and summer, it might
be a good time to ramp this effort back up.

Chris NØJCF

On Saturday (03/04/2006 at 04:29AM -0600), KB0DCO, Thomas wrote:
> 
>    Hello,
>                   Just got a chance to catch up on my emails....  NØTWP Bill,
>    and I Thomas KBØDCO, went out with our DFing stuff a long time ago around
>    1991 - 1993 or so. Bill used to live in an apartment complex on Cleveland
>    Ave. (the one closest to 35W on the 3rd floor).... if I remember right,
>    north of Hwy. 36 and south of 694.
>                    Bill used to do work stations on OSCAR 13. When he pointed
>    his KLM antennas towards the Shoreview towers.... he was getting that arcing
>    noise back then too. He took his Yaesu FT-736R and my 4 element beam with
>    attenuater in my car. As we were hunting the noise out, as we got closer to
>    the base of the tower (the single one not the double ones.) And the signal
>    disappeared! We went south from the tower on the road just north of 694. The
>    signal came back. I had the beam set up for vertical polarization the signal
>    was week pointing back at the tower.
>                    Then I had Bill point the beam up towards the top of the
>    tower.  Signal  came up. I told him we should try tuning the beam to a
>    horizontal polarization. THEN the signal came way up! Eyeballing from back
>    of the beam..... it seemed to be around the second red light down from the
>    top.
>                    Bill talked to the engineer there, but I don't remember what
>    happened after that. Far as I know it went away after awhile. I no longer
>    live in the area, so not sure if "this noise" is still happening or not. One
>    more thing to add.... When it was very windy.... that's when it made the
>    most noise.
>                    Just thought to post this..... It seems to me that the issue
>    never really went away.
>    P.S. After moving into Mcleod Co., I heard the same type of noise out here.
>    It brought me back to this story and hope it was not coming from the same
>    source. Possibly another radio tower in the area. Lucky for me.... I have
>    not  heard the same type of noise since about 1996. Hope they get that
>    problem fixed.
>    73
>    Thomas
>    KBØDCO
> 
>    Chris Elmquist wrote:
> 
> 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