[NLRS] 6M operations at KTCA

[Chris Elmquist]

Perhaps if tower work is going to take place, as a club, we might want
to provide some significant input that they address the arcing elevator
cables that have produced wide-band hash across the VHF spectrum for the
more than 20 yrs I have been licensed and operating from the northern
suburbs.

Whenever the wind is up, there is a perpetual "frying" noise at s2 to
s9+ levels on 2m coming from the towers.  Many of us have reported this
over the years with a response that nothing can be done until the next
scheduled tower work.  But, it persists with no real improvement some
20 yrs later.

Around 1990, I participated in a test with some engineers at Shoreview,
where I monitored this frying noise while they turned off the FM
transmitters (late at night).  The noise went instantly silent.
So, we know the source.  We also had success in another experiment
where the elevator was parked half way up the tower.  This kept the
cables from moving too much in the wind and also killed the noise.
Whatever improvements learned from those experiments have slowly faded
away over time and the problem persists today just like when we first
encountered it.

I realize your contacts are with the KTCA folks and this problem is from
the FM broadcast guys but my understanding is that the towers are a common
resource administered by one organization and that the KTCA antenna and
the FM broadcast antenna are on the same tower. If that's true-- I'd sure
like to see this issue brought up again ahead of any scheduled tower work.

My guess is that once they try running a weak signal receiver over there,
6m or wherever, they too will be "fried" by this issue.  It's probably
one of the biggest spark gap transmitters ever operated.

Chris NØJCF
 
On Wednesday (11/05/2008 at 08:31AM -0600), Doug Reed wrote:
>
>
> I've been talking with friends over at KTCA to find out what their plans 
> were for after the analog TV stations go dark next February. The answer is 
> they plan to play radio on 6M, of course....
>
> Scott, Don, and Ray are inclined to put a 6M SSB/CW station on the air from 
> Shoreview using the Ch 2 antenna after the analog stations go dark. Scott 
> likes to say it only requires a few watts into the main amplifier, but 
> where are you going to find a TR relay capable of handling the output?  :-)
>
> In the real world, they intend to have a double-shielded coax coming out to 
> the ham equipment from the main antenna feed. Scott has already purchased 
> one of the 8 or 10 section DCI 6M filters. It has claimed attenuation over 
> 120 dB by the time you hit the FM band. Hopefully that will be enough. If 
> anyone has experience doing this, please comment on the required filtering 
> and remaining RF noise. By the time we attempt this, the closest remaining 
> stations will be in the FM band and channel 9 digital. But that doesn't 
> mean we still can't get knocked out by simple broadband RF hash from the 
> nearby transmitters. We will not know until we try.
>
> The very best news is that no tower work is scheduled on the antennas until 
> mid-August at the soonest. That means we have a super antenna site to play 
> with for 6 months, including at least 3 contests and the summer Es season. 
> The down side is the companies involved will probably NOT allow wide-open 
> visits by the horde and assorted friends. I'm just saying don't be too 
> disappointed if the ground rules include limited access, certainly only 
> when an employee is available.
>
> Once we have proof-of-concept and make required changes to get things 
> working, and the three contest weekends are out of the way, what other 
> suggestions do you have for potential activities? Where would NLRS want to 
> participate in events? Or are there only a few more people who want to 
> play?
>
> If I don't hear anything better, my own suggestions are along the lines of 
> a PropNET PSK31 propagation beacon on 50.291 for most of the summer. The 
> propagation beacon might be useful spotting openings and it would certainly 
> be interesting to compare results from one station at 200 feet and another 
> at 1100 feet.
>
> Or (possibly and) a temporary 6M FM repeater or a remote base on 52.525MHz. 
> The repeater or remote base would be fun for the rest of the ham community.
>
> It might even be interesting to try one day or weekend where that station 
> is run at the legal limit, just to see how far we can talk when the band 
> isn't supposed to be open.... That is where it would be interesting to have 
> an "activity day" scheduled for late February or early March when all the 
> Ch 2 - 3 stations we can find nationwide get on the are with high power at 
> the same time. Then see what the paths look like... But we've been using Ch 
> 2 for a propagation beacon for a long time now, so the results probably 
> wouldn't be that different or exciting....
>
> No, I will not be at this breakfast, but I hope to read some discussion on 
> the reflector.
>
> 73, Doug Reed, N0NAS.
>
>
>
>
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-- 
Chris Elmquist
mailto:chrise at pobox.com