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Micheal Salem <[log in to unmask]>
Reply To:
OU Amateur Radio Club <[log in to unmask]>, Micheal Salem <[log in to unmask]>
Fri, 24 May 2013 11:28:23 -0500
text/plain (6 kB) , text/html (9 kB)

Thank you to you and Peter.  I have written you both separately withsome 
thoughts about how to proceed.  I don't know yet if this is a temporary 
problem or an end of life situation.  I have some backup equipment that 
could go into service, but needs to be crystalled up.I made some 
measurements before taking the system down and I have been reviewing 
them, the schematics, and my maintenance logs.  I have a couple of ideas 
that I will try. I apologize to the club that this happened right before 
the tornado.

Micheal Salem

On 5/24/2013 9:15 AM, Gerry Creager - NOAA Affiliate wrote:
> Guess I need to get a list of active repeaters in the area or bring my 
> spectrum analyzer (bench queen) up and start sniffing. I'm wondering 
> if this is just a case of 2-system products or if there's other 
> systems involved that might (also) be dirty, e.g., a commercial 
> high-band system. It'd be worth looking for rust and corrosion 
> (dioding points) on antennas, connectors and mounting brackets.
> Michael, if there's something I can do to help, let me know.
> 73 gerry n5jxs
> On Fri, May 24, 2013 at 8:48 AM, Laws, Peter C. <[log in to unmask] 
> <mailto:[log in to unmask]>> wrote:
>     The 88 repeater is off the air temporarily for technical reasons.
>     I'm in-touch with Mr Salem and will keep the club up to date on
>     progress.
>     --
>     Peter Laws / N5UWY
>     National Weather Center / Network Operations Center
>     University of Oklahoma Information Technology
>     [log in to unmask] <mailto:[log in to unmask]> (Remote)
>     College of Architecture, Regional and City Planning, MRCP '16
>     ________________________________________
>     From: Micheal Salem [[log in to unmask]
>     <mailto:[log in to unmask]>]
>     Sent: Monday, May 20, 2013 02:52
>     To: Laws, Peter C.
>     Subject: 88 Repeater and Broadband noise on 2 meters
>     Peter:
>     I wanted to let you and the club know that I had to take the
>     repeater out of service.  Ken N5KUK alerted me to some hum on the
>     repeater.  He also indicated that he had been tracking some
>     broadband noise. I am not sure it was not coming from 88.  The
>     repeater is not really usable at this time.
>     I went over to check it and tried to figure out what was wrong.  I
>     also took some measurements.  I will study them tomorrow when I
>     check my repeater maintenance logbook at the office.  I can't tell
>     if there is a problem with the xciter or there is some oscillation
>     in the receiver front end because the first limiter is bouncing
>     all around.  There is hum when the reciever is unsquelch, but
>     there is more hum than usual on the xmtr squelch tail.
>     I checked my two local supplies that run the micor squelch card
>     and the repeater controller.  They had the correct DC voltages and
>     neither of them had more than .003 volts of AC on them, so I don't
>     suspect those as the power supply problem.  It must be internal to
>     the receiver and is probably some internal oscillation.
>     I finally decided to take the repeater off.  Unfortunately, I will
>     not have any time to work on it until Friday as I have a very
>     important brief due on Thursday.  I am going to take the service
>     manual for the repeater with me to the office.
>     I have a VHF Micor (and also a UHF) repeater as well as an MSR2000
>     VHF repeater in the 148 Mhz government band.  I intended to use
>     one of these as an eventual replacement.  I wanted to take out the
>     old Motrac and put the new repeater in the outdoor cabinet so that
>     it would stay clean.  Not sure if I can do that yet.
>     I will try to keep you and the club informed of the repeater
>     status.  I apologize for this problem.
>     73,
>     Micheal N5MS
>     On 5/19/2013 10:52 PM, Micheal Salem wrote:
>     Ken:
>     Thank you for your email.  I noticed the hum noise a couple of
>     times on 88.  At first it sounded like skip because it occurred
>     early in the morning.
>     A long time ago I had broadband noise on 88.  I traced it to a
>     leaking CATV line over on Acres street before calling the cable
>     company.
>     I also had a key up on the repeater when another repeater was on
>     the air.  I finally figured out that it occurred when someone
>     keyed up on another repeater while driving close to the 88
>     repeater site.  Their uplink mixed with the other repeater's
>     downlink in the repeater's receiver and if somebody keyed the 88
>     repeater, the 88 transmitter frequency mixed with the other
>     frequencies and produced a 600 khz offset close to 146.28 Mhz that
>     would stay on until one of the frequencies went away.
>     But the problem you describe sounds like there is something wrong
>     in the tuning of the 88 transmitter which is producing some spur
>     that is causing your problem.  Have you looked at 88 with a
>     spectrum analyzer and seen any spurs?  I have a Tektronix 2710 at
>     the office and an  HP8558B here at home and I will try to take a
>     look at it.
>     I just tested the repeater using my TYT radio and it does seem to
>     have a problem.
>     I am going to take it off the air and try to go over to the
>     repeater site.  If I can't figure out what the problem is, I will
>     leave it off the air.  I have some work that I have to get done by
>     Thursday and will probably not be able to look at it again until
>     Friday.
>     Thanks for writing.  If you have any other thoughts about this,
>     please let me know.
>     73,
>     Micheal N5MS
>     On 5/19/2013 7:16 PM, [log in to unmask]
>     <mailto:[log in to unmask]><mailto:[log in to unmask]
>     <mailto:[log in to unmask]>> wrote:
>     Mike,
>     We have been chasing some broadband noise that is obliterating
>     both the input and output of the 147.06 repeater. It seems to peak
>     about 147.220 but I found that it only occurs when the 146.88
>     repeater is keyed up. Also 146.88 has a lot of what sounds like 60
>     cycle noise on the carrier. Maybe a power supply problem there.
>     Ken Brown, n5kuk
> -- 
> Gerry Creager
> 405.325.6371
> ++++++++++++++++++++++
> “Big whorls have little whorls,
> That feed on their velocity;
> And little whorls have lesser whorls,
> And so on to viscosity.”
> Lewis Fry Richardson (1881-1953)