Gerry:
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
> NSSL/CIMMS
> 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)
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