Thank you to you and Peter.  I have written you both separately with some 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:
[log in to unmask]" type="cite">
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]> 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] (Remote)
College of Architecture, Regional and City Planning, MRCP '16
From: Micheal Salem [[log in to unmask]]
Sent: Monday, May 20, 2013 02:52
To: Laws, Peter C.
Subject: 88 Repeater and Broadband noise on 2 meters


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.


Micheal N5MS

On 5/19/2013 10:52 PM, Micheal Salem wrote:

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.


Micheal N5MS

On 5/19/2013 7:16 PM, [log in to unmask]<mailto:[log in to unmask]> wrote:
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
“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)