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)