Repeater Site Expedition Report - 2018-01-27

A number of us visited the county yard on Friday the 26th (N5UWY, KD5UGO, N5HZR, W5HLG, WE5Z, WB5ULK, AG5DB, AG5LB, KB5LSB).  We looked only at the VHF system and not the UHF system.

A couple of numbers for posterity:

  • Squelch opens at 0.2 μV.
  • Full quieting is reached at 1.0 μV
  • Modulation  bandwidth is 9 kHz
  • Deviation of repeated stations is 3.5-4 kHz
  • Transmitter frequency error +30 Hz
  • Power output is 20 W
  • 70 dB reject on transmit.

KD5UGO provided several tons of test equipment and knowledge to operate it.  We looked at the parameters quantified above.

We listened to the input frequency through the duplexers as well as straight from the antenna and we were looking at it on the spectrum analyzer at the same time; No unusual signals were heard or seen, only the signal of the HT (or the service monitor) we were using to key the repeater. 

We "swept" the Bp (Tx) and Br (Rx) sides of the duplexer and found no anomalies.  Yes, we wiggled wires and tapped on connectors while watching signals, none of which had any effect.  We checked their tuning and were able to coerce another 2 dB of rejection from the receive side (I do not have the initial or resulting values, only the 2 dB difference).  We saw no evidence that the transmitter on 147.06 was being heard by the receiver on 147.66 via the antenna system.

Bottom line:  No Trouble Found.

Clearly, there is a signal from somewhere mixing with the signal being received from stations trying to use the repeater.  None of the tests we did yesterday revealed the source of that signal. In fact, we saw no evidence of another signal. But it's there because we heard it on repeated stations within an hour of our visit.  It's real, we just have yet to find it.


Callsign Cobwebs From The Mental Attic

Heard some chitterchatter recently on one of the repeaters regarding callsign structures. I thought I'd clear out some of the stuff in my mental attic, so here goes:
  • By international treaty, the USA is allocated W, K, N, and AA-AL, technically WAA-WZZ, KAA-KZZ, NAA-NZZ, AAA-ALZ (AMA-AZZ being allocated to other nations).
  • Internally, the FCC decides how to break up those allocations into the various services.  
  • Way back in the day, when their were true regional offices for the Department of Commerce (before the Federal Radio Commission or the Federal Communications Commission), each district office had a number. Oklahoma's licenses were handled out of the New Orleans office, which was #5. You see where this is going.
  • Initially, US hams got a number (corresponding to the issuing office) and then letters assigned in sequence starting at AA. When they got to WZ, they started again at AAA (because for a while, if the first letter after the number was X, Y, or Z, it had a special meaning). There was also a period when some stations, usually a portable station operated by an amateur away from his usual address, that had 4 letters after the digit.
  • After one of the international radio conferences, c.1923, everyone agreed that all callsigns should start with the letters that had already been assigned, so US hams all grew Ws ahead of the digit.  
Skipping LOTS of trivia ...
  • For about 40 years now, more or less, in the Amateur Radio Service, callsigns have been grouped. Amateur Extra Class licensees were assigned calls from Group A, 1x2 or 2x1 starting with W (e.g., WE5Z, W5TC) . When those ran out (and in the 5th district they ran out about 1992 or so) they "refreshed" the group with calls starting at AA5AA. Advanced Class licensees (none issued since 2000) got calls from Group B, 2x2 starting with K (e.g., KK5IO). Technicians and Generals got assigned calls from Group C, 1x3 calls starting with N (e.g., N5ZZM). Remember, until 1987, the only difference between the test or Tech and General was the Morse code, so they got calls in the same group - the written exam was the same and if you passed the 13-WPM test, you got General, if not, you got Technician. Group C was exhausted in our district about 1992 as well (N5ZZM just squeaked in!) Novices (none issued since 2000) got calls from Group D, which were 2x3 calls starting with K. Once Group C was exhausted, instead of "refreshing" it with some other pool, the FCC started pulling from Group D, which is why all new Tech and Generals get 2x3 calls.
  • Now, then. When it comes to vanity calls, you are still restricted to the group that corresponds to your license class. So Technicians and Generals can get any available 1x3 callsign (starting with an N, K, or W) or any available 2x3 call (starting with WA-WZ, KA-KZ, NA-NZ, or AA-AL) with some restrictions. To get a 1x2, a 2x1, or a 2x2, you have to hold an Amateur Extra license.


Edit: Looks like Group A in the 5th District was exhausted on 1987-06-02 from looking at QRZ's 1993 database causing the FCC to start at AA5AA after WZ5Z was issued. 


OUARC Repeater Update

Your host is not only the Technical Committee Chair for SCARS but also a member in good standing (and past treasurer) of the OUARC so he ends up working on the OU repeaters, too (D-STAR on 444.7500 MHz, DMR on 443.8250 MHz, and good old FM on 146.8800 MHz).

Several weeks ago, the DMR system fell off the network. The RF side was still up and usable on the local talkgroups; only the remote talkgroups were unusable.  N5HZR and your host visited the site and were able to get the repeater connected back to the network.  

The next week, same thing.  Appeared, over the network, to be the same problem so your host visited the site but determined that the repeater was unrecoverable.  What your host didn't realize, possibly because the lightning was closer than absolutely necessary, was that the .88 FM repeater was also dead.  

Another visit was organized and it was determined that the power supply for the .88 repeater had taken a hit.  We removed the power supply as well as the DMR repeater as both would need to be repaired.  We're not 100% certain, but we are assuming that Thor played havoc with the equipment.

Forward to today and N5HZR, AG5DV, and your host returned to the site with a new DMR repeater (the other is being repaired and will be used elsewhere) which was placed in service.  We have some other clean-up work to do there so we'll be back soon.  Hopefully, we'll have the repaired power supply for the .88 repeater by then and we'll get that back on the air as well.