Assorted mods & mtce
Today I spent about five hours working on the repeater tending to an eclectic assortment of items. Some related to the new controller installation, others that would fall under 'routine maintenance'.
I checked both the main and secondary receivers for both the 444.725 and 52.92 repeaters and found all four to be of normal sensitivity and without noticeable transmitter desense.
The Six meter Voter (an LDG unit) was checked and found to be favoring RX-3 (100' up the tower) over RX-1 (330' up the tower) by a fairly wide margin. This was corrected and the alignment of the RX-2 (the receiver located at the W8TVC location) was brought more into calibration. Hopefully the system will vote properly for the receiver with the best signal.
The DStar 145.36 repeater duplexer tuning was inspected and found to be 'on the money'. The RG213 coax jumpers from the duplexer to the DStar repeater were replaced with equivalent lengths of 1/2" superflex heliax and after measuring there were modest improvements with the better coax.
While on the topic of DStar, late in the evening on 7/19 it was noticed that the DStar repeater was off the air. On arrival at the site about 11:30am today I found the physical appearance of the system to be normal. The DStar repeater came back to life after power cycling. Power cycling of the DStar system is possible remotely via the 'FCC Legal' control system-- I should have thought to do that on Thursday night--- and save having the system offline for so long.
Hopefully, the apparent 'crash' of the DStar internal computer does not become a routine occurrence.
I opened up the new RC210 controller chassis and installed a hex buffer from two sections of a CD4049 in line with the COS signal from the six meter voter. This should improve operation of the switching circuits as the logic level was a bit marginal due to the high source impedance combined with a low load impedance. This brings into match the wiring of both the wI0OK/r and W8TVC/r controler chassis.
I attempted to upload the 'quack5.wav' file in order to reinstate the old DTMF test from the previous RC210 and the DVR (Digital Voice Recorder) in the controller but it did not play out. I tested the DVR with a local recording via RF and it does function. Perhaps the encoding of the WAV file required by the newer RC210 is different from the older versions.
Thankfully, the DTMF decoding of this new RC210 appears to still be functioning. I'm still crossing my fingers that the intermittant open trace on the board has been eradicated. I did notice that from my SyntorX certain DTMF tones from 6m were not decoded. All tones decoded properly from my Yaesu VX7, so it looks as if I may need to tweak the audio equalization at some point (most likely the culprit is the 'new' PL filter in the new RC210 chassis-- this filter is derived from an RCA700 radio, whereas the older chassis used a filter from a Motorola Motrac).
I also verified the reception sensitivity of the 440.05 link setup and found that the receiver had adequate sensitivity but that there was excessive loss (about 10db) in the duplexer (the 440.05 receiver is fed from a Cellwave Stationmaster at 100' and the RF is split with the control receiver and the 3rd 449.725 receiver via the duplexer.) I will replace this 'mobile' duplexer with a different unit later this year, hopefully providing a greater fade margin for the link from the W8TVC/r system.
Sadly, I neglected to verify that the transmitters and receivers were on frequency--- oops. while it's simple to verify the transmitters (I can do that from home), the receiver adjustments require a visit to the site. These adjustments will be tended to soon, on a 'seasonally cool' day. Today would have been a perfect day, but alas-- I didn't give frequency drift a second thought. Harumph. For the most part, the radios appear to be functioning properly, but there is a question as to whether the link from Empire to W8TVC/r is properly netted on frequency--- it sounds about 5khz off at times. It's been about two years since the frequencies were netted.
More news as it happens--- or within six days.. ahem....