[BC] Problems that make you want to scream!

[Alan Alsobrook]

Ok I'm looking for company for my misery, I really don't think anyone 
can offer me any solutions I haven't already thought of but you never know.

This started a couple weeks ago, One of my stations (100 miles away) all 
of a sudden went off the air. Some quick over the phone diagnostic 
procedures indicated that the STL (Marti STL-10) wasn't working. The 
transmitter was transmitting, but the receiver wasn't receiving.  I was 
on the road some 400 miles away on a different emergency job. I 
contacted a back up person and he was getting ready to go to the site 
when it just came back on it's own. So... I take a wait and see attitude.

Sure enough the next morning the station goes off the air again, but 
this time the Transmitter (Gates 5) is down. It won't respond to an on 
command from the remote control, but wait, if you give it an of command 
and then an on command it comes right back up at full power. (scratch 
head some more) this continues for several days, I go in and check 
everything thinking this might be related to some sort of VSWR trip and 
or something going flaky with the STL receive antenna I agitate the 
tower in every way I know, everything runs fine. After I give up and I'm 
driving out of the site, the carrier drops.

Of course I spin around and run back into the site to hear that 
wonderful sonalert sounding (airflow shutdown) in the back of the Gates. 
{Side note: I think the airflow sensor circuit on the Gates series 
transmitters was an after thought, since the only indication of it is 
the sonalert.} Instantly I'm kicking myself, I knew about the way that 
airflow sensor worked and I didn't think of it as the problem, but then 
again I had just cleaned the filter not long ago.. hummmm. Checking the 
filter I see that the wonderful Harris foam has gone sort of gooey and 
the filter has collapsed on itself partially occluding the intake. I 
pulled the filter out everything is fine.  Or is it?

Yesterday morning I get a call (yes one of those damn 0600 calls) the 
transmitter is on we have no audio. Here we go again, I get down their 
as fast as I can. I find the following The STL receiver has not receive 
signal, looking at the STL feed line with the SA I see other STL signals 
but not mine. A quick line sweep shows the line & Antenna looks the same 
as when the STL was working. Ok.. studio problem.. Off I dash when I get 
to the studio I set up the SA real fast and look for the STL.. NOTHING!! 
ok great I've found the problem. When I get inside the STL transmitter 
has no rf output. Since I brought another STL-10 with me I quickly pull 
them apart and swap crystals and tune up the backup transmitter. Slip in 
in the rack and turn it on, everything looks fine except still no audio..

Grrrr.. did I forget to hook the STL receiver back up? Dash back to the 
tower to  check, Nope it's hooked up and nothing.. Of course I didn't 
bring the SA with me, it's at the studio where I was setting up the STL 
transmitter.  Go back to the studio and sweep the STL line and antenna, 
they don't look great, but appear to be ok. Recheck the freq of the STL 
transmitter yep it's right. I went to the roof and did an visual check 
of the antenna and feed line even climbed the 40' rohn 25 tower on the 
roof shaking connections and agitating everything, no change.

Load up everything to go back to the tower site, do another parking lot 
check and yes the STL is there and seems to have good signal. Drive 
towards the transmitter site, just as I'm getting to the last turn thump 
thump thump audio.. It's now 115945, The Jock does a quick ID, and were 
into news followed by Rush.. At this point since it's on I don't want to 
mess with it. I head home for some sleep (did I mention I had just gone 
to bed when he call came in).

So this is where it sits, my thoughts are it's either the STL receiver 
or the studio transmission line/antenna. Unfortunately I don't think I 
saved the sweep of the studio line when it wasn't working to see if 
their are any differences when it is working. The path is about a 3 mile 
grazing path, and I could not see the tower site from the top of the 
studio tower. Yet when it's working I have full signal strength at the 
tower site. I didn't see anything that could cause a path problem I 
might have to drive the path to make sure.

-- 
Alan Alsobrook CSRE AMD CBNT
St. Augustine Fl. 32086 904-829-8885
aalso at Bellsouth.net