[BC] Problems that make you want to scream!

[Brian Urban]

Well, it might be the RX.  Had a similar situation with a Marti STL in
another (recent) life.  Station would go off, no audio.  STL transmitter
good, power & audio, no RX signal. Changed the RX and AFIK it's still on.
Of course, this was all happening while the station was on LMA pending sale
to the LMA holder.

How did you find enough terrain in FL to not have line of sight over 3
miles?  I thought St Augustine was flat like most of the costal area.  But
then it's been many years since I was there.


On 10/12/05 12:51 PM, "Alan Alsobrook" <radiotech at bellsouth.net> wrote:

> 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.

-- 
Brian Urban
KUT Radio
University of Texas at Austin
Office 515-471-1085
Cell 512-940-4757