[BC] Problems that make you want to scream!

[Alan Alsobrook]

cldube wrote:
>> 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 no receive 
>> signal, looking at the STL feed line with the SA I see other STL signals
> 
> Since the SA didn't see YOUR carrier- we know you're not transmitting at 
> this point.

Or not transmitting on the Correct frequency, I looked for that too :)

I didn't mention that when the jock called at 0600 the STL transmitter 
was indicating RF output. When I arrived it was not.

>> studio 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.
> 
> Can you check your reflected power during failure times? This will 
> confirm whether or not the tx antenna system is involved.

Yes, reflected and forward power remain the same working vs/not working.
But does it confirm the TX line and antenna are not at fault?  Obviously 
if their was a shift you would know to suspect the line & antenna. The 
question is can you dismiss them because their wasn't a change. I do 
want to resweep the txline and antenna while it seems to be working and 
see if I can see any change in characteristics.  At 950 MHz it's 
possible that a carbon sooty connector could be providing a load, 
rendering the VSWR readings meaningless.

>>  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.
> Did you see any receive signal indication at this point?

Nope not a drip.

> Since we now know that you are transmitting (do you have a scanner or 
> something to confirm you are modulating your STL 100% of the time?), at least that you have a 
> carrier, confirm that at your receive antenna
> and then focus on the signal path from that antenna backwards. 
> Unfortunately it'll probably have to fail again before you can find the
> trouble. You have changed one potential failure point- the transmitter. 
> If your cable and antenna seem OK and can't be forced into failing at 
> the studio end, you can now focus your energies on the receiving end. 
> Obviously this is a case of multiple faults happening, each one 
> resulting in the same thing- an unreliable STL.

That's for sure.. I confirmed a STL TX failure, You would normally think 
that was enough. I'll go back this evening and replace the STL receiver. 
I would have really been happy if I had had the SA with me to see if I 
was receiving the STL at the tower site when it was failing. That of 
course would have confirmed an intermittent receiver. Since I wasn't 
able to do that it still leaves doubts as to 100% for sure where the 
problem is.

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