- Brother Kenneth Locke
On Oct 25, 2012 11:30 PM, "Mark Bohnett" <email@example.com> wrote:
> Dear Sirs:
> Sorry for stealing so much bandwidth tonight. But I am "beating myself
> up" and wonder if someone might be able to shine some light on a problem I
> have with a translator.
> If you just want a short question jump down the "THEREFORE" below:
> When I came to the present job position about one year ago, my first trip
> to one of our translator sites resulted in the discovery that the main
> power amplifier had been damaged and the translator was actually ONLY ON
> because the 20w exciter was still operational. The decision was made to
> abandon site and move it about 30 miles further north. In the process I
> pulled down the antenna, the cabling in-between the bays and the
> I sent the power amp in for rebuild/repair and began the process of
> building the new site with the hope of using the original equipment as much
> as possible. We had the antenna re-mounted using the same cable in-between
> the bays, built the radio shack, placed NEW transmission line (transmit and
> receiver) on the tower.
> About six weeks ago, I took the transmitter in and placed it on the air.
> The transmitter was a BE500 (BE 20watt exciter and Power amp). When I
> placed it on the air for the first time, I could only get 275watts (max)
> with 2 watts reflected. I contacted BE and questioned them on the output
> no reaching the 500watt output wit respect to the new repaired amplifier.
> They had me check MANY things and I made a trip to the site about every
> other day.
> Each time I visited there the TPO was different. Finally, I parked in
> front the of unit and just watched and and discovered that the power was
> constantly jumping for 50 to 150 to 75 to 250, etc. Note: The final
> output, is driven by a variable power supply and it appeared that it was on
> its last leg. BE confirmed my observations, but stated that the unit was
> too old (only 17+ years) and they no longer made THAT supply ... but for
> about $4,000, I could place a new power supply (and associated wiring) into
> the old box.
> By the end of the day, the BE unit went to zero ... red light came on and
> it was pronounced DEAD. I placed our standby unit on line. Again about 320
> watts with 2 watts reflective. We order a new Nautel SV300 transmitter.
> About two DAYS later the "spare" transmitter fails (a short in the power
> supply)!!!. I place the original exciter on the air for some signal and it
> displayed a HIGH VSWR at first. I back down the power to keep it safe and
> the unit continued to work. About two days later the VSWR was normal. I
> raise the power and everything appears to be fine. This makes me nervous!
> (dry conditions)
> Then came this last Tuesday!! I reluctantly placed our NEW SV300 into
> service (did I say new!). First day, 200watts 1.5 reflective, working like
> a charm, sounds great, everything to spec sheet. Second day, 300 watts 2.5
> watts reflective, everything is great. Fourth day, DOA!!!!!!!!!
> The Nautel SV300 is a smart transmitter and keep a log of EVERYTHING it
> does. The problem (High VSWR) began around 12:30am of the third day and
> progressed (or digressed) for about 20 hours, when it finally shut down. I
> haven't determined if the extent of damage is high! I have to return
> tomorrow with a load and watt meter.
> According to the SV300 the VSWR increased SLOWLY as the day progressed.
> We had a very light misty rain during the day so I believe that it has to
> do with moisture and the lines. Supposedly the connectors were water tight
> (and no I didn't personally inspect them). [Note: the two other units
> failed during drought conditions at 60 - 70 degree days.]
> Is it possible for an antenna bay to de-tune during a rain storm causing a
> failure, only to return back to normal, when the bay dries up?
> The original "cabling in between" (which I wanted to replace but we
> decided not to) is an RG-8. Is it possible for the outer casing could
> break down over time and allow moisture to slowly seep in and short the
> output? [I checked the cable and the outer case was very dirty and dingy,
> but I saw no breaks, chips or open sections and it was still flexible.]
> With all my mental gymnastics I am wondering if it is possible that the
> original failure (that I found a year ago with the dead amp) might have
> been caused by either the original antenna cabling or one of the bays (or
> both), and I just move the problem from the original site to the new? We
> assumed that age played a part in the RF amp failing.
> Anyway ... Nautel believes that their transmitter might have protected
> itself, but this installation has been one mystery after another not to
> mention a great expenditure of the Lord's money!
> As always ... with regard to the two questions above ... any assistance
> would be appreciated. Prayer wouldn't hurt either!
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