2/11/13
On the evening of Friday, February 8th, as the recent New
England blizzard was reaching the height of its furry, I was taking
advantage of a rare night off from my job to add a large amount of
music to the Troubadour 1700 format. In the midst of my work, I
detected the smell of either burning plastic or a burning electronic
component. I first assumed that I had placed a cardboard box (with a
line of cellophane tape across its top) a bit too close to the wood
stove. A quick inspection of the box revealed that although it was a
bit warm, no tape was melting. I then turned on one of my radios
and discovered that all of my FM signals were off the air with the
exception of 102.9, The Voice of the Resistance. Unlike the three
other FM's, the 102.9 signal utilizes a vertical dipole that is
sheltered from the weather under a wooden roof. As I moved
toward the 87.5 FM automation computer and transmitter, the smell
was particularly strong. The computer was functioning normally, but
when I put my fingers on the transmitter, the entire unit was hot to
the touch! I immediately shut it down, and when I took it apart, I
found three surface mount chip resistors that were cooked. The smell
was powerful enough to give me a low level headache for 24 hours. When
I inspected the transmitters for 95.1 and 97.9, they were only slightly
warmer than usual with no visually obvious destroyed components. Yet it
was evident that their final output stages were largely destroyed and
they were providing hardly any measurable signal output.
I was able to get 87.5 back on the air rather quickly with a lower
powered back up transmitter I had right in the house. When I tested the
connection to the antenna with an SWR meter, it indicted a normal
connection, or at least a normal connection had been restored by that
point, even though the blizzard was still raging. Later, I was able to
connect another lower powered backup transmitter for 95.1. Again, the
SWR meter indicated a totally normal connection to the antenna. Finally
on Sunday afternoon, with access to my shed cleared, I was able to
fetch an audio connector I needed to restore 97.9 with another small
backup transmitter. Again, everything was normal with no signs of any
distrupted connection to its antenna.
At this time, it remains a mystery as to what exactly caused the
destruction of the output stages of these three transmitters. All three
use the same style of thin, low profile quarter wave ground plan
antenna. Due to the thin elements, it is possible that in the
hard, wind whipped snow, ground elements and the vertical whip
elements touched each other at various times, or bad
connections in all three occurred for long enough periods to destroy
the output stages of the transmitters. Another explaination would be
that electrical energy from the storm hit all areas of the property at
the same instant and struck all exposed, elevated, metalic objects. But
there was no trace of thunder or lightning during the entire blizzard,
and the two AM transmitters were unaffected, which is unusual, because
1700 AM has a history of a weak connection in its antenna system.
It is usually the first to be affected in wet windy weather. The
AM antennas also reach a bit higher in elevation than the FM's. So it
is more likely that the behavior of this particular FM ground
plane antenna in wet, windy, cold conditions had something to
do with it. But the exact cause I still can't determine.
The back up transmitters have either somewhat or significantly reduced
signal coverage, depending on the frequency. The backup operating at
97.9 has only slightly more power than the typical
Satellite-Radio-to-FM Converter and reliable coverage is now limited to
3/4 of a mile. I would like to buy new transmitters and sell the old
ones for parts because it would save the time required for diagnosis
and repair, which would be significant. I also have little experience
with surface mount components and finding the correct replacements for
them. To make matters worse, no schematic of these transmitters appears
in either the user's manual or on the internet. I simply do not have
the time to diagnosis and repair them, even though they represent a
combined investment of $450.
If you are able, please consider a contribution to our replacement FM transmitters fund on our advertise and contribute page. Thanks for your consideration.
