Tom,
This transmitter is most likely a solid state unit. (some very high
power tube transmitters are still made but those are overseas.) Today's
solid state high power AM units are broad as a barn broad band designs
and use agile synthesizers to allow them to be off the shelf from 530
to 1700 Mhz. Each of the PA's is connected to a combiner. If good
output BP filtration is not used and the antenna match is very close to
the coax impedance, all kinds of mixing products can occur. A loose or
arcing connection of modulation peaks, as these are all PDM type units
for the most part, will cause also cause these types of problems across
the spectrum. The sputtering on 1853 is most likely related to a very
simple fix of isolating the arcing or mixing, which ever the case. It
most likely could have its origin in the synthesizer. WTJS is on 1390
Khz. If you multiply the frequency by 2 (2780 Khz) and then dived the
result by 3 you end up with 1853Khz. If this signal is not stable a
sputters and splatters across the lower portion of the 160 meter band,
there could be arcing in the antenna or combiners used to mix the rack
of solid state amps used in these new transmitters. WTJS claims in their
ad they are a clear channel station which could mean that they are
running 50KW. This also could be two 25KW units into a combine which
gives some redundancy but also can raise some other mixing issues if not
set up properly.
I recently installed a new solid state 5 KW FM (104.9) and found a very
strong undistorted repetition on 106.3 that could be heard across the
island. When I changed exciters the problem was still there. When I
changed the length of the cable between the exciter and IPA and added
some radio shack snap on ferrite beads the problem disappeared.
May this information can be passed on the CE (if they have one) at WTJS
through their web address http://www.wtjs.com or to them directly at
(731) 427-3316
73
Herb, KV4FZ
Tom Rauch wrote:
>By catching a clear callsign and city name, I've positively identified the
>strong BC station buzzy broken carrier on 1853 that is splattering and
>spitting from 1810 to 1880. (The broken-up carrier on 1853 is over S9 here.)
>
>It is WTJS in Jackson Tn.
>
>The engineer tells me they installed a new transmitter three weeks ago. They
>have been aware for several days now the transmitter has a problem, but have
>not even bothered to call the manufacturer that sold them the transmitter
>yet.
>
>Interesting change. I remember when I used to do BC Engineering work in the
>70's. We would either immediately correct a problem or pull a transmitter
>off the air if it had a problem like that. Now they don't even bother
>looking at it.
>
>73 Tom
>
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