Additional IBOC Hash Experienced
Thu May 10 15:02:16 EDT 2007
"WRKO-1360" also appears on my car radio at my home a bit less than 3
miles from their transmitter.
It's definitely the car radio's fault. A good communications receiver
with a passive tuned loop shows clean WLYN.
That said, it is also entirely possible for large metallic objects in
the near field of transmitters to "stray-rectify" if there is corrosion.
This can produce harmonics with more coverage than what is actually
coming out of the transmitter itself at 2 or 3 times its frequency.
Besides simple harmonics, corroded metal connections can produce
intermodulation products when there are two or more strong signals in
the area. For quite a while something at the G.E. Lynn Works was
blending 950 and 1030 to produce an intermod signal on 870 (= 950 -
(1030-950)). Because the site was right on the coast, the signal
really carried, especially towards the southeast to the point that I
was able to hear it in West Yarmouth on sensitive equipment (R-390A)
back in the '70s before Maine came on 870. The Fore River Shipyard in
Quincy, due to its waterfront location, large cranes, high-tension
power lines / poles, and maze of pipes was another hot-spot for stray
rectification, especially back when Quincy had 1510 at 50 kW besides
1260 and 1300 (not to mention 1030 close by in Hull).
Mark Connelly, WA1ION - Billerica, MA
At my QTH, WRKO has a killer signal--more than 200 mV/m according to
V-Soft. On my car radio, and ONLY on my car radio, WRKO's second
harmonic wipes out WLYN (but not WFEA). The fact that the phenomenon
occurs only on one radio and a radio with a front-end tuned-RF
stage--but not on at least one other radio with such a front-end stage
(GE Super Radio III), demonstrates convincingly that the problem is in
my car radio and not at WRKO. There is sufficient nonlinearity in the
car radio's front end to generate a bit of second harmonic from WRKO's
strong signal. If the car radio tuned up in the ham bands, I doubtless
would have the problem at 2300 (WTTT), 2940 (WAZN) and 3020 (WWZN).
Although a problem at WNNW may exist, it is more likely that, umm, the
problem is in your set.
Dan Strassberg (firstname.lastname@example.org)
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