Thread: No QRM?
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Old October 24th 04, 06:36 PM
Dave Platt
 
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Now I'll get to the point - I've had many rigs over the
years and ALL have recieved the TV colorburst QRM
on 3.579 & harmonics. - All except this radio!


Is it me or does this rig have something differant in it's
design? 14.318 is absolutly quiet where with my FT-857D
it was unuseable +/- 1.5kc.


Maybe it's your new QTH...I've never experienced the problems you cite.


I suspect that it may have to do with shielding of the radio itself,
perhaps. A radio with poor chassis shielding might tend to pick up
near-field emissions directly from the TV, or colorburst leakage
coupled back through the AC power lines. A radio whose chassis has
good shielding, and which has good filtering on its power wiring and
circuitry, would be less prone to near-field pickup and would detect
only the colorburst harmonics which actually reach the antenna.

I just ran a quick check here at my home QTH, and noticed something
similar (and interesting). Last year, after I bought a used Ten-Tec
Scout, I hooked it up to my wire dipole and used the 20-meter
colorburst harmonic as a standard for trimming the frequency-display
reference oscillator. The colorburst harmonic was clearly audible.
However, today, when I looked for the harmonics with my Kenwood
TS-2000 (on the same antenna, with the same power supply) they were
rather difficult to hear, even with my color TV 15 feet away turned
on.

So, there may be both pickup-path differences between radios (direct
pickup vs. antenna-only pickup) and QTH differences (well-shielded TVs
versus leaky ones).

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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