Re: Gary's PL-360 antenna arrives! - FARMERIK


sdwillingham
 

Hi Stephen,

According to Zip Signal, KMRB's field strength is a whopping 3,149.9
millivolts/meter - that's over THREE VOLTS!!!! Wikipedia says a
station's blanketing interference contour is one volt/meter. Am I
expecting too much to be able to hear 0.15mV/m stations 10 kHz away? (I
was also unsuccessful trying to log any TP or TA stations on 1431 kHz.)
This would require a radio with dynamic range exceeding 86 dB
(20*log(3150/0.15)), which is higher than all commonly available
consumer gear. Even then, the adacent-channel rejection is always
de-rated relative to the radio's ultimate dynamic range.

A good experiment for you would be to try to log all the stations you
are interested in using your car radio. Higher-end car radios have
performance exceeding almost all consumer-grade radios and are
scrutinized for behavior in high-power situations. If you could
experiment with a radio from a luxery car, that could be illuminating.

Of course, high-perf car radios use heavy-duty DSP chips consuming
several watts of power and have room for sophisticated front-end filters
and attenuators. No portable radio running on AA batteries can meet the
same performance goals.

So.... is my situation utterly hopeless for being able to use an
ultralight-priced-and-sized (including the antenna if not contained
within the cabinet) radio for daytime barefoot listening of fringe (on
radio-locator) stations 10kHz away from powerful or IBOC locals,
especially when visiting my grandparents? :(
This, I can say, is generally impossible for any radio with an
omni-directional antenna. IBOC stations broadcast digital information
up to 15 kHz away from their carrier at powers of about 25 dB less than
the carrier. So your adjacent fringe stations are obliterated in the
airwaves before your poor radio even "sees" them. Only a directional
antenna with nulling can help in that situation.

-Scott-

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