borderblaster said:
I often drive within a quarter mile of both WBBM 780 and WGN 720 on Interstate 290.
With one of my old cars with late-60's technology of tuned RF input and tuned RF output and 262.6 khz IF, the 50kw ers
only widen out to maybe +/- an extra 10 khz of "dial space", for example 720 also wiping out 740 where in the not-too-far away
area 740 Toronto is a perfectly listenable signal.
2 other old cars have the same tech, but 455 khz IF, and both WBBM and WGN "appear" to widen out to +/- 15 khz.
This effect is notable only within a mile of the towers.
Now, in rental cars, it's a very different story, modern varactor tuned input, PLL, and op-amp filter-shaped IF "response"...
Within a mile of either 50 kw er can be heard up to 200 khz away from the towers if there is no signal otherwise on channel.
Usually in amazing hi-fidelity since it's "walking through" the IF. Then on channel they're usually overloaded.
Within one or two channels to the side the "active IF" keeps the big signal out, but after 30-40 khz it walks through if it's really strong.
When traveling I would always take advantage of this effect on Delco radios to listen to high quality AM in the presence of a
very strong signal.
Getting back to the desensing isssue, the newer type radios totally lose reception of WLS 890, 40 miles away, again, for maybe a mile.
My old radios do not receive any interference and no desensing at all on 890 in the same situation.
It will depend on the radio.
FM wipeout? That certainly does happen. No argument there.
