Re: WCRB signal

[umar@nerodia.wcrb.com]

On Sun, 25 Jun 2000, A. Joseph Ross wrote:

> Because I've heard the interfering signal identify itself.  It's WROR.

The problem is that receivers within a mile or so of the Pru get
overloaded by strong signals from the Pru stations. When more than one
signal overloads a receiver, spurious sum and difference products are
generated inside the receiver. These products can involve not only the
fundamental frequencies of the stations in question but also harmonics. 

For example, some listeners to WFNX in the Newton Highlands - Needham
Heights area used to hear WODS on 101.7; they did so because 

	(2 x 102.5) - 103.3 = 101.7

There is nothing WCRB as a broadcaster can do to improve reception
downtown; however, listeners have several options:

1) If you're using a radio with a telescoping whip antenna, try retracting
it. If you're listening from a concrete and steel building, try moving the
radio into the interior of the building, away from windows. Either of
these methods will reduce the amount of RF reaching the radio and perhaps
eliminate the overloading.

2) Get a new radio. Find a store near the Pru and look for a radio that
will receive WCRB in the store.

3) Get a bandpass filter tuned to 102.5 and install it between the antenna
and the receiver. These are not cheap, but you can order them from
Microwave Filter Company. Dr. Ferguson's W243AI translator in Newport, RI
uses one to receive WCRI from Block Island.

4) To eliminate the intermod product on top of WCRB it may only be
necessary to notch out one or two of the Pru stations, and you can make a
notch filter out of a piece of coax by trimming it to precisely one
quarter wavelength at the frequency of the offending station. Connect one
end of the coax across the antenna terminals; leave the other end open. An
open circuit 1/4 wavelength away translates to a short, and if you are
careful you can achieve 40 dB of suppression this way. I have found that
two or more of these simple filters can be connected in parallel to
suppress more than one station.

5) If all else fails, listen to WCRB via the Internet.


Rob Landry
umar@nerodia.wcrb.com