On Thu, 23 Feb 2006 04:36:29 GMT, HFguy wrote:

Lisa Simpson wrote:

I can hear more than one station on some freq's . . .

"John S." wrote in message
oups.com...

Lisa Simpson wrote:

Fishing for recommendations for antenna preselectors that would work

well

with a Radio Shack DX-394 & Eavesdropper C antenna . . .

Lisa,

As you probably know, it's not uncommon for more than one shortwave
station (country) to be using the same frequency at the same time.
However if one or more of the stations you're hearing is not actually
transmitting on that particular frequency, you have either an *image
rejection* problem or *intermodulation* (Google those two topics). The
first is caused by insufficient selectivity in the receivers' front-end,
while the latter results from not enough dynamic range. A passive
preselector should help to reduce both of these problems.


Image is caused by multiple IFs being present. It is an inherent
design quirk in single conversion receivers. Unless a receiver is a
TRF style, it is not expected to have any front-end selectivity beyond
broad bandpass filters.