[VHFcontesting] DEM 432-38 Receive Problems

[Jimk8mr@aol.com]

For most, if not all, of the many years I've had my DEM 432-28 transverter  
I've been bothered by a swath of crud covering much of the useful 432  band.  
Being about 2 miles from a tower loaded with pagers, two FM  broadcast 
stations, and who knows what else, I kind of figured I just had to  live with it.
 
Recently, however, I've taken another look and determined that the  offending 
stuff was the mixing product of a TV channel 23 visual carrier  (525.26MHz) 
and an FM station at 93.1 MHz creating the FM signal at  432.160.  The amazing 
thing was that the TV station is 30 miles away  and the FM station 10 miles 
away.
 
Yesterday I was able to check things with a FT-847, which was clean, and  
also to add a DCI 435-10 bandpass filter in front of the DEM transverter, which  
also cleaned up things.
 
This seems like very poor front end performance in the DEM  transverter.  
Have other people experienced this problem?  Any  suggestion as to what might be 
going wrong with mine if this is not a normal  condition? The transverter 
otherwise seems to be working... the several birdies  I could hear on both rigs 
seemed even stronger on the DEM than on the FT-847  (and went away on both with 
the antenna disconnected).
 
 
73  -  Jim   K8MR