[R-390] R-390a Image problem?

[Tim Shoppa]

Gord wrote:
> Someone else wrote:
>> I also have a 50KW broadcast station in my area. It causes problems on 
>> both of my R-390A's, 51S-1 and R-392. The cross over distortion is 
>> mostly heard in the broadcast bands. I built a highpass filter with 
>> about a 3MHZ roll off. Put it in series with the antenna lead, going 
>> into the multicoupler and it works great. Ended the problem, can still 
>> receive broadcast bands with the filter inline because they are so 
>> strong. 

>We had a problem like that on field day one year.  (This wasn't on an 
> R-390)  The cure was a can.  We build a helical resonator to suck out 
> the AM station.
> It was about 160 turns of #12 magnet wire on a 12" sonotube in a 45 gal 
> drum.  I like titanic engineering.  The next year I used the R-390 
> without the can.  No
> problems at all.

I am less than a mile from a local 5kw broadcaster, and if I just stick
a scope probe on my 80M dipole I see about 12V P-P on modulation
peaks at 630 kc :-).

That said, my R-390A's  do fine in this
environment. The third harmonic of 630kc falls smack dab in
the 160M band, and since IBOC the region +/- 25kc of 1890
is pretty much unusable. I'm 99% sure that the harmonics are
coming from outside the radio because 630kc filters do nothing
to the 1890kc harmonic. I don't know whether it's the transmitter
or rain gutters, though!

Even the "good" consumer shortwave radios pick up images
of 630kc all up and down the bands - but these evidently
have no front end preselection.

My Ten-Tec RX-320 does pretty well without a filter
in front of it, but obviously does have images due to the
630kc station unless I have the filter in front.

Tim.