[R-390] Re: Images

[SHELLY199 at aol.com]

Hi Guys,

I’ve got two R390a’s  sitting next to one another.  Both are fed thru a HF 
Multicoupler from a  Pro-67 antenna.  The pro-67 is 2 elements on 40 mtrs with 
the normal stuff  for a multielement beam above that.  The audio from each 
rcvr is fed into a  16 channel Roland mixer.   The Multicoupler is 50 ohms in and 
50 ohms  out and has a 10 db switchable pre-amp.  The balanced antenna is 
being used  with the one side grounded.  Both rcvrs were aligned with a 50 to 120 
ohm  10db pad between the generator (HP 8656B) and rcvr.  Both rcvrs, one a 
67  EAC and one a 63 Imperial, were both totally restored within the last  
year.  That means completely torn down and any suspect component from any  of the 
units replaced.    All bands of both rcvrs have a 10db  S+N/N sensitivity of 
>.5uv

The qth here is the north end Staten  Island, 3 or 4 miles from lower 
Manhattan.  We have a great deal of very  strong signal am broadcast stations in this 
area.  I’ve been following the  thread since day one.  I’ve always noticed 
that on all my r390a rcvrs there  is some image activity in the 2 and 3 mhz 
bands.  Some time back, I’ve gone  to the trouble of sitting 3 ea. r390a’s side 
by side and observing exactly the  same thing on each rcvr.

As an example from today, 1560 KHz and  1130 KHz are both coming in on 2690 
KHz.  Both 1560 and 1130 are about 95  db on the carrier meter.  Listening on 
2690 and detuning the antenna  trimmer to 4 increases the audibility and 
decreases the rcvr noise. The birdie  sig strength on the carrier meter is about 35 
db.  Turning on the preamp  increases the signal level of the birdie by 20 db 
while increasing an actual  signal by only 10 db.  Another example, 2790 is 
the birdie and 1130 with  1660 are combining.   Also see that 1280 is coming in 
on 2560.   1280 also comes in on 2410 with some other signal and read 52 db on 
the carrier  meter.  There are a total at least 14 birdies between 2 and 3 
MHz and all  from broadcast band signals.  The antenna was also connected 
directly to  the antenna without the multicoupler and it made no difference.

I  have listened with both rcvrs on the 3 MHz band and don’t hear anything 
that  shouldn’t be there.

I also listened for birdies on the IC781 and  found none from 2 to 3.5 Mhz.

What’s this mean?  I have a  headache from listening to the radio right now.

73’s 
Rich  wd2q




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