[R-390] To un-mod or not

[wwarren1@nc.rr.com]

It's even easier than that, simply disconnect the plug bringing the 455 kHz IF signal from the RF deck to the IF deck and use that signal to go the auxilliary receiver.  Yes, one misses the mechanical filters of the 390A, but one also misses the intermod of the first IF stage, which according to some of the documentation, is one of the main sources of troubles.  However, with that setup, you'd be getting the image rejection and selectivity of the 390A front end.

Remember that the IF deck is set up for 150 microvolts input at 455kHz for -7 volts on the diode test point.  Thus, the RF deck as the front end to the aux receiver may still be too hot.  That is, approximately a 2-4 microvolt input to the 390A antenna will deliver 150 microvolts to the RF deck, and that's about a -83dBmw signal.  -83dBmw shouldn't overdrive the aux receiver, but with presumably no AGC on the 390A RF deck, the signal will go up very considerably (should be linearly) with increased antenna signal strength.

Hope this all makes sense.

Tom, W4PG


----- Original Message -----
From: Bob Camp <ham@cq.nu>
Date: Friday, April 23, 2004 10:13 am
Subject: Re: [R-390] To un-mod or not

> Hi,
> 
> One option might be to move the IF pick off point closer to the 
> start  
> of the IF chain. Obviously this involves modification to the radio 
> ...   
> One good option might be to use a scrap IF strip that's missing a  
> couple of the filters. That would leave your "real" IF strip intact.
> 
> 	Take Care!
> 
>        	Bob Camp	
>        	KB8TQ
> 
> 
> On Apr 22, 2004, at 11:42 PM, D. ball wrote:
> 
> > The buffer amp in the 390a does a good job, but regardless i 
> have to  
> > use 60db of attenuation between the IF out and the kenwood 930. 
> The  
> > signal is too hot otherwise, here you get a perfect 50 ohm load 
> for  
> > the 390's IF out. The 60db is a must, you will overdrive your HF 
> rig  
> > without it.
> >
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