[Premium-Rx] RF-590 VLF sensitivity improvement

[John Reed]

----- Original Message ----- 
From: <ToddRoberts2001 at aol.com>
To: <premium-rx at ml.skirrow.org>
Sent: Friday, February 24, 2006 2:39 PM
Subject: Re: [Premium-Rx] RF-590 VLF sensitivity improvement

I was able to get rid of that display noise completely by converting the
display switching power supply to an analog design using 60 Hz AC and DC.  I
had to add one small power supply in the power supply module to do this.

If someone is interested in making the 590 better on VLF, I can give you
some pointers on doing this.  Also MiniCircuits has a mixer that should work
better for VLF.  It is the RAY-6U, rated from .01 to 100 MHz.  The downside
to this is you lose about 5 dB in dynamic range with this mixer.

John Reed



> After some careful listening today I noticed the RF-590 does have some
> fluorescent display noise at about 15.6KHz with a rough audible broad 3rd 
> harmonic
> around 46-47KHz and this can drift in frequency a bit. The fundamental at
> 15.6KHz is audible even with the antenna disconnected, I would say about 
> an S-1
> signal level. Interesting that this fluorescent display noise frequency is 
> very
> close to the standard horiz. osc frequencies used in standard TV sets. 
> Using an
> outboard upconverter with a 4MHz LO the noise can be just about eliminated
> with the receiver tuned to 4015.6KHz and using shielded antenna 
> connections to
> an outside antenna. Display noise on VLF would still be a problem if using 
> a
> loop antenna or any antenna in close proximity to the receiver though. 73 
> Todd
> WD4NGG
>
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