[Premium-Rx] RF-590 VLF sensitivity improvement

[Carcia, Francis A HS]

Here is a little trick you can do with double balanced mixers. I've run the
antenna into the IF port through a Balun. Now take the higher IF frequency
out of the RF port. I did this in my homebrew receiver. The IF port usually
goes down to DC so the only limit will be the value of the coupling cap
value. Take a nice clean oscillator and use it as a source. Square wave
drive is actually better. 5 volt dip oscillators will work fine if you find
a clean one. RF port will go directly into the radio. The input/IF port you
might want to use a low pass filter. The 590 will still tune, the input
frequency will be oscillator plus the frequency you want to monitor. A
diplexer on the output between the mixer and radio would reduce the image
and maybe a low pass in addition.   

-----Original Message-----
From: premium-rx-bounces at ml.skirrow.org
[mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of
ToddRoberts2001 at aol.com
Sent: Wednesday, February 22, 2006 3:59 PM
To: premium-rx at ml.skirrow.org
Subject: Re: [Premium-Rx] RF-590 VLF sensitivity improvement

In a message dated 2/22/2006 3:52:34 PM Eastern Standard Time, 
n4vic at hotmail.com writes:
John,
Any ideas on improving the sensitivity of the RF-590 for VLF below 30 khz?
I 
have one that I love using but am new to VLF for monitoring.  I've used VLF 
for aeronautical navigation but thats all.  I'm not highly trained
technically, 
so something outboard of the receiver would be better for me even if I had
to 
build it.  Thanks.
N4VIC
Victor

Victor, I think using a high-quality up-converter in front of the RF-590 
would be the best way to go for full sensitivty reception of VLF below
30KHz.  The 
RF-590 already has outstanding sensitivity at MF-HF. Something that would 
convert 0-500KHz to 4.0-4.5 MHz is nice to have. AMRAD has a good converter 
design that was featured in QST. 73 Todd WD4NGG.

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