[ARC5] 75 Mtr to LF Converter - Ideas?

[Neil Barnett]

David

The input network consisting of the 0.39 uH inductance and
the two 0.008 uF capacitors is described as a high pass filter,
but it is in fact a LOW-PASS filter.
Also, the component values appear to be inappropriate for
the quoted 3.6 MHz cutoff.
If you don't want to bother reconfiguring the network and
re-calculating the component values, here's a quick solution:

Remove both 0.008 uF caps, the 0.39 uH inductor, and the
12 pF cap.
If the 3.3 uH and 33 uH inductors are a single coil tapped at
about 10% (as I suspect they are), then connect the antenna
direct to the tap.
If they are separate coils, then remove the 3.3 uH inductor and
tap the remaining 33 uH inductor at about 10% after grounding
its bottom.
A quick calculation shows that about 35 uH in conjunction with
about 75 pF of the variable cap will resonate at 3.8 MHz.

73 de Neil, ZL1ANM
in Auckland.



----- Original Message ----- 
From: "David Stinson" <arc5 at ix.netcom.com>
To: <ARC5 at mailman.qth.net>; "Boatanchors" <boatanchors at theporch.com>
Sent: Tuesday, January 11, 2005 7:06 PM
Subject: [ARC5] 75 Mtr to LF Converter - Ideas?


> I've uploaded a diagram, formated for printing, of a simple
> converter I built to receive 75 meters on a Beacon Band
> (200-400 KC) receiver.
> It is at:
> 
> http://home.mindspring.com/~arc5@ix.netcom.com/convertr.jpg
> 
> It works, but images are a problem with that low IF, of course.
> I didn't hope to eliminate them with this simple design,
> only minimize them.  But they are more annoying than I expected.
> The net is full of people smarter than me.
> May I ask for your suggestions?
> Thanks.



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