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Re: RE: Another interesting preamp story



Hi Wayne, W9AE

If you plan to buid the K3PGP filter for 70 cm using PCB board 
than you are in trouble because for RF current circulation the inner 
copper of the PCB must be soldered all the way inside the square tube 
and this will be impossible to do internally around both ends when 
they are shut.

In addition using PCB the flange of both connectors and one terminal 
of each diode cannot be soldered  inside.

If you cannot find a 1 inch square (brass or copper) I suggest to cut
two copper sheet 1/16-inch thick  6" long and 2" wide and bend it at
90 degrees in a vise after that you can solder both angulars all the 
way long to form a 1" x 1" square tube 6" long and if you use copper
you don't want to silver plate the filter.

Have fun and 73" de

i8CVS Domenico 


----- Original Message ----- 
From: "Wayne Estes" <w9ae@charter.net>
To: <amsat-bb@amsat.org>
Sent: Thursday, March 30, 2006 8:06 PM
Subject: [amsat-bb] RE: Another interesting preamp story


> Jerry K5OE/M0MOE wrote:
> 
> Installing a diplexer on the 70 cm input is a cheap and effective 
> solution, but there is a penalty in system performance as you are 
> introducing a couple dB loss before the first active device (the preamp).
> 
> Wayne W9AE replies:
> 
> First I want to thank everybody for their great responses, especially 
> I8CVS and WA6FWF.
> 
> Second, I want to encourage everybody to look at the "432 MHz filter" 
> link that I8CVS mentioned.  http://www.k3pgp.org/432filter.htm
> This 432 MHz bandpass filter can be homebrewed and it only has 0.062 dB 
> attenuation in the passband.  It won't noticeably degrade your receive 
> noise figure.
> 
> Can anybody recommend a source for 1-inch square (brass or copper) 
> tubing?  McMaster-Carr is my usual source for stuff like this, but they 
> don't seem to have square tubing in this size.  Or should I just build 
> the tube using "blank" PCB material?
> 
> Wayne Estes W9AE
> Oakland, Oregon, USA, CN83ik
> ----
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