Newsgroups: rec.radio.amateur.misc
From: bryan@edgar.mn.org (Bryan Halvorson)
Subject: Re: W2A receiver modification
Message-ID: <1993May02.043741.25872@edgar.mn.org>
Reply-To: bryan@edgar.mn.org
Organization: Electronics 101. Apple Valley MN
References:  <1993May1.155436.1@vaxc.stevens-tech.edu>
Date: Sun, 02 May 1993 04:37:41 GMT
Lines: 54

In article <1993May1.155436.1@vaxc.stevens-tech.edu> u95_dgold@vaxc.stevens-tech.edu writes:
> I've heard of a mod to increase the UHF out of band receive sensitivity of the
> W2A.  Could anyone please send me or post more information about this.

I've got a diagram that shows how to do it but it's not real good at
labeling pin numbers so I'll try to describe it.

One word of warning. The parts involved here are surface mount and are
very tiny. It's very easy to screw something up and loose UHF receive.

You need to open up the the UHF unit inside the radio and look at the
component side of the board.

Q7 is a 5 pin surface mount IC that is near the edge of the board, about
a half an inch from the URF unit. There are 2 pins on the side nearest
the URF unit. You must lift the one nearest the edge of the board. Most
of the people that I know who've tried this have broken off the IC leg
or lifted the pad from the circuit board.

I don't see Q7 in the schematic, I think it's D7 in there.

Q3 is a surface mount transistor thats near the center of the board
about three quarters of an inch from the URF unit.

Once you've lifted the pin on Q7 you attach the cathode end of a 1N34
diode to it. The anode end of the diode goes to the pin on Q3 that only
has one pin on that side.

It sounds easy but Q7 is in a very tight corner. Here's an attempt at
diagramming the locations. The "<-" mark where the connections should
be.

-----------------------------------------------------------




                                              Q3
                                               _
                                  ___         |_|<-
                                 |L1 |
-----------                      |___|     ----------------
          |                                |
   VCO    |                        Q7      |
   UNIT   |                         _      |  URF unit
          |                        | |     |
          |                        | |     |
-----------                        |_|<-   ----------------
-----------------------------------------------------------


-- 
Bryan Halvorson                bryan@edgar.mn.org
N0BUU                          bryan@n0buu.tcman.ampr.org