Re: [amsat-bb] Starting out on the cheap

["Jim Shorney" <jshorney@xxxxxxxxxxxxx>]

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On Fri, 25 Feb 2000 01:50:58 -0600, David Mullenix wrote:

>And get the uPD858 spec sheet.  It has a pin that converts channel
>spacing from 10 kHZ to 5.  Tweak the clarifier a bit and you have
>pretty much continuous coverage.  You'll have to change a crystal or
>two to bring all the channels up into 10 meters, though.  


The approach I used to use was to place a 1.5 uH choke in series with
the clarifier VXO varactor - easily gives +/- 5 KHz range.  Hang a set
of BCD thumbwheel switches on the PLL program pins, and you have direct
frequency entry of a sort, with no skips.  Otherwise, the skipped
'channels' can be picked up with a SPDT center-off toggle wired to the
least significant bit.  There was also a device made for a while called
a "Digi-scan" that would control the PLL program pins for you and give
you the actual frequency readout.  The same thing could be accomplished
with a couple of EPROMs cleverly programmed.  Or, use one of the
digital displays that someone else mentioned.  I never tried the 5 KHz
mod myself, never needed it.


>If you don't convert to 5 kHZ, all you have to do is put in some
>switches and retune a few coils because the chip logic has so many
>channels in it, that it can cover 10 meters with the CB crystals.


A couple of minor connection changes in the transmit strip allow
coverage of roughly 3 MHz in the 26 to 30 MHz range before performance
starts to drop off and the PLL drops out.  Add a hamfest bargain
2-meter allmode rig and some homebrew antennae, and you've got a good
mode A station for easily under $500US.

>(Not that I ever tampered with a CB of course.  Oh no.)


CB?  What's that?

- -- 
Jim Shorney                   -->.<--Put complaints in this box
jshorney@inebraska.com
nu0c@amsat.org
NU0C
Lincoln, NE, USA
EN10KA
http://incolor.inetnebr.com/jshorney/
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