DID TEURS

Fred Comps KBKUl
28610 FIOlence
Cardffi Cify M/48135
Help for the HW-2036
- hum mods for Heath-equipped hams
Almost im med iate ly after
I put my Heathkitl!l
HW·2036 on the air,
two problems cropped up.
First. th ere was a terri ble
hum on the transmit audio
whenever I tried to work
through a repeater, and seco
nd, the phone plug coax
connecto r kept coming
loo se. Da unted bu t not de-­
fe ated, J put the thing back
on the bench and proceeded
to dig into the problems
with great exubera nc e.
If you live in an area tha t
doesn 't require a Private
Ltne"
(PL) for repeater access
you may never have
noticed the hu m. But if you
use Pl you undoubtedly
have been t old that you
have a noticeable - if not
o b jec t iona ble- h u m o n
your signal. It's not humm
ing because it doesn't
know the words, it's humm
ing because the injection
level is simply too high. Unfortunately,
Heath did not
see f it to include a level adjustm
ent. Enter m odification
#1 .
The square-wave outpu t
from the tone generator is
fed thro ugh severa l stages
of RC f iltering to R134, a
470k resistor. (See Fig. 1.)
Although R134 is part of the
waveshaping network , its
actual va lue does not appear
to be critical. Replace
it with a pot and you'll have
a tone level ad justment.
Photo A. This shows the completed modification. The PL adjustment pot is mounted
horizontally behind the deviation pot. Note the coax pigtail at the antenna iack.
In my f irst attem pt at this
mod, I used a 7S0k potand
promptly ran out of adjustment
range! A second
trip to the junk box produced
a 2 .S~meg
linear PC
board pot that worked very
well. Actually, any value
from 1 t o 5 meg will work.
The low er th e val ue, the
easier it is to ad just-but
the more you risk ru nn ing
out of adjustment room .
To prepare the pot, first
96 73 Magazine. April, 1981