Collins S-Line Knob Weights

[Glen Zook]

I recently came into posession of an additional 75S-1
receiver that I have finally put into operation as a
second receiver for working DX on 40 and 80 meter SSB.
 This replaced the 75S-3 receiver that I traded off a
couple of years ago for a really nice 75A4 (the 75S-3
was in just good condition but worked great - I just
couldn't pass up the deal for the 75A4 - it was the
other guy's idea).

Since I "transceive" with my 75S-3A / 32S-3
combination, and since the DX is usually transmitting
outside of the 200 KHz bandswitch allotment, use of a
second receiver is pretty much mandatory unless you
want to go through the effort of uncabling the
receiver from the transmitter.  Also, use of two
receivers allows listening to the frequency on which
the DX station is listening and thus you can "zero
beat" the station that is being worked, etc.

Anyway, although I have the Collins "weighted" knobs
added to my other S-Line receivers, the 75S-1 didn't
come "standard" from the factory with the weighted
knob.  Since the tuning of an S-Line PTO is MUCH
smoother with a weighted knob I decided to add weight
to the knob.

Of course this is pretty much "old hat" and there have
been various methods of doing this presented on all
sorts of websites and even on the various Internet
reflectors.  Each article on doing this used various
items to accomplish the weighting and what I am doing
is giving still another item to be used.

Several years ago for Christmas, my 3 daughters bought
me a reproduction 1851 Colt Navy revolver which is a
"black powder" side arm that fires a .36 calibre
bullet.  Actually, what is used are lead balls that
are 0.375 inches in diameter.  Well, although I carry
this weapon doing Living History concerning the Civil
War, I actually have never live fired it.  I have
fired "blanks", but never put a single ball into the
chamber to live fire.

Therefore, I had a full box of 100 0.375 diameter lead
balls that my daughters had obtained to go along with
the weapon.  The cost for the box of 100 balls was
$5.95 and they came from a local gun shop.

Anyway, it seems that these are just "made" for adding
weight to the S-Line knobs.  On the knob that does not
have the finger hole and has the 3 ridges inside, each
compartment just holds 3 of these lead balls.  I
applied a liberal amount of fast hardening epoxy to
the compartments and put the balls into the knob.  It
is best to let the epoxy "set" for a couple of minutes
before adding the balls to make sure that they stay
along the outside of the knob.  Then, after a couple
of hours I added a second layer of balls thus making
the weight of the knob about the same as the "factory"
weighted knob.

On the knobs with the finger hole, there are no ridges
inside and you can get 10 balls around the perimeter
of the knob.  Again, put in the epoxy and let it set
up a couple of minutes and then put in the balls.  Add
the second layer several hours later.

The second layer of lead balls comes out just a
fraction of a inch below the level of the skirt on the
knob thus making the entire assembly fit perfectly.

By adding the weight to the knob the 75S-1 now tunes
much smoother making "split" operation on 80 and 40
meters much easier.  The knob, plus the connection box
that I manufacture which allows either receiver to
control the transmitter, makes this type of operating
much easier than using a separate receiver with a
separate antenna for "split" operation.

Anyway, about $6 for the box of lead balls gives
enough lead to do at least 5 knobs and they are much
easier to handle than trying to use the small "shot"
pellets that are often used to add weight.  Also, you
don't have to buy a large quantity of material to get
enough to do a relatively small number of knobs.

Glen, K9STH

=====
Glen, K9STH

Web sites

http://home.attbi.com/~k9sth
http://home.attbi.com/~zcomco

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