|SLUG TUNED COIL WORK (29 September 2014).
Work I am doing for a fellow in USA who wants to restore his dads' old radio.
Work I am doing for myself as well! I am a natural born experimenter and have
a curious mind! -- 73 Earl VE3AB - 29-Sept -2014
|Hamelectronicsmagazine.com / earlandrews.com
**** mirror sites **** since 2005
FREE ON-LINE MAGAZINE and mail order parts as well !
|I received an email yesterday from a fellow who wishes to repair a family owned radio.
What I do here with this "hobby business" of mine (not a money maker but an
interesting retirement activity) is help people who have older radio equipment of
sentimental value they wish to restore.
I offer my services at a much lower than average SHOP RATE. IN this case.. I have been
wanting to do some measurements with slug tuned coils..so his email gave me added
impetus to do some measurements on some of the slugs Ive gathered over the years
and some of the older slug tuned coils Ive gathered from old discarded radio
|Above the photo that the fellow sent me of the coil form that the slug was broken from.
Isn't email great! - I have some real useful information to go on when trying to find a
replacement SLUG for this gentleman. --
|BY THE WAY.. I QUOTED A PRICE OF $5 (U.S.
DOLLARS) for replacement slugs. I thought of 3
replacement slugs but I think I will send him a
$5.00 -- Im not in it for the money! - Sometimes I
just do things for my own interests sake..AND.. I
write articles for this "on line magazine" --
which are of interest to other radio and
Gives me a feeling that all this "junk" - Ive
gathered up is not pure JUNK at all..but useful
pieces of equipment ! Hey-- I have a purpose
ABOVE (and below left pictured) : THREE slug
tuned coil forms that look to be of the same sort of
winding arrangement as the one PHIL has.
|Above right: the coil slugs were removed and they all appeared to be the same size.
Just slightly less than 1/4 inch diameter and the thread style and dimensions all
seemed to be about the same. I guess the coils are in the category as STANDARD
COMPONENTS. When I worked in NATO Cataloguing.. there were certain components
that were "standard" and fell under NATO Standardization Agreements (STANAGs).
I never worked with coils and inductors (NATO SUPPLY CLASS 5950) but I did work
with Microcircuits (5962 Class) and Resistors (5905 Class). 5905 and 5962 were
"standard components" and the physical dimensions and characteristics were all
cookie cutter sort of deal. I guess it must be the same (as a general rule) with coils
|To measure the electrical characteristics of the coil slugs..I needed to
make a coil. I wound a coil on one of my tuning wands as per above. It is
about 6 turns of enamelled wire. I will be keeping this coil for safe
keeping and will use it to measure other slugs as I continue working on
this sort of thing.
DO YOU NEED ANY WORK DONE like this??? I work cheap! Retired Civil
Servant who just enjoys projects to work on!! email me at:
firstname.lastname@example.org and we can make arrangements.
and we can make arrangements.
I dont have any commercial advertising on my site..but.. I do toot my own
horn every once and awhile.
|Slug all wired up ready to go!
|I tested this inductor (slug removed from COIL NR. 1 at .510 microhenry.
It is important to note: These measurements are relative. If I were to
remove the wire coil and then put it back on the same slug and measure
the inductance again..the coil might measure at .527 or .498 uh. -- alot
depends on the positioning of the windings and the figures I am using
are BALLPARK or CLOSE BALLPARK figures.
I'm using inexpensive (but very useful) test equipment from China and I
bought the test jig from EBAY. -- Its important to have a few known
standard Inductors to double check the measurements.
Doesnt hurt to do that..(lets put it that way)!
|Both the slugs from coil number one and
coil number 2 produced (about) the same
test inductance. Now I was going to try
number 3 slug.
Number 3 slug was slightly different in color
and larger. With a larger (longer) slug..one
could make a general rule of thumb that the
inductance the slug was trying to produce
would be greater and I (expected) the
resulting test would give me a larger
inductance reading. See below picture:
YES..inductance is higher with this slug.
|I got thinking of things! The slug the fellow needs is for the OSCILLATOR COIL for the broadcast band of his Knight Star Roamer radio.
What is a Knight Star Roamer radio?? see below snip from a web page (towards the bottom of this page. I have never owned or seen one of
these radios before. Radios are one thing that has sentimental value (quite often)! - I have great sentimental value I associate with my old
Ten Tec Argonaut 505 radio! I used it (often) during the early 1970s and can recall one qso in particular with a W6.. W6RR?? a very tough qso but
he pulled me out! Many other qsos and operating situations I can remember using that old 505!
|Next .. I measured the test winding
without the slug!
BE sure to calibrate your
inductance meter frequently when
This is only a $30 instrument and is
amazing..but sometimes I think it
gets stuck on a reading and might
be way out of whack! YOu cant
expect anything else because
these lower priced instruments
can act up! --Sometimes..I start
scratching my head -- ready to tear
a chunk of hair loose!! because I
think something is out of whack! Is
it me or is this thing playing tricks
on me! -- HAVE SOME KNOWN
VALUE (SIMILAR INDUCTANCE)
COILS ON HAND TO MAKE SURE
THE INSTRUMENT hasnt developed
some sort of brain cramp!
I bought this little tester off ebay.
Amazing what is comming out
Amazing but don't take it as gospel
every single time.
|BELOW: the BIG PICTURE below shows cracks in one of the slugs from my coils. Iam not going to send this core to this fellow. The
core (when I was removing it) needed a little extra force to get the motion started. This extra force probably caused the cracks.
This happens (often). I have read where crazy glue can be used to repair broken or cracked ferrite slugs. I could probably "google"
it ..but -- right now.
|NOTE to self: Measured Slugs and related coils to be stored either in a box
or bin labelled: MEASURED Slug Tuned Coils.
|I have several small drawers with SLUGs from various slug tuned coils. For example: I have about 7 slugs removed from a junked Heathkit
HW32 20 meter monoband Transceiver. --- These slugs (I would guess): would yield a lower inductance reading when wound with my 6 turn test
winding. This is because the HW32 has IF frequncies of around 3 mhz or so and the fundamental frequency of the radio is 14 mhz. My guess
was right! - The test winding of the HW32 cores yielded a measured inductance of .242 microhenry. -- I CALL THIS SLUG AN HF SLUG. (Rough
sort of Approximation/Rule of Thumb).
|LEFT pictured..some slugs I removed from a junker
Motorola Surplus transceiver. I did not try any of these
cores with a test winding.
The cores are about 1/8inch diameter and -- I do expect
if I were to measure the inductance..it would not be as
much..relative to the HF Slug or the LOWER HF
Right now..I did not have time to do very much more
testing or experimentation.
|I chose two cores as shown in the
above left photo. One is 7/8 inch
and the other 5/8 inch. They were
previously removed from an old
slug tuned coil.
I think these two cores might show
an inductance reading of higher
than the .5 uh. Reason: because
they are longer slugs and typically
the inductance would be greater
when used in a slug tuned coil.
I was right. Measurements yielded
one at 1.1 uh (the long one) and
the shorter one gave a reading of
I will be sending both of these
cores to Phil. In all ..I have decided
to send 5 different length cores
with slightly different
characteristics. It is hoped that
one of these slugs will do the trick
5 cores for $5 ! -- Thats a dollar a
core. Plus..you count all the work
involved! - As I said before..I am
not just in this game for money!
I enjoy experiments.
IF YOU DO COME TO ME WITH A
JOB LIKE THIS (I am in Elliot Lake,
Ontario CANADA)..and I work by
mail order from home! .,,I might not
be able to give you quite as sweet
a deal..but ..I DO WORK CHEAP!
and I take on jobs like this for
people from time to time!
I ALSO BUY OR TAKE DONATIONS
of stuff like this..for experiments
and helping out those who have
|These cores packed up with protective padding will cost about $4 to send to
USA. In Canada the cost would be $2 in postage. Other parts of the world might
cost $6.50 or so by mail.
|Above: the coil slugs ready to be mailed out to Phil. I will be interested to hear if he
gets the radio going or not.
|BELOW: THE KNIGHT STAR ROAMER RECEIVER. --- Probably Phil has many fond memories of this old radio! I used to
have a Heathkit HR10B and I spent many hours back in 1971 listening to W1AW and struggling to try and copy the
code for my Amateur Licence. -- I liked to listen to some off beat guys on 75 meters ..namely WA8RYE and WB9KQY
and the fellows on 3830 and also a group on 3835 khz. -- They were strong signals that the HR10B would easily pick
up. -- So..radio does have some strong memories when you really get into it like I did.
|----- THE END --- 73 Earl VE3AB -- ps. I will be fine tuning this article a bit in the next few days.
|IF you need a small service
from me..ie replace a broken
slug or perhaps check out and
repair a printed circuit board..
Please feel free to write me an
email for a quote! NO HASSLES
MY EMAIL LINK IS __>>HERE <<
MY HOBBY SHOP RATE is only
$10 per hour!!! OF course there
is no real overhead because I
do this stuff for free (a hobby)
|When I send out small orders of parts..I use
creative packaging to minimize the costs.
Postage rates are not all that bad for small
packages and padded envelopes. For boxes
(even small boxes) the rates are quite high
and I cannot compete or even come close to
many of the Chinese and Taiwanese and Hong
Kong electronics suppliers.
SO.. I DO SMALL ORDERS! I LIKE THE OLD
PARTS (PRIOR TO THE 1995 PERIOD). IF YOU
HAVE OLDER SOLID STATE PARTS OR COILS
AND STUFF LIKE THAT..I WILL BUY THEM FROM
YOU -- I AM ADDICTED TO COLLECTING THESE
PARTS and researching them and selling them
too! I ALSO do trades!
|more slugs and slug tuned coils .375 inch size
|The ferrite sleeves above (the ones without the thd rod) measured .314 in. diameter. I did a test winding of about 4 turns on the outside that
measured (about) .2 uh without the slug inserted and went up to about .8 uh with the sleeve/slug fully inserted.
----->> this page appended with some additions May 1st 2015 -- I buy sell trade compoents like these coils to people who homebrew or fix
ham radio equipment and short wave listeners ect
|Here are the ceramic coils that are 3/8 inch
diameter and they have either red mix
or green mix slugs. I only have 3 with the green
A couple of the ones for the red mix dont have a
slug (it was removed).
I HAVE OTHER SLUG TUNED COILS HERE IN
IF YOU HAVE SPECIFIC NEEDS - JUST WRITE
ME AN EMAIL AND I CAN QUOTE YOU DETAILS
MEASUREMENTS PRICES AND SO ON.
MY PRICES ARE MOST REASONABLE. SEE
THE PRICES I ASSIGNED TO THE RED CORE
SLUG TUNED COILS ABOVE.
SOME MAY BE USED BUT ALL WILL BE IN
GOOD WORKING CONDITION.
IM ALWAYS ON THE LOOKOUT TO BUY MORE
OF THESE ITEMS FROM OLD COLLECTIONS
OF PARTS (I PAY THE POSTAGE AND GIVE
YOU BETTER THAN FLEA MARKET PRICES
FOR OLDER PARTS (even used parts. )
|$2.75 US dollars for the Cambion ceramic form - red core ferrite slug
|$2.50 US dollars for any of the ceramic forms with the red ferrite cores
|$1.75 each ceramic forms with red ferrite slugs
|$1,50 each the wax/cardboard smaller slug tuned coils with red slugs