Matching up a replacement Ferrite Core for slug tuned coil. Finding a replacement
ferrite core through comparision measurement. This is for the 15 meter TX driver coil
in the Ten Tec Argonaut 509.  new article 23 August 2016 by Earl VE3AB
for ham
electronicsmagazine.com
Note: I do this at a hobby rate of $10 labour for matching up cores like this. Iam retired Civil Servant and I do it mainly out of my own personal interest and
to serve Amateur Radio and those who still enjoy experimentation with electronics and radio.
IF YOU HAVE A RADIO AND YOU NEED A BROKEN CORE
REPLACED - I can help you out. Any small profits I generate go into my two web sites: this one: http://www.ham
electronicsmagazine.com --
which is a hobby of mine writing technical articles in this "hobby magazine" FREE AND FREE of advertising as well -- and my hobby
business:  http://www.nettyelectronics.com -- my parts supply business for hams and electronics experimenters.


Dear Earl,
I have removed the remaining lower ferrite core from the 15m coil of my argonaut.
I have wound 10 windings of 26 Cu enamel wire ( same as Elecraft is supplying with their kits) tightly around the core. The result is 33uH with my Dim7000
device, you can see the coil with the core inside on the attached snapshot.
I have no means to calibrate the device, but its no cheap chinaware, hi. Its a development of a German lab for electronics enthusiasts. I never had
anything bad about it.
MY NOTE (Earl VE3AB) - the instrument I was using was a Chinese Ebay tester that I bought for $30 -- It seems to work well but I am
careful to calibrate it against known values of inductance or capacitance - MY thoughts are on the 33 uh reading.. perhaps this instrument is very good at
higher inductance readings but not so good with lower inductance readings.
-- What I did is I made a test winding on my own Argonaut 15 m coil. There was lots of space on the coil form to wind on a 10 turn test winding. My result
was

Would be great if you could find of these cores. Here in Germany its close to impossible to find a loose core like this. Maybe on a hamfest, but they are
closing one after the other due to the decline of our wonderful passion.
73, K (in Germany -- Identity protected)
Here I am just starting to wind the nr 26 enamelled wire onto the 15 mtr coil form As you can
see the slug is set well down the coil form and there is lots of room for the test winding.
Above the 10 turn winding on its own.
Below..I used some masking tape and
squished down the coil to compress the
windings and I measured the inductance at a
little over .5 uh.
Above a 1 uh fixed inductor to calibrate the inductance
measuring instrument.
Trying to compress the 10 turns around the 15 meter coil form. I will soon be using masking
tape to secure the wire in place.
Here is the measurement of the 10 turn test winding on the
15 meter slug tuned coil. 1.173 uh -- which sounds about
right  to me anyways.
The test winding of 10 turns on the ferrite core
above pictured gives a reading of .925 uh. I
later compressed the coil windings together
and that produced a measurement of about
1.2 uh depending on how tight the coils of wire
were compressed.
Years ago I parted out an old Heathkit HW32 20 meter monobander
SSB transciever. These are the slugs I removed from the slug tuned
coils. I figured these might work or at least be in the ballpark for a
possible replacement slug for the Argonaut 15 meter coil. I was
right..seems to be a good candidate.
This Ten Tec Argonaut 509 owned by a fellow ham
operator in Germany has a broken slug as can be seen
in the photo left. This is in the "TUNING RACK" area for
the RF input to the receiver and the Transmitter low
level stages as well.

He needs a new slug just like the one pictured on the
right hand side.

What I do here at my shop is I have a good selection of
old slug tuned coils and I have spare slugs as well. I
have the person do a test winding of the broken slug
(if possible) and I try and match one up for him.
I do this at a $10 charge for labour and $1 for each slug
I send out.
Dear Earl,
as promised, please find the documentation of the successful repair of my Argonaut 509, kindly supported by the ferrite core you were able to supply..


Conclusion: repair vusscessful, many thanks again for your kind support. Without your core, no chance to get this thing running.

Meanwhile, I have converted the temporarily useless 10m band to 30m, as proposed in TenTecWIKI. Works perfecty.

By the way: I have used your 1uH inductivity on my measurement device, Result: 32uH. Something is wrong, or I do not use it correctly..

Fortunately, the designer is still in business, although the device is from the 80s. IIt was a kut, I have ordered the build/operations manual. Next repair job...

Many many thanks again.

The 509 will now get a 25kHz marker device and then I will build a 500Hz quarz filter for it.
BELOW: PICTURES THAT KAI SENT ME WITH EXPLANATIONS. THE REPAIR WENT VERY WELL.  He has a nifty piece of test equipment that
allows him to adjust these double core inductors to give the proper passband. Im going to look into perhaps getting this equipment or
something similar as it seems to work very well.
Pic 6.: t,his is the object, my vontage 509. Works well after repair of the driver, except 15m due
to a split ferrit core. You can well see the damaged coil, which I had to cut a bit in order to
remove the broken core.

Pic 9.: thts is the MetroVNA 180 touch antenna analyser. This 400$ device allows wobbling
of filters.
Pic 11.: the MetroVNA will be connected to the middle "taps" of the coills.
Pic 12.: this is how a filter curve should look like. This is the 40m coil.
Pic 14.: this is how the 15m filter curve looks with one core in it. It is no supercritical coupling, but
just a normal sharp filter curve with a low Q. Resullts in 2W output.

Pic 17.: this is how the curve looks with your 2nd ferrite core in it after
wobbling. Shown at 30MHz spectrum

Pic 19.: this is the 15m coil with your ferrite core as 2nd core in it. The core protudes a little bit,
because I had to cut the coil.
Pic 20.: this is the output after the repair. Like with any
other band, it´s now 6W on a dummy load.
Many thanks to KAI  for sharing this information (the above photographs and explanations). I might mention my
services here are very affordable. I think I only charged about $10 for 2 cores plus $5 for labour to find them and
measure them. Im retired Civil Servant and these activities (including doing my own repairs to my own collection of
gear ie Ten Tec Argonauts 505 through 515 and some others) -- selling parts pays for my two web sites:
http://www.ham
electronicsmagazine.com AND http://www.nettyelectronics.com -- plus it gives me a few bucks to
spend on hobby stuff. --- 73 Earl VE3AB
March 30th 2017 update.

Due to popular demand.. I have gone out and bought over 120
replacement slugs from Surplus Sales of Nebraska. 100 of these
being the 1/2 inch long types. I sell them at $1.25 each US dollars
and I can ship in padded envelope to USA for $5.50 small AIR MAIL
package. As well.. I have the blank coil forms Ive ordered in as well..
see the pictures ..
Pictures of the slugs from Surplus Sales of Nebraska
along with pictures of me testing them to go in
this space. as noted: 10 april 2017