ED,
The 229 and 238 were similar, with the 229 matching the old Omni A,D,C gear in
looks, the 238 matching the newer Omni V/VI gear.
Both used the dial cord and sliding indicator for displaying the tuning
position.
Bluntly put, that was CRAP.
The 238A was the first model to incorporate the turns counter which enhanced
reset-ability considerably.
The difference in the 238A and 238B was simply enclosure color. Forget it.
The 238C incorporated a cross-needle watt meter which was a nice improvement,
but IMO not worth the money if you already have a 238A or B.
All of the units prior to the C had what I would call "under-dimensioned"
switched fixed capacitors.
Many of us replaced them with low-cost Russian door-knob caps which are much
more robust.
I have never seen inside of a "C" so I won't/can't comment on what its switched
fixed capacitors are like.
Perhaps they should be replaced too, BUT ONLY IF your are running more than 1kW.
73,
Rick, DJ0IP
(Nr. Frankfurt, Germany)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Edward Mccann
via TenTec
Sent: 24 February 2018 20:02
To: tentec@contesting.com
Cc: Edward Mccann <edwmccann@yahoo.com>; ag6cx1@gmail.com
Subject: [TenTec] Ten-Tech Matchbox 229 vs 238 series.
Thank you to those who replied.
Yes, I mixed up the nomenclature.
Was trying to suss out improvements/changes from the 229 to the newer 238 KW
series.
Senior moment, caught by all.
Great answers from several of you.
I include below a snip of a response from another extremely knowledgeable
source addressing a related question on another great web site, since there may
be others reading without specific Ten-Tec Matchbox experience.
FYI:
“Balanced Matchboxes:
Technically, there is no reason for the T to have a broader matching range than
the L.
Mechanically there is.
The L has a couple of challenges.
First, it must have its variable capacitor switchable from input to output.
Second, it sometimes requires A LOT MORE CAPACITANCE, which is impossible to
obtain with a variable capacitor that fits inside of a desktop box.
The simple solution is switched caps.
There are/(was) those who understand this and know how to deal with it.
For about 30 years, TEN-TEC built a “Model 238” ( then 238A, 238B, 238C).
They even built similar before that but I’ll begin with what they did their
last 30 years.
The 238 has a roller inductor and a single 500pF capacitor.
In addition, it has 4 fixed capacitors, each 440 pF (if my memory serves me
correctly), that can be switched in, in parallel to the 500 pF.
That totals 2260 pF.
However, especially when matching openwire fed antennas, even that is sometimes
not enough.
So Ten-Tec provisioned for adding an external high voltage capacitor on the
rear panel of the matchbox.
They even included a 1000 pF disc ceramic capacitor with the matchbox.
This enabled 3260 pF!
In practice, after 25 years of owning these matchboxes, I have used the
external capacitor twice.
· Once was on my short 80m vertical dipole in Oklahoma. See Pics:
www.dj0ip.de/my-station/oklahoma-2010/
· The second time was here at this QTH when I first put up my 160m
antenna in a November snow storm. I had to match it with the matchbox and
needed an external cap for that too. In the springtime I was able to tune the
antenna an match it at the feedpoint and then I didn’t need any matchbox
anymore. But this external cap feature enabled me to participate in CQWW DX CW
on 160m back in November.
BTW, I did not use the 238’s built-in 4:1 voltage balun with the 80m Vert.
Dipole. That balun is rubbish!
NEVER USE ANY 4:1 BALUN AS YOUR MAIN TUNER BALUN.
ONLY USE A 1:1 GUANELLA!
(If needed, you may also use a 4:1 transformer in front of it, but ONLY if it
is absolutely necessary).”
73,
Ed McCann
AG6CX
Sent from my iPhone
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