[TowerTalk] Johnson Matchbox Question - Ten Tec 228/229

[Edward Mccann]

Timing is everything! But Ironic. 

Maybe worth while  and informative to the group to  perform an autopsy with pictures of the balun. Would reveal windings, current or voltage, etc.

A non-human sacrifice.

73 
Ed
AG6CX

Sent from my iPhone

> On Mar 14, 2022, at 8:19 AM, Tom Hellem <tom.hellem at gmail.com> wrote:
> 
> Ed-
> I did find one website touting the Annecke tuner and suggesting a mod for
> the Matchbox that I might try.
> It involves adding a 4 position switch and using it to tap the link coil in
> several places, along with a 270 pf variable cap in series with the input.
> I have long since gotten my money's worth out of the MB so not afraid to
> drill a couple extra holes in the front panel.
> I would love to hear from anybody on TT (or elsewhere) that has tried this.
> 
> Re the TenTec 238, I have one of those also. It's been a good tuner up
> until ARRL DX CW a few weeks ago.
> I hooked it up to a 75 meter  dipole fed with about 70' of 450 ohm line.
> Worked OK for a while until I hit it with a KW. The SWR meter indicated an
> arc or flashover, but didn't see anything obvious upon removing the cover
> and inspecting. My money is on that it's the balun.
> 
> 73
> Tom
> K0SN
> 
>> On Mon, Mar 14, 2022 at 8:49 AM Edward Mccann via TowerTalk <
>> towertalk at contesting.com> wrote:
>> 
>> Interesting trip down memory lane re EFJ.
>> 
>> Internet posts elsewhere show back in the day then-available Annecke
>> tuners best the Matchbox; various mods suggested. Unfortunately,
>> suggestions present minimal proof of results, however, probably due to
>> determining “performance” actually dependent on the aerial used and
>> environment.
>> 
>> It seems the manufacturing rage that followed in the search for tuners
>> offering solutions for “balanced”
>> antennas led OEMs to inclusion of baluns in the output circuit. Most of
>> them appear to be voltage baluns as opposed to 1:1 current baluns,
>> apparently chasing the notion that a 4:1 transformation at the back of the
>> box made an efficient hook-up to twinlead or ladder line at the shack wall,
>> without consideration of Z shack not necessarily Zo.
>> 
>> Another website has recently tried ti evaluate the balun of the
>> then-popular Heathkit 2040/2060 series, with the observation they used a
>> ferrite transformer design.
>> 
>> Does anyone have any accurate observations on the characterization of Ten
>> Tec 228/229 tuner baluns? Would be interesting to know.
>> 
>> Best from the West,
>> 
>> Ed McCann
>> AG6CX
>> 
>> 
>> Sent from my iPhone
>> 
>>>> On Mar 14, 2022, at 4:13 AM, Rob Atkinson <ranchorobbo at gmail.com> wrote:
>>> 
>>> The "link" (that's the larger outer coil) originally had two taps.
>>> One just one or two turns from the grounded end.  That was the 50 ohm
>>> unbalanced input.  A second tap was a  few turns over from that.  It
>>> was for 300 ohm receiving line.  A lot of receivers had terminal
>>> strips on their back panels for the option of 300 ohm twin lead
>>> balance line for receiving, in the 1950s and '60s.   A Matchbox that
>>> doesn't have the link has been extremely modified into something else.
>>> It can no longer be a link coupled balanced line network.  Which
>>> brings me to a question:  Are you using your Matchbox for coax, or
>>> ladder line to your antenna?
>>> 
>>> I have one in regular use here with ladder line and a dipole.  It will
>>> be easier to determine what's going on with it if you get it out of
>>> its cover and run it in the open so you can see what's going on WRT
>>> capacitor meshing.  Just unscrew the zillion screws and put the knobs
>>> back on and connect the feedlines back up and you'll be able to see if
>>> you are running out of capacitance, or don't have enough etc.
>>> 
>>> 73
>>> Rob
>>> K5UJ
>>> _______________________________________________
>>> 
>>> 
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