TopBand: QST Antenna Tuner Review

[Garry & Yelena]

George Guerin wrote:

>      I know they are no longer made, but the TenTec Models 229 and 238
>      tuners are not all bad.  Being L-network tuners, they cover a very
>      wide range.  They have an internal 500 pf 2 KV air variable capacitor
>      and padding in four steps of 440 pfd, so the internal capacitors can
>      have a total value from 40 to 2260 pfd.  Also both models have an
>      external terminal for another 1000 pfd parallel padder for 160 meters
>      which raises the total shunt capacitance up to 3360 pfd!
> 
>      The roller inductor is good quality and covers 20+ uhy.
> 
>      So, although QST cannot review it, these models make sense, and have
>      the ability to be used effectively on 10 through 160 meters.
> 
I have owned a TenTec 238 since about 1990. I use it daily on 160
meters--on antennas cut for the heart of the band. I would add the
following to George's comments.

I like:
* the reversible L-network design.
* the capacitance range.
* the four-position antenna selector

I don't like:
* the anemic range (capacitor) switch--a conventional ceramic wafer
easily destroyed by a hotswitch at moderate power.
* the roller inductor--the coil form is ceramic, and the coil has a
variable pitch, but the end plates are epoxy/glass PC board, and the
roller tap wheel is skimpy. I wore mine out (the tap wheel literally
wobbled on the shaft) and replaced it with a roller inductor and counter
mechanism from a BC375E.
* the sliderule dial mechanism--I repaired it countless times until I
just threw it away, and it was not readable without the dial lights--nor
was the meter.
* the SWR/power meter--very inaccurate and nonlinear. Good for relative
indication only.
* the case--typical TenTec. Frequent disassembly lunched the end trim
pieces--I threw them away. Coax connectors were pop-riveted, but worked
loose over time, creating intermittent ground connections. Replaced all
rivets with screws, starwashers and nuts.
* the balun, a 4:1 unit. Most baluns in single-ended tuners---if not
all--are useless unless operated near the design center. This one smoked
early on, and I tore it out. If you want to use balanced line, build a
balanced-line tuner.

General construction reminds one of a homebrew project--useable but
cheaply-made couplings, shafts. knobs and other components. In short:
good electrical concepts, mediocre execution. This unit has helped
dissuade me from buying other TenTec gear.

Just my opinion.

-- 
Garry Shapiro, NI6T
Editor, "The DXer," newsletter of the NCDXC
Visit the Northern California DX Club 50th Anniversary page:
http://www.aa6g.org/ncdxc50.html

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