Hi all. I just bought a used 238B from a ham in CA. (I'm in OH). I received
the tuner yesterday and have been testing it out. I've never used a 238
before, nor have I used a tuner with a roller inductor before, so those are new
items to me. I thought I would post a few points and get some feedback from
other 238 owners. (My testing has been primarily done with a 135ft dipole fed
with 450-ohm balanced line. I have the transmission line connected to the
balanced inputs plus the extra wire going from one balanced terminal to the
single-wire terminal. Thus far, I have only run 100W thru the unit).
1. I opened the tuner and have not noted any burn marks or evidence of arcing
or abuse. The only thing I noted visually was that the roller inductor wheel
seems to be a little rough to me. The coil turns are perfectly smooth, but the
traveling wheel doesn't seem to be as smooth as I would expect. The unit
overall is in perfect condition cosmetically, so I don't see any signs that the
previous owner abused it.
2. This tuner doesn't seem to be 100% healthy to me. The 1.5:1 bandwidth (>5%
of the band) reported by ARRL in their QST review doesn't seem to be available
in my unit. On 40m, 5% equates to about 350 KHz, or coverage of the entire
band with 1.5:1 or better. My 238B is showing about 115 KHz, which is LESS
THAN HALF of the expected value. Is this because I may be using an improper
switch setting on the High/Low-Z switch? (For the record, my 40m settings were
High #1, Cap @ 4.8, and Inductor @ 9.9 using the antenna I described above.)
3. I found tuning to be VERY difficult. I followed Tentec's instructions, but
it was a lengthy process. Once I found matches on the various bands, they have
been repeatable, so this difficulty should hopefully be a one-time problem, but
it was not as intuitive as I expected. When I tried different switch settings
on the High/Low-Z switch, it didn't seem to make much difference in most cases.
Most of the matches that I found used either Low #1 or High #1 settings. Does
this sound right? Finding a match in most cases involved several minutes of
hunting.
4. The meter on my unit was totally out of whack in terms of accuracy. The
SWR readings are way too low and the forward power readings were way low. I
was able to adjust the pots to fix the forward power discrepancy, but I have
not been able to fix the SWR reading. It is still too low. I have the set
knob adjusted correctly and have tweaked C16 as described in the manual. While
my radio and external Palstar meters are showing a 2:1 VSWR, the 238B meter is
showing about 1.3:1 or so. I can't seem to get it to get any closer.
5. The roller inductor is not nearly as smooth as I expected. I've already
mentioned that I've never used a roller inductor tuner before, so I'm not
certain what I should expect. When I spin the knob on the roller inductor
using the little knob protrusion, it takes enough force that I usually move the
tuner around physically. It doesn't spin effortlessly. I usually have to hold
the tuner with one hand to keep it still while I adjust the inductor. If I
just adjust the knob slowly using the entire knob instead of the little
protrusion, this obviously isn't a problem. I have opened up the unit to
inspect the roller inductor while I adjust it and can't really see anything out
of alignment. What should I expect on this?
I would appreciate your feedback on this. I hate to think that I may have
bought somebody else's problem child. So far, the tuner is certainly usable,
but I would have to say that it's not what I expected in terms of quality and
performance.
Thanks and 73,
Dave / K8JDC
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