[TenTec] TT 238B Question(s)

Sun Sep 25 08:04:29 EDT 2005

That just connects the balanced output to one side of the 4:1 internal 
balun.

73
Bob, K4TAX

----- Original Message ----- 
From: "W1GOR" <W1GOR at Maine.RR.Com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Saturday, September 24, 2005 12:51 PM
Subject: Re: [TenTec] TT 238B Question(s)

> You stated, "I have the transmission line connected to the balanced inputs
> plus the extra wire going from one balanced terminal to the single-wire
> terminal."
>
> Why is the "...the extra wire going from one balanced terminal to the
> single-wire terminal." ???  It seems to me that this 'extra wire' is
> unbalancing a balanced feedline.
>
> Re-read the TT instruction manual... Try removing the "extra wire"...
>
> 73, Larry - W1GOR
>
>
> ----- Original Message ----- 
> From: <k8jdc at sbcglobal.net>
> To: <tentec at contesting.com>
> Sent: Saturday, September 24, 2005 1:15 PM
> Subject: [TenTec] TT 238B Question(s)
>
>
>> 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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>
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