[TenTec] 238 Manual Addendum (extra cap)

Rick at dj0ip.de Rick at dj0ip.de
Wed Jun 23 08:04:58 EDT 2021

I have had to use the external cap a few times.  In my case, 500 pF (additional) was enough.

It is necessary when you have a very short antenna on 160m or even 80m.
In that case you strap it in, but you must remove it when changing to higher bands.

Most people will probably never need it.

For instance, when living in Oklahoma 10+ years ago, I built a short vertical dipole, 2x 9 meters (2x 29' 6") long, center-fed with openwire.
I used it only on 160/80/40.
Had to add the cap on 160/80, but not 40.
See photos:  https://www.dj0ip.de/my-station/oklahoma-2010/ 

IMPORTANT:  When matching openwire fed antennas, never-ever use the 238's lousy built-in BALUN.
You should use a good 1:1 BALUN.
See:  https://www.dj0ip.de/balun-stuff/tuner-baluns/ 

73 - Rick, DJ0IP
(Nr. Frankfurt, Germany)
May the Sunspots be with Us!

-----Original Message-----
From: TenTec <tentec-bounces+rick=dj0ip.de at contesting.com> On Behalf Of Andy W3LI
Sent: 22 June 2021 19:58
To: Discussion of Ten-Tec Equipment <tentec at contesting.com>
Subject: Re: [TenTec] 238 Manual Addendum (extra cap)

​Hi Guys, just took a look at the back of my TT 238B tuner. The CAP is between the external wing nut and ground. Never used it as it came out of the box.????

Maybe info will help.

Andy... W3LI


If you add the extra cap to the back of the 238 tuner, it is added to position 3, 4, and 5 ---  not just 5. I found this out while doing a repair. The schematic seems to indicate this, but the verbiage in the manual implies it is only added to position 5.

I don’t know if this true of later versions (e.g. 238A), but I confirmed it on two original 238’s.
This means if you decide to just leave the cap there under normal usage, you are missing a large chunk of capacitor range between the end of 1-2, and 3-5 plus the cap.



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