[TenTec] Antenna help

[Rick - DJ0IP / NJ0IP]

GM Tony,

About 35 years ago I burned up the tiny balun inside of my tiny MFJ-901
matchbox.
I was running my Ten-Tec OMNI Analog and a dipole fed with 300 Ohm line.
I removed the balun, bought a larger one and always used it externally after
that.

Realizing how easy it was to burn up baluns inside matchboxes, I never used
an internal balun again.
I have always used an external balun, located as close to the matchbox as I
could get it.
The openwire feedline has always run into the shack.

Keep in mind that I often used symmetrical tuners but when I was using a
combination asymmetrical plus a balun, I always used an oversized balun
directly behind the tuner.

Example: First picture in the gallery in my shack in OKC
http://www.dj0ip.de/my-station/oklahoma-2010/ 
The RG-213 stub is about 10" long.

Now to your specific problem.
On things like that you just have to try things.
One simple thing you might try is to cut a piece of wire 33 ft. long,
connect it to the chassis of the 238, and run it along the room, laying on
the floor.  Might help clean up 40m.  Might also make things worse.  You
just have to try stuff.

You could also place an RF choke in the coax lead, immediately where it
comes through the house.
In this case I would recommend the "mid-bands" choke as proposed by GM3SEK.
It is cheap and easy to build.
See choke "C4" on this page:  
http://www.dj0ip.de/cmc-test/the-components/the-chokes/ 
This one is specifically for 7 MHz and has over 4K Ohms impedance at that
frequency.
If you wish to build it, I'll send you instructions.

BTW, the internal balun in the model 238 is a disaster, typical of how all
matchbox manufacturers were building them years ago.  I strongly recommend
not using it if you are running more than 100w through it.  This is not a
Ten-Tec slam; ALL manufacturers had it wrong for many years.  Only recently
have a few realized the correct way to do it and begun winding multi-core
1:1 Guanella baluns inside of their high power matchboxes.  (Thanks to lab
work published by W8JI and to K9YC's guidelines on baluns).

73 - Rick, DJ0IP
(Nr. Frankfurt am Main)


-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Tony
Lelieveld
Sent: Wednesday, December 31, 2014 3:17 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Antenna help

Hi Rick,

Did you have the 1:1 near the radio or outside with a piece of coax in
between?  I run an extended Zepp, fed with ladder line, hooked directly to
the balanced terminals on my 238B.  The only band it gives me a little grief
sometimes is when I am on 40 mtr running about 500 Watt with a Heathkit
SB-200.  It makes the phone ring, which is an electronic beast hi..hi.  The
regular Bell phone does not have that problem.  I never took the time to
play with the feed line length and if/when I do, it will have to wait till
summer.

73, and Happy New Year, Tony VE3DWI.

----- Original Message -----
From: "Rick - DJ0IP / NJ0IP" <Rick at DJ0IP.de>

snip>
> At this point I will throw in a plug for Ten-Tec.
> With my Model 238B and an external 1:1 current balun, I have been able 
> to match all sorts of openwire antenna systems, though I often must 
> add the external capacitor on the back.  However I run just 600w these 
> days. If you run legal power, you will need to replace the high 
> voltage capacitors in the 238.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)

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