[TenTec] Re: Ten Tec antenna tuners

[Jim FitzSimons]

Sherrill, my balun is made with a T-200-2 powered iron toroid.
A T-200-2 toroid is not small and it is not ferrite.
The band width on my balun is not as wide as a ferrite
balun but it will never saturate.
Large powdered iron toroids are higher Q than air wound 
coils of the same size except at VHF frequencies.
The balun needs to be protected from water and ice like
any coil or connector. Powdered iron toroids do not absorb
water. 
My house is made of metal and glass. It is a modern design
and it would not look good to have a ladder line coming 
through the glass. I can hide the coax. The house makes 
a great counterpoise.  
Best regards, Jim W7ANF

Sherrill WATKINS wrote:
> 
> Carl:  Very good question about the feasibility of bringing balanced line into the shack.    I am aware of two methods to do this.
> The first and easiest method is to use two pieces of equal length coaxial cable, in parallel.  Just tie the shields together at each
> end.  The two center conductors form a shielded balanced line. ( This can be extended to the center of the dipole for a sheilded
> balanced line.)  However, in most cases this is not necessary).  The twin shielded balanced line will have  a nominal impedance of
> twice the impedance of the coax; i.e. two lengths of RG-11 (75 ohms) connected in parallel will give a 150 ohm balanced line.  Also,
> this is can be connected directly to 600 or 450 ohm ladder line with no problems. The two lengths of coax can be "snaked" through
> wall sections, etc. just like a single length of coax.   The second and more "graphic" method is to locate the rig with the antenna
> tuner in front of a convenient window.  Remove the glass window pane an!
> d replace it with clear acrylic or equivalent plastic.  (This will require new window putty and possible paint to install the
> plastic. ) The plastic should be the same thickness as the glass so it will fit right in the sash.)  Then drill holes in the plasic
> acrylic window pane and install grommits in the holes to fit the wire or coax size.  Then just run the open wire line (or twin coax)
> through the grommits in the window!!  I did this with open wire line through both a double sash window with an exterior aluminum
> storm window and it worked great!!  (I did replace the storm window glass with acrylic sheet).   The only draw back(?) is that this
> arrangement made my shack look like a shipboard radio room  from the 1930's!  (This was amusingly intimidating to visiting CB
> operators!)  It also interfears with opening the window.  Also, contrary to what most people have the mistaken opinon, if installed
> properly, open wire line does NOT radiate.   It only will radiate if one has an i!
> mbalance in the antenna, i.e. one side of the antenna longer than
> radiating many years ago when hams connected one side of it to the end of a wire zep antenna, instead of the center, thereby creating
> a gross imbalance.)  Also, when I was using my open wire system brought into the house, my tv set was about 15 feet from the rig. The
> tv was connected to 450 ohm tv twin lead to an outside antenna.  I had no problems with tvi from my Drake TR4C running 300 watts.
> Finally, it is worth stating that I believe it is a mistake to use a small, cheap, ferrite type balun in an open wire system.  This
> has been discussed several times in QST.  The fact that one is mistakenly assured by a low vswr reading may be an indication that the
> balun is acting like a load resistor and converting some of the transmitted R.F. into heat. This gives a false sense of security
> because the swr meter is reading low.  Also, I believe it is a mistake to mount any balum outside because of the effects of moisture
> will cause the balun to also start acting like a dummy load. -  !
> Sherrill W.  k4own.

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