Message-ID: <m119GXx-0003QlC@fwd08.btx.dtag.de>
Date: Wed, 28 Jul 1999 01:22:09 +0200
To: rsgb_lf_group@blacksheep.org
References: <m117igN-0002SpC@fwd07.btx.dtag.de> <3.0.1.16.19990726095047.2eff9c40@mail.cc.kuleuven.ac.be> <379CBAFF.652B@xtra.co.nz> <379CE90B.350F600A@netins.net>
Subject: Re:  LF: Ground systems
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII; format=flowed
Content-Transfer-Encoding: 8bit
From: "Hans-Joachim Brandt" <hajo.brandt.dj1zb@t-online.de>
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

Doc Gruis schrieb:

> 	This following episode was told to me by an old time BC engineer about
> an early station located in the state of South Dakota.
>
> 	It was not at all unusual for stations, studios, anyhow, to be located
> on the top floor of some building.  It was not so common for the
> transmitter to be there as well.  But in this case, that is where the
> transmitter was indeed situated, perched proudly above the highest
> prominence on the roof of this particular hotel.
>
> 	The testing of the station went very well.  It was in the middle of the
> night.
>
> 	But on the day of the official sign-on, and there were several
> dignitaries there, it was impossible to keep the station on the air
> because it was impossible to keep the antenna tower in tune.
> 	
> 	It had been mounted on the top of the elevator (hoist) shaft!  And as
> the greeting crowd and other business started for the day the elevator
> acted like a very large tuning slug!

This reminds me of a problem I had encountered when still living in Munich, with 
much restricted space for antennas. For all HF bands I just had a 21 meters 
end-fed wire available, with a wire counterpoise in the loft, also connected to 
the house ground and the TV antenna mast.

On 160 meters I had to employ base loading, but I wondered that the VSWR often 
was higher than normal, until I discovered that optimum VSWR depended on how 
many apparatus I had connected to the mains in my shack (which had been just 
below the loft), thus varying the number of radials for 160 meters!

To cure this problem, I had to insulate the counterpoise from the house ground 
and TV-mast for RF, using a big toroid choke, and to feed the antenna for 160 
meters via a 1:1 separation transformer. Now the 160 meter antenna may have 
looked like an asymmetrical dipole, but the tuned section had to use the 
insulated counterpoise only as the other antenna end. Tuning of the antenna now 
had been entirely different from the previous setup, but the mains wires 
remained neutral.

/3 Ha-Jo, DJ1ZB