Topband: Broadband DHDL

[GEORGE WALLNER]

David,
I have modeled both side-by-side and in-line phased DHDL arrays, but I have 
only tested the in-line version.
NEC indicates that a RDF of 12 dB is possible. The in-line DHDL array that I 
have tested was good, but I did not measure the RDF.
For phasing I used a magic T splitter with one of its outputs going through 
180 degree transformer. The "front" antenna had  a longer feed-line to 
compensate for the propagation delay, which is proportional to the distance 
between the two antennas. (Allow for coax VF.)
The DHDL receives from the transformer end. The terminating resistor is 
placed at the other end (back-end). For best results the antenna should be 
made quite symmetrical across its center. To get the best front-to-back 
ratio you can tweak the loading resistor. I use a small 1.8 MHz transmitter 
which is placed about 1000 feet behind the antenna. (The transmitter should 
be "outside" the near-field.)
73 and GL,
George,
AA7JV



On Sat, 27 Jul 2019 17:44:46 +0000
  "Rodman, David" <rodman at buffalo.edu> wrote:
> My QTH is awkward for putting additional beverages BUT I am intrigued by the DHDL if it can be phased broadside (I have enough room for that), per the reference from IV3PRK:
>
>
> http://www.iv3prk.it/user/image/..-rxant.prk_tx3a.pdf
>
>
> I have a few questions that would need to be answered.
>
>
> 1.  Where in the physical layout of the antenna is the terminating resistor located?
>
> 2.  I could build the transformer to match, but does anyone know a commercial product that would do the 12:1 transformation??
>
> 3.  What would be the details to phase and combine the two (what length?) antenna feed lines to a 50 or 75 ohm transmission line to the station with a 2 antenna broadside configuration??
>
>
> Thanks.
>
>
> ---
> David J Rodman MD
> Assistant Clinical Professor
> Department of Ophthalmology
> SUNY/Buffalo
>
> Office 716-857-8654
> _________________
> Searchable Archives: http://www.contesting.com/_topband - Topband Reflector