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@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
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