My G5RV at QRO stopped working when the purchased bead choke at the
coax/ladderline junction got so hot it melted the coax. They need
several thousand ohms of choke impedance, usually not found in most of
the off the shelf bead chokes.
OTOH two 80/40/20 fan dipoles (at right angles) I modeled and built
worked super at 65' high. They worked on 15m with a tuner (<2.5:1 swr)
and perhaps on 10m if the coax is cut for a match or there is enough
loss. I separated the ends by 24" using 3/8 sq pvc rod which makes for
mechanical complexity and difficulty winding it up (I use 10" diameter
concrete column forms). Eznec models are reasonably accurate if you
follow the recommendations on modeling by Cebik, #108-111 at
http://www.antennex.com/w4rnl/
re VE7RF's conjecture that the center of every dipole may not need to be
connected: Since I had a working EZNEC model, I disconnected the
transmission line connections to the 40 and 20m dipoles and fed only the
80m. There is coupling but very poor swr; 4:1 on 40m, 10:1 on 20m, 8:1
on 15m, so it's not a good idea.
Grant KZ1W
On 4/26/2015 1:26 AM, Steve Hunt wrote:
The 51ft "G5RV" performs well on 40m, 20m and 10m - bands where the
SWR(50) at the ladderline/coax junction is moderate. On other bands
the SWR(50) is high, and how well it performs will depend on the
length and quality of your coax run.
On 40m you will notice little difference compared to a half-wave
dipole; on 20m it has a small amount of broadside gain over a
half-wave dipole; and on 10m the azimuth pattern has broken into 6
major lobes, with best performance at 45 degrees to the direction of
the wire
Using a good CM choke at the coax/ladderline junction is important -
it will reduce radiation from the ladderline section and noise pick up
on the coax run.
Steve G3TXQ
On 25/04/2015 21:11, Dick NY1E wrote:
I'm operating from a small lot in Florida winters, I have a 40M
dipole up but it doesn't quite fit my opening, it is into the
branches 5 or 6 feet. I wonder what the 51' G5RV would perform like
compared to the dipole on 40, and as a bonus I might get some other
bands... Any ideas???de Dick NY1E/4www.ny1e.com
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