Topband: Re: [Topband] HF2V
vr2bg at harts.org.hk
Mon Jul 14 02:27:21 EDT 2003
As requested by K8GG, here's a little more description of my HF2 at my old
One can see a bit of the base at:
And the overall situation at:
Three top loading wires came off from the top of the third section of
tubing from the
top. The length of the top loading wires was chosen so that solder lugs on the
end of the wires could be secured to hardware below the 30m bits when not
deployed. Some light ropes guyed the radiator itself a few sections
from where the top loading wires were attached.
The far ends of the top loading wires were tied to the guying points when
which were about 5m out from the antenna (pulley & light line took care of
that went out to the end of the bamboo pole).
Radials consisted of four #12 THHN runs extending into the jungle in two
a house in another & to a telephone pole for the fourth - probably sloping down
about 20 degrees or so for all. As I mentioned in a previous post, all the
band radials made a big improvement in performance - I think I commented once
here that I was hard pressed to work JAs before I discovered that the 30/40/80m
radials contributed to its topband operation (I had as many as eight stub-tuned
radials plus several single band wires deployed at this QTH before one of the
village clan started hacking them up on me).
With the 160m coil fully extended, the antenna was reasonant somewhere around
1830 kc, with almost 15 kc usable bandwidth. Fine tuning was accomplished
by slightly compressing or expanding the turns of the coil.
When the top loading wires were deployed, reasonance on the other bands goes
on walkabout, with 30 & 40 beyond hope. I therefore added clips to the 80m
to allow shorting out of a number of turns to bring 80m reasonance back
not working 160, the top loading wires are pulled back in & the far ends
a jumper goes across the 160m kit & the jumper comes off the 80m coil.
Mounted on about 1m of pipe in a bucket of concrete jammed into the corner of
the roof, all this mucking about was possible by standing on a 1.5m step ladder
& reaching up as far as I could (1.9m tall with long arms). When the winter NE
monsoons blew (with little attenuation from UA0 over that open salt water),
changes were a bit of a challenge & it was never any fun when it rained. This
arrangement probably will only work on a flat roof or other reasonably
mounting locations - there was a fair amount of coil tweaking required.
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