In message
,
Gregg writes
On Jun 11, 9:44*am, dave wrote:
Gregg wrote:

Hmm, I've never seen that. I have seen the radio whips that have wire
around them but they are then encased in plastic, like some CB
antennas are.

On a Firestick, the wire is real.

I know that.

I once made a helically compressed 80m halfwave dipole by winding each
leg of around 66' of PVC insulated wire on 33' of the type plastic line
used for rotary clothlines/airers (making sure, of course, that the
inner core was nylon, and not steel).

I marked the line every 6", and the wire every 1'. After a few false
starts, I soon got the knack of getting the spacing of the turns
correct. I suppose that diameter of the line was around 1/8", and I
needed to space the turns at around 3/8".

Obviously, I had dipole consisting of 132' of wire, but I have no idea
whether the turns were close enough to make a significant increase in
the inductance per unit length, thereby loading the antenna, and making
it electrically longer than a halfwave.

I only used the antenna once, at a scout 'Jamboree on the Air' event. I
put it up as an inverted V, with the centre at about 30', and the ends
at 20'. I used 300 ohm feeder. It was very sharply tuned (using a
balanced Z-match tuner). Daytime conditions on 80m were not very good,
but the antenna seemed particularly poor. I think I only managed a
couple of contacts, with only S5 reports where I would have expected
s9+.

40m was a bit better but, at the end of the day, just before we packed
up, things seemed distinctly lively on 20m. I got a 59 from 350 miles
away and, surprisingly, another from 40 miles (extremely short skip
conditions, it appeared, which may have explained the poor conditions on
80m).

I haven't bothered to try the antenna again. I have no idea if it was
working OK on 80m, and the poor performance was simply poor conditions.
I've still got it somewhere, so maybe one day, I'll get around to it.
--
Ian