On Sat, 02 Oct 2004 18:27:14 -0400, pete365 wrote:

Just installed a Hustler mobile antenna on my van and while tuning it,
it got so hot that the coil started to melt ( the cover) . What would
cause this?

Hi Pete,

A poor, resistive connection (resistance in general).

Antenna was mounted on a trailer hitch mount, 42" fold-over
mast, and with the 40 meter coil installed.

Which would lead to a radiation resistance (for a one fortieth
wavelength antenna) of 2 Ohms.

At the time, the SWR was
less than 1.5 to 1,

Which could be explained (by other than tuning) to have been achieved
by inserting a resistance of 30 or 40 Ohms.

and running less than 100 watts. Is it normal for
these coils to run hot,

Even 50W into 30 or 40 Ohms gets things toasty.

even when matched?.

A dummy load matches just as effectively and warmly.

The 20 meter coil

Which would lead to a radiation resistance (for a one twentieth
wavelength antenna) of 8 Ohms.

started to
get hot too.

And probably a lower SWR too.

If this is normal, how much power am I loosing in the coil.

Ah! The $64000 question. Probably all of it. The better question is
where is all the resistance coming from that makes this heat?

Antenna seems to work well, everything else seems ok. Any Thoughts?
Pete N1AGV

Antennas working pretty well and getting hot simultaneously should
give pause to re-examining the concept of "working pretty well" (by
what criteria, SWR?).

Follow the heat (literally). Wait for things to cool down and then
key-down for a shorter period and try to narrow in on that part that
warms first. Try one of those fish tank thermometers that is a sticky
press on type using liquid crystal phase shifting displays (AKA mood
ring technology). The heat is where the resistance is (and wire does
not often qualify except at a poor connection point).

73's
Richard Clark, KB7QHC