Yes the top hat would help out on 2 and 4 mhz frequencies. Problem is
where to put it where it is not in the way.

A loading coil on the stay would also help out but it would work even
better if it was up high nearer to the top of the stay.
Problem is that usually only one antenna is available for all bands on
a boat. At the higher frequencies that loading coil would act as a
choke and effectively disconnect the upper portion of the antenna.
Which may not be all that bad if there is sufficient length below the
coil for the higher frequencies.

The other problem that you may run into is that the auto tuner may not
like the impedance it sees. Most auto tuners do not like to see a
resonant antenna near 50 ohms. But on 2 mhz it would probably help a
lot.

Regards
Gary


On Thu, 29 Jan 2004 12:20:07 -0500, "Vito" wrote:

Tests of mobile antennae in the Amateur Radio 75 meter band (4MHz) yielded
the following results:

* Well-designed Bugcatcher or Screwdriver with top hat 0 dB reference
* Bugcatcher or Screwdriver with no top hat -3 dB
* Hustler or Outbacker -9 dB
* Hamstick -12 dB
* Whip with autotuner -14 dB

This suggests that the common insulated-backstay-with-autotuner used on
sailboats could be improved by adding a capacitive top hat immediately below
the upper insulator and/or a tapped coil in parallel (ie around) the lower
insulator to tune whatever length of antenna one can physically accomodate
to resonate on or near the Marine frequencies of interest, such as 2182 MHz.
Has anyone any experience doing so?