Is it feasible, for any given HT, to tune/mark telescopic antennas for optimal utility?
In practice, I haven't found that it makes much difference.
My first observation is that you don't want to be using a
telescoping whip in motion if you can help it. When I
worked for the Forest Service in Alaska they gave me
a radio with a telescoping whip, and it took me about a
day to break walking through the bush. Turns out the
standard procedure was to listen with the whip down
(where it was protected inside the case), then stop and
pull it up when someone called you.
As far as finding the optimum length, you can do that
by setting the radio in a fixed location and measuring
the relative field strength at a distance as the length of
the antenna is changed. But I haven't found any significant
difference between, say, an 18" whip and a 20" whip for
operation on 2m. A full quarter wave antenna has a
reasonable wide SWR bandwidth, and most HTs aren't
too fussy anyway, given the range of antennas that they
get used with.
If you try to mark it, you need to make sure that you
pull the sections out in the same sequence if it isn't
fully extended. Probably something like "3 1/2 sections
extended" is close enough. If you need more accuracy,
then attach a piece of string to the antenna jack and
mark that as a guide to the required length. (If you use
a quarter wave radial, just pull out the antenna until it
is the same length as the radial.)
My best results so far have been with flexible quarter
wave whips, but I don't use 440 much while in the field.
For dual-band operation, one of the short 2m quarter
wave whips that works as 5/8 wave on 440 is probably
the best approach, although I'd also consider just using
my 2m antenna on 440 for simplicity if I didn't need
high gain.
Generally, you don't want to go longer than 1/2 wave
on an HT, not just due to stress on the antenna connector,
but because a
5/8 wave whip only gives the expected
gain when mounted directly over an infinite flat ground
plane, and that isn't the case with an HT.
For serious use while in motion, the best antenna I've
used is a 1/2 wave whip (the radiator from a CB mobile
antenna) mounted on the top of my packframe, with
the HT in a pocket of the pack and a speaker mic
clipped on my chest. That maintained communications
in some pretty tough areas when I was out with Search
and Rescue (although knowing how to pick a good spot
to transmit from also helped a lot). I'm now in the
process of trying to build a replacement, as I gave the
original one away years ago, and I need to design a
different mount for my current packframe.
On the other hand, over the last 25 years I've spent
more time carrying a 2m yagi with me when running
through the forest, but that is because I use it for DF.
They are generally built using tape measure for the
elements, so the elements snap back into place after
bashing through the bushes.
Counterpoise wires are said to enhance utility.
I'm a big believer in using a counterpoise on an HT.
I ran a study years ago where we measured the signal
strength with multiple antennas, both with and without
a counterpoise, and on average the counterpoise added
9 dB to the received signal strength for antennas up to
1/4 wavelength tall. Not bad for a cheap little piece of
wire!
Now, there were some unexplained quirks in the data,
and other measurements haven't always given the same
results, but in my experience it makes a significant
improvement on 2m, especially as radios have gotten
smaller over the years.
Of course, you could make a homebrew version of
Radio Shack's "Exclusive Range-Boost Circuitry" that
they advertised for their CB handhelds, and just provide
a piece of metal where you grip the case to turn your
body into a radial.
No need for a weight on the end. #22 or smaller
insulated hookup wire works quite well, and if it is
solid (like #30 wire-wrap wire) then it should be
stiff enough that you can shape it to hand down, but
I haven't had problems with stranded wire that had
a bit of a curl to it. I just twist a loop in the end to
fit under the antenna connector and slip it over the
antenna jack before installing the antenna.