I threw together a twinlead folded dipole for 2m (like those FM broadcast band ribbon antennas, except smaller) and used a TV balun to convert it to 50 ohm coax to the HT.
This antenna has a much wider bandwidth than a Jpole, and is a little smaller too. And a
decent SWR. Good for packing for a business trip where there are repeaters around. The antenna
is 97cm long, but cut the twinlead a little longer (like a cm longer) so you can short the pair
of conductors in the twinlead at the end
together (and likewise the other end). At the midpoint cut only one side of the twinlead. Strip a little length the wire, to
get a gap equal to the 300 ohm cable on the TV balun. Trim off any lugs off the balun, and solder
these balun leads to the midpoint wires you just prepared. TV balun? Yes, it's still a 4:1 balun,
was 300 to 75Ω, here it now is 200 to 50Ω, to match some RG58 coax to feed your 2m HT. Use
an F to BNC adaptor. These baluns can handle around 10 watts no problem. Another reason for the
balun is to avoid common mode RF current, in which the RF current on the outside of the coax
affects the antenna pattern.Using a Rigexpert antenna analyzer, I trimmed the ends to get the antenna resonant in the 2m band. Be sure to have the feedline perpendicular to the antenna for a minimum of ¼ wavelength and more is better (I used some string to hang this antenna up away from stuff) to get valid measurements and good performance. Or use suction cup hooks and string on the glass of the sliding balcony door to hold the antenna and feedline. With an HT, it hits my test repeater at 146.955 well.
A calculator that shows the final finished dimensions of the antenna (after joining the twinlead
conductors together at each end). If you don't know for sure the velocity factor of the
twinlead you have, and If you have an antenna analyser
(If the analyser has a velocity factor measurement, use that), or use 1.0 for
the velocity factor, then see what frequency the resulting antenna has the lowest SWR at.
Should be lower than
what you really want (probably around 120MHz instead of 146MHz), but you can identify the velocity factor of your twinlead. Divide
the frequency you got the lowest SWR at by the desired frequency. Then with this newly found
velocity factor (should be between at lowest 0.6 and highest 0.9)
rerun the calculation. But only trim the antenna by 3/4th of the excess length (you don't want to
overshoot and end up too short!) and test it again, and trim again a little bit. Iterate until you
get it spot on. The caluclator: