Hi Dave

Assuming you build a 1/4GP with a large enough counterpoise (ie dont
rely on the case of the scanner) I think the figure of merit is around
6-12dB. You may however be better off making a turnstile about 3/8
wavelength over a mesh ground so the thing points roughly where you want
it. That will also help with polarization changes as the baloon rotates.
Maybe a similar antenna on the ballon as well?

Cheers Bob Vk2YQA

wrote:
I'm tracking a high altitude balloon on 2m via a handheld scanner, and
in the past have used the standard rubber-duck antenna that the scanner
came with. However, reception isn't too great at times. What kind of
gain increase could I expect to see if I were to replace the current
rubber-duck antenna with a quarter-wave antenna (designed for 2m and
70cm)?

Thanks in advance for any insight!
Dave