To answer an earlier question: yes, I still use multi-element di-poles and
marconis.

Rich B. ...
^ Does the factor of 234 equal a full wave or partial wave
^ like 1/4? 3.3"

It's roughly a quarter wave.

^ sounds shorter than I'm used to seeing.

This is a receive antenna. A receive antenna will work over a much broader
spectrum than a transmit antenna will, so being precise is often wasted
effort.


^ Is there any reason, other than the result being too tall of a
^ device, to use an antenna that is not a full wave?

I tried a full-wave for 800 MHz and it didn't work as well as the
quarter-wave.


^ Would there be any harm in tuning for 2 wave lengths?

Probably not. I receive vertically polarized 800MHz signals very nicely with
a 10 foot horizontal di-pole.


^ I seem to remember that 850 mhz was full wave at 13.8" so
^ a half wave for 425 mhz is 13.8" too, is this right?

Again, you don't need to be that precise for a receive antenna, but the
formula for a quarter wave wire is:

feet=3.28*(meters=VF*75/MHz)

where VF is the velocity factor of the wire, a value usually between 0.6 and
0.95. But I doubt that you could find equipment sensitive enough to measure
the difference between receive antennas with and without the VF applied. For
a quarter-wave Marconi you use one of those wires, for a half-wave di-pole
you use two.

What you are referring to above is the use of harmonics in designing an
antenna. If one or more of the bands you are receiving are on a harmonic of
another band then you can eliminate those shorter wires in your multi-element
di-pole. A harmonic is an integer multiple of the frequency. For 106.25:

1 106.25
2 212.5
3 318.75
4 425
8 850

Theoretically you should receive best around each of those frequencies with
an antenna cut for about 106.25MHz. But I have not had to be that precise in
order to receive well. I suspect it would be like measuring sugar into a
cookie mix by counting the individual grains of sugar when you could probably
be off by a half-teaspoon and no one would notice the difference.

Frank