Eric H wrote:

> I used to be an Amateur Radio operator, so the problem is SWR.

  I'm a bit worried about you when you make that association.  If you'd
said a CB'er, it would not surprise me however!

> An SWR of 1:1 means that you have no signal returning to the
> transmitter.

  So far, so good.

>  A 3:1 SWR is very bad, meaning you are getting more power returning
> to the transmitter than is going out.

  Wrong on both counts, I'm afraid!  3:1 SWR is half scale on the meter
and indicates therefore one quarter reflected power.  This is a loss of
1.5dB; significant but not fatal unless you are pushing your output
devices to their power limits, which is hardly the case with the devices
in question.  It *does* however imply a corresponding 1.5dB loss in
receiving too.

>  You can purchase a SWR meter at HAM stores.

  Mmm, you can, but what are you going to do with it?  The common ones
have two little problems here, the power is too low to measure
accurately, and the instrument is only calibrated to just over 100MHz,
maybe 150MHz.  You need a purpose-built one for 420MHz, and a special
version for low power.  Not only that, but the conventional instrument
is as big as the antenna in question, so it is a little hard to figure
out which part is being tuned.

  Which leads to an important consideration about antennae on these
mini-systems.  A quarter-wave antenna needs a counterpoise or
ground-plane.  If the (metal part of the) device is smaller than a
quarter-wavelength, you have no groundplane and you can't tune the
antenna.  It is possible to use a half-wavelength antenna instead, but
this has a very high impedance at the end feed-point, so a different
transmitter/ receiver configuration is needed.

  A simpler approach is to add one or more quarter-wave ground radials
to the outside of the coax or transmitter enclosure at the point of
connection to the base of the antenna, and pointing either at right
angles to, or away from the antenna element.  Note that the antenna has
directional characteristics.

> It may be a good idea to get the maximum signal out the antenna.

  Indeed!

  Cheers,
        Paul B.