mr1956 wrote in
:

....

What I have been finding out is developing a matching circuit for the
output of the transmitter is not easy, at least for me and at that
frequency. It could be done if I was a cell phone manufacturer. I
think much will be gained by using the 1/4 wave as opposed to the 1/2
wave on the airframe and a yagi or helix antenna on the ground
station.

The easy solution is the one I suggested.


I will post a link to some images of the project when I have time.
Information on the flight can be found at www.lokiresearch.com and
look for information about the Proteus 6 flight at the Balls 17 event,
Black Rock, NV September 2008.

I'll also add some thoughts about how I intend to proceed based on
everyone's great input from this forum. One quick question: Am I
correct in assuming that the ground lead of the rocket mounted antenna
should be as short as possible? i.e., the connection between the
shield of the RG-178 and the metal airframe.

Loss on the coax can be much worse when it is mismatched. I gave you
figures for a 2000 ohm load (representing your end fed half wave antenna).

The loss for 0.3m with a 30 ohm load is 0.5dB, it is 90% efficient. If you
shorten it, you will reduce the loss, but I wouldn't obsess over it. The
problem you have right now is due principally to high standing waves on the
line and unsuitable transmitter load, and you solve much of that using a
quarter wave antenna.

Without a diagram, we are at great risk of misunderstanding. If you cannot
affort the time to invest in making a drawing, you take the risk of
misinterpretation of your words. The connection from the shield to the
metal air frame and presumably metal skin should be short. Regard that the
effective length of the antenna in that case is the distance from the
shield to the tip of the whip.



Owen