On 7/19/2011 7:26 PM, ray conlon wrote:
On Jul 19, 5:37 pm, Eric wrote:
I have a Rainco ground station antenna I bought from Graham Thompson
about a millennium ago. The construction is 2' of 1" diameter aluminum
tube at the bottom with a 4' whip on top. The coax attaches at the base.

My problem is it's VSWR at 123.3 is 2.5; at 118.1 it's only 1.5. I'm
assuming it's too long, but maybe there are coils or such inside that do
the adjustment. Does anyone know how to tune this antenna?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl

VHF antennas are tuned by adjusting the length of the radiator
element, usually the vertical one, lower freq the longer the element,
the higher the freq the shorter...

I'm hoping there is some way to adjust the Rainco antenna without
cutting off pieces of the whip, which has a nice ball formed on the end.

I used to have the instructions, but I can't find them in my records any
more.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl
- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
you need to know tinyurl.com/yfs7tnz