A question about Quadrafiliar Helix antennas
 

Over the years I have built several Quadrafiliar antennas for 137.5 Mhz
polar orbiting weather satellite photos. I have the dimensions pretty
well refined to get horizon to horizon reception but they have all been
copper tube on a PVC pipe. I have some 3/8" stainless tube left from a
watermaker project and thought I might use it and a piece of Max-Gain
fiberglass tube to make one that would look nicer and hold up at sea. I
have a couple of questions about changing over to stainless but don't
know where to ask them.

The resistance of the stainless tube is the thing that worries me. The
balun design I came up with balances 1/2" copper tube to 50 ohms almost
perfectly but changing the diameter to 3/8" stainless is going to change
the impedance. I just don't know how much and in which direction.

There is plenty of info on the web about QHF but I can't seem to find a
newsgroup or forum to ask questions. Anyone else here dabble in
quadrafiliars?


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

That is what I am worried about. Stainless has about 15% the
conductivity of copper but I have seen outrageously expensive stainless
QFH antennas on some big outrageously expensive yachts that work great.

ON5MJ wrote:

Hi Glenn,

I have always heard that stailess steel is a bad conductor of heat and
electricity. So ...

73 de Jacques - ON5MJ



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Glenn Ashmore" wrote in message
news:G8Vsb.1221$0K4.376@lakeread04...
That is what I am worried about. Stainless has about 15% the
conductivity of copper but I have seen outrageously expensive stainless
QFH antennas on some big outrageously expensive yachts that work great.

Long term, they might do better than copper, which wouldn't last as long.

That is what I am worried about. Stainless has about 15% the
conductivity of copper but I have seen outrageously expensive stainless
QFH antennas on some big outrageously expensive yachts that work great.

Long term, they might do better than copper, which wouldn't last as long.

.................................................. ..............

An antenna has both radiation and loss resistance.

Suppose a VHF copper dipole is 99% efficient.

If it is replaced with stainless steel which has 10 times the resistance
loss then the efficiency will fall to 90%.

Nobody will be able to detect any difference except that in 5 years time in
a marine environment the stainless steel dipole will still be working.

An understanding of ohms law is useful.