Re: Q: Biquad Antennas

Jeff Liebermann <jeffl@xxxxxxxxxxxxxxxxxxxxxx> hath wroth:

Even the smallest amount of exposed
center conductor will cause an impedance mismatch. Fortunately, it's
not too horribly critical in the connector extension (as evident from
my use of 75 ohm coax) as long as it doesn't radiate. That's where I
think you missed my previous remarks. Using two wires in place of the
coax feed are a problem because the wires will radiate. If I have
time, I'll do an NEC2 model of this wrong way to build a biquad and
demonstrate the problem.

Sigh. Well, the above is wrong. I hate it when that happens.

I built a model of the screwed up biquad antenna construction method
with 4NEC2. I expected to find lousy gain, a weird pattern, and sky
high VSWR. What I got instead is normal gain of about 10.5dBi, a
normal antenna pattern, but a sky high VWSR (6.7:1). See:
http://802.11junk.com/jeffl/antennas/biquad-junk/index.html
If you want to play with the NEC2 model, see:

http://802.11junk.com/jeffl/antennas/biquad-junk/biquad-annotated-02.nec

It's still a lousy way too build a biquad due to the very high VSWR,
but it's not as lousy as I originally predicted.

Grumble, grumble...

--
Jeff Liebermann jeffl@xxxxxxxxxxxxxxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
.