Jeff Liebermann wrote:


And what do you do when they don't work? Cut-n-try is a rather
expensive way to build something that works. Given infinite time and
materials, it will eventually result in a functional antenna. You
could probably do that at HF frequencies where construction errors are
about equal to calculation errors. However, don't try it at microwave
frequencies. While it's possible to cut-n-try various microwave
structures, it's messy, difficult, prone to error, and not very
effective. The techniques used to build a coat hanger ground plane at
VHF just are not going to work at X-band.


Well, ya', an adjustable whip(s) is good, especially with the cost of
copper and the pain in "resoldering your prunings." LOL

The only way to get it close to right the first time is to calculate
first, calculate again, have someone check the calculations, drink
some wine, and check your calcs again. Then build it.


You have wine? Why didn't you say so, that changes everything:

1) Put antennas away.

2) Have a glass of wine and contemplate the design/construction.

3) Repeat 2) until ALL wine is gone.

4) Take a nap.

5) Now get the antenna(s) back out and begin work ... LOL

A few times, I have just grabbed up some tubing/wire a variable
condenser or two, and "eyeballed" the construction--past experience
provided "ballpark" figures/placements/wiring, testing, trimming and
adjusting got me the final result ...

Yep. That will work at HF because the lower frequencies allow for
much larger construction errors. Your antenna lengths could be off
many cm and still work. Your xmitter can also tolerate a substantial
VSWR and still be considered functional and useful. You match box
could be grossly inefficient trying to match your constructed antenna,
and work well enough. Now, try that at microwave frequencies, where
every milliwatt is precious, where VSWR is too crude and reflection
coefficient comes close to describing the ultimate goal of a perfect
match, and where cm errors are disastrous. Some broadband antennas
(helix and horn) are very forgiving and can be build fairly crudely.
Others (stripline, phased arrays, cavity backed antennas, etc) have a
higher Q and require more accuracy than the eyeball can provide.


Or, to summarize, the more complex the antenna, the more meters you are
going to need ... LOL

Mainly, I point this out so as not to "obsfucate" that layman, or
discourage him ... the men who first started/awakened my interest in
such things never gave any indication, to me, they had an understanding
of calculus, only basic-math/algebra, and of course, geometry!

Same here. My original mentors were operators first and technical
types last. However, I saw the light (and the distinction) between
amateur and professional when I went to college and saw that radio
things were easier and better if they were calculated (and understood)
first. I have several humorous examples of hams operating in a
professional environment (engineering lab at a radio manufactory) and
failing miserably using cut-n-try methods popularized by ham radio.


Indeed, mine drank beer too! grin

Indeed, at least one passed away without ever expressing any real
interest in learning it!

There are suspicions that math may hasten one's demise. Perhaps he
tried to do a calculation before he died?


If away from my laptop, the programmable calculator is always in my
pocket! (I mean, my gawd man, I have space invaders on it!) straight-face

...

Also, I assembled a small list of tech patents that appear to be
bogus. I was going to post the list on the web but my attorney
advised against it. Even holders of bogus patents can sue for
damages. Oh well.


.... some patents are NOT what they used to be ... but then, there has
always been some suspicion about the politics involved, not to mention
courts ...

Regards,
JS