Charles H. Harpole wrote:
> If the gain on these beam antennas is so small, why is it that my beams
> always give at least double the received signal compared to my dipoles
> (even if the dipoles are a little lower) and more importantly,
> why is it that my beams fry ducks on the horizon where the dipoles can't
> even warm their behinds? -- that is, on xmit.
> de K4VUD
As usual, we all like simple figures ... as in "how much gain does that
Oh, 13 pink db's! Neat. That's a lot better than Forge 90's model that
only has 4.5 green db's! I like pink db's better anyway. Goes with my
What we really need is someone to test these competing antennas who is
not beholden or with a financial interest in whose antenna wins. Use the
same setup to test em all, publish the heights, equipment, procedures,
and results (What!, you say, K7LXC holding us all in suspense until
Then anything in THAT comparison can be compared. Run a test a year
later on a newer model and compare it against the old comparison? Won't
The idea of publishing modeling parameters and letting us work the
models is the best thing come along in a while. But I notice that nobody
has put up the parms on the money makers. No, not the 7 element
whiz-bangs, I mean the tribanders that they sell a zillion of. I wonder
if they are afraid that the heavy investment in their particular design
tradeoffs will be lost, or that the real truth about tribanders all will
become widely known. Really, 3 or 4 db's better than a dipole at the
same height. That's all?
But, (big but) dipole = 8.22 dbi max at 13 degree takeoff up 74' over
EZNEC2 high accuracy ground (stock backyard dipole model comes with
program). Dipole has 8.22 pink db's!!?? But the 20M5ELYA 5 element yagi
model at 74 ft over same ground only shows 15.10 dbi max (also) at 13
degrees takeoff. That's only 6.88 dbd! You mean my rip-snortin' horizon
smokin' 5 el 20 m fire breather only has 6.88 green db's!!?? Yeah,
that's right, but it's got awesome f/b & f/s, and you can *HEAR* stuff
Yep, someone said their super-cannon tribander has 6.5 average dbd.
Under what conditions? I can guarantee that if they publish lengths,
tubing thicknesses, coil and cap values along with their measured Q's,
etc, that they won't get 6.5 dbd in model space. Not if a 5 el yagi gets
I'll tell you something else, though I think most folks understand this
intuitively, model space gives the MAXIMUM results. Real world is ALWAYS
less. Corrosion at joints, grasshoppers in the traps, etc, etc. But you
don't want to trust antenna modeling space?
OK, this is what you ask for:
Get a compendium of amateur interests to buy an abandoned airstrip with
a one mile runway. Spray paint the runway with aluminum paint. Repaint
it every year just before Measurement week. Cover it with one foot of
calibrated dirt. Wet it down. Cover the whole thing in Saran Wrap to
keep it from drying out. Put up a a multi-tethered baloon on one end of
the runway up to about 2500 feet, with one vertical tether. At every
degree intercept point on the vertical tether put a RF field sensing
transponder. Put a tower at the opposite end, 74 feet. Put up a resonant
dipole for the frequency in use, #4 bare wire. Measure all intercepts on
the tether. Rotate the antenna. Measure the 3D pattern. Repeat every 50
khz in the bands claimed for operation. Do the same for all the
submitted antennas. Give folks a mulligan, in case their super-blaster
tribander inexplicably tests awful. If they get it fixed, delete the
earlier results. If not, make em look really bad... Publish the results:
Abandoned Airfield dbd's, maximum at x degree takeoff, year xxxx test,
3D attached, every 50 khz. All measurements published. You don't take
your antenna down to the AAdbd, everyone will see that you are chicken
and noone will buy your antenna until you do.
This year's results expire at next AAdbd test. Found out we don't really
know how to calibrate the dirt, or the water for that matter. Can't ever
compare one year's readings with another. ESPECIALLY, can't compare
AAdbd numbers with private measurements. Can't compare those green db's
with purple or pink db's, ever.
Nah, never happen. Let's just start measuring all these antenna's
(including trap resonant freq's and Q's) we have and put the figures on
the internet, let the modellers go crazy. Especially the tribanders. I
guarantee we'll find out more than they want us to know.
Then, again, it was nice to think that snake-oil remedies really worked.
I like pink db's.
Sorry, guess I'm in a strange mood.
73, y'all. Hope the one you bought smokes 'em.
Guy L. Olinger
Apex, NC, USA
'AV since '74, previously K4VDL, K3FKJ, W2HVA.
(Remember those? Get in touch!)
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