[TowerTalk] rotating delta loop

[Jim Lux]

On 8/30/13 7:18 AM, Gene Fuller wrote:
> Yes. That's why ARRL will not print advertiers'  "claims to gain".
>
>
sure they will, if you can back it up with antenna range measurements or 
a credible simulation.  Oddly, nobody seems to have that.

I think antenna mfrs are a in a no-win situation there..  If I 
advertised a dipole and published the gain as 1 dBi (-1 dBd) (which is 
probably about what you'd get with a typical dipole, as implemented, 
accounting for copper losses, matching losses, etc), nobody would buy 
it.  They'd all go "I know a dipole has 2.15 dBi gain, so that W6RMK 
dipole is a pile of junk".  I'd have 50 reviews on eHam, half of which 
would be 1s and 2s from people who hadn't even bought the antenna or 
even seen it, but comparing it against the hypothetical gain figures on 
the shipping carton of their wonder antenna.

"Our special matching network provides up to 12dBd gain on any amateur 
band with no tuning when installed between two trees in your backyard"

(and when you ask the company about that claim they go.. Oh, it was a 
typo, it should have been -12 dBd, but we already had all the boxes 
printed before we caught it)

Then there's the "spec sheet prepared by someone who doesn't know what 
they're doing".. A radio shack Vertical with a sort of interesting 
tuning network ( couple of threaded rings that moved up and down. 
essentially a tuned load.).  They had the return loss and gain 
backwards.  No, it's not 15 dB gain and 1 dB return loss (at least if 
properly adjusted)


Nope.. the best you can do is go buy the report from someone who 
actually tested them.

I've been trying to convince the radio club at JPL that we should, as a 
public service, do an HF antenna gain measurement festival on the Mesa 
antenna range. We've got calibrated gear, multiple transmitter sites at 
1200 feet, 3000 feet, and more, with big valleys in between.

What we don't have is (and this is the hard part, as the TriBand antenna 
report authors will confirm)
1) A pile of antennas to test
2) A bunch of labor to run those antennas up the tower and back down. We 
have a bucket truck to make that easier, but it's still a lot of work.

And in practice, you could probably get the antennas loaned, but they 
come dismantled, so you need an ever bigger pile of labor to assemble 
them for the test and dismantle them afterwards to ship back.