Antennas

It's either isotropic, or it's a dipole. It can't be both. Isotropic radiators are imaginary point source radiators.

The Amazing Seismo

"Robert Smith Consulting - Bob Smith" wrote in message news: snipped-for-privacy@4ax.com...

Oh-oh. You've found where I've been hiding.

As usual, I beg to differ. Many clueless companies simply subtract

2.15dB from the isotropic gain rating to yield dB over a dipole.

Everyone lies, but that's ok because nobody listens.

Sorta. I've had the ratings on one of my ancient designs tweaked by marketing. The short version is that I wanted to keep the return loss under 15dB (about 1.5:1 vswr) and the built in filter group delay constant within about +/- 10nsec over the 2.4GHz ISM band. That's not easy to do with a high gain antenna. The result was that I had to compromise on the gain specs. Although it did everything the customer wanted, the lousy gain spec made it look like an inferior antenna. So when marketing decided that there was a potential market, they just changed the gain spec to be the same as a similar size competitors antenna.

You're comparing apples and oranges. Equinox make reflectors for use with Motorola Canopy products. None of their antennas have feeds or pigtails. The 29dBi gain is based on the reflector itself, without the usual -3dB reflection loss, illumination losses, VSWR, etc. They finally got smart and derated their antennas to the "common" 24dBi gain spec used by similar sized antennas.

PacWireless doesn't make such a Canopy reflector. So my guess(tm) is that you were testing: includes the feed and pigtail.

The problem with the Equinox reflector has less to do with the gain of the dish portion than with the gross inefficiency of the Canopy radio illuminating the dish. My guess(tm) is that there is considerable overspray from the Canopy internal antenna, and that's why your gain and performance stunk.

Yep. About what I would expect with an inefficient dish feed.

I've used lots of PacWireless dishes. They work. However, I prefer the more expensive cast aluminium dishes instead of the painted steel. Incidentally, remind me to show you my do it thyself corner reflector made from welded steel storage shelves (Creative Cubes). Same material as PacWireless but MUCH cheaper.

I don't think it will make much difference. I can lie as well in dBd as I can in dBi. However, I'm a believer in testing to verify the computer calculations, not the other way around. I grind the numbers on the NEC design program, and then verify that my construction technique matches the calcs. If not, I find whatever I screwed up and fix it. Back in the dark ages B.C. (before computers), my numerical guesswork was far worse than today, when I have a decent modeling program to play with.

Well, yeah. That happens with "distributors and resellers" that don't have testing facilities. In this case, it appears that Equinox did run a field test on their 24dBi reflector:

looks like real data to me.

Masochist. Towers are for suicidal maniacs, indestructible kids, and lynchings. My tower climbing days are over. With all the safety paraphernalia required these days, I just let the "certified" and insured tower climber do the dirty work.

AE6KS (Extra Class or no class whatsoever).

That reminds me. Time to haul off all the old QST magazines.

Ok, you beat me. Novice in about 1960 at age 12.

Hi, Jeff,

I've been reading your info for about a year, this is a pretty good group. I stand corrected on the db difference, it was only 3dB, 3 db is still twice the gain,,,,,

The pac wireless antenna that I used is below-it's the 26dbi model

As to the antenna you referenced in the answer for the Equinox antenna

this isn't the antenna.

The antenna they were selling isn't for sale any longer (or at least it isn't on their website). A representative picture is on the website below. It was rated at 29dbi

I guess Equinox saw the writting on the wall and got out of the antenna business and is just making Motorola antennas (or maybe just distributing motorola antennas)

I guess you know the story of Equinox antennas,, they use to be the sole distributor for PacWireless. Then they got greedy and started doing their own aluminum made in canada. Looks like they did thereselves in,,, only Motorola antennas now, the rest were hyped junk.

Well anyhow,,They were both grid parabolics with feedhorn, coax and connectors installed. The Equinox antenna had a mounting bracket that didn't look like it would ever hold up in any kind of wind, let alone being mounted at 2200' on the Sutter Buttes. But it was a sort of a dream to line up, christ the beamwidth must have been 20-30 degrees because it didn't really care where you pointed it, just sorta toward the other point. hehe.

Anyway, the PacWireless antennas worked and they have been on the Buttes for almost 1 year with 15-20 mb throughput 24/7/365 without a bobble.

The next project is 26miles with trango's new 5.2/5.8 setup using a

24" dish on the Buttes and a 36" dish at 26 miles. I'm using the smaller dish on the buttes because of the wind (50-70 mph) is normal in the winter. It flattens you against Rohn 45,,,

We can't get a ground mount point for the Buttes Dish so we are going with a tower mount and Radome,,, but 4degree beamwidths at 26 miles is going to be the challenge..

Back to you,,

Bob Smith Robert Smith Consulting snipped-for-privacy@na6t.com Wisp Consulting and Installation (I love towers) ARS NA6T (extra Class) ARRL Life Member

1st licensed in 1958

As in "lies, damn lies, and tech specs"?

I'll try not to ruin it.

That's enough when comparing antennas side by side. However, it's a small amount considering the age of my test equipment.

Oh, that thing. There were some nasty remarks about it in another mailing list. I forgot the details.

Actually, I didn't know the story. Pacific Wireless used to be local, in Aptos CA. When they moved out, I lost track of what was happening to them. Thanks for the info on Equinox.

Oh-oh. Such wide beamwidth is usually a sign of major sidelobes, main lobe anomalies, reflector distortion, or the usual crappy feed "horn". I don't have time to test all my antennas, but I do have a method to my madness. We have a local CW beacon on 2.4 and 5.6GHz on a mountain top that's about 5 miles away from my house. It's line of sight and I know it's EIRP quite accurately. I have a joke of a rotator on my roof and spin the antenna to see what it will do. I've gotten more than a few suprises from commerical antennas.

I'm not at all thrilled with the mounting on the older PMANT PacWireless dishes, but I hear the new versions are much better. For some unknown reason, all my dishes tend to end up on the end of a unistrut arm, where adjustments are impossible. This was not planned but is the result of the site owner demanding that no antennas be mounted directly on his towers. Argh.

Don't tell me you climb towers in a 50-70mph wind. I can barely handle a light breeze. I dunno about 26 miles at 5.6Ghz. Are you gonna use a solid 24" dish inside a radome? That will work, but watch your wind load from behind the dish.

I've never tried anything that far and have no clue if it will work. Incidentally, one trick I use is to duct tape a cheap plastic telescope to the dish and do a boresight alignment test. None of these narrow beamwidth dishes are even close to boresight center axis. When I install the antenna, I do the optical aiming trick first, and then remove the telescope. It saves considerable tinkering. Incidentally, 4 degrees is no big deal as the average DBS dish and ground station must deal with a 3 degree satellite spacing.

Good luck.

: the air is much thicker here from all the bull sh*t we are given so it takes : more power.

Heh, our air isn't clear either.

: Is 100mw really the max for a PTP in Poland?

No one cares if it's point-to-point or point-to-multipoint.

100mW of EIRP. Nothing more. Measured 10 meters from the antenna (don't even ask why ;>)

: Here it is 1000mw into a 6 dbi antenna and for every 3dbi over the initial : 6dbi you : have to reduce the intenional radiator by 1 db (for 2.4ghz)

Here you mean in the US? Isn't it 4W for PtP?

Anyway, USA is a little bigger than Poland, so you need more power to push through the sky ;-)

Oh, 2.4 GHz is dead here presently..

m.

I found out the little trick with the cheeeeap telescope from the wireless list about a year ago, it works with dishes and parabolics..

I keep it under my hat,, you know "black magic",,

about Pac Wireless, they are in Utah now, building , designing and shipping from one location, courtesy of the State of California TAXES..

Well, were straying way off the original topic, so

next subject,,,,,

good talking to you jeff, I'll call you on the telephone this week and we can catch up of things,,

see ya in the funnies,

Bob