• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

FM antenna array picture.

Hey Radio, the booster was 1500 watts split in to 2 five element beams mounted at 45 degrees and pointed at downtown. Not sure how legal this was but they're trying to achieve a signal that was as close to circular polarization as they could get. The new booster uses a similar lash up but with 3 beams and no way to tell how much power will legitimately be in each.

As for the original topic, I'm guessing the Virgin Islands or Puerto Rico. The antenna on the left is a multi-element TV antenna, the right a single bay FM.
 
Even though 45 degrees looks like vertical it is "slant" CP.

Wondered about the TV aspect but this is a radio board. With the small cable must be VHF and very low power?
 
I once read about a 7 bay circularly polarized antenna of odd design. Any IEEE members out there search their website for a "fan vee" and see if any pictures or descriptions match this thing. Just a wild guess.........
 
engine ear said:
...the booster was 1500 watts split in to 2 five element beams mounted at 45 degrees and pointed at downtown. Not sure how legal this was but they're trying to achieve a signal that was as close to circular polarization as they could get.
Click to expand...

Just to note that true circular polarization has free-space fields that are constant at all rotation angles. This condition is impossible for an antenna/array comprised of radiators all lying in a single physical plane such as the typical "beam," Yagi or log-periodic.

A linear radiator rotated 45 degrees from the horizontal plane produces a free-space field that is equal in the horizontal and vertical planes, but it will be zero at a rotation angle 90 degrees from that of the linear radiator. Even with equal fields in the H and V planes, the c-pol axial ratio of such a radiation source will be infinite (in theory).
 
Mr Fry tell your friends at the FCC. With all the Reserved band FM stations Staff floated no more vertical only and antenna manufacturers and antenna modelers then began using slant as Circular.

Rule changes do not allow vertical only polarity and car radios would die if a station broadcast Horizontal.

This was followed by a presentation by Staff that resulted in a white paper that concluded something to the effect: it really doesn't matter how the signal is sent as it is received at various angles.

I was amazed. I am with several vertical only stations and have yet to see the true world result of slant broadcasting.
 
I really wished the FCC would lighten up on stuff like this (no vertical only unless the channel 6 thing) and start actually getting people for causing harmful interference. The FCC sends out people these days that barely know anything technical with a clipboard and camera yet they worry about polarization. Honestly, if a station doesn't care to waste power horizonially, who cares?
 
Yes, but take a close look at car radio antennas nowadays. My 2007 Focus uses a whip raked back at a 45 degree angle. My new Malibu has a window antenna--in a slanted back window.

Considerable advantage to circular polarization.
 
Stations can still license horizontal only if they desire, just not vertical only unless it is a channel 6 problem. I worked for a station that was horizontal only up until an antenna replacement a couple of years ago. HUGE difference going CP. It can be done, but why anyone would want to, is beyond me.

Back to the picture at the start of this thread... What the hell kind of antenna is that on the left?!? It looks like a high school project or something a not very talented ham would attempt to pass off as an antenna. The bays aren't even lined up vertically, and I can't for the life of me figure out where the feed points are on it. Looks like a bunch of coat hangers arranged to be an FM antenna. Yikes. This has to be one of the worst installations I've even seen (and I've seen some bad ones).
 
RadeoEngineer said:
WMC-FM in Memphis is licensed for (with beam tilt) 300 kW H and 100 kW V.
Click to expand...

How on earth would you go about setting that up?! Two different antennas, but how to get such a huge power difference?
 
Lazy J said:
RadeoEngineer said:
WMC-FM in Memphis is licensed for (with beam tilt) 300 kW H and 100 kW V.
Click to expand...

How on earth would you go about setting that up?! Two different antennas, but how to get such a huge power difference?
Click to expand...
I've seen a couple of ERI's old style 1105 type antennas with custom H/V gain ratios; the newer rototillers might be even easier to tweek this way by changing the angle of the elements.
 
What scares me.whats all those loose ends of wire going nowhere.especailly the one at the bottom of the photo.
Click to expand...

Don't be afraid of them. They are just there to facilitate the "bonus" frequencies from the tower.
 
Jack Beanstalk's tower service is climbing the tower this afternoon and we've put a helmet camera on him.... Hopefully: "film at eleven"
 
It's a pirate, homebrew antenna.

Just my guess.

That old antenna on the right looks rather sad missing the rest of its bays.
 
Forget all that crap on the side of the tower, now we get a slightly closer look at that platform on the top and tidbits of antennae sticking out on each side of it. Dont you think that is more interesting? I mean, that appears to be a BIG platform! How tall is this tower? How about a distant pix of the whole tower and site??
 
We got these pictures during last week's climb and now we're trying to find our best course of repair/replacement. This array was built by a Dallas Texas man who's last name is Shoemaker. I don't know any more about him|?|

Anyway, one picture shows a bay that's been bent and I drew some lines showing where the bend should be.

http://dl.dropbox.com/u/15067584/113_0179r.jpg

We think it's repairable and/or another could be built but we will need to stay on the air.

So now we're confused about how to keep the candle lit without causing more damage.

The picture of the power divider leads me to think it's a simple 8-way connector.... ???

http://dl.dropbox.com/u/15067584/113_0174r.jpg

How would you proceed?
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom