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Discussion Starter · #1 ·


I talked to a custom-build antenna designer yesterday about this unique UHF antenna.


He claims it is much better than a corner reflector yagi,4-bay or 8-bay design antenna,and has a more even(almost flat)gain over the entire band which seems to work best for 8-VSB reception.


I placed an order for one to see how it compares and will post back later with results.


Is anyone using this type of antenna or ever here of it"s design?
 

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Discussion Starter · #2 ·
Well,

The weather finally warmed up a little last Sunday so I lowered the tower and replaced the CM-4228 8-bay with the new U-92 passive wave loop antenna.

It appears to have more gain (higher readings on DTC-100),less ghosting,and better directionality.The F-B ratio is not as good(17db),but in my location,it's a non issue.

I did have a rare opportunity to do some "DT"Dxing Weds. around 1:00am and captured Chicago's WLS (DT-52)@209mi.with it.

If anyone's interested you can check out Ed Hanlon's new website at www.antennaperformance.com/new .He also builds custom designed single channel models for VHF that are humongous!





[This message has been edited by MAX HD (edited 02-09-2001).]
 

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I looked and saw two UHF antennas on that site, but do you know if they have 300 ohm or 75 ohm outputs? When I went back the site was no longer there. Do you know if Ed Hanlon's webpage still works?




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George at WNDU
 

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Just my luck, when I clicked on either UHF-only antenna on this web page it says "The parameter is incorrect." I still cannot determine from the web site whether their outputs are 300 ohm twinlead or 75 ohm coaxial. The site also sells RG-6 coax cable under Accessories but not 300 ohm downlead nor 300-75 ohm matching transformers, which makes me wonder.


Anyway, I would prefer a 75-ohm antenna because I once had a 300-75 ohm matching transformer fail after 12-15 years way up there and I had to wrestle my antenna down to fix, so I switched to an antenna with a 75 ohm connection (so that I wouldn't have to wrestle again when I'm even that much older). But that was for local UHF reception, and with DTV I'm now interested in longer distance, so I'm looking around for a light but rugged UHF antenna with high gain, narrow beamwidth, good forward-to-back ratio, flat response, and 75-ohm output. I plan to erect a UHF antenna for DTV atop a 2nd story chimney-mounted 15/20-ft mast and figure a 75-ohm antenna and a 10/15-ft RG-11 jumper would allow preamp accessibility from the rooftop plus eliminate any chance of "wrestling down" due to a faulty transformer, preamp, or twinlead jumper.


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George at WNDU
 

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George, the Hanlon antennas are all rated at 300 ohms. As for your objections to matching transformers, keep in mind that nothing is forever, and, frankly, after 12-15 years, anything is subject to deterioration (ourselves excluded of course... http://www.avsforum.com/ubb/smile.gif ). I also suspect that current matching transformers - particularly the quite solidly built but reasonably priced one from Channel Master - are probably better designed against weathering effects than the one that failed for you. Whether this actually helps or is just a "feel good" procedure, I don't know, but I've made it a point to wrap from the 300 ohm "pigtail" to a bit beyond the 75 ohm connection in an overlapping spiral with electrical tape to seal against moisture and UV exposure.
 

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Discussion Starter · #7 ·
Hi fellas!


Sorry I haven't been back here sooner but the Webtv has been acting up lately.

Ed Hanlon's new webpage is currently under construction but is working better now.


George,

I think the Winegard CA series 9065 thru 9095 might be the only 75ohm output consumer antennas available-they still use a transformer-but it's built into the boom.As an alternate solution you could use 300ohm twin lead down to a 300ohm in/75ohm out pre-amp.I think I read somewhere that shielded twin lead is available which would be better for UHF.


As far as antennas go,the U-92 seems to be very good,but I don't have to deal with high multi-path at my location either.Also,if you are wanting to reach out past 50-60mi. I can personally recommend the CM-4251 Parascope.Just make sure it's anchored down properly(7-1/2sq.ft. windload including mast)


Ray,

According to the *Ham* experts,if you wrap a connection with electrical tape you should cover it with that liquid plastic type stuff or coax seal from Radio Shack.They claim moisture will seep in no matter how tight you wrap a connection.
 

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You're actually better off to keep it from being air-tight. Most preamps, you notice, are not water tight, just have the cover extend over the base plate. The reason for this is that when the unit heats up during the day, a slight pressure is created inside, and when it cools down at night, the moist damp night air is drawn in to the vacuum that results, and then the water has nowhere to escape. This means that over time, the box has continuous water vapor inside during the day, making things worse. Letting the box "breathe" is a much better approach. Anything less than a hermetic seal will have this effect


Bob Smith
 

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By the nature of the design, virtually ALL TV antennas are going to be 300 ohm impedence. Some may have the transformer/BALUN internalized, but the feed from the actve elements is going to be 300 ohms (or at least, NOT 75 ohms).


Matching transformers/BALUNs are not bad things. Cheap ones are because they are inefficient and lossy...but a decent quality unit does no harm.


Most of the UHF antennas (stacked bay, bowties) are basiclaly either a dipole or loop (or folded loop) dipole, which have characteristic impedence of ~300 ohms.


The combo antennas are generally "Log Periodic Dipole Arrays" or (LPDA). They're identifiable by the rear-to-front taper, and most elements are driven. The UHF section, either in the corner reflector, or fish-skeleton, is basically one or a series of dipoles with reflecting elements. Characteristic impedence is also ~ 300 ohms.


A yagi generally only has one driven element, typically a loop or folded dipole, with a series of directors (front elements, slightly shorter than the driven element) and reflectors (rear elements, usually slightly longer than the driven element). Yagis are typically optimized for one small frequency range. Their characteristic impedence can run from 150 to 300 ohms depending on the design of the driven element.


FWIW


Scott



[This message has been edited by ScottMac (edited 03-29-2001).]
 

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Discussion Starter · #11 ·
JoeR,

I can't remember the specifics of your install/location.but I'm sure Ed could tell you if the U-92 could help in your situation.


He might also tell you more than you want to know on antenna theory and design-he went over my head real fast on this subject!
 

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Discussion Starter · #13 ·
JoeR,


He didn't reply to my e-mail either-so I called him.I've called 3 or 4 times around lunch time and he was there every time I called.
 
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