Antenna Gain - Is it the ultimate measure of a better antenna? - Page 7

FOX TV · 10-08-2009, 12:12 PM

Quote:

Originally Posted by Tim58hsv

Agreed.

What I'd like to see is a re-release of that old, legendary to the point of being almost mythical Radio Shack 15-624 2-bay antenna.

Oak Entertainment Centers and Home Office Furniture, TV Antennas, Audio/Video, Satellite, Cable, DSS was selling them via Antenna Craft up till about a year ago but the RS 15-624 is no longer available from there or anywhere else that I'm aware of.

I own one of those and that dude picks up WWHO from 54 miles away without any drop-outs what so ever.

What I'd really like to see is for some enterprising company to take the same design and turn it into a 4-bay or better yet an 8-bay antenna. Heck, with an 8-bay version of the RS 15-624 I could be sitting here in Ohio watching the Fishing Network out of Puget Sound, Wa.

OK, that last bit was a big exaggeration (mythical) and only for laughs but that is a great UHF antenna and the potential of a 4 or 8-bay version of it would be interesting to say the least. And the RS 15-624 is right around 20% smaller than other 2-bays.

Here's a pic of the one I have planted in my attic.

What are the dimensions of the butterfly elements, the distance between the elements top to bottom, and the side to side distance between the butterfly elements? This would be an easy antenna for me to fabricate if I had all of the dimensions off of an original antenna.

The first thing I see is that the back plane could be made from an old refrigerator or oven rack, or if you can weld, it can be made from round stock or brazing rods and welded together and sprayed with cold galvanizing spray to keep it from rusting, and lexan pieces can be used for the insulators.

It looks like I already have all of the stuff I would need to make one in my garage, if only I had the dimensions... I even have an old stove in my basement I could steal a rack out of to use for the back plane if the spacing is close, but I normally prefer a screen reflector back plane over an open grid or rods.

Even though the picture gives a lot of detail, the measurements could be helpful for anyone who wants to fabricate a copy of this antenna, since it is no longer in production, and I assume the patents ran out a long time ago if it was sold in the 1960's. I would like to build one of these and see if the "LEGEND" is true.

Don_M · 10-08-2009, 01:18 PM

Quote:

Originally Posted by FOX TV

What are the dimensions of the butterfly elements, the distance between the elements top to bottom, and the side to side distance between the butterfly elements? ...

Even though the picture gives a lot of detail, the measurements could be helpful for anyone who wants to fabricate a copy of this antenna, since it is no longer in production, and I assume the patents ran out a long time ago if it was sold in the 1960's. I would like to build one of these and see if the "LEGEND" is true.

You might be interested in Ken Nist's take on this antenna. He lists some, but not all, of its dimensions.

Radio Shack called this antenna the "Golden U" and sold it from when I worked there in the mid-70s until it was discontinued circa 1990. It was probably our biggest-selling antenna since it was so cheap and worked so well. No wonder: Most of Boston's UHF broadcasts at the time were above channel 35, where this design is strongest.

Tim58hsv · 10-08-2009, 05:29 PM

Some of these measurements are approximate due to wear an tear and may be off by an 1/8" give or take.

RS 15-624 dimensions

Reflector screen: 12.5" X 12.5"
Spacing between reflector and dipoles: 2"

Bowtie dimensions
Length: 5 3/4"
Width: (flat bowtie) 1" to 5 1/4"
Width: (folded bowtie) 1" to 3 7/8" (outer tip to outer tip of each bowtie). The center of each bowtie is 1" wide.

Horizontal space between bowties is 1"
Vertical space between bowties is 4 1/2" for the outer edge of bowties and 8 1/4 from center of upper bowtie rivet to the lower bowtie rivets center.

Phasing bars are 9" long with 1 3/4" in between bars.

Good Luck and let us know how it goes.

Tim58hsv · 10-08-2009, 06:12 PM

Quote:

Originally Posted by Don_M

You might be interested in Ken Nist's take on this antenna. He lists some, but not all, of its dimensions.

Radio Shack called this antenna the "Golden U" and sold it from when I worked there in the mid-70s until it was discontinued circa 1990. It was probably our biggest-selling antenna since it was so cheap and worked so well. No wonder: Most of Boston's UHF broadcasts at the time were above channel 35, where this design is strongest.

Thanks for the link, Don.

Ken says it was a Channel Master antenna and not a Antennacraft model which was what I mistakenly thought. Ken also calls it a 15-623. I understand that was it's original ID but was later known as the 15-624. Maybe the difference was (which EscapeVelocity spoke of earlier here) that the 15-623 was the sturdier model and the 15-624 was it's more flimsy cousin. Not sure which one I have but it did come from Radio Shack and seems pretty sturdy.

I've often heard that it's not great on the lower uhf channels and that sounds right. It's great for picking up channel 53 (WWHO rf 46) at 54 miles away but does have trouble with channel 19 (WXIX rf 29) at 42 miles away.

EscapeVelocity · 10-13-2009, 03:29 PM

This as regards the Corner Reflector and Plane Reflector Bowtie antennas from MJ Salvati's TV Antennas and Signal Distribution Systems...page 182.

Quote:

...The deciding factor for front-to-back ratio of uhf antennas is essentially the quality of the reflector. For example the antennas witht he best front-to-back ratios in Ch. 3 were those having wire-mesh or steel grille plane reflectors, or corner reflectors with apex and closely space rods. Corner reflector antennas and corner reflecting yagis missing an apex rod (typical of there type) have sizable backlobesat the highend of the band where the refelctor is no longer sufficiently opaque. Finally, the very-high gain AntennaCraft Hoverman G1483 array has the worst front-to-back ration of the recommended antennas because ti has just a few widely spaced half-wave elements to act as a reflector for the large area of the driven element. While an antenna of this type is excellent for fringe areas (where ghosts rarely are a problem), it is a poor choice for a metropolitan area (where ghosts usually are a problem). The best ghost fighting antennas for uhf frequencies are of the 4 bay bowties or the Corner Reflectors with apex rod reflectors. Both of these style antennas also have good vertical-plane discrimination, so they are better than most others for rejecting ground and aircraft reflections.

Also note that the corner reflector UHF yagis, tighten the beamwidth at the upper frequencies around the resonant frequency of the directors....then gain drops off severely above that resonant director frequency. So the horizontal beamwidth tightens significantly on the upper UHF channels....from say around 45 degrees for a 4 bay to around 30 degrees for a Corner Reflector Yagi. On the lower end of UHF both the 4 bay bowtie and the Corner Reflector Yagi are around 60ish degrees beamwidth.

Hope that makes sense.

EscapeVelocity · 10-13-2009, 07:15 PM

Gavin CR-5 aka Radio Shack 15-1629

From MJ Salvati's TV Antennas and Signal Distribution Systems...

Quote:

Another good corner reflector with useful and unusual characteristics is the Gavin CR-5. This antenna provides 7-10 dBd gain over the entire UHF band from channel 14 to 83, a respectable performance considering its rather small size. Unlike most other antennas, the gain of the CR-5 does not fall off after Channel 70k, but remains near the 10 dB mark. The beamwidth is very consistent across the entire UHF frequency spectrum, something unusal for corner reflectors. This antenna is the lowest priced of the corner reflectors.

Note, mine has a apex reflector rod directly behind the unit, which is different from the pic in Salvatis book. This is good, as it improves F/B ratio at higher UFH frequencies and slightly increases gain.


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