Empirical Antenna Solutions

**elder** · 08-01-2009 11:47 AM

When my DT13 moved to VHF it was a stretch for my LaCrosse antenna. Antenna position for analog ch13 was always a multi-path battle which changed with seasons.

As I was re-pointing the LaCrosse my wife noticed that reception was better when I was touching the coax. I tried various things like grounding the shield at the feed point, but the final empirical solution was to twist a wire around the coax connector and connect the other end to a half folded dipole (J ) made of wire and inserted in the space between the planes of the LaCrosse.

Crazy, maybe but it took me from no bars to one or more on 13 and 33.

**highdefjeff** · 08-21-2009 01:11 PM

This homemade antenna, GrabBit Ears, is really a wonder, a gift of the LORD! It is the empirical solution to receiving ALL UHF and ALL VHF reception, and its performance is truly amazing! GrabBit Ears are a substantial improvement over current store bought designs. GrabBit Ears are the only solution that I have found to work in extreme multi-path cases. If you used to struggle with a lot of ghosting, a.k.a. muti-path interference, then GrabBit Ears will help!

If rabbit ears USED to work, then GrabBit Ears WILL work! Here's how to make them:

GrabBit Ears

**elder** · 09-03-2009 01:00 PM

GrabBit Ears look like my kind of antenna. I am thinking of a computer USB tuner and GrabBit Ears looks like the right antenna for that experiment.

Thanks!

**highdefjeff** · 09-03-2009 06:35 PM

Please let us know how they work for you!

**CowboyDren** · 09-14-2009 04:49 PM

I need to see one of these run through a proper simulation, and for that to happen, there needs to be more data. Wire gauge, for starters, feed spacing, distance from the fractals to the whiskers, etc. You can fumble into a working solution pretty easily, but whether that solution is actually better than a factory-built design is the important question.

**highdefjeff** · 09-14-2009 06:55 PM

Originally Posted by CowboyDren

I need to see one of these run through a proper simulation, and for that to happen, there needs to be more data. Wire gauge, for starters, feed spacing, distance from the fractals to the whiskers, etc. You can fumble into a working solution pretty easily, but whether that solution is actually better than a factory-built design is the important question.

Cool! I'll do what I can.

All of my research is relational to how Grabbit Ears work, versus the variety of rabbit ears and antenna that I have used in the same locations over the years.

They definitely are an improvement over the all rabbit ears I've tried including a 50 db amp RCA digital. All I know for sure is that if rabbit ears used to work, these will work. (And much easier!) They are also really good in extreme multi-path and high interference locations.

I use metal hangers. I don't know the gauge. It doesn't seem to matter which ones, or even if they're mixed types (as long as you sand the painted white ones).

I assume the feed spacing is the distance between the two halves?
1.25" +/- .25"

I haven't been real precise when I make them and they've all performed just as well in the field, and according to the converter box meter I use at home. It has a signal power reading and a signal quality reading.

The distance between the whiskers and the fractals is 3.5" +/- .25". I try to get them near 7"- fractal to fractal - after bending of the connector piece. I bend a loop at the center and each end.

I usually assemble them with small screws, washers, and nuts.

Anything else? Let me know.
Thanks!

**bebop** · 09-15-2009 02:54 PM

Originally Posted by highdefjeff

I use metal hangers. I don't know the gauge. It doesn't seem to matter which ones, or even if they're mixed types (as long as you sand the painted white ones).

I assume the feed spacing is the distance between the two halves?
1.25" +/- .25"

The distance between the whiskers and the fractals is 3.5" +/- .25". I try to get them near 7"- fractal to fractal - after bending of the connector piece. I bend a loop at the center and each end.

I usually assemble them with small screws, washers, and nuts.

I just printed a b&w image from the site and assembled it myself. I used some lengths of copper wire from a left-over job installing a 120 Volt fan, 14 guage I think.

I made a loop on each end and in the middle as well, and didn't even notice at the time if you had done that on your version, so I guess great minds think alike!

Idea: I found that working with copper wire compared to a hangar was much easier to bend into the right shapes & attach with screws/washers. I guess it depends on the type of hangar. The copper was still stiff enough to hold its shape.

**CowboyDren** · 09-15-2009 05:20 PM

Originally Posted by bebop

I found that working with copper wire compared to a hangar was much easier to bend into the right shapes & attach with screws/washers. I guess it depends on the type of hangar. The copper was still stiff enough to hold its shape.

Well, if you'd tried to make a 4-bay bowtie out of 14ga Romex, and made an identical unit from coat hanger wire (closer to 11ga) you'd find that there's a big difference between "works" and "works well." This perfectly illustrates the point that when you're in the UHF spectrum, EVERYTHING affects the driven elements. The downlead gauge, downlead spacing, element gauge, and element spacing are all critical, which is why I'm skeptical about this particular design.

I'm not calling ANYONE a liar, I just need to see more evidence, and I'm fully prepared to be pleasantly suprised...

**bebop** · 09-15-2009 08:49 PM

Originally Posted by CowboyDren

Well, if you'd tried to make a 4-bay bowtie out of 14ga Romex, and made an identical unit from coat hanger wire (closer to 11ga) you'd find that there's a big difference between "works" and "works well." This perfectly illustrates the point that when you're in the UHF spectrum, EVERYTHING affects the driven elements. The downlead gauge, downlead spacing, element gauge, and element spacing are all critical, which is why I'm skeptical about this particular design.

I'm not calling ANYONE a liar, I just need to see more evidence, and I'm fully prepared to be pleasantly suprised...

What do you mean by 'works' and 'works well'? Which is which?

I get all the channels I want with the above solution - so no need to be too skeptical.

It is just as functional as the 4 bowtie version with coathangars for what I need. I don't know what's going on with channel 6 (see my tv fool posting in the other thread here).

Why don't you try making it yourself? It took me like 30-45 minutes.

**CowboyDren** · 09-15-2009 09:07 PM

There's a lot of stuff going on as the electrons dance along the outside of an antenna wire. The Romex version of the 4-bay does not work as well in most situations as the coathanger version, because the wires are too small, and it throws off all of the other electrical properties of the design.

To answer, "Why don't you just try it," designing and simulating it will take longer than fabricating it. The up side to doing the simulation is that once the design is done, you can adjust factors like wire gauge and element spacing in seconds, re-run the simulation, and see if one configuration really outperforms the others. So far, I've seen no simulations at all, which means that there's no empirical data to back up the anecdotal claims of this thread. If I were to just buld one and report, I'd be no different from a guy who says, "I wrapped my niece in aluminum foil, hooked her up to the TV, and she works great!"

I use 2-bay bowties in most situations, which come from a factory [in China] that makes them of heavy aluminum wire (something like 8-gauge), and are designed to be put outdoors. This $15 package also includes a reflector, mounting brackets, and a balun, which makes it pretty unbeatable when you calculate the total value of the package. A decent balun alone is $4, and it looks like there's about $4 worth of wire and fasteners in this design, not to mention the spine/backplane, which leaves about $7 worth of my time to fabricate it. This also assumes that the gain on this antenna is high enough to be useful in non-urban environments. I'm just saying...this antenna is attached to some pretty big claims.