EV, I always use on rabbit ear suggestions to go 15 inches per side and start with them in a Vee equally spaced then if that doesn't work, lay them out flat.

My reasoning is 15 inches is close to channel 10 as half a dipole.

And the Vee thing is because polarization tends to twist coming in a structure, so at a Vee it will capture any twist in the polarization coming in the house.

What do you think of my idea?

Originally Posted by EscapeVelocity

Here is KYES Rabbit Ears page with lengths and tips....for the OP.

That's good advice, except that the forward V shortens the length of the dipole in relation to the wave. I would go longer with that suggestion.

It also depends on the Channels being attempted. And the shorter wavelengths work much better on a "too long" dipole than the longer wavelengths on the "too short" dipole.

Its better to err long than short....especially if you have a spread on VHF High. But then again this is a generalization....as the strength of the different local VHF High signals also come into play.

Does that make any sense?

I used to use them as inverted vees, which is the same thing but inverted with the apex highest and not at the base. If you built a dipole that was turned, then hung it as an inverted vee, you had to prune it shorter. I presume something in the interaction of the two elements.

So incident to an incoming wave the tips are closer together than in a dipole or straight out configuration, I agree. But I have always thought of each half of a dipole as somewhat (not totally) independent antenna. Hence the reason you shorten an inverted vee due to it's interaction with the other half of the dipole. I also found back in the day an inverted L antenna worked great on 40 meters due to the twist of the ionosphere at the lower HF frequencies. The inverted L is just one dipole horizontal and one dipole vertical, like a vee turned another 45 degrees. I also had to prune this dipole type antenna below the .95 wavelength formula compared to free space. (Aside I found the inverted L out performed my dipole and inverted vee on 40 meters but has little to do with TV reception.)

So based on that, I would guess one might have to make the whips on rabbit ears slightly shorter buy an inch or so in a Vee configuration.

That said it's all a little of a guessing game for another factor. If you look at various rabbit ears, the distance between the feed ends of each half are not the same distance apart. This will cause them to have difference impedance depending on the distance. Or make them longer than they appear if there is a wire inside each side feeding the twin lead out or an internal balun.

From my reading making the dipole a little longer than needed is less damaging than shorter, as the reactance or susceptance changes more gradually (less slope) on the long side of resonance than on the short side.

Then throw in the effect an inch won't make much coupling difference into a receiver the way it effects a transmitter. I am not sure it makes much difference. Note Kyes never goes over 16 inches per side on Channel 7. I pretty sure his calculations are based roughly using .95 of the wavelength in free space for a standard wire dipole.

I would say if Kyes is correct and I do agree with his numbers, then if I am right and say a Vee needs to be shorter, but an element too long is better than one too short I would conclude to just use Kyes charts for Vee shape of a rabbit ears.

After all there is not guarantee the reactance is zero with the elements set to Kyes lengths for ever set of rabbit ears anyway.

It's all a good scientific guess how long to make them. I don't think an inch or so will make much difference hence why my canned answer is make each side 15 inches, which is easy to remember and puts it on Ch9 about the middle of the band.

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Now one tip I have yet to see on rabbit ears that just hit me as well. Broadbanding the rabbit ears. A thicker diameter wire used as a dipole makes it broader in it's bandwidth range.

So when someone measures the 15 inches, they should use the thicker telescoping parts to extend and keep the thinnest tips parts retracted. In other words extend the rabbit ear from the bottom and not pull out the top.

This will also make them less likely to break if hit or if they fall, since the thicker part is stronger and exposed.

Originally Posted by EscapeVelocity

If you want to lengthen the VHF elements on like a RCA ANT751, for boost on VHF Low gain, you can use the old ball of tinfoil trick.....which you attach to the ends of the driven elements.....golf ball to baseball size. This gives an effect of virtual lengthening of the elements.

They used to do this with Rabbit Ears back in the day.....for channel 2,3, and 4.

Yes, technically this is called a capacitance hat. It results from too short of a dipole being inductive. Adding this mass as a ball to the end of an element increases the capacitance of the antenna making it appear longer to the radio waves.

However someone that has not bought either might want to just buy a Winegard HD7000R which is half the price of the RCA ANT751 and does have some reception on VHF low (not much).

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As an aside way back in the day , me and a buddy put up a 120 ft of Rohn 25 and literally 100 radials on it's base as long as we could make them in the yard (not tuned). We shunt feed the tower on 1.9 MHz. The tower was close to being right for 160 meter band (2 MHz takes a 117 ft Marconi 1/4 wave and the bottom of the band at 1.8 MHz takes 130 ft).

Later we added a 5 element 20 meter beam to the top with a 10-15 meter dual band over it. A 20 meter beam has elements about 30 feet long and the boom was about 60 ft long, monster yagi. The one above it was about half it's size.

We had to seriously adjust the shunt feed (at the very bottom of the tower) after installing the yagis to the top of the tower. They effectively gave us a longer antenna. It got us closer to being a real 1/4 radiator on the bottom of the band where we operated CW (Morse code). The guy who owned the tower claimed he noticed improvement near the bottom of the band, but I really could not tell. Then again he used the antenna hundreds of times more than I did operating over at his house.

However someone that has not bought either might want to just buy a Winegard HD7000R which is half the price of the RCA ANT751 and does have some reception on VHF low (not much).

Certainly so. I have a high regard for the Winegard 7000R. Its one of the better smaller antennas....and the Channel Master 3016 (and old RS UV-75RX), Delhi Super and Super Too, RCA ANT751, Digitenna Suburban/Metro.

Originally Posted by EscapeVelocity

Certainly so. I have a high regard for the Winegard 7000R. Its one of the better smaller antennas....and the Channel Master 3016 (and old RS UV-75RX), Delhi Super and Super Too, RCA ANT751, Digitenna Suburban/Metro.

Yea, sorry, I meant to credit you that idea and got lost in a LONGGGGG post. You did mention the fat part and deserve first known to me credit! What can I say, I am a pig!

[Intentional Silliness] I used to have a capacitance hat I wore to ham club meeting and swap fests....

Dang it, now you have me wanting to look up that list of antennas. Most of them I don't know or at least by name.

One thing rather interesting is someone in the Gainesville thread had a Silver Sensor in the attic and received our flea power CH9 ok, but had trouble on a 31 that was 20 miles out of town. I suggested the CM2016 because they have a large spread on other UHFs and well if they were receiving Ch9 on a SS, then anything should work right? Nope. They lost channel 9 though it fixed their 31. It left me baffled. It's those days I want to stop suggesting antennas.

Originally Posted by EscapeVelocity

As regards the polarization tending to twist (when it enters the building), Ive noticed on my RS 1880, that it does best at this angle (sometimes I tweak it a little depending on the station, but generally this angle is in the range of best). Seen here with a Quantum FX Indoor antenna.

Ive also seen a pic of the focus of a CM 4251 parabolic (which has a double bowtie with reflector at focus) rotated in a similar way. It got me curious about that.

The black on the left is set to almost exactly horizontal as far as I can see. The white one is slanted a little from horizontal.

I am not too sure why anyone would tilt a CM4251 (wish I owned one!) feed horn that way. Man, that was the best engineered UHF antenna ever built for TV. Channel Master 4251 Tribute Page

Originally Posted by EscapeVelocity

Quick Answer yes give them a starting point, encourage them to deviate from it in trial and error, but give them a range of lengths to focus on as well.

Bingo! And for the record, I prefer the Rabbit Ears that come in close together to those that are situated far apart like on some newer models like this Terk TV-2.

yes, use Kyes for a starting point then experiment.

I agree, that those two rabbit ears are so far apart that it is not as good. Another case of antenna designed for looks and not functionality.

Sometimes I think those mini Chinese beams are built that way. They come up with a cool looking antenna, run it through modeling software, adjust and sell it. Cool first, function second. But remember I am one that if it doesn't appear to look like a traditional antenna my first reaction is to start running the other way Which I admit is a prejudice but not in a lot of cases.

Originally Posted by EscapeVelocity

Here is KYES Rabbit Ears page with lengths and tips....for the OP.


Thats good advice, except that the forward V shortens the length of the dipole in relation to the wave. I would go longer with that suggestion.

It also depends on the Channels being attempted. And the shorter wavelengths work much better on a "too long" dipole than the longer wavelengths on the "too short" dipole.

Its better to err long than short....especially if you have a spread on VHF High. But then again this is a generalization....as the strength of the different local VHF High signals also come into play.

Does that make any sense?

Found something interesting today on a site I read a lot but not their indoor section much.

Trouble is Kyes and Nist I both respect with the highest possible regard and they don't agree on rabbit ears!
How to use Rabbit Ears

Who do you believe?