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Kaltman Reactions Circular Polarization Antenna


soundtrane

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As far as compensating for cross polarity losses by using circular antennas

you could just turn a sharkfin to 45 degrees and get the same :)

 

"linearly polarized antennas will work with circularly polarized antennas and vice versa. However, there will be up to a 3 dB loss in signal strength."

 

"In a linearly polarized system, a misalignment of polarization of 45 degrees will degrade the signal up to 3 dB"

 

http://www.astronwireless.com/topic-archives-antennas-polarization.asp

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Nothing really mysterious about RF.

 

As far as numbers go don't pay much attention to  a manufactures gain numbers stated in dBi.

Its kind of like selling ocean front property in Arizona.

If they give you a number in dBd sit up and take notice.

The physical length of antenna in wavelengths is a much better indicator.

 

In simple terms an antenna with gain will have 3 basic components.

 

The driven element, usually a dipole.

A single reflector, larger than the driven element. This pushes the RF away from it.

Director elements, smaller than the driven element. these "shape" the outward pattern.

The more directors the sharper the pattern and thus more gain.

 

 

Some basic things

 

Antennas will react with objects near them

RF bounces around similar to audio.

One size fits all antennas are performance compromises.

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Nothing really mysterious about RF.

 

As far as numbers go don't pay much attention to  a manufactures gain numbers stated in dBi.

Its kind of like selling ocean front property in Arizona.

If they give you a number in dBd sit up and take notice.

Why should we ignore dBi? The difference between dBi and dBd is 2.15dB, to convert dBi to dBd take away 2.15dB. Simples. As you say: nothing really mysterious about RF!

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Indeed it is, with a gain of -2.15dBd.

 

dBi is often used by manufacturers to make the gain figure look better to the uninitiated.

 

Factor in the return losses on some of these wide frequency designs

and random piece of wire hung in the air might look like pretty good alternative :)

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Awesome video Andy, thanks for posting that.

 

Question on diversity- does it always mean the receiver is both horizontally and vertically polarized? I thought it just means that the receiver chooses which antenna has a stronger signal. Most bag-based receivers have both antennas pointed in the same direction, so does that mean they are both vertically polarized?

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Low gain antennas like the sharkfins are not that directional.

 

Your radiation pattern is probably very similar to this.

 

I might have overlook another very important factor.

It could also be the BNC cable connection that was compromised while it was outside braving the wind.

Hence explains why I have better reception inside the van just behind the windshield.

 

If I'm understanding correctly only metal objects will have an effect on the radiation?

Glass/plastics is forgivable?

 

Another factor to consider is when you hand-held an antenna,

the body contact (hand-held) with the antenna could have been detrimental to the reception?

Like how Lectrosonics advise to wire the mic away from the antenna to avoid RF loop-inteference.

 

Thanks for the feedback given.

 

I am going to make an order for this antenna anyway (and have a standard Yagi as a backup)

 

E-mail conversations with Mark (the founder) reveals that Whit tried it on a tracking shot,

so yes am very interested to find out how it holds up (whether it's better or just similar to a standard sharkfin).

 

-P

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Just remind everyone what this antenna looks like, small image posted below. I think we're all still waiting for someone to actually take it out for a spin and report back to us here. The company does offer a 15-day trial and I think Whit Norris took them up on that (but I haven't heard from Whit regarding this antenna).

 

post-1-0-32770400-1359777545_thumb.jpg

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If I'm understanding correctly only metal objects will have an effect on the radiation?

Glass/plastics is forgivable?

 

Another factor to consider is when you hand-held an antenna,

the body contact (hand-held) with the antenna could have been detrimental to the reception?

 

All objects in close proximity will effect the antenna.

Just depends on the object and proximity.

 

Anybody that has ever adjusted a set of rabbit ear antennas on a TV should be able to verify this :)

 

Metal objects are especially good at bouncing RF, maybe what happened in your situation.

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I have ordered a pair and should receive them early next week. I will test them in our lab and report findings on here. If they work as stated then they could be very interesting as they would remove one of the main causes of dropout: cross polarisation (in linear polarisation when at 90 degrees you get, in theory, total dropout).

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  • 2 weeks later...

I have ordered a pair and should receive them early next week. I will test them in our lab and report findings on here. If they work as stated then they could be very interesting as they would remove one of the main causes of dropout: cross polarisation (in linear polarisation when at 90 degrees you get, in theory, total dropout).

Any news / update on these please?

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  • 3 weeks later...

" Question on diversity- does it always mean the receiver is both horizontally and vertically polarized? "

no

" it just means that the receiver chooses which antenna has a stronger signal. "

no, not necessarily...

" Most bag-based receivers have both antennas pointed in the same direction, so does that mean they are both vertically polarized? "

mostly yes, but they are also typically too close together...

" only metal objects will have an effect on the radiation?  Glass/plastics is forgivable? "

mostly metal objects will have an effect on the radiation, Glass/plastics are more forgivable...

Edited by studiomprd
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  • 2 years later...

Oh man, it's been a long way since I have been here.

Here's a video to show the Kaltman's CP antenna in action.

 

Few things to keep in mind:

 

Transmitter is UH200D (boom tx, up in the air)

You will see the Lectrosonics ALP antenna is mounted but if you freeze frame you can see that the BNC is unpatched

Distance measured in Google Maps is roughly 130 meters / 427 feet (over water) and I was behind a shack

The phone was in Airplane mode :)

 

Hope this helps some of you make your decision.

 

http://www.youtube.com/watch?v=zDlcMkyWwxE

 

My non plussed opinion on the antenna is the mounting style. It's not very rigid.

The build of the whole antenna is plastic, and I would prefer a male BNC port embedded on the body itself instead of a wire coming out (more points of failure in terms of wear and tear). This antenna would be great for fixed indoor venue/stadium or any set that doesn't require you move/relocate position as much.

 

Still, I am glad I own one.

 

Cheers.

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