Cross Field Antenna

[Carmine5]

Interesting article in the 12/16 issue of RW on Cross Field Antennas. CFA, Ltd. hopes to submit test results to the FCC in about 4 months.

The advantages of a CFA are obvious, of course; no ground radials, requires only a small tract of land or can be mounted on a building, less vulnerable to wind and ice, etc. Apparently some of the early design flaws in the CFA have been corrected and seems to be working very well in installations in Egypt.

Here is the article: http://www.nxtbook.com/nxtbooks/newbay/rw_20091216/#/26

Also, check out this site:

http://www.crossedfieldantenna.com/

I can tell you in my own case, I had to give up on an AM CP because of the land requirements for a directional antenna array and associated NIMBY issues. Had the CFA been available (and could be made directional) things might have turned out differently.

c5

 

[boiseengineer]

Cross Field Antenna = SMOKE & MIRRORS?

http://www.antennex.com/shack/Jul00/cfacrit.htm

Major consulting firms have concured.

 

[Carmine5]

Re: Crossed Field Antenna

Cross Field Antenna = SMOKE & MIRRORS?

http://www.antennex.com/shack/Jul00/cfacrit.htm

Major consulting firms have concured.

Well, apparently CFAs are being successfully used in other countries. It will be interesting to see what the FCC findings reveal concerning this unique antenna. With land use issues affecting AM stations more and more, particularly new entrants, there needs to be some fresh thinking on antenna design.

For that matter, the Valcom whip is an effective antenna. Too bad the FCC won't allow its use in a directional array. According to a Valcom rep I spoke with, their antenna works very well in a directional array.

c5

 

[LA_Guy]

These is no free lunch!

I'm sure that when you put power into a crossed field antenna, some power gets radiated into the air. How much (and where is it going) are the questions that haven't been answered to anyone's satisfaction so far.

I've loaded my ham rig into an aluminum rain gutter before. Did it work well? NO! The fact that you can ram power into something doesn't mean it's an efficient radiator!

With regards to the Valcom: The FCC has determined that it meets the minimum field required of class B, C and D stations located above 1200 kHz and using 150 foot radials. We put a 92 foot one in at an 1180 class D and it also met minimum efficiency using a full ground system. These were all confirmed by actual fiend intensity MEASUREMENTS!
Again, we are talking minimums here. Is that what you want? For your station to be a minimum performer?

The FCC will allow Valcoms to be tried in DAs with an STA. Once doen however, YOU will (as the 'first one in') have a lot of field intensity measurements to do to prove the DA works as proposed. The trouble is, they sway in the wind, which can cause the pattern to 'wander'.

In our case, we were facing a CP expiration and using the Valcom allowed us to get the station built and on the air quickly.

So far, the crossed field antenna's measurements haven't passed muster.

 

[Carmine5]

Re: Crossed Field Antenna

Here is an email I received from Susan Crawford at the FCC regarding the Valcom whip:

"In the Public Notice announcing simplified application procedures for AM non-directional use of 75-foot and 85-foot Valcom antennas for operation on AM frequencies 1200 kHz to 1700 kHz provided certain conditions are met, the Commission stated that the Valcom antennas may only be used for non-directional operation. Here is a link to the Valcom antenna Public Notice:

http://fjallfoss.fcc.gov/edocs_public/attachmatch/DA-08-448A1.pdf

The Commission currently does not permit the use of any non-standard AM antennas, including the KinStar and Valcom antennas, in directional antenna arrays. In order to secure FCC approval for use of a non-standard AM antenna in a directional antenna array, an applicant would have to submit a study such as the one Star-H Corporation and Kintronics Laboratories submitted when seeking approval for non-directional use of the KinStar antenna. Of course, a study filed in support of an application specifying use of a non-standard antenna in a directional antenna array would require a much more detailed study."

So as a matter of course, the FCC will not allow the use of a Valcom antenna in a DA but might be used as such after an extensive study.

c5

 

[BobOnTheJob]

Re: Crossed Field Antenna

Here is an email I received from Susan Crawford at the FCC regarding the Valcom whip:

"In the Public Notice announcing simplified application procedures for AM non-directional use of 75-foot and 85-foot Valcom antennas for operation on AM frequencies 1200 kHz to 1700 kHz provided certain conditions are met, the Commission stated that the Valcom antennas may only be used for non-directional operation. Here is a link to the Valcom antenna Public Notice:

http://fjallfoss.fcc.gov/edocs_public/attachmatch/DA-08-448A1.pdf

The Commission currently does not permit the use of any non-standard AM antennas, including the KinStar and Valcom antennas, in directional antenna arrays. In order to secure FCC approval for use of a non-standard AM antenna in a directional antenna array, an applicant would have to submit a study such as the one Star-H Corporation and Kintronics Laboratories submitted when seeking approval for non-directional use of the KinStar antenna. Of course, a study filed in support of an application specifying use of a non-standard antenna in a directional antenna array would require a much more detailed study."

So as a matter of course, the FCC will not allow the use of a Valcom antenna in a DA but might be used as such after an extensive study.

c5

I'm not holding my breath until someone buys several of these antennas, does the exhaustive field work & then rolls the dice on FCC approval. Only way that's going to happen is if the manufacturer fronts the expense to prove their product.

My breath, likewise, will not be held on the Cross Field antenna. Lot of smoke on this one a few years ago, but like those stories in the National Enquirer about the 4 armed 27 pound man in Africa, until there's one in Muncie,Indiana that I can drive to & see in action, count me out...

 

[Tom Wells]

Before he passed away I spoke with Ed Hershmann of Valparaiso Technical Institute regarding the Kinstar antenna.
He told me it was uncannily similar to designs his father had designed for the dept. of defense back in the 40's, and he referred to it
as a "peeled banana" type of antenna. Not the best in efficiency, but for some situations, very advantageous, and inexepensive.
I would expect it to have some pretty distinct minma and coverage lobes.

 

[rfry]

Before he passed away I spoke with Ed Hershmann of Valparaiso Technical Institute regarding the Kinstar antenna. ... I would expect it to have some pretty distinct minima and coverage lobes.

That could seem correct based on the four horizontal wire sections. But the net, far-field radiation from those wires is about nil -- they only serve to top load the vertical wires to raise the radiation resistance and efficiency of the system. Only the vertical wires produce useful radiation.

Tables 1 & 2 in the paper at http://www.star-h.com/publications/nabpaper.pdf show that the measured radiation patterns of the Kinstar configurations tested are nearly equal to that of a full-sized, 1/4-wave monopole, when all are using a "standard" r-f ground system consisting of 120 ea, 1/4-wave, buried radials.

RF

 

[DanStrassberg]

That could seem correct based on the four horizontal wire sections. But the net, far-field radiation from those wires is about nil -- they only serve to top load the vertical wires to raise the radiation resistance and efficiency of the system. Only the vertical wires produce useful radiation.

Tables 1 & 2 in the paper at http://www.star-h.com/publications/nabpaper.pdf show that the measured radiation patterns of the Kinstar configurations tested are nearly equal to that of a full-sized, 1/4-wave monopole, when all are using a "standard" r-f ground system consisting of 120 ea, 1/4-wave, buried radials.

So why wouldn't a KinStar with more than four (say, 12) horizontal top loads either permit shorter top loads or produce higher radiation efficiency than the prototype, which, IIRC, has four top loads, each approximately 1/4 wavelength long?

I realize that the "if some is good, more must be better" rule doesn't always apply, but in this case, more horizontal wire in the air would appear to increase the capacitance from the umbrella to ground and also improve the circularity of the horizontal radiation pattern. Also, if more wires allowed the use of shorter horizontal top loads, the use of such antennas in DAs would seem to become more feasible.

 

[rfry]

So why wouldn't a KinStar with more than four (say, 12) horizontal top loads either permit shorter top loads or produce higher radiation efficiency than the prototype, which, IIRC, has four top loads, each approximately 1/4 wavelength long?

The Kinstar test used 4 ea 100 ft horizontal sections, which at the test frequency of 1680 kHz were about 0.17, rather than 0.25 wavelengths.

It could be true that more, although shorter top load sections could produce the same radiation efficiency and az/el radiation patterns as the present configuration, although the cost to do so may be greater if more supports are needed for the far ends of the added number of horizontal sections.

It won't be possible, by doing this, to improve Kinstar radiation performance much at the tested frequency, as the measurements taken of the present configuration are VERY close to those of a standard, unloaded, 1/4-wave monopole over the same r-f ground system -- which themselves are not much less than the theoretical limit for such a system when using a perfect r-f ground.

... more horizontal wire in the air would appear to... improve the circularity of the horizontal radiation pattern.

Sorry, but the far-field, h-plane circularity of the v-pol radiation from this Kinstar configuration is a function of the four vertical wires in it (only) -- not the length and number of horizontal sections used to top-load those vertical wires.

The h-plane circularity of those four, parallel vertical wires is the same as that of a conventional, series-fed monopole of any height, which in theory is nearly perfect.

//

 

[HowardMBurgers]

Several years ago when the whole Cross Field Antenna claims came out, a well known consulting engineering firm asked to see the antennas in use (somewhere in the Middle East I believe), but were denied access.

From a physics aspect, the CFA is a joke. Whereas it's true that one could drive a coffee can with enough power to radiate, it certainly wouldn't do so with any efficiency. That's essentially what the CFA are; big cylinders with a complex matching network being driven with a bunch of power.

I tried to build a model version at 160M, but the phasing harness design was impossible to build with the goal of even a fair match.

The KinStar antenna seems to work okay, but it's still a vertical radiating element. Nothing like what the claims are of the CFA.

 

[littlejohn]

Well, I respect the King's oprganization. And Mr Fry's opinion as well as that of several other longtime consulting Engineers, all of whom have in coarser or nicer terms pronounced 'BS' on the cross-field. As Mr Fry points out, Kintronics took a field meter and measured the results of their design - and they have decasdes of experiences in the field.
When whomever is pushing the cross-field sets one up where I can take my GPS and trusty FIM and see what field intensity it produces, I'm interested. Till then, count me with the skeptics. When Mr Rackley and Mr Sellmeyer propose one, I'm interested.

 

[Tom Wells]

The cross field looks like a badminton birdie. If they'd like to donate one for me to test on my part 15 AM, I'd be very happy to do some testing. How would the FCC measure such a beast .... on the upsweep curved surface, or actual "tape measure" height?

 

[DanStrassberg]

It won't be possible, by doing this, to improve Kinstar radiation performance much at the tested frequency, as the measurements taken of the present configuration are VERY close to those of a standard, unloaded, 1/4-wave monopole over the same r-f ground system -- which themselves are not much less than the theoretical limit for such a system when using a perfect r-f ground.

Umm, what's magic about 1/4 wave? You make it sound like the be-all and end-all of conventional vertical radiators. Why not a configuration that uses, say, a 60-degree (or shorter) vertical segment and, through top loading, tries to emulate the horizontal radiation efficiency and vertical pattern of a half-wave or a 5/9-wave (that is, 200-degree) series-fed vertical radiator? I have no idea whether that's possible, but it would seem to be a worthwhile goal.

 

[K4WRF]

There are just no exceptions to the sets of equations developed by James Clerk Maxwell back in 1864. Many have tried, all have failed…

 

[rfry]

Umm, what's magic about 1/4 wave?

Nothing, but an unloaded, 1/4-wave monopole was used as the reference of comparison for the tests on the present configuration of the Kinstar.

Why not a configuration that uses, say, a 60-degree (or shorter) vertical segment and, through top loading, tries to emulate the horizontal radiation efficiency and vertical pattern of a half-wave or a 5/9-wave (that is, 200-degree) series-fed vertical radiator?

The height of the Kinstar in the test report linked earlier was 45 feet, which at 1680 kHz is about 28 degrees.

The design goal for the effort that developed the Kinstar is shown this way in the abstract of its test report:

"The lengths and arrangements of the wires are designed by computer optimization methods to provide the best compromise between reduced antenna height, antenna gain at the horizon, and frequency bandwidth."

Agree that it would be interesting to investigate other configurations.

RF

 

[DanStrassberg]

Agree that it would be interesting to investigate other configurations.
RF

Since the FCC's generalized model for sectionalized AM radiators allows for top loading of the vertical sections, something that might actually be worth trying is a center-fed sectionalized vertical radiator in which each of the two relatively short vertical sections was massively top-loaded, KinStar style (or with different numbers and maybe different lengths of horizontal load wires). Any sectionalized radiator requires extensive computer modeling before construction and extensive measurements before being licensed. If it worked, the configuration I have described, though not cheap to design or construct, would probably, over the long run, be much more cost effective than the existing sectionalized radiators (e.g. KFBK and KSTP). Unfortunately, a new sectionalized (I'm not talking just top-loaded here) AM radiator is built in the US no more often than once every 25 years or so--if that. So who would be willing to risk the expense to prove out the idea? However, if the idea were proven to work, it could become quite profitable. Could have saved KFI's butt and likely at lower cost and in less time than the new top-loaded tower.

 

[Carmine5]

These is no free lunch!

Maybe there's no free lunch but nothing says we have to content ourselves with antenna designs that are stuck in the 30's and 40's especially with the advent of computer modeling.

I'm not saying that the Crossed Field Antenna is an efficient design but I like the (pardon the cliche) 'out of the box' thinking behind it. Perhaps this can spur even more innovating on what is basically an old technology.

c5

 

[HowardMBurgers]

To that point, what is the use of spending money and time developing new antenna technology for a dying Medium Wave band? Certainly the CFA is nothing more than snake oil anyway. When it comes to antenna technology, one thing is constant; that being the laws of physics have yet to be broken.