"Ionic Liquid" Antenna

[rfry]

Below is a link to a video describing the development work
on an interesting concept for an antenna:

http://www.youtube.com/watch?v=9tIZUhu21sQ

RF

 

[DanStrassberg]

Below is a link to a video describing the development work on an interesting concept for an antenna:

Fascinating! He doesn't claim that the frequency range extends down to MW, however. 2 MHz is the lowest and requires a 70-80' column of water. I was envisioning fountains (as opposed to flagpoles) on a golf course. I believe that a long-dark AM 1540 in Aptos CA had a DA that consisted of three or four flagpoles on a golf course. I can just hear the consultant telling the applicant, "No, it has never been tried as far as I know, but let's run it up the flagpole..." AFAIK, the FCC has never approved Valcom Fibreglass whips for use in AM DAs, but didn't those flagpoles on that CA golf course have to be constructed more or less like Valcom whips?

 

[w9wi]

Fascinating! He doesn't claim that the frequency range extends down to MW, however. 2 MHz is the lowest and requires a 70-80' column of water. I was envisioning fountains (as opposed to flagpoles) on a golf course. I believe that a long-dark AM 1540 in Aptos CA had a DA that consisted of three or four flagpoles on a golf course. I can just hear the consultant telling the applicant, "No, it has never been tried as far as I know, but let's run it up the flagpole..." AFAIK, the FCC has never approved Valcom Fibreglass whips for use in AM DAs, but didn't those flagpoles on that CA golf course have to be constructed more or less like Valcom whips?

What's a quarter-wave on 1540, about 150'? That'd be a pretty big flagpole, but there's an auto dealership 20 miles north of here that's got a few I believe are that big.

 

[rfry]

As this ionic column essentially is a monopole, a very good r-f ground will be needed for best system efficiency. So unless this column is centered on, and driven against a conventional "broadcast type" set of buried radials or mounted just above the surface of the sea, it would not be the equivalent of a metallic conductor of about the same height and diameter.

For upper HF and VHF the r-f ground could be provided practically by centering it over a circular pond of some kind of an ionic liquid, with the pond being about a one wavelength in diameter.

The video states that the radiation pattern and gain of this antenna haven't been measured yet. Those parameters may not exactly match a metallic conductor of the same dimensions, but the design still may be useful for emergency 2-way communications or other non-broadcast applications.

RF

 

[DanStrassberg]

What's a quarter-wave on 1540, about 150'? That'd be a pretty big flagpole, but there's an auto dealership 20 miles north of here that's got a few I believe are that big.

However, Valcom whips have a greater electrical length than you would predict from their physical length--and there are valid technical reasons for the seemingly anomalous electrical length. The antenna is helically wound on the Fibreglass core. As a result, the antenna is a transmission line with series inductance and shunt capacitance, which produce a propagation velocity lower than that of free space. Therefore, every degree of physical length represents more than a degree of electrical length. In addition, there are lumped loads at the center and at the top of each whip. The longer MW whip is 94' and Valcom says it is suitable for use at 1200 kHz and higher. (Actually, the very first 94' whip in the US is in use at WFYL, King of Prussia PA. WFYL is on 1180.) Supposedly, the 94' whip at 1200 has a radiation efficiency equal to that of a 60-degree antenna of conventional design. A 60-degree antenna at 1200 would be 137' high and, with a ground system consisting of 120 1/4-wavelegth radials, should have an efficiency just slightly greater than the Class B/D AM minimum, so you can calculate the propagation velocity in the whip as being 94/137 or 68.8% of that of free space. Valcom's older and more popular 74' model is in use at several US stations that operate at frequencies slightly below 1500 kHz. If all of the parameters scaled correctly, that would mean the 94' model ought to work acceptably below 1200 and below 1180--perhaps down to 1100.

Valcom has been very reticent about developing larger sizes. I don't know anything about the structural issues, which must be significant--Valcom whips are self supporting and are WAY narrower at the base than any conventional self-supporting tower of similar height. But if the structural issues can be solved at reasonable cost, it might be possible to design a whip that is (just barely) shorter than 200' and thus would not require illumination in the US and would also work all the way down to 540 kHz, the lowest AM frequency in the US. You just know that Valcom MUST have worked on such a whip and the fact that they don't offer one suggests that they could not overcome the structural problems or could not do so at a price they thought anyone would be willing to pay.

 

[rfry]

However, Valcom whips have a greater electrical length than you would predict from their physical length--and there are valid technical reasons for the seemingly anomalous electrical length. The antenna is helically wound on the Fibreglass core. As a result, the antenna is a transmission line with series inductance and shunt capacitance, which produce a propagation velocity lower than that of free space.

John Kraus in Antennas for All Applications, 3rd edition states that a vertical monopole antenna utilizing a helical conductor has nearly the same radiation resistance as a linear conductor of the same height (see link below).

The ratio of the radiation resistance to the sum of all the resistances in the antenna system determines antenna system radiation efficiency, so other things equal, would a Valcom perform much differently than any conductor of the same outline dimensions as that Valcom?

http://i62.photobucket.com/albums/h85/rfry-100/Helically-woundVertical.gif

RF

 

[DanStrassberg]

John Kraus in Antennas for All Applications, 3rd edition states that a vertical monopole antenna utilizing a helical conductor has nearly the same radiation resistance as a linear conductor of the same height

But there is no indication that the helical antenna in the Kraus reference is wound on a core having a dielectric constant higher than that of free space. That is the case with the Valcom whip. I don't know the dielectric constant of Fibreglass, but it is probably in the neighborhood or 2.5 and is probably responsible for the Valcom antenna's reduced propagation velocity, which, in turn, is responsible for the antenna's higher-than-anticipated radiation efficiency.

 

[DanStrassberg]

Valcom has been very reticent about developing larger sizes. I don't know anything about the structural issues, which must be significant--Valcom whips are self supporting and are WAY narrower at the base than any conventional self-supporting tower of similar height. But if the structural issues can be solved at reasonable cost, it might be possible to design a whip that is (just barely) shorter than 200' and thus would not require illumination in the US and would also work all the way down to 540 kHz, the lowest AM frequency in the US. You just know that Valcom MUST have worked on such a whip and the fact that they don't offer one suggests that they could not overcome the structural problems or could not do so at a price they thought anyone would be willing to pay.

Hmmm... Regardless of the theoretical considerations, there is very practical consideration that I failed to mention in the above posting: How would you transport a 200' Fibreglass whip antenna from its point of manufacture to its point of installation? The shorter antennas (74', 94') must either fit on large flat-bed trucks or be looped into large-diameter circles that can travel on truck beds. Not so with a 200' unit, which, I think, would have to be built in sections that could be assembled on site.

 

[w9wi]

However, Valcom whips have a greater electrical length than you would predict from their physical length--and there are valid technical reasons for the seemingly anomalous electrical length.

I probably didn't make it clear that my point was that the 1540 California operation could possibly have been a traditional (non-helical) vertical radiator system, using unusual radiators but of something along the lines of 90 degrees in both electrical *and physical* height.

I'm quite familiar with the fibreglass helically loaded antennas, on a much smaller scale. I use them for my mobile ham station, to considerable success despite the rather poor ground system. (a 2007 Ford Focus is nowhere near a proper ground system on 3.5MHz!) That said, a fair amount of high-angle radiation is not a big deal on the amateur radio bands...

Valcom has been very reticent about developing larger sizes. I don't know anything about the structural issues, which must be significant--Valcom whips are self supporting and are WAY narrower at the base than any conventional self-supporting tower of similar height. But if the structural issues can be solved at reasonable cost, it might be possible to design a whip that is (just barely) shorter than 200' and thus would not require illumination in the US and would also work all the way down to 540 kHz, the lowest AM frequency in the US. You just know that Valcom MUST have worked on such a whip and the fact that they don't offer one suggests that they could not overcome the structural problems or could not do so at a price they thought anyone would be willing to pay.

I wonder why there seems to be no such thing as a guyed Valcom?

Obviously using guy wires would negate part of the advantage of the small footprint self-supporting design, but I'd think it would still be a considerable improvement over a guyed tower of "normal" physical height.

I suspect your comment about shipping difficulties may be much of the reason.

 

[Nostalgia]

According to Valcoms website their antenna's are shipped in pieces and assembled on site.

 

[rfry]

But there is no indication that the helical antenna in the Kraus reference is wound on a core having a dielectric constant higher than that of free space. That is the case with the Valcom whip. <earlier> Supposedly, the 94' whip at 1200 has a radiation efficiency equal to that of a 60-degree antenna of conventional design. A 60-degree antenna at 1200 would be 137' high and, with a ground system consisting of 120 1/4-wavelegth radials, should have an efficiency just slightly greater than the Class B/D AM minimum, so you can calculate the propagation velocity in the whip as being 94/137 or 68.8% of that of free space.

For consideration...

Dr. George H. Brown investigated the performance of reduced-velocity monopoles for his paper A Critical Study of the Characteristics of Broadcast Antennas as Affected by Antenna Current Distribution, which was published in the Proceedings of the I.R.E. in January, 1936.

In this section of Brown's paper he states,"Several methods of loading might be utilized. One arrangement might be to arrange the antenna wire in a spiral. The velocity of propagation might also be decreased by surrounding a vertical conductor with a mass of dielectric. We shall not interest ourselves in the methods of accomplishing this condition, but shall note the consequences of such an arrangement."

Figure 29 from that paper is linked below, and shows that a vertical antenna that is 60 degrees in physical height needs to be loaded to a v/c of about 0.55 or less to provide a useful increase over an unloaded antenna with a v/c of about 0.95 (a typical value for a "tower" antenna).

Figure 29 does not show loaded verticals with an actual (physical) height below 60 degrees, such as the 41.3-degree, 94-foot Valcom on 1200 kHz -- but the trend seen in the chart might lead to a similar conclusion as the 60-degree case.

It appears that Brown and Kraus are in agreement about the performance of reduced-velocity verticals.

http://i62.photobucket.com/albums/h85/rfry-100/Dec_Velocity_Monopole.jpg

RF

 

[DanStrassberg]

For consideration... Dr. George H. Brown investigated the performance of reduced-velocity monopoles for his paper A Critical Study of the Characteristics of Broadcast Antennas as Affected by Antenna Current Distribution, which was published in the Proceedings of the I.R.E. in January, 1936.

But the actual behavior of the Valcom whips, which has been confirmed by numerous proofs of performance, suggests that Valcom's assertion of reduced propagation velocity is valid. And the Valcom construction wasn't offered for sale until at least half a century after Brown's paper was published. I suppose you could assert that the performance of the whips is the result of Valcom's use of center and top loads, which I have never seen described (other than that pictures show the top load being contained in a small spherical enclosure). Could these lumped loads be Valcom's "secret sauce"? Or are you suggesting that the proofs of performance on the whips were inaccurate or falsified?

The FCC, which I believe has granted type approval for the whips when used as omnidirectional AM radiators with standard ground systems (essentially invalidating any claims of small-footprint), has not approved use of the whips as elements of DAs. I have to assume (whether I am entitled to do so or not) that the FCC's reservations about use of the whips in DAs results from the failure of the proofs of performance to demonstrate to the Commission's satisfaction that the whips' vertical radiation characteristics are equivalent to those of conventional antennas of equal horizontal-plane efficiency (that is, marginally superior to Class B/D minimum efficiency).

 

[kenglish]

All this takes me back to my 1960's high school days, and the "Popular Science" article about using an ionized flame to create a speaker.
Did it ever take off? ;D

 

[rfry]

But the actual behavior of the Valcom whips, which has been confirmed by numerous proofs of performance, suggests that Valcom's assertion of reduced propagation velocity is valid.... Could these lumped loads be Valcom's "secret sauce"? Or are you suggesting that the proofs of performance on the whips were inaccurate or falsified?

Based on the engineering report by DL&R used in support of FCC Public Notice DA 080448 about the acceptability of the Valcom, there is no doubt about the efficiency values accepted for it by the FCC.

According to the quote shown below as taken from that DL&R Engineering Report, the reasons for the relatively high efficiency for that physical height are related to the top loading provided by the "Valcosphere," and reduced dielectric losses in the earth around the base of the antenna.

Ron Rackley: "The observed unattenuated field values of Valcom poles exceed those shown for
their physical heights on the graph which appears as Figure 8 of Section 73.190 of the FCC
Rules. Two aspects of their design are responsible for this, their Valcosphere top-loading and
their loading coils that are situated far enough above ground to reduce the antenna-to ground
voltage in the base region which, in turn, reduces dielectric losses in the nearby soil. The
effects lead to antenna efficiency improvements that are predictable and measurable."

A reduced v/c for the Valcom is not mentioned there as a contributor to efficiency. Is there a link to a paper showing this?

RF

 

[317C50KW]

All this takes me back to my 1960's high school days, and the "Popular Science" article about using an ionized flame to create a speaker.
Did it ever take off? ;D

The great John Eargle talks about the concept here:
http://books.google.com/books?id=Tw...AEwAw#v=onepage&q=ionized loudspeaker&f=false

 

[frankberry]

Ionic Liquid antenna wouldn't work too well in the wind.

 

[Tom Wells]

When I was in Jeddah, Saudi Arabia about a month before the first Persain Gulf War, what was that..91? I was amazed at
King Fahd's gigantic jet pump fountain off to the east. I don't know how far out it was, or how high it was spurting,
but with salt water, that would be the one I'd put on a low band MW.


You could tell it was quite aways off, and you tell it was the biggest dang fountain jet you were ever gonna see in your life.
Wouldn't you need a completely unbroken column or have massive variable detuning and efficiency loss?


Somewhere I have that issue of Popular Electronics dicussing the flame speaker.
I don't recall it mentioning any of the drawacks as compression and rolloff of efficiency at higher audio frequencies.
I may have forgton other details, or they weren't mentioned, such as the RF modulation between plates.
Maybe they glossed over it or it was kept mum, as this sure would have seemed patentable at the time.
But pulication is disclosure, so they must have applied by then. I'l have to look that up,
or maybe someone aready knows the followup history on this device.

 

[DanStrassberg]

A reduced v/c for the Valcom is not mentioned there as a contributor to efficiency. Is there a link to a paper showing this?--RF

The reference to a paper must be in the caption of one of the figures on the page to which you provided a link. I don't remember the paper's title, but I do remember the date: January, 1936.

 

[rfry]

A reduced v/c for the Valcom is not mentioned there as a contributor to efficiency. Is there a link to a paper showing this?--RF

The reference to a paper must be in the caption of one of the figures on the page to which you provided a link. I don't remember the paper's title, but I do remember the date: January, 1936.

That paper was the one by Dr George Brown, which (of course) could not refer to specific characteristics of the Valcom antenna.

What is missing is a link that anyone could provide to a paper showing that at least part of the radiation efficiency of a Valcom broadcast monopole is the result of its reduced v/c -- if indeed that is true.

RF

 

[MickeyD]

Ionic Liquid antenna wouldn't work too well in the wind.

You are right about that but the land version in the plastic tube seems like it would resolve that problem.