eHam.net - Amateur Radio (Ham Radio) Community

Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net



[Articles Home]  [Add Article]  

Radiographic Examination of Rubber Ducks

from Stephen Dubin, W3UEC on July 30, 2018
View comments about this article!

Radiographic Examination of Rubber Ducks
By Stephen Dubin, W3UEC

Please note: This article is not intended to be scholarly or exhaustive. Just think of it as a one-sided “rag chew.”

A new antenna (Signal Stick)(1) for my handy talky (HT) seemed to work particularly well. Noting the simple design of this antenna, it dawned on me that I knew very little about my other HT antennas. Consulting my main brain prosthesis (AKA Dr. Google), I learned:

“The rubber ducky antenna (or rubber duck aerial) is an electrically short monopole antenna that functions somewhat like a base-loaded whip antenna. It consists of a springy wire in the shape of a narrow helix, sealed in a rubber or plastic jacket to protect the antenna. Rubber ducky antenna is a form of normal-mode helical antenna.” (2,3)

Delving further into the same articles, I learned that the first rubber ducky was built by Robert Johnson who stretched a screen door spring into a six meter antenna, while he was a resident at Lyman Hall (a reform school). The antenna’s name is, arguably, attributed to Caroline Kennedy, referring to the flexible antenna on a Secret Service agent’s radio. The same articles have ample information about rubber duck electrical properties.

In an excellent article on the structure of some flexible antennas, “What’s in your Rubber Duck?”(4) Bob Witte boldly stripped away the coating on three of his antennas. In a way he was doing an anatomic dissection. Such a radical approach provides magnificent information, but might leave the “patient” in poor condition.

As with many hams, I like to take things apart and see their “innards.” However, with my ducks, I wanted a cheaper and less invasive approach. A brief moment of mental clarity led me to think about radiography (X-ray pictures). Fortunately, through the kindness and patience of Dr. Harold Russell and his staff at GlenCroft Animal Hospital(5), I was able to obtain (and share) some radiographs of flexible portable antennas. I suggest you look at and compare them with Bob Witte’s excellent photographs.

A few words about radiography: Most folks are somewhat familiar with radiography (making images using X-rays) since it is used in our medical and dental care, surveillance at airports and in industrial testing. I will only briefly review some aspects that may affect its use in the evaluation of antennas or might otherwise be of interest to ham radio operators.

Wilhelm Conrad Röntgen, in November 1895, was investigating external effects from various types of vacuum tubes. He looked at the ability of different materials such as lead to stop these rays. Soon after, he took the very first picture using X-rays of his wife Anna Bertha's hand. Radiography depends on the property of X-rays that structures with higher radiographic density (generally a combination of higher atomic weight and/or greater thickness) more effectively retard the passage of the radiation. The image results from excitation of phosphorescent chemicals, sensitization of silver salts in photographic film; or, more recently, direct excitation of semiconductor materials. Conventionally, a radiographic image shows dark where the radiation penetrates and lighter where it does not. For example; bones, which contain calcium, appear light while flesh which is mostly water, shows dark. Metallic structures, like jewelry or dental fillings show up quite white.(6)

My earliest recollection of radiography comes from the fluoroscope machines used to check the fit of shoes. These were used in brightly lit shoe stores, and were a source of amusement for kids who needed to wait for their turn. In a way, it was also my introduction to negative feedback systems. The more siblings you had, the more radiation to your gonads.(7)

Some years later, during veterinary school and practice, I spent many hours in the darkroom developing radiographs. Fortunately now in most radiography equipment the image is formed on a digital sensor device rather than photographic film or a fluoroscopic screen. This provides for a high quality image with less radiation. A picture is available almost immediately, as compared to the long developing time required for film. Furthermore, the image can be manipulated and transferred electronically.

In clinical radiography, the radiation is usually generated in a Coolidge tube (8) – a sort of “diode on steroids.” A very high voltage (conventionally referred to as the “kilovoltage” or KVP for “kilovolts peak”) accelerates electrons from the cathode towards an anode which usually includes a “target.” In clinical and industrial X-ray tubes, the construction details vary to allow for heat dissipation and beam forming. Only about one percent of the energy expended is actually converted into X-rays. Another commonly used term in clinical radiography is the “MAS.” This is the product of the current flowing from cathode to anode with the time of exposure. MAS stands for “milliamp seconds” and describes the overall amount of radiation. While many modern X-ray machines take care of the exposure factors (KVP and mas) automatically, I feel obliged to report that, for my antenna pictures, the parameters were 67 KVP and 15 MAS.

Please note that a radiograph is a two-dimensional projection of a three-dimensional object. In effect, all of the information is “smashed down” onto a flat plane. That is why, for example, in taking a chest X-ray, at least two views at different angles are necessary. Fortunately the flexible antennas are symmetrical around their long axis, so a single view is enough. Also, as compared with my animal patients, these ducks stay nice and still.

Some images:

Figure 1 is a radiograph of the antenna that came with my Baofeng UV-5. It clearly shows the SMA connector, the spiral antenna element and a translucent connecting section with a hint of a finer wire coil.

Figure 2 shows an X-ray view of the YHA-63 antenna supplied with the Yaesu FT817 transceiver. The lower part of the radiograph shows the BNC connector and has the shorter (144/430 MHZ)cap on the main shaft of the antenna. The upper part of the picture shows the long cap section intended for 50 MHZ operation.

Figure 3 shows a collection of longer thinner VHF/UHF antennas that are offered as improvements over the standard duck. These have a uniformly straight element with a hint of a thin coiled connection to the base connector. Using both electronic and optical magnification, I was not able to detect any finer (helical) structure in the long straight elements at the resolution that was available – which is pretty high.

Figure 4 is a “family portrait.” It includes a standard Ducky (top), two of the thin types (right side) and the very flexible Signal Stick (coiled) in the center.

As an additional non-invasive investigation, I (roughly) checked the magnetic susceptibility of the antennas using the base of a “mag mount.” The shaft part of all of the antennas were strongly attracted to the magnet EXCEPT for the Signal Stick. This is consistent with the idea that their helical and straight parts are steel for strength and flexibility and may be coated or covered with better conductors like copper, silver or gold. The signal Stick is made of Nitinol.(9) Nitinol is an alloy of nickel and titanium which has many interesting characteristics including shape-memory and superelasticity. Not surprisingly, when I looked up the magnetic susceptability of Nitinol, it is much lower than that of steel.

As a final possible justification for my ducky foray, I hope to have contributed another point in the WTF (“What’s that for?”) X-ray scheme for identifying things swallowed by Labrador Retrievers.





1) https://signalstuff.com/antennas/

2) https://en.wikipedia.org/wiki/Rubber_ducky_antenna

3) http://www.abominablefirebug.com/RDuckey.html

4) http://www.k0nr.com/wordpress/2016/07/whats-rubber-duck/

5) http://glencroftvet.com/

6) https://en.wikipedia.org/wiki/Radiography

7) https://en.wikipedia.org/wiki/Shoe-fitting_fluoroscope

8) https://en.wikipedia.org/wiki/X-ray_tube

9) https://en.wikipedia.org/wiki/Nickel_titanium

Member Comments:
This article has expired. No more comments may be added.
 
Radiographic Examination of Rubber Ducks  
by W4FID on July 30, 2018 Mail this to a friend!
Thanks for a very good read. Some basic stuff. Some "neat to know" stuff. Some backed up science and references stuff. The "picture" in my mind and much of what I thought is now confirmed.
 
RE: Radiographic Examination of Rubber Ducks  
by AF6AU on July 30, 2018 Mail this to a friend!
As a lab Geek myself, I enjoyed this... I have a scanning electron microscope at work that uses emission X-rays to identify elements in a material.

And yes, to get 6 meters in a short whip, it has to be helical, or use a lump inductor, not very efficient.

The longer gain whip elements are straight flexible wires of 1 sort of another, some with inductors, but all pretty much fall into a 1/4 wave catagory. Again, your point of silver plating (also add Tin to your list) for a surface effect low resistance/high conductivity is a good point.

All of these share the fault issue of "How many times until the conductor breaks", usually at the connector..

If it's too rubust, the connector breaks in the H.T., as discovered by guys trying home made whips made from various brass rods. ;-)

In the case of my Alinco 220MHz factory helical it was a matter of the rubber jacket rotting off. It's now a bare spring and a BNC connector, no secrets there.... but it does work still.

Be interesting to see X-ray shots of some of those cheap whips coming from China look like.

Interesting though, all the helicals are fairly constant pitch, not a coarse pitch in the lower 1/2 then progress finer to the top. Easier to make a plain old constant pitch spring.

Thanks again for your work.
 
Radiographic Examination of Rubber Ducks  
by DL8OV on July 30, 2018 Mail this to a friend!
It's amazing how helpful local vets are with non-medical matters providing:

a) You know them well
b) You don't pester them too often
c) You compensate them for their services

In my case he x-rayed a keyboard for me so I could find the break in a track and in return I serviced his PC.

Peter DL8OV
 
RE: Radiographic Examination of Rubber Ducks  
by K9MHZ on July 30, 2018 Mail this to a friend!
If you go way up in frequency, flexible antennas actually can be quite good in performance. One Laird 33cm band antenna is a vertical dipole, fed midway. Sure beats the ridiculous springs that are supposed to be 2-meter HT antennas.
 
RE: Radiographic Examination of Rubber Ducks  
by W4KVW on July 30, 2018 Mail this to a friend!
A local ham friend & I tried over a dozen HT antennas on an MFJ 259B analyzer & they were all terrible no matter the model or brand.The SWR was terrible on them all.Some were mono band some were dual band & some were tri band & the SWR on all of the bands was well over 2.5 on them all except one which was a JetStream Tri band model JT776SMA.We were only able to test it on 2 meters & 440 mhz since the 259B does not cover 220 mhz.Some had an SWR well above 3.1.I guess those HT's come with much better finals than mobile & base radios if they can take that kind of SWR?

Clayton
W4KVW
 
RE: Radiographic Examination of Rubber Ducks  
by KD6VXI on July 31, 2018 Mail this to a friend!
We were only able to test it on 2 meters & 440 mhz since the 259B does not cover 220 mhz

It doesn't cover 70 cm either!

--Shane
KD6VXI
 
RE: Radiographic Examination of Rubber Ducks  
by KB5ZSM on July 31, 2018 Mail this to a friend!
Should have mentioned that the old xray machines were a major cause of cancer. Neat article though. I used to have an xray of my old Nikon 3 with a 200mm lens. Someone else thought it was neat also and as a result it disappeared :-(

73s
Win
 
RE: Radiographic Examination of Rubber Ducks  
by K0UA on July 31, 2018 Mail this to a friend!
For those with "rotted off" rubber and bare springs showing, that is easily remedied. Just buy some Plasticoad/Plastidip material designed for you to dip your hand tool handles in to recoat them. It comes in various colors and just simply dip the antenna into the can repeatedly, letting it dry between coats.
 
RE: Radiographic Examination of Rubber Ducks  
by W4KVW on July 31, 2018 Mail this to a friend!

"Quote",We were only able to test it on 2 meters & 440 mhz since the 259B does not cover 220 mhz

It doesn't cover 70 cm either!

--Shane
KD6VXI

You are correct & maybe I was mistaken about the model of MFJ analyzer we were using but I know it would test a 440 mhz antenna but NOT a 220 mhz antenna.Thanks for the correction. {:>)

Clayton
W4KVW
 
Radiographic Examination of Rubber Ducks  
by KI7AAR on July 31, 2018 Mail this to a friend!
Please keep in mind that medical X-ray equipment is optimized for good tissue and bone contrast while minimizing the dose to the patient. Having worked in industrial X-ray for 30 years I find the resolution of attached images quite poor. Interesting radiographs and topic but, not a good example of what is possible with modern industrial X-ray technology.

Sorry for the side track on the topic, just don’t want to see potential customers thinking this is the state of the art.
 
RE: Radiographic Examination of Rubber Ducks  
by SWMAN on August 1, 2018 Mail this to a friend!
Hmmm, Looks good to me.
 
Radiographic Examination of Rubber Ducks  
by VE3WGO on August 3, 2018 Mail this to a friend!
W3UEC, thanks for this really informative antennas article! I enjoyed your innovative application of the tools at hand to find out some very interesting new facts.

73, Ed
 
Radiographic Examination of Rubber Ducks  
by KA6TPR on August 3, 2018 Mail this to a friend!
Nicely done. Informative, not to long, good bibliography. Bravo
 
RE: Radiographic Examination of Rubber Ducks  
by KI4SDY on August 3, 2018 Mail this to a friend!
I wish the rubber duck analyzer test had been done with a limp wire counterpoise attached, like some hams have attached to their HT antenna connector. Most say it is an improvement, but I notice that they don't leave it on there for long. Probably the inconvenience of the dangling wire.
 
Radiographic Examination of Rubber Ducks  
by KA0USE on August 4, 2018 Mail this to a friend!
THIS is so cool!
i've wondered for years what rubber ducks looked inside.
THANK YOU THANK YOU THANK YOU for letting us see something in a different way!

btw an aunt tells me of having her feet x-rayed as a child when being fitted for shoes in the 1940s.
my feet have been x-rayed many times at the v.a. hospital and i find it fascinating (not the results- i'm a wreck, but the images themselves).

what a breath of fresh air!
 
RE: Radiographic Examination of Rubber Ducks  
by KA0USE on August 4, 2018 Mail this to a friend!
that's good stuff! other uses, too!
 
RE: Radiographic Examination of Rubber Ducks  
by KA0USE on August 4, 2018 Mail this to a friend!
i took my mfj 259-c analyser along to a ham radio outlet store some years ago when shopping for a 2m rubber duck.
oh, boy.
they weren't very happy with the results, and neither was i. a couple didn't work at all.
since the analyser is a sort of radio i'm going to put a mouse tail on the ground terminal and see what readings i get.
i have a duck left over from a radio shack htx-202 and it works the best. the radio was purportedly made for rs by icom. no idea who might have made the antenna.

i did make a mouse tail for my ft-817 and it does help the 2m part of the antenna that came with the radio.
now that mr. dubin got me thinking, i'll make 'tails for 440 and 6m and use the analyser to see the results.

at least 2 commercial 'tails are available:

https://www.universal-radio.com/catalog/hamantht/2714.html

https://rattailantenna.com/

https://www.eham.net/reviews/detail/3039

http://mparam.s3.amazonaws.com/RatTail.html

you can make your own:

http://www.hamuniverse.com/htantennamod.html
 
RE: Radiographic Examination of Rubber Ducks  
by KM1H on August 6, 2018 Mail this to a friend!
"i took my mfj 259-c analyser along to a ham radio outlet store some years ago when shopping for a 2m rubber duck.
oh, boy.
they weren't very happy with the results, and neither was i. a couple didn't work at all."

You really didnt think that was an accurate test? Without knowing the details of the antenna and radio design it doenst even approach a feel good maybe.
 
RE: Radiographic Examination of Rubber Ducks  
by KA7EKW on August 9, 2018 Mail this to a friend!
Just a thought, but when I was working with highly-sensitive semiconductors (BOY, was it easy to hurt their feelings!), I wore a conductive strap around my shoe, to make contact with the metal-impregnated floor cover and keep me grounded.

I wonder if there would be any effect from running a ground wire from an HT to such a strap, using a remote speaker mike and leaving the HT clipped to the belt.

I remember a NASA paper from about 1980, detailing the use of wrist bands and body EMF conductance as low-power antennas at certain VHF and UHF frequencies.
 
Radiographic Examination of Rubber Ducks  
by K5DH on August 10, 2018 Mail this to a friend!
Thanks for an interesting read!
 
RE: Radiographic Examination of Rubber Ducks  
by LYFAN on August 10, 2018 Mail this to a friend!
Interesting to see that they are not all simple helicals, but that some use different sections of different construction. Which pretty much explains why so many "identical" rubber ducks vary so much in performance. Nice to finally know!
 
RE: Radiographic Examination of Rubber Ducks  
by W3UEC on August 14, 2018 Mail this to a friend!

Please take into account that a major (if not most important) limiting factor to the useful clarity of the images presented here is the size and resolution of the monitor or screen on which we view them.

VY 73 de W3UEC
 
Radiographic Examination of Rubber Ducks  
by K0FF on August 17, 2018 Mail this to a friend!
Thanks for the well written and interesting article.

Geo>K0FF
 
Radiographic Examination of Rubber Ducks  
by XE1UFO on August 20, 2018 Mail this to a friend!
Great read!

Let me add that you can purchase "tool handle dip" at your local Wal-Mart, which does a great job of replacing the rubber on your rubber duckie, if you have peeled it away, either deliberately or accidentally. We also can use it to protect our home-made coils and traps from the weather.

73 de XE1UFO a.k.a. KA5SUT
 
RE: Radiographic Examination of Rubber Ducks  
by N4TRC on August 26, 2018 Mail this to a friend!
When the plastic of my HT duckie antenna went bad, I just peeled it off bit by bit, then replaced it w/ heat shrink wrap... a little hot glue in the tip, seems good as new!
 
Radiographic Examination of Rubber Ducks  
by KC5YN on August 29, 2018 Mail this to a friend!

Thanks for taking the time to share this well written and general interest article.

I have often wondered why there are not CQ or QST tests (that I could find) on the 'Duckies'.

Fred
 
RE: Radiographic Examination of Rubber Ducks  
by K3GAU on August 31, 2018 Mail this to a friend!
The problem with trying to measure "rubber ducky" SWR is that they are only half of the antenna just like most other vertical antennas. What forms the rest of the antenna (the ground plane) critically affects how the ducky performs and the SWR you measure.

We got into that some years ago when we were trying to design a ducky antenna for manufacture. Small HTs and even the 259s don't form much of a good ground plane at 6 mtr, 2 mtr or even 70 cm and what effect does your hand, arm or other body part have?

I think most rubber ducks are designed with a bit of a "one wet finger in the air" approach or the designer uses what they think is 'roughly equivalent' to what they will be used on unless they know for sure what it will be mounted on. :-)
Dave K3GAU
 
Email Subscription
You are not subscribed to discussions on this article.

Subscribe!
My Subscriptions
Subscriptions Help

Other Antennas Articles
Nearly Cheap Homebrew QRP Vertical