Anyone with a VHF or UHF handheld transceiver (HT) probably uses the standard “rubber duck” antenna for casual use. I often refer to the rubber duck as The World’s Most Convenient Crappy Antenna. To be fair, all antennas are a compromise…the rubber duck optimizes small size and convenience at the expense of performance. The Wikipedia entry describes the rubber duck antenna as “an electrically short monopole antenna…[that] consists of a springy wire in the shape of a narrow helix, sealed in a rubber or plastic jacket to protect the antenna.“
Being curious about what really is hiding inside the typical rubber duck antenna, I decided to take a few of them apart. I did not try to assess the performance of the antennas but just examine their construction.
Baofeng UV-5R Stock Antenna
I started by dissecting a Baofeng UV-5R antenna, which took some aggressive action with a diagonal wire cutters to split the rubberized jacket near the bottom. After that, the jacket slid off to reveal the classic spiral antenna element inside. You can see some white adhesive near the top of the spiral element (upper right in the photo).
The Baofeng antenna had a female SMA connector.
Note: You can access high resolution versions of the photos in this article by clicking on them, allowing you to see lots of detail.
Yaesu FT-1DR Stock Antenna
The Yaesu antenna was easy to disassemble. In fact, I chose this antenna because I noticed that the outside jacket had come loose and was starting to slide off the antenna. A steady pull on the cover exposed the antenna elements without any further antenna abuse. (I plan to reinstall the cover with a few dabs of glue and expect that it will continue to work fine.)
The construction of this antenna is quite different from the Baofeng. The main element is a very tightly-wound spring…so tight that I expect that it acts like a solid wire electrically. In other words, it doesn’t have the spiral configuration that makes the antenna act longer electrically. At the bottom of the antenna, there is a coil inserted in series with the radiating element (connects radiating element with the center pin of the SMA connector).
The photo to the right shows a closeup view of the male SMA connector and the coil.
Laird VHF Antenna
Next, I wondered if antennas for commercial radios used different design or construction techniques. Laird makes high-quality antennas for the mobile radio and other commercial markets, so I purchased one of their VHF rubber duck antennas to dissect. This model is intended for use with Motorola radios requiring a threaded antenna stud.
This antenna was a challenge to cut open. I used a sharp knife and diagonal pliers to cut the rubberized jacket and peeled it back using a needle-nose pliers. The rubberized coating was embedded into the spiral antenna element, so it did not come apart easily. It took over an hour fighting with the antenna and I gave up before getting the entire spiral element exposed.
The Laird antenna is clearly the sturdiest of the three antennas. The spiral element is much thicker than the Baofeng and the rubberized coating is tougher and molded tightly into the spiral element.
The Baofeng and Laird antennas use the same design concept…just take a spiral antenna element and apply a protective cover. However, the Laird construction was far superior, but not a surprise given that Baofeng is a low-cost provider in the ham radio (consumer) market.
My disappointment is with the Yaesu antenna. The antenna came apart after one year of not very heavy use. I expect I can put it back together with some adhesive, improving on the design in the process.
Anyway, I found this interesting and wanted to share it with you. What’s in your rubber duck?
73, Bob KØNR
Disappointed to not see any of the Kenwood handheld’s ‘exposed’. (TH-D72A or the TH-F6A, 2 very common handhelds
Sorry, Joe. I already destroyed two antennas.
If you have a Kenwood antenna to contribute, send it to me and I’ll dissect it.
73, Bob K0NR
I wonder if the black material inside the spiral at the connector end of the Boafeng antenna is some sort of carbon loaded stuff, to make it wider band by adding some loss.
Not uncommon to see that done in some of the “Home Base” CB verticals, a series resistor feeding the single element.
Put 50W up it and see if it gets hot!
I’m not sure what the black material is, but it is flexible.
Also, note that the spiral element is more closely spaced near the bottom of the antenna.
Bob,
Just for giggles, if you think you can share those stripped out monopoles, i can run real world radiation pattern and a gain measurement out of those antennae(possibly check if they match to specs..if i can get the antenna specs from Baofeng) in my lab here and share the details out with you.
Then you can add on to this article on it’s REAL measured gain and radiation pattern of a typical electrically short monopole.
Let me know if you think that’s a cool idea.
KEØIDV
I’ll be shocked if you can find a Baofeng spec for their antenna.
It would be interesting to test a bunch of rubber ducks and compare their performance. In the past, I’ve performed some measurements on HT antennas and its kind of tricky. You need to create a test setup that mimics an HT, ideally without any cables connected to it.
Love your article, I’ve been studying antenna’s since getting a few that made no sense. I took a meter and found the ground connected to the emitter. The center pin matched to nothing, ground nor radiator.????? After asking a few elmors they told me they where bad antenna’s. The Baofeng looks like the coil radiator is connected to ground. Is there a Capacitor under the black cover. I think the antennas I’ve been working with have high pass filters built in. Because those antennas work really great when hooked up. A high pass filter would exsplain alot. I have seen pics of other antennas taken apart and some have capacitors in them.
A standard multimeter measures ohms at DC, not AC, so you have to be careful interpreting the results. As you have encountered, DC measurements of antennas can be confusing. Depending on the design, an antenna can be a 50 ohms at its operating frequency but a short or open for DC (0 Hertz). A capacitor acts as an open circuit at DC and an inductor acts as a short circuit.
For the Baofeng antenna, you are correct, the spiral element is connected to the outside of the SMA connector. There may be another circuit element hiding inside the black thingy. I have not torn that open. The DC ohms reading between the center pin and outside shell of the SMA is an open circuit.
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Although the various construction of the rubber ducks is interesting what most should know is performance. I think all of us know they are lousy antenna, but as mentioned they are a compromise. Performance as compared to each other, who has the better poor RD and compare to the 3rd party longer and also simple 1/4 wave vert would be good to know.
But does not take long to see RDs perform poorly.
thanks for the article
The tightly wound radiator on the first antenna is nothing more than common automotive speedometer cable. Universal cables can be purchased at auto parts suppliers if one would like to repair and or experiment with rubber ducks.
I came across an interesting alternative HT antenna that uses a whip. It is an end fed 1/2 wave with loading coil on its base. It is not overly long on 70 cm and has much more gain than a duck. 73 from the country where the big five live.
I’ve always been curious about what’s actually inside these rubber duck antennas, but never had the nerve to take one apart. I’m not surprised the Laird had superior construction compared to the Baofeng, but it’s disappointing to hear about the Yaesu falling apart so quickly. Makes me think I should start paying more attention to build quality when picking antennas, especially for long-term use.
After comparing antennas from various manufacturers as well as radio design, that Baofeng antenna disassembly confirms what I suspected. I believe Baofeng runs their antennas reverse polarity. Meaning they radiate (and receive) by the ground part of the SMA, not center pin. This also explains why when I put an aftermarket high gain antenna with standard polarity on a baofang radio it hears worse than the stock duck. That’s because the aftermarket antennas are giving a better center core element which feeds opposite to what the baofeng needs.