Posted on 19 Comments

Improving the SMA-F connector caps

It’s interesting how sometimes small side effects can add up over time to be a real problem.  Recently I’ve had a couple of concerning support requests which led me to start taking some measurements, and I discovered something concerning: our SMA-F connector covers have been gradually changing over time, slowly enough that I had not noticed until it started being an issue for a few customers.

Keep in mind, this is not a problem which affects most customers — users of most Baofeng radios would not likely see an issue — but it revealed a flaw in our design and process which was just a little concerning.

The old glue cap

We refer to those plastic covers as “glue caps” — though it’s true that they make our antennas look a lot nicer, the design is actually intended to hold the adhesive (glue) where it will do the most good.  I’ve gotten a lot better over time at designing 3d models, but it’s been awhile since I really looked at our glue caps.  One thing that did not previous occur to me (when I first was learning to design 3d-printable models and made the glue caps we use today) was that with the modeling tool I use (openscad) it’s very possible to design while using a cross section view, allowing me to see a dimensionally accurate approximation of the connector inside the gluecap as I work.

Looking at the old cap, it’s easy to see where the problem came from:

As you can see, it’s the tapered portion that is intended to prevent the connector from going too deeply into the glue cap. Changes over time have primarily focussed on better holding the glue in the glue cavity at the top… unfortunately, that’s resulted in less resistance to putting the connector in too far and less protection against the connector getting crooked.

It’s important to note that the antennas should still work, but they did result in some cases with insufficient threads coming out the bottom.  Note that if you have an antenna where this is an actual problem, please RMA the antenna and we’ll get you the new module. 99% of you will not have an issue even with the “flawed” version of the caps.

The new glue cap

I redesigned the new glue cap from scratch: I remeasured the connectors with high resolution calipers, built it from the ground up using a cross section mockup, and integrated a “connector stop” which should prevent the connector from going in too far as well as do a much better job of keeping the connector straight.

It’s interesting to note that I discovered that the connector caps can actually be smaller while still actually being stronger; this is because the primary strength of the connector comes from the high quality adhesive we use during the manufacturing process which the new cap does a much better job of holding in the critical places.

Side by side comparisons

For those interested, here is a side by side comparison of the finished result:

Photograph of the old and new connector caps
Old gluecap (left) and new gluecap (right).


More photos

19 thoughts on “Improving the SMA-F connector caps

  1. Its extremely refreshing to see a company/owner/operator take the time to listen and to use the feedback to improve the product. Everyone benefits from this approach. An honest owner doing honest work. Thank you!

    1. It’s basically impossible for us to compete with Chinese companies on price; thus we try to compete on durability, warranty, service, and responsiveness =]

      Also it’s just in the spirit of DIY. I suppose it could be considered a bad idea to post so much information publicly — someone could probably use the photos in this post to recreate our STL files and compete with us — but while we do like to make a living we also feel it can be done in more of a cooperative way where everyone wins, and I for one find this stuff really interesting and enjoy sharing =]

  2. 1. You do not use PayPal for a method of payment?

    2. I do not have a card reader. How does the stripe method of my credit card work?

    3. Do you have 220 MHz version? I have a Kenwood 220 MHz HT that uses a BNC connector.

    Terry Morris, KB8AMZ

    1. We absolutely do accept PayPal! If using stripe, you simply key in the credit card number, expiration, etc like any other ecommerce site.

      There is a 220 version, you can select “220 monoband” on the antenna page.

    2. Okay, thanks for the reply. I will try again as I have items in my basket. Later after asking the question about 220 Mhz, I discovered you do have an antenna for that band.
      I was trying to setup PayPal as a payment method on my profile page but I did not see it available. I will try again later so I can place my order.

  3. Was directed here by the good people over at Ham Study, thanks for the attention to detail.

  4. which filament do you 3D print the connector caps with?

    1. I’ve experimented with a number of different types, but lately I’ve mostly been using a high quality PETG because it’s given me the best results and still retains a fair bit of heat tolerance. I have at times used PLA but feel that deforms too easily at temperatures that hams frequently use and I’ve used ABS but I dislike it because it’s toxic (which makes printing large amounts of it safely more problematic) and PETG is more environmentally friendly in about every way anyway.

      I may change again in the future; I’ve thought about using PolyCarbonate and might even try a higher temperature thermoplastic if the prices come down at some point. I tend to tweak the design on average about twice a year (usually in very small ways) and each time there is a chance I’ll change plastics as well if there is a reason to do so.

  5. Is the rubber washer need for a Baofeng UV-B5?

    1. The washer is never *needed* — the antenna isn’t heavy enough to put significant strain on the connector. That said it is rarely useful for a SMA-F connector

      1. There is a visible gap between the antenna and the radio on my Baofeng GT-5R. I wish I would have bought the rubber washer with the antenna, now I can’t order just a washer because the minimum purchase is $10 and I don’t need anything else at the moment. My recommendation to anyone buying an antenna, just get the washer, it’s only a $1.

        1. It’s worth noting that it’s *very* uncommon for this to happen, but Baofeng radios, for all that is nice about them and the low price, have a surprising amount of variation in some areas — one is that some the SMA connection is much lower than others.

          If you run into an issue like that email us with pictures and we’ll see what we can do to help.

  6. does super elastic signal stick cover the entirety of the 2M & 70 cm frequencies ?

    1. The full answer to that is complex and involves a lot of hemming and hawing, but in essence, yes it does. The nature of antennas in general and HT antennas in specific means that some parts of the band will work a little better than other parts, but it should be completely usable across both bands.

  7. Hello
    I am very new to ham radio. I am going for my Technicians exam. I have been searching for a hand held that is best for emergencies since I travel in a motorhome. I do not know which radio I want at this point…mostly because it gets confusing for me at this point. I read about some tri bands that would get me more frequencies and it sounds appealing to some degree since I would need to get information and or reach out for personal help. I also read that many radios can be loaded through software to get me all the frequencies i want. However one thing for sure is that I would want your elastic antenna ( that coils). The reviews are great. I do not see a tri band elastic antenna on your site.
    If I should get a tri band radio do you have such an antenna? Thank you

  8. I have bought your Super-elastic Signal Sticks for my Ham HT radios and they work great!
    I have a set of BTECH GMRS-V1 HT radios which are FCC Certified GMRS versions of the BaoFeng UV-82 radio. I have a GMRS license – WQYV240. Can you make me a pair of SMA Female Super-elastic Signal Sticks that are specifically tuned for the GMRS 462.550-467.725 MHz channel frequencies? I will be using these radios on GMRS repeaters so, (like the 70CM Ham bands) the repeaters receive on the high end of the band so I need to be able to transmit well on the 467 MHz frequencies. If you are unaware of the specific frequencies for the GMRS channels, here is a link that describes them –

    Thanks and 73,
    Bob – KG5SQJ/WQYV240

  9. Greetings from KI7MBR,
    Have used one on the Icom T70 ht for a couple of years. Works good hereabouts on 2m and 70 cm. The model is the basic black unit. A rubber washer has proven useful. Modification; I added a band of whiteout around the tip that greatly aids its visibility. The antennas is longer than its predecessor, a Diamond dual band, but the “stick’s”superior flexibility is nice to have.

    Keep up the good work. 73 KI7MBR

  10. Dear sir, as a teenager who is very interested in acquiring a license, I am still in the “Scanning stage. would a long whip antenna be recommendable for wide band RX from an Ailunce HD-1? also what does the central loading node do for an antenna? thanks. this is a great website.

    1. As a fellow teenager, I would say that if your “rubber duck” antenna is not sufficient, go ahead and try the signal stick! It goes to support the service that I, and many other hams, used to get their technician licenses and other licenses. Also, if you are still interested I would recommend checking out a club called YARC (Youth Amateur Radio Club), it’s a club mainly on discord with a lot on knowledgeable teenagers, and overall a great club.

      73, Patrick

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