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My friend just got a 2006 Chevy Calorado and it came installed with an 3.5mm SMA cable running from the roof to under the dash. It was a park ranger vehicle so it would make sense that they needed a large antenna. We recently got into ham radio and would like to utilize this antenna.

But our Baofengs have the standard SMA male connector, while this cable ends with a 3.5mm male SMA. I looked online for adapters and I see them for around 100$. I would like to know if a Baofeng can run a large antenna like this, and if there's a cheaper solution. Or any entry level hams that would suite this antenna better. Thank you.

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    $\begingroup$ As I mention in my answer, feel free to edit your question to post clear photos of the connector(s) in question, and tell us the specific radio model. You also are not clear if there is already an antenna installed, or what frequencies you hope to work. But SMA is basically SMA. It's just that there happens to be a number of kinds of SMA. $\endgroup$
    – user21417
    Commented Jan 17, 2022 at 18:25
  • $\begingroup$ A quick search for "sma" here also found this answer to a closed question that might give you more details: ham.stackexchange.com/a/859/21417 $\endgroup$
    – user21417
    Commented Jan 17, 2022 at 18:30
  • $\begingroup$ Ebay and Amazon are good places to buy random adapters and jumper cables, depending on how soon you want them. $\endgroup$
    – tomnexus
    Commented Jan 18, 2022 at 0:24
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    $\begingroup$ Is there an antenna or just a cable installed? What's at the other end of the cable? It's possible the installed antenna is for SiriusXM or something, which will be no use for ham radio. $\endgroup$
    – tomnexus
    Commented Jan 18, 2022 at 0:26
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    $\begingroup$ Getting an adapter or a pigtail (a short cable with different connector types on the two ends that is used as an adapter) is easy, but what does the cable go to? An antenna mounted on the vehicle? Is it for ham frequencies? If the antenna was used as part of the ranger's duties, then the antenna probably isn't for ham frequencies, and you'll need a different antenna to connect to a ham radio. $\endgroup$
    – rclocher3
    Commented Jan 27, 2022 at 0:40

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But our Baofengs have the standard SMA male connector while this cable ends with a 3.5mm male SMA.

For such low frequencies I highly recommend you to buy the part out of Aliexpress for very cheap ( 2$/piece). I have used such adapter extensively, and measured their performance with a VNA and everything is fine.

I would like to know if a Baofeng can run a large antenna like this, and if theres a cheaper solution.

Size isn't really the problem here the problem is more of the resonnant frequency of the antenna.*** You might want to make measurements to be sure. The nanoVNA is a cheap option that will bring you many answer. You want to look for the S11 of your antenna, it should be below -10dB if you want to consider an antenna as an actual antenna. everything below is greater! If the antenna is ok, you might want to measure the antenna through the cable to verify it is in good condition. Someone have said you should verify the cable characteristic impedance (50 Ohms is what you want).

Or any entry level HAMs that would suite this antenna better.

If you want to use a frequency between 100MHz and 450MHz you might consider a quarter wave antenna, place upon the center of the metallic roof, it will have a very good ground-plane.

**(For purist : Yes I know resonnant frequency depend on size, but a dish antenna is large but run on high frequency... You get me)

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You say "this antenna" but you don't say what sort of antenna you have or are planning to use. Being specific about the radio model, and posting photos of the connectors in question would help, as well.

But at most common Amateur frequencies the coax you have installed will certainly work well enough to experiment with.

You just need to find the appropriate adapter or pigtail. It sounds like one or the other of these connections is RP-SMA so it should not be that hard to find some mating adapters. See https://en.wikipedia.org/wiki/SMA_connector for some pictures of the kinds of SMA connectors you might find. It basically comes down to inner-thread vs. outer threads, and centre pin vs. no centre pin.

The only question is if the SWR of the feedline and antenna exceeds the values in the radio documentation (check to be sure) and if that matters at the wattage you intend to use.

But once you sort out the connector(s) then you should inspect the coax to make sure it is the usual 50-ohm stuff so you can make your informed decisions about what to hook up between the radio and the antenna.

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  • $\begingroup$ Indeed, check somebody like Digikey for low-volume pricing of SMA connectors of various types. $100 is way over what it should cost. $\endgroup$
    – Jon Custer
    Commented Jan 17, 2022 at 20:41
  • $\begingroup$ Per this comment, an adapter cable might not be enough. You seem to assume that the antenna is resonant at the OP's desired frequency, and that is very unlikely. Downvoted. $\endgroup$
    – Mike Waters
    Commented Jan 27, 2022 at 14:10
  • $\begingroup$ @MikeWaters I did begin with stating that we had incomplete information, and I even added the bit about being sure to consider SWR and power which directly addresses the question of resonance. With some assumptions we can at least direct the OP in the direction of sorting out the kinds of SMA connectors one can run into which is literally step one. As with all things Amateur it is up to the operator how they run their equipment. Merely informing someone about a connector without an entire essay about resonance (which can be found elsewhere around here) is not the purview of Q&A sites. $\endgroup$
    – user21417
    Commented Jan 27, 2022 at 15:37

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