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I'm starting to tinker with an RTL-SDR (generic, and cheap, so nothing fancy in any respect, hence the "pragmatic" in my question title).

It's clear that the antenna provided (about a foot long retractable stick thing) is not really helping my application. It works, and the signal that I'm primarily interested in right now (120 MHz AM, airband, from within 1 mile of the airfield!) is perfectly readable, but I think it's worth a modest investment in being able to make my own antennas (probably just 1/4 wave whips--not talking anything very fancy here), partly to improve this particular signal, but mainly so that I could play (and at this point "play" is a carefully chosen word :) with other signals, perhaps the ADS-B/UAT stuff in the 1 GHz range, maybe other things I've not thought of yet.

To pursue this, I clearly need to be able to connect to the MCX female socket on the USB stick, and bring this to something "more manageable". I'm considering a pigtail that comes to the kind of bayonet-fixing co-ax connector (I think it's called BNC) that we used to use on the venerable 10 Mbps ethernet, in large part because I have a bunch of this connector, and cable, still in my cupboard from a couple of decades ago. That said, I'm open to other ideas if they're "cost-effective".

I don't anticipate the cable being very long, perhaps a foot, and I'm hoping to avoid spending more on this than the cost of the RTL-SDR device (there's that "pragmatic" again :). If I find myself fascinated by this whole thing and wanting to do more, I'll buy a better SDR first.

So, any recommendations? Is my plan to use that coax connector foolish, or will it be "pragmatic" for the time being? Are there considerations that might push me to something better--in the context of this particular, very modest, SDR device?

EDIT: in the end I realized I also wanted to buy a pair of ADS-B antennae, and these happened to come with a pair of MCX - SMA pigtails anyway, so I went with that route, but it's a great reassurance to know that the choice isn't critical for receive-only. Thanks to all for your comments.

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    $\begingroup$ ebay is your friend for these cables, or amazon if you're in a hurry. Consider also an MMCX-M to SMA-F adapter, to save one more dangling cable joint. $\endgroup$
    – tomnexus
    Oct 12, 2021 at 17:44

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BNC is fine. SMA is probably more common in this application, but BNC is widely available, and easier to swap around than SMA. Since this is receive-only and the pigtail will be short, coax loss isn't a real concern either — you probably want to choose something fairly thin and flexible to minimize the stress on the fragile MCX connector.

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BNC work well, make a positive connection, and are simple to crimp. I would suggest that you purchase a pigtail rather than manufacturing one because the SMA connectors are a beast to crimp.

As far as the cables themselves, provided they are still in good shape, both RG-58 used by 10Base2 and RG-8 used by 10Base5 are 50 ohm impedance coax, which is exactly what we "typically" used in amateur radio.

I say "typically" because, of course, some use ladder line and other types of wire with much greater impedance.

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  • $\begingroup$ I don't think I've ever seen a ladder-line pigtail ;) $\endgroup$
    – rclocher3
    Oct 14, 2021 at 13:57
  • $\begingroup$ Isn't that what my RG-58 to BALUN is? :) :) @rclocher3 $\endgroup$
    – David Hoelzer ♦
    Oct 14, 2021 at 14:12

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