I am currently trying to build a pyramidal horn antenna. The horn antenna is designed for the hydrogen line at 1420 MHz. The copper probe at the end of the waveguide is soldered onto a 4-hole SMA panel mount.

I'm using this LNA and this SDR and this SMA Connector Kit. I am struggling to find a 4-hole SMA male panel mount which I can use to solder the copper wire on to. Are there any alternatives which I can use to fix this issue?

Here is a link to the documentation I am following: https://physicsopenlab.org/wp-content/uploads/2020/07/Hydrogen-Line-Project-Documentation.pdf

  • \$\begingroup\$ up to which frequency does this need to work well? What's the size of your horn antenna? What does a panel mount SMA connector have to do with all this? \$\endgroup\$ Mar 4 at 10:47
  • \$\begingroup\$ Are there any alternatives <-- Alternatives to which part? \$\endgroup\$
    – Andy aka
    Mar 4 at 11:23
  • \$\begingroup\$ @MarcusMüller I've made an edit which should make what I'm asking a bit more clear \$\endgroup\$
    – Skantzy
    Mar 4 at 11:32
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    \$\begingroup\$ sorry, that helped very little: "soldered to the end" of what? I can guess you mean a feed? But what kind of feed? We can't read the construction plans in your head, sadly ;) \$\endgroup\$ Mar 4 at 11:34
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    \$\begingroup\$ @GrahamNye I've added a link to the documentation I am following, hope it helps \$\endgroup\$
    – Skantzy
    Mar 4 at 12:58

1 Answer 1


A Google search for "panel mount sma" shows a selection of devices from major electronics distributors. (Here in the UK Mouser, Digikey, RS, Farnell. Elsewhere you may have a different selection.)

this SMA Connector Kit.

Try to minimise the number of adapters you string together especially for the weak signal connection between the horn and the LNA. If the horn is rigid enough you could use a four hole male plug on the waveguide section and attach the LNA directly to the horn.

If the horn is less rigid so that the weight of the LNA would make the waveguide to co-ax SMA probe flex you could use a four hole female jack on the horn and buy a pre-made short male-male SMA lead to connect it to the LNA.

After the LNA it's less critical to avoid adapter losses but the fewer adapters you use the more reliable your connections will be. Try to plan your cables to use the correct connectors without adapters where possible.

For readers mystified by what OP is trying to do I assume they are trying to build their own waveguide to coax transition (because commercial ones are really expensive).

  • \$\begingroup\$ Determining the placement, length, and orientation of the "probe" seems to be a bigger problem than the type of coax connector that is used. \$\endgroup\$
    – SteveSh
    Mar 4 at 12:28
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    \$\begingroup\$ @SteveSh Probably so but OP isn't asking about that. So either OP has adequate build instructions for the probe or they'll be back with a second question. I'd find it harder to answer that one, beyond "look at Google". \$\endgroup\$
    – Graham Nye
    Mar 4 at 12:33

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