Building a poor man’s quarter-wave 433MHz antenna: Antenna’s construction

RE: Building a poor man’s quarter-wave 433MHz antenna: Antenna’s construction

dougw — Mon, 26 Dec 2022 07:35:28 GMT

Great to see an article here on building an antenna.

RE: Building a poor man’s quarter-wave 433MHz antenna: Antenna’s construction

kmikemoo — Mon, 13 Jan 2020 05:25:43 GMT

[mention:3bf627874ebf4e7ab0372b11f5098b75:e9ed411860ed4f2ba0265705b8793d05] Awesome project! I really like your SMA ground plane antenna. With the connector being so small, it must have been quite a challenge to work on.

Since you have your NanoVNA, velocity factor for your radials doesn't mean as much since you can measure your antennas response and trim accordingly.

I have read that wire has a velocity factor of 0.95. I believe that value is for bare wire since many long wire antennas use bare wire. Insulation lowers the velocity factor so your radials can be slightly shorter. You can't beat a measurement though.

RE: Building a poor man’s quarter-wave 433MHz antenna: Antenna’s construction

DAB — Sun, 12 Jan 2020 19:48:13 GMT

Good posts.

Building antennae are not for the feint of heart.

It is a lot of work and you need to pay attention to detail otherwise you lose a lot of power needlessly.

DAB

RE: Building a poor man’s quarter-wave 433MHz antenna: Antenna’s construction

stevesmythe — Sun, 12 Jan 2020 16:49:57 GMT

Nice blog post! You could alternatively have used a coat hanger or a metal tape measure.

RE: Building a poor man’s quarter-wave 433MHz antenna: Antenna’s construction

shabaz — Sat, 11 Jan 2020 23:23:21 GMT

Hi Fabio,

Awesome blog post, clearly showing how you designed the antenna and tested it!

That SMA bulkhead connector looks like a very useful base for an antenna : ) I might order some for small antenna experiments too.

I think the effect may be slight, so maybe no need here. but since your design was fortunately with the exact type of connector that you had for your OSL calibration pieces, ideally the calibration could be done including the IPEX adapter and the SMA-IPEX cable, i.e. all the way up to where the antenna connects. A bit harder to physically do though.. the cable would need to be clamped so that it is in the same position as when the antenna will attach. The reason for doing the calibration there, is so that when the antenna is connected, the measured phase is only due to the antenna, and not due to the added SMA-IPEX cable length. Anyway, the difference may be minor as mentioned, for the return loss measurement.

It was great to see that antenna tuning is so straightforward with the Nano VNA! Although I do not have it, I too was unsure about the small screen for a complex instrument, so it's nice to see it being driven from the computer software.

At my first place of work, I think there was just one VNA from memory (or at least very few!), and only one or two people were familiar with how to use it, due to the expense.