Laird TRA9023P antenna with very high VSWR

Wireless and IoT RF and Wireless
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1

Hello,

I just bought two TRA9023P’s to test out on my Sensecap M1 miners that works at 905-915 MHZ. Before attaching any antenna I tend to test the VSWR of the antenna and the cable to make sure there isn’t too much reflection in the setup in fear of blowing or hurting the radio card.

I just tested the TRA9023P’s with a cable and was reading between 3-6 VSWR. I could get it to about 1.5 with my hand wrapped around the antenna. I could definitely manipulate the VSWR depending how much of my hand was touching the antenna. But with nothing touching it (inside and outside the building) I was getting a very high VSWR.

To verify that it wasn’t the cable, I tested that cable attached to a PAR90209H-FNF (VSWR of 1.2-1.3). And to triple check I switched out the cable to a different one and tested both the TRA9023P’s and PAR90209H-FNF and got the same 3-6 VSWR for the TRA9023P’s and ~1.2-1.3 for the PAR90209H-FNF.

I also tested a Rak 5.8 omni directional with a compatible cable and got 1.1 VSWR.

Is there something wrong with these TRA9023P’s? Or are these a bad choice for this application? Or is there something else I am missing or not understanding?

Any help with this would be greatly appreciated,

2

@user48

Looking at the information for that antenna that Laird lists.
They list it having a VSWR of 2.

With the cable in question I can then see the total being higher than 2 for the antenna + cable system.

3

Thank you Nathan for your quick response.

But with the same cable on the PAR90209H-FNF I was getting ~1.25 VSWR.

TRA9023P + cable1 = 3-6 VSWR
PAR90209H-FNF + cable1 = 1.2-1.3 VSWR

So if TRA9023P is about 2 that would mean the cable introducing 1-4 units of reflection but with the PAR90209H-FNF only about 0.05?

This doesn’t seem right to me.

4

Hello, Have you tried with the antenna mounted on a ground plane? (this is required per Laird) https://www.lairdconnect.com/rf-antennas/public-safety-antennas/vehicle-antennas/phantom-antennas/phantom-series-vehicle-antennas

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5

See I thought I was missing something. Thank you Scott. No I haven’t and didn’t realized that was required for the part I ordered…

Can one buy a grounding plane assembly or is that only a DYI kind of thing with bare copper wires like I just googled?
Or is it just buy the right part you silly. You wanted the TRA9023NP not the TRA9023P.

6

Ok so there are zero TRA9023NP in stock but 461 TRAB9023NP in stock. Am I correct that the only difference in the two is the first is white and the second is black?

7

Hello, Yes only difference is color (B is black). If you wanted to use a metal ground plane, the rule of thumb for 900MHz is about 6" diameter .

8

Scott you are awesome! Thank you.