Author Topic: Weird antenna problem, low RSSI [SOLVED - with proper grounding]  (Read 3002 times)

WhiteHare

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Re: Weird antenna problem, low RSSI [SOLVED - with proper grounding]
« Reply #15 on: February 08, 2016, 11:01:14 AM »
WhiteHare,

RF can be pretty mysterious.
However, I suspect that the ground-plane may be more for the matching network than the antenna.
A good matching network can make almost anything radiate.

Regarding antennas:
I have experimented with a single radial, multiple radials, a large ground-plate, a counterpoise and a J-pole antenna.
None of those 'grounds" or antennas were significantly better than the straight-wire antenna soldered to the radio.

So, do you suppose executival may have, in effect, added a capacitor, resulting in better impedance matching?  http://www.semtech.com/images/datasheet/AN1200-16_SX1232_API_RF_ST.pdf

When cuddling it, his body may have acted as the capacitor (capacitive touch sensors rely on that effect).

Just a thought, but if so, maybe one could start with a larger piece of sheet metal, and then iteratively trim it down until you discover the optimal size.  Or perhaps even the thickness of the Kapton (is that what it is?) insulation film figures into this?

Whatever it is, it seems like a good chance discovery by executival that the size doesn't have to be large in order to make a considerable difference.  The size he chose seems to be about the same footprint as the RFM69HW, and if that turns out to be an optimal size, then woohoo!
« Last Edit: February 08, 2016, 01:42:04 PM by WhiteHare »

john4444

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Re: Weird antenna problem, low RSSI [SOLVED - with proper grounding]
« Reply #16 on: February 08, 2016, 01:24:09 PM »
Quote
So, do you suppose executival may have, in effect, added a capacitor, resulting in better impedance matching?
As I said, that would be my guess.

Although, Executival may be correct about the counterpose in his situation.
Felix's circuit board acts as the ground-plane for the RFM69 on Moteinos.
I believe that is why the different grounds & counterpose had little effect when I tried them.

Good work by the way with your RSSI testing.
I've been following it closely.
John AE5HQ