Author Topic: Small loop antennas @ 433 Mhz  (Read 25920 times)

joelucid

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Re: Small loop antennas @ 433 Mhz
« Reply #45 on: June 03, 2016, 07:45:33 AM »
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Thanks, I will try this out. It's pricey though for what it is.

True. Performance was a bit better than with wire though which I found impressive. Maybe we should open one up and see if you can do it as trace. I bet it's a short stub loaded with a small loop.

Felix

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Re: Small loop antennas @ 433 Mhz
« Reply #46 on: June 03, 2016, 08:35:50 AM »
Apparently they have a patent (pending) so that might not go so well :)

TomWS

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Re: Small loop antennas @ 433 Mhz
« Reply #47 on: June 03, 2016, 08:40:49 AM »
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However, not having a vna, I've lately been wondering what the alternatives might be.

This may not be what you're looking for, but I just tested the linx splatch antenna yesterday (http://www.digikey.com/product-detail/en/linx-technologies-inc/ANT-433-SP/ANT-433-SP-ND/1679578). It claims to be very stable, no tuning required. And it really is, it's working very well even though I didn't even connect all pads and there's no matching.

It should make for a great travel companion:


This reminded me of the predecessor of my Dust Collector project (https://lowpowerlab.com/forum/index.php/topic,918.0.html).  I used the Splatch antenna on the controller and the remotes.  They worked well enough for that application although I don't have any metrics on performance.


joelucid

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Re: Small loop antennas @ 433 Mhz
« Reply #48 on: June 03, 2016, 09:06:57 AM »
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Apparently they have a patent (pending) so that might not go so well :)

Well pending doesn't mean granted and granted doesn't mean that there aren't good ideas in there that don't relate to the patent. BTW if there is a patent pending I couldn't find it.

WhiteHare

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Re: Small loop antennas @ 433 Mhz
« Reply #49 on: June 04, 2016, 09:27:54 AM »
Hmmm..  Looking at the datasheet for the uSplatch and splatch antennas.  If I'm reading them right, they both seem to assume the existence of a proper ground plane: 
https://www.linxtechnologies.com/resources/data-guides/ant-916-usp.pdf
https://www.linxtechnologies.com/resources/data-guides/ant-916-sp.pdf

I wonder: would it work to simply attach a sufficiently large uniform antenna ground plane to the back of the moteino with, say, double sided tape so that the splatch has a sufficient counterpoise?  Just solder GND to it with a wire?  It's so simple it's probably worth a try.  I've been meaning to try it underneath just the RFM69 module (execuval already did a very small one to good effect in a different context, so I thought I'd try something bigger), but maybe the RFM69 doesn't need to be separated like that for it to work.  However, lacking the proper measurement equipment, I'm reticent to mess with it, as it might require a lot of blind experimentation to get anywhere with it.
« Last Edit: June 04, 2016, 11:32:06 AM by WhiteHare »

joelucid

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Re: Small loop antennas @ 433 Mhz
« Reply #50 on: June 04, 2016, 11:49:10 AM »
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If I'm reading them right, they both seem to assume the existence of a proper ground plane

They do require a ground plane, but not a full one. A 433 mhz monopole would need at least a 36cm diameter ground plane disk to be considered fully grounded.

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would it work to simply attach a sufficiently large uniform antenna ground plane to the back of the moteino with, say, double sided tape so that the splatch has a sufficient counterpoise?

In my setup the ground plane on the Moteino serves as antenna ground plane. But yes, adding an uninterrupted ground plane maybe even of the recommended dimensions should certainly improve things. If you put the antenna on top you should also put the ground plane on top to shield components and pcb.

As I said though even the very ad-hoc mounting I used already provided better reception than the wire antenna in my measurement which I found quite sufficient for this purpose (travel kit).

WhiteHare

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Re: Small loop antennas @ 433 Mhz
« Reply #51 on: June 05, 2016, 01:26:22 PM »
As I said though even the very ad-hoc mounting I used already provided better reception than the wire antenna in my measurement ...
You mean better eve than the typical straight piece of wire?  Or the loop of wire you've been working on recently (the OP)?

joelucid

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Re: Small loop antennas @ 433 Mhz
« Reply #52 on: June 05, 2016, 03:45:29 PM »
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You mean better eve than the typical straight piece of wire?  Or the loop of wire you've been working on recently (the OP)?

I directly compared a 443mhz Moteino with 17,3 cm wire against the modded Moteino with uSplatch. The uSplatch performed consistently better.

TomWS

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Re: Small loop antennas @ 433 Mhz
« Reply #53 on: June 05, 2016, 03:54:07 PM »
I directly compared a 443mhz Moteino with 17,3 cm wire against the modded Moteino with uSplatch. The uSplatch performed consistently better.
Is this with the uSplatch perpendicular to the Moteino plane or parallel with it.  I think your photo showed perpendicular but I think Linx specs parallel (ground plane to the pad edge of the antenna).

Tom

joelucid

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Re: Small loop antennas @ 433 Mhz
« Reply #54 on: June 05, 2016, 04:22:21 PM »
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Is this with the uSplatch perpendicular to the Moteino plane or parallel with it.  I think your photo showed perpendicular but I think Linx specs parallel (ground plane to the pad edge of the antenna).

Yeah it's with the perpendicular mount that I did just to try it out. I also only connected two of the three pads - one to the antenna out and the other to the gnd pin opposite of the ftdi header. I'm very aware that's not the recommended mount so the results surprised me quite a bit.

WhiteHare

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Re: Small loop antennas @ 433 Mhz
« Reply #55 on: June 05, 2016, 06:52:02 PM »
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You mean better eve than the typical straight piece of wire?  Or the loop of wire you've been working on recently (the OP)?

I directly compared a 443mhz Moteino with 17,3 cm wire against the modded Moteino with uSplatch. The uSplatch performed consistently better.

Wow, that ranks as a really important find then, and the fact that it's so compact makes it even more awesome.   8)

So, I just ordered a couple to try out.   Hopefully I'll get them by next weekend.

« Last Edit: June 06, 2016, 12:00:52 AM by WhiteHare »

WhiteHare

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Re: Small loop antennas @ 433 Mhz
« Reply #56 on: July 04, 2016, 09:37:03 AM »
I tried the 915Mhz uSplatch antenna on a node. Looking at the RSSI, it's noticeably more directional, but with a dipole gateway I'm not worrying about it.

I haven't yet tried comparing it to a helical.
« Last Edit: July 05, 2016, 02:58:11 AM by WhiteHare »

joelucid

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Re: Small loop antennas @ 433 Mhz
« Reply #57 on: July 04, 2016, 03:11:10 PM »
Did you also find it performed on average better than the wire?

captcha

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Re: Small loop antennas @ 433 Mhz
« Reply #58 on: September 03, 2016, 08:00:25 PM »
As mentioned a few posts back I have finally completed testing and uploaded my dipole-on-pcb boards to OSH park.

See related post on this forum for full details:
https://lowpowerlab.com/forum/rf-range-antennas-rfm69-library/easy-pcb-dipoles-for-433-868-and-915mhz/

WhiteHare

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Re: Small loop antennas @ 433 Mhz
« Reply #59 on: October 14, 2016, 06:22:48 PM »
@JoeLucid
I'd like to modify my custom temp-rh node's pcb to use a splatch and send it to the fab sometime soon. Looking at the ANT-915-USP datasheet (https://www.linxtechnologies.com/resources/data-guides/ant-916-usp.pdf), I notice it is recommending it be connected to a rather long and wide PCB (3.145" x 1.53") PCB with what looks like a dedicated ground plane.  Have you found the micro splatch to be especially sensitive to those dimensions?  If so, then I might try modifying the bigger experimental node's PCB instead (see attached).