John,
RP-SMA or Reverse Polarity SMA connectors were developed so that personal users of RF devices could not easily switch antennas on devices with ones that exceed legal limits. From what I remember, the FCC allows RP-SMA connectors as acceptable for compliant devices. All that the RP-SMA connector does is switch the center contact from female-to-male and visa-versa in the jack and plug. This is why your antenna will not correctly connect to the regular SMA connector.
I have used both omnidirectional 3dBi and directional patch 8dBi external antennas from Hyperlink Technologies on the Tmote Sky platform. You can purchase the RP-SMA bulkhead connectors for attaching to the motes from digikey.com. It is easy to attach these to the motes and if you have a heat gun, moving the capacitor on the board to switch from the onboard antenna to the external is easy as well (consult the Tmote user manual). We had significantly improved transmission distance using the external antennas, though antenna selection requires consideration more than just distance requirements. You should balance the requirements of signal directionality/placement requirements, costs, size (if applicable), and overall gain. Keep in mind as well that if your signal is very strong, you can reduce your transmission/reception power, which saves the battery, so in some applications having a more expensive antenna saves in the long run.
Good Luck,
Matt Whelan
[EMAIL PROTECTED] wrote: -----To: [email protected]
From: John Griessen <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
Date: 01/07/2006 12:15PM
Subject: [Tinyos-help] Best external antenna for Tmote Sky on Texas hillside?
I am buying parts for a sensor network of 30 Tmote Sky transceivers on 88 acres
of hillside near thehill top with plenty of wind sun and rain that should last
at least 7 years outdoors.
The Tmote Sky
has SMA connector 5 hole mounting pattern on the board. What is the least cost
way to connect when bulkhead connectors are not planned, (I plan to run the SMA
cable through a rubber squeeze-down water tight fitting thru the box wall).
Does Moteiv supply a SMA five hole circuit board connector they have tested?
Is it left off so you can choose between SMA or TNC or R-SMA?
I am thinking a female SMA connector on the circuit board, then male male
SMA cable, but I see the antenna suppliers talk of reverse SMA connections and
cables that are SMA one end and type N on other end....
I'm seeing I don't know enough yet, because a WAP card antenna I see has
female center conductor, and it screws onto a female SMA bulkhead connector I
have, but without making a conection.... Is that antenna connector one they
are calling R-SMA or reverse SMA?
Thanks,
John Griessen
Robert Szewczyk wrote:
> We've had good luck with Hyperlinktech.com and with www.fab-corp.com
> as vendors, but without knowing any specifics about your application I
> cannot advise you on a particular choice of antenna.
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