stevech

Member Since: July 9, 2006

Country: United States

  • Product WRL-11634 | about a year ago

    900MHz does have less attenuation per “mile” than 2.4GHz, for sure. Laws of physics. And the “B” model radio does say it has up to 250mW transmitter power. Lots more than typical 2.4GHz products. In the US, FCC regulations restrict the transmitter on-time (duty cycle) in this band, in a complicated combination of data rate/bandwidth and duty cycle. Products that use frequency hopping are allowed higher duty cycle/bandwidth. These radios do use frequency hopping spread spectrum. Amazing for the cost.

    But 28 miles, even with the required high gain antennas for that line of sight range - is a marketing stretch. You might get that with a 9dBi yagi (big antenna) and with both ends elevated to clear the “Fresnel” zone for that long distance.

    But for sure, 100mW or (the cheaper one) at 900MHz with modest antennas and some non-LOS is a good thing for range well beyond what 2.4GHz can do.

    This 902-928MHz band is No. America only. I don’t think the EU (ETSI) has anything comparable - their 868MHz unlicensed is not enough spectrum to do FHSS like the 902-928MHz band.

    The 902-928MHz band, in the US, has lots of “SCADA” users in it, but that’s very low duty cycle.

  • News - Upcoming XBee Class | about a year ago

    Class description says “ how to configure and connect coordinator and router ZigBee Series 1 radios together.”

    Wrong terms. Big confusion. Digi’s trademark is XBee. And XBee is used for both Series 1 and Series 2 XBees. But Series 1 and 2 are totally different animals…

    “ZigBee” is the ZigBee Alliance’s trademarked name of a network layer meshing protocol usable on XBee Series 2 (Ember chipset). ZigBee is available on many vendors' RF modules. The Series 2 (S2) XBees can run ONLY ZigBee and not the simple, non-meshing point to point or hub/star network “topology”.

    Xbee Series 1 (S1) are not ZigBee capable, and often that’s a good thing. They can use either basic 802.15.4 with or without a PAN coordinator, and address data to any node based on the 64 bit MAC address. That’s a good choice for simple projects and for beginners. Like the MAC address of an Ethernet interface; or S1’s can use Digi’s own mesh protocol called DigiMesh. Arguably better than ZigBee.

    IMO, beginners should use S1 without meshing. Most simply projects don’t need the complexity of Meshing, nor the complications of “iDigi” which is Digi’s enterprise scale management system.

  • News - Upcoming XBee Class | about a year ago

    In the photo, the XBee modules are marked “MaxStream”. That company invented the XBee and broke new ground. Digi International acquired MaxStream many years ago and retired the name MaxStream.

    So those XBees are really old. Almost collector’s items.

  • Product WRL-11215 | about a year ago

    No RF-way to solder on an antenna where there already is an antenna. Disrupts the impedance. There are XBee’s with u.FL connectors so you can plug in a coax going to a variety of antennas.

    PCB antenna to me means antenna formed by copper traces on the XBee. That’s what’s talked about in the WRL-11215. There is/was an XBee with a similar antenna, in the form of a (blue) silicon chip antenna that mounts on the PCB. That kind of chip antenna is widely used in WiFi and Bluetooth. The antenna has poor/negative gain and an irregular radiation pattern. The PCB trace antenna is likely very similar to the chip antenna, but less costly.

    The wire antenna, if you have the space, and if the XBee isn’t inside a ferrous metal box, is the best choice. If in an aluminum box- you may be surprised as to how RF-transparent aluminum is, vs. steel.

  • News - SparkFun Gets a Subpoena | about 2 years ago

    Can SFE and others just NOT SELL mag stripe readers? Would that kill the company?

  • News - New Product Friday: Switc… | about 2 years ago

    Sparkfun… Please respect those of us who say that items like the Fio v3 - ATmega32U4 sku: DEV-11017

    Are way overpriced.

    More attention to overhead, margins, and other costs is needed.

  • News - March Caption Contest | about 2 years ago

    Caption: “My red-haired puppy! The father’s hair was, er, I didn’t notice!”

  • Product COM-11108 | about 2 years ago

    Who would EVER need more than (this circa 2004 chip’s) 368 bytes of RAM?

  • News - Eagle 6 Has Landed | about 2 years ago

    I agree muchly with this prior comment…

    There is also DipTrace, which I never hear anyone talk about. It has schematic and pcb layout, and a freeware version. I love it, and it was much easier for me to learn than Eagle.

  • Product TOL-10892 | about 2 years ago

    I don’t understand why the manufacturers “over there” are so cheap as to not spend just a little for a native-english speaker to edit their user manuals. From the manual:

    “Press the key in the gear of frequency can switch between the frequency and the Duty Cycle.Press the key in the gear of AC Voltage or AC Curren can switch among the voltage, current, frequency and duty cycle”

No public wish lists :(