Sparkfun Wireless Modem

[Steve McBride]

I am looking at this model:

http://www.sparkfun.com/commerce/product_info.php?products_id=559

for long range transmission of GPS data (using either a Geko 201 or Sparkfun's 20 channel GPS). I could go with a smaller model:

http://www.sparkfun.com/commerce/product_info.php?products_id=155

but it has a range of approximately 500 meters compared to approximately 2500 for the first one.

I'm not looking at autonomous flight. What I would like is to be able to see the altitude and position of the model in flight on a map in real time. Plans are to use a model for live video and photography of remote areas while retaining the ability to pinpoint the location of the area the images are from. Plans are to aid firefighters in determining the extent of wildfires as they happen and perhaps law enforcement in searches of inaccessible areas.

The cost of these units would be fairly cost effective if I can get decent range out of the modems.

Any insight or feedback would be greatly appreciated. Other options that would allow me to achieve the desired results would be appreciated too.

Steve

[clolson]

Interesting, only 9600baud, but it seems like you get a lot of functionality for the price. 1500m should give you a solid connection within visual range (if you are flying by line of sight.) 9600 isn't fast, but it's fast enough for 1hz position updates and you could probably send a few other things up and down the pipe if you were careful.

I would also be interested in hearing how well these units work in the field. If you go with maxstream/aerocomm, you are into it for several hundred dollars right out of the gate (although they offer faster speeds and longer ranges.) That is a bit out of my hobby budget right now, but < $100 might be something I could slip in under the wife's radar screen.

[radiohound]

You might be interested in this one from maxstream. The also make a 900xtend module,but it is more expensive.

http://www.maxstream.net/products/xbee/xbee-pro-oem-rf-module-zigbee.php

http://www.maxstream.net/products/xtend/oem-rf-module.php

Walter
www.uavs.net

[Steve McBride]

My problem is that I only know enough about this stuff to be dangerous ;)

The HAC-L96 has a transmission data rate of 9600 baud. This is not selectable by the user. Is there any problem with feeding it data at 4800 baud which I believe is the standard NMEA rate? Just curious - I've not played with serial data where the two devices were set at different data rates.

It's certainly within my budget so I may give it a shot if I can answer that question.

Steve

[Steve McBride]

Thanks Walter - I'll go through the data sheets and manuals and see how it looks. My first concern would be the 2.4ghz freq and how it may interfere with my video transmitter, also at 2.4 ghz?

I appreciate the great help I am getting!

Steve

[muc]

Steve,

If you can stand updates every two seconds then you could use the audio channel of your video transmitter to send the GPS data. You could use a TinyTrak to do this - http://www.byonics.com/tinytrak/. I made my own version that gave me a little more flexibility. Info on that can be found here - http://www.rcgroups.com/forums/showthread.php?t=407911. I’ll try to reply to any questions but I’m traveling and have very limited access to email and the web.

Mark

[Mr.RC-CAM]

As suggested above, using the wireless video's audio channel for APRS applications is simple and very low cost. You can use a notebook PC's sound card as the receiving modem. The web is full of examples on how to do this (search APRS and/or TinyTrak).

[mckaneorg]

I use the maxstream. I have 2 sets and love em. It is more expensive but the range is extremely impressive.

[Steve McBride]

I love the ability to do 1200bps over the audio channel. However I want to retain the ability to track the location in the event that the model drops the video and audio signal. I know that flying via GPS or camera is frowned upon, but if the model gets briefly obscured by smoke, I need to know that I have reliable GPS data coming back at least as far as I can see the model (about 1/2 mile).

I have no doubts about the maxstream XBee pro being up to the task. Do any of you think that the ISM 2.4ghz frequency that this operates at would cause interference with the 2.4ghz video link? I honestly have no idea and appreciate the feedback.

A few things about the Xbee that I like are it's size, weight, price and 'configurability' through software. The XBee Pro development kit would cost about the same as two of the Sparkfun modules and provide greater range and the ability to have higher data rates.

Thanks again guys - I'll poke around and search on the XBee. If you think there would be no interference between the video and modem let me know.

Steve

[typicalaimster]

I have no doubts about the maxstream XBee pro being up to the task. Do any of you think that the ISM 2.4ghz frequency that this operates at would cause interference with the 2.4ghz video link? I honestly have no idea and appreciate the feedback.


Based off of what the Spektrum DX-6 did.. The Video link will interfear with the 2.4ghz Maxstream. You may want to check into the 900mhz Maxstream units instead. I've tested the 900mhz setup in my plane and had very good results.

[Steve McBride]

Ok - that takes me back to the Spark Fun modules based on cost. However the Spark Fun modems are factory set at 9600 baud. NMEA GPS data runs at 4800. Would this be a problem?

Thanks guys! If the data rate is not a problem then I'll order a couple and let you know how they work.

Steve

[Tuner]

I have done me research and maxstream seems to be the way to go or im missing something.

Scott

[Steve McBride]

I'm looking at the cost of a 900mhz maxstream setup as being prohibitive. I have no doubts that they work great though. The problem is that there is no info that I can find regarding the Spark Fun modems so I guess I'll have to go out on a limb and try it for myself. I would love to be able to use the small and inexpensive XBee Pro but the frequency interference would be unacceptable. I guess I could change my camera transmitter/receiver to a different frequency though. I'll have to weight the cost difference.

I've received some comments back from Spark Fun. 4800 baud into a 9600 baud modem is a no-no so this changes my GPS to one with a configurable baud rate. I am considering the following:

HAC-LN96 Low power 9600 baud radio Modem (2 ea) = $179.90

http://www.sparkfun.com/commerce/product_info.php?products_id=559

12 channel Lassen IQ 12 channel GPS (1ea) = $49.95

http://www.sparkfun.com/commerce/product_info.php?products_id=163

Lassen IQ RS232 eval board (1ea) = $29.95

http://www.sparkfun.com/commerce/product_info.php?products_id=167

Antenna (1ea) = $17.95 (NOTE – need to see if it is included with eval board)

http://www.sparkfun.com/commerce/product_info.php?products_id=178

Grand Total = $277.75 plus shipping.

The modems are powered from 7.2V and the RS232 eval board is powered from 4-10v so powering from a 2 cell lipo should not be a problem. The units are small and there looks to be a bit of weight savings to be had by hard wiring everything.

Anyone see any problems with this setup (other than it's not been tested)?

[AntonK]

A note on the audio channel of a sound card option. You can acheive 4800 baud doing this. The paparazzi autopilot project has a demodulator for the soundcard to acheive this. If you need more information contact stop by #paparazzi on freenodes.

Anton

[typicalaimster]

I'm looking at the cost of a 900mhz maxstream setup as being prohibitive. I have no doubts that they work great though. The problem is that there is no info that I can find regarding the Spark Fun modems so I guess I'll have to go out on a limb and try it for myself.

I've also seen the Sparkfun modules. I've been eye'ing them for about a month now. Right now I'm flying short range. They were a good idea for long range communication. Let us know how it goes..

[Steve McBride]

OK - Sparkfun offers a Lassen IQ starter kit for $99.00 that includes the GPS unit, Mag mount antenna, Serial board, cables and software. The mag mount is heavy and I don't need the cables. The software is available off their website. So for about $3 less, I get the smaller embedded antenna and none of the other stuff.

The key to the setup I outlined above is the IQ GPS and it's ability to match the modem's 9600 baud data rate. I have some reservations about the ability to stream NMEA at 9600 baud though (double it's standard rate). Plans are to order the GPS serial starter kit and see how well the NMEA mapping software works with data at 9600 baud. Anyone have experience with this data rate and NMEA streams?

Should have the GPS come late next week - I'll let you know how it works if anyone is interested. If all works, the next step will be to order the modems and see how well they work on the ground. The GPS board outputs TTL. Should be an easy process to eliminate the serial board in the kit and build a small TTL - RS-232 circuit.

Thanks again for all the help and advice.

Steve

[XJet]

I've been using the Sparkfun modem and Larsen GPS in a UAV for quite a while now and it works extremely well.

We some old video from the very early flights can be found online at: http://www.simplejets.com/uavclips.htm

These show how the GPS data was (at that stage) relayed back to the ground-station where the UAV's position was indicated on a computerized map.

We obtained fairly solid comms beyond 1Km using just the standard rubber-ducky antennas although there were some drop-outs at low altitudes. This was greatly improved by a switch to 1/4wave antennas.

The ink is now handles GPS position reporting, onboard telemetry (airspeed, engine RPMs, temperature, etc) and also allows uploading new waypoints and configuration data from the ground.

We're now replacing the sparkfun modems with more powerful units as we start our long-range testing. In fact it's so long-range that we're using another orbiting UAV as a repeater for the telemetry because we need "over the horizon" comms abilities.

[Steve McBride]

Thanks for the confirmation XJet. It makes me feel better about the modems.

Which GPS did you use? I've been reconsidering my choice of GPS because the Lassen IQ does not do waypoints. I don't need that ability, but it would be good to have if I wanted to have a return to home feature. I don't suppose if anyone knows if the Geko 201 works at 9600 baud does it?

Thanks again,
Steve

[XJet]

I used the Lassen -- the waypoint facility is handled by our own processor so that's not an issue.

In its simplest form you can just configure the Lassen to output at 9600bps and wire it straight to the modem using TTL level signals. A piece of cake!

[radiohound]

I don't suppose if anyone knows if the Geko 201 works at 9600 baud does it?


My Geko 201 can only do 9600 baud in text mode, not NMEA mode. I looked at the firmware updates on the GARMIN site, and they do not seem to include anything that will let you change the baud from the 4800 while on NMEA mode.

[typicalaimster]

FYI from Maxstream..

April Web Special

9XStream Development Kits - $249 each* (regularly $409)

The 9XStream Development Kit has everything you need to get your wireless project headed in the right direction. The 900 MHz OEM RF modules come with RS-232/485 interface boards and all the necessary software, cables and accessories to communicate right out of the box.

This special April offer makes it simple to incorporate wireless connectivity into nearly any electronic application.

For more details visit www.maxstream.net/web-special, or call MaxStream toll-free 866-765-9885.

*Offer valid April 1-30, 2006. This offer includes the 9XStream Development Kit. This offer cannot be used in combination with other discount. Special pricing applies only to new orders placed during April 1-30, 2006. Customers with blanket PO 's or contract purchases will not be extended special pricing from website specials on any shipments. Offer limited to supplies on hand. Customer must accept all products ordered in one shipment. Please allow up to 4 weeks for delivery on each website special ordered.

[Steve McBride]

Sounds like a great deal! Too late for me as I've already ordered the Sparkfun setup. Power output is 800mw so I'm hoping for great perfromance with a good set of antennas. I like that the Maxstream modems consume a lot less power at a lower voltage though.

Thanks for posting though - hopefully someone will get a good deal. If the Sparkfun modems don't cut it, I may still have time to order the Maxstream setup.

Steve

[ElectroLawndart]

Hi All,

typicalaimster - Thanks for the heads up on the Apr Special on the Xstream. I'm going to be digging through my couch for enough change to get it.

I do have on question. The Maxstream modules put out 100mW of power for 20 mi. range and the Sparkfun modules put out 500mW of power for 1.5Km range. Is the Maxstream data based on a directional antenna like a Yagi or something? Or is it better filtering and signal discrimination.

What kind of real-world ranges are people getting with the Xstream in the 900Mhz and 2.4Ghz bands.

Thanks
Dart

[LukeZ]

Whoa! Aimster, that's a good deal! I don't visit their site often, but is this something they do regularly?

What I'm really wanting to get is the 9XTend set - only slightly more expensive, but at 1 watt has a 40 mile potential range. If anyone catches those things going on sale, let me know. I'll be checking their site more often now that I know they even do sales....

Luke

[typicalaimster]

That was from a newsletter that Maxstream sends me every month.

If you read the specs on the card I think the 40 miles is with their 'special FCC approved high gain antenna'. I don't think you'd want to put a 25" 1.68lb antenna on your plane.

http://www.maxstream.net/products/accessories/antennas-high-gain.php

The Dev kit I have comes with a standard dipole antenna on one card and a 1/4 wave wire antenna on the other...

The park that I tested my Maxstream 900/200mw setup in a park. The park was I was testing in was only a 1/4 mile wide. I left my GPS in the car while I wondered out into the park with my laptop. I was able to send a NMEA sentence across the park w/o a problem...

I then removed the GPS connection and installed the loopback adapter. I then loaded up Maxstreams config software, X-CTU. I ran a range check using 32 bits of data updating at about 250ms. This ran fine across the park without a problem. I only ran into an issue when trying to send VERY large packets of data (1024+) at VERY high rates of speed (under 100ms).

I have the Maxstreams and they work fine for what I do. From SparkFun i'd love to pick up a pair of these...

http://www.sparkfun.com/commerce/product_info.php?products_id=279

I figured I could get two pre-paid SIM's from one of the major 3 GSM providers in my area. I know one of those providers has a 'dial a friend' plan where you can dial the other person for free.

[Steve McBride]

Found out something interesting - even though sparkfun's website lists the modems at 7.2v and the data sheet they offer says 7.2v, the modules are indeed 5v. They are labeled as such. The manufacturer lists 5v as stock and can be ordered as 7.2v operation. I assumed, after reading all the supporting Spark Fun documentation, that these were configured for 7.2V. Nope - they get hot fast at 7.2V.

I prefer 5v really, however the output power is less. I was up until 1am this morning trying to figure out what was wrong. When I dropped the voltage to 6v they worked fine. Have not performed any range tests yet.

Steve

[bbstriker]

I used the Lassen -- the waypoint facility is handled by our own processor so that's not an issue.

In its simplest form you can just configure the Lassen to output at 9600bps and wire it straight to the modem using TTL level signals. A piece of cake!
Hi

I've just bought a Lassen IQ GPS and plan to connect it to a wireless modem also.

Would you mind sharing the the connection diagram with me? I'm not an expert and would feel sick in frying either GPS or Modem or both!

I've PM'd you.

Thanks