Maxstream special for May

[typicalaimster]

This just arrived in my mailbox...

May Web Special

9XTend Development Kits - $299 each (regularly $499)

The 900 MHz, 1 Watt 9XTend Development Kit has everything to get your wireless project headed in the right direction.

http://www.enflyer.com/s/r?ib=1260;159926;410940;11023;126468;7050&id=310146

I've used the 900 / 200mw systems in one of my planes for telemetry. I was up and out about 1500' and didn't have a problem getting the data back to the ground. I can only imagine the 1 watt ones...

--Scott

[Medve]

hey Scott. So what's the deal with this set then. Is it the complete set up for both ends?
Is it pretty much plug and play, or do you have to fiddle with it? Been thinking it would be great to hook up the the GPS to it with a "Y" harness (one side to the UAV controller, the other to the Maxstream) and get all the info right down to the laptop where all I'd have to do is run some standard GPS mapping software and it would show up as a moving map display. Also, at 900Mhz. it would probably not interfere with a 2.4 gig video TX on board.

[Steve McBride]

Good info - thanks for the heads-up

Medve - 900mhz should not interfere with your 2.4ghz downlink. I am using Sparkfun.com 900mhz, 500mw modems for real time moving map display and they do not interfere with my 2.4ghz video. FWIW - I have not exceeded the range of these modems except on the ground (appx 2500 feet) but note that I have not gained the nerve to fly via video or GPS at this point so I can't comment on the range but would expect 500 mw to easily do 3/4 mile in the air with the stock stubby antennas - I would imagine that 1 watt would easily double that range and with good antennas much more.

Good luck!

Steve

PS - yes, the Maxstream system is for two units.

[typicalaimster]

hey Scott. So what's the deal with this set then. Is it the complete set up for both ends?


Medve,
It is for both ends. The system acts like a bridge and is transparent to both the computer and the device. I bought the 200mw setup when they had the deal running last year. I ran it along side my 600mw 2.4Ghz setup from Black Widow. I didn't see any interference from either unit. I was able to run up to about 1000' AGL without any dropouts. That was with the 1/4 wave and a dipole on the 900mhz setup... The 1 watt setup should be MORE than what you need.

--Scott

[LukeZ]

This is exactly what I have been waiting for! Actually I just checked their web special page this morning and it still had the April deal up - so they must have just changed it today.

I'm calling them tomorrow and getting it!

Now if only Aerocomm would run the deal that you had seen Maxstream do earlier, aimster - buy the competition's and get theirs free. ;)

Luke

[jackc]

This is exactly what I have been waiting for! Actually I just checked their web special page this morning and it still had the April deal up - so they must have just changed it today.

I'm calling them tomorrow and getting it!

Now if only Aerocomm would run the deal that you had seen Maxstream do earlier, aimster - buy the competition's and get theirs free. ;)

Luke

Aerocomm's 1000mW 900MHz dev kit is only $199.00 Cheaper and better than MaxStream. See http://www.aerocomm.com/rf_transceiver_modules/rf_design_tools_wireless_development.htm

Jack
Rockhampton,
Australia

[LukeZ]

Jack,

Hmm, I hadn't seen that deal.

However, what in your opinion, is better about the Aerocomm's 1w transceivers than the Maxstream?

First of all, I can't really tell any difference between Aerocomm's two 900 mHz, 1w transceivers - the 4490 and 4790. All I can really see is that they have a different antena and slightly different input voltages (the 4490 can accept 3.3-5.5, whereas the 4790 only takes 3.3v). So to begin with I'm not sure which one of those is better, or what niche they are each intended to fill.

Compared to the Maxstream 9XStend, they are slightly smaller in size but no lighter, apparently. The Xstend has a higher potential RF data rate - selectable 9600 baud or 115.2 Kbps. Whereas the RF baud rate for the Aerocomm 4790 is set at 76.8 Kbps (the 4490 doesn't list an RF baud rate).

All in all the differences don't look too large. Except for the price, as you pointed out.

Any one else have thoughts on this?


Luke

[LukeZ]

Here's a thread on Mr. RC-CAM's forum that discusses some of the differences between the Aerocomm and Maxstream modules: click here (http://www.rc-cam.com/forum/index.php?showtopic=648). (Sorry aimster, I guess it was Kilrah who had seen that deal, not you!)

However they are mostly discussing the 2.4 Ghz modules, rather than the 900 mHz. The thread kind of peters-off before any field testing reports are given.

In that thread, they are talking about the possibility of actually using the modules to send the R/C signal to control the craft. I am not really interested in doing this.

What I intend to use this for is telemetry data primarily, as well as control of some flight parameters of the on-board computer, but not actual direct control of the aircraft's flight - that will remain by R/C or else by the onboard autopilot. So I don't need extremely high data throughput, though higher is better. I think what I particularly am after is range, and I suppose, reliability, but the latter is dependent perhaps more on the environmnental conditions/antena setup than which manufacturer's device one chooses - am I right?


Luke

[clolson]

What I intend to use this for is telemetry data primarily, as well as control of some flight parameters of the on-board computer, but not actual direct control of the aircraft's flight - that will remain by R/C or else by the onboard autopilot. So I don't need extremely high data throughput, though higher is better. I think what I particularly am after is range, and I suppose, reliability, but the latter is dependent perhaps more on the environmnental conditions/antena setup than which manufacturer's device one chooses - am I right?
Luke

Here is one data point that I can provide.

We were using aerocomm 900Mhz units to send real time telemetry data to the ground (primarily roll/pitch/yaw and lon/lat/elev from our IMU/GPS.) We were feeding this data (in real time) into FlightGear and using FlightGear as a real-time ground-based synthetic display for our uav. We can overlay flight instruments, draw restricted airspaces, and lots of other fun stuff.

The ultimate goal was to fly the airplane only from the synthetic view. But so far we have not been successful primarily because the aerocomm link has been very bursty and it retransmits some data when it does get going again. It could be a dumb configuration problem on our end but we have tried a lot of things and haven't been able to improve the performance.

So the end result for us is that with the aerocomm's we'll get a 1/2 second of good data followed by a 1/2 second of nothing followed by a 1/2 second of data with some repetition/overlap of the data we previously got. The actual timing of the bursts and pauses is randomly distributed, 1/2 second is probably worst case scenario for our pauses. The result is a very jerky display with frustratingly long pauses at very inopportune times.

We ended up with way too much latency and way too many pauses to physically control the aircraft using this data link to drive our visuals. On a bumpy day you can do a 180 degree turn in a second with an R/C airplane. That doesn't mix well with 1/2 second delays in the data stream.

I'm not enough of a serial communication expert to blame aerocomm on this, but at some point I would like to try the maxstreams and see if we have the same sort of issues.

But, time + funding is always the big problem. My dang day job keeps getting in the way of my fun!

Curt.

[LukeZ]

Curt,

Yeah, what would really be great is for you to try the Maxstreams, and compare. You would then have a better idea if the problem was you, or Aerocomm.

I wonder, have you contacted Aerocomm about the problem?

Also, in regards to your stop-start issue: you say it will sometimes pause for a bit, then begin to re-transmit, with some overlap of old data - however, do you also get the data that you missed during the pause? In other words, irregardless of the intermitent nature of your reception, and apparently some duplication, is there much data lost?


Luke

[Medve]

Curt,
thanks for the info. Keep posting any results or new info you learn. It would be good to know before others of us jump for one or the other of these units.

[space_case]

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.

I think I like this part the best! Thanks a lot for the heads up, looking into it.

[Tuner]

Thanks I have been waiting on getting one of these at this price it is perfect.

[clolson]

Curt,
I wonder, have you contacted Aerocomm about the problem?

Also, in regards to your stop-start issue: you say it will sometimes pause for a bit, then begin to re-transmit, with some overlap of old data - however, do you also get the data that you missed during the pause? In other words, irregardless of the intermitent nature of your reception, and apparently some duplication, is there much data lost?


We probably lost 30-40% of our data coming down. These issues weren't noticable when we were connected up to the aerocomm application with a little glass cockpit-like display, but when you try to fly off the data and use it to create a synthetic world view, the errors really jumped out at as. I'm the software guy/pilot on the project, but I don't think our hardware guy tried to contact aerocomm. I'm sure he figured it was a software problem. :-)

[LukeZ]

We probably lost 30-40% of our data coming down.Hmm... that's not too good. I mean, some lost telemetry coming down I can probably live with, but command and control packets being sent up need to make it to their destination. I could code some acknowledgment routines but isn't that kind of what these transceivers are supposed to handle already?

Luke

[jackc]

Hmm... that's not too good. I mean, some lost telemetry coming down I can probably live with, but command and control packets being sent up need to make it to their destination. I could code some acknowledgment routines but isn't that kind of what these transceivers are supposed to handle already?

Luke

Yes, IF they are run in RF acknowledge mode. If broadcast streaming mode is used, data can be lost and the radios will not attempt to recover lost data.
You could have several ground radios multiplexed together as a sort of qasi diversity system, to receive the downlink streaming data and sort it at PC software level. Broadcast streaming allows a higher data rate, due to no acknowledgements being required, before the originating radio sends more data etc. IF the originating radios buffers are swamped by the host device, some data will be lost, and never sent at all.

Jack
Australia

[Medve]

So it seems there are two directions to go. Either on TX for the video and one for the telemetry. (this means two TX's, more weight, more power drain, but an easier plug and play setup), or we go with the single video TX, and bring telemetry down the audio channel. (lighter, lasts longer on battery, cheaper too, but we have to mess with telemetry coming in on the audio port, and most computers, or software do not like pulling data from there. The best I've seen was ok, but took some more know how). Not having any programing knowlege, and just going from what I've read here, do I have the picture correctly? If we could get a decent moving map display, and maybe a dashboard program runnning off the info coming in on the audio channel, I think we'd have something.

[LukeZ]

Medve, these are data modems - I don't think you'd have much luck sending video over them. :confused:

Luke

[typicalaimster]

Medve,
If your looking to do just a moving map, then using the audio channel on your video Tx would be a more logical way to go. If your looking to do some bi-directional communication between the ground station and the plane.. Then the data modems would be the way to go. I was running a glow powered plane when I was using all the equipment. Weight was not an issue at that point in time.

[Steve McBride]

Medve, these are data modems - I don't think you'd have much luck sending video over them. :confused:

Luke

Luke - he's referring to using the audio channel of a video/audio transmitter to send telemetry (although very slowly). If all you need is NMEA sentences sent back for moving map, you can do it this way and save adding a wireless modem. The downside is that the position data on the map updates a little slower than standard.

I chose to go with modems and video transmitter for redundancy though. If I loose video and am sending NMEA down the audio channel, then I've lost that data too. At least I'll be able to hopefully retain live video or GPS if one fails.

Steve

PS - if you are interested in a simple modem setup that requires no software configuration, the sparkfun modems work great for moving map display. Their problem is that they are 9600 baud only and therefore need a GPS unit that can send NMEA at this rate. Standard NMEA is 4800 baud and therefore many commercial softwares only use this rate. There are a couple ways around this though that work great.

[LukeZ]

Well, I went ahead and ordered the MaxStreams. I figure that if for some reason I really don't like them, the Aerocomm's are inexpensive enough that I wouldn't feel too bad about buying them as well, especially if I just bought the radios and not the whole development kit. But probably not so much the other way around, given the MaxStream's usual price.

Although they say on their site to allow 4 weeks for delivery, the guy said I should have them by the end of the week.

It will be a few weeks before I get a chance to try them out - but I'll post my thoughts when I do.


Luke

[hugo_vincent]

I should point out that we have been seeing exactly the same symptoms that Curt was describing with the Aerocomm modems with our UAV project (http://www.albatross-uav.org). We spent considerable time trying different options and configurations, and tried contacting Aerocomm several times (always no response...), and convinced ourselves it is a problem with the Aerocomm modems. We also had a problem whereby the modems would saturate each others receivers and corrupt the data if there was less than about 20m between the antennas (we were using 6dB antennas and 1W 900 MHz AC4490 modems). I can only strongly recommend you do not get Aerocomm modems!!!

Please let me know how you get on with your MaxStream modems.

[jackc]

I should point out that we have been seeing exactly the same symptoms that Curt was describing with the Aerocomm modems with our UAV project (http://www.albatross-uav.org). We spent considerable time trying different options and configurations, and tried contacting Aerocomm several times (always no response...), and convinced ourselves it is a problem with the Aerocomm modems. We also had a problem whereby the modems would saturate each others receivers and corrupt the data if there was less than about 20m between the antennas (we were using 6dB antennas and 1W 900 MHz AC4490 modems). I can only strongly recommend you do not get Aerocomm modems!!!

Please let me know how you get on with your MaxStream modems.

I am not surprised, New Zealand 900MHz band is 920 to 928MHz? IF you were using the Aerocomms on the U.S. FCC band 902-928MHz, you would get/cause inteference to/from N.Z. 900MHz commercial services?

Jack
Australia

[defy]

I bought 3 maxstream zbee-pro's (I'm also in nz and cant use any 900mhz units) for shorter range (1 mile) telemetry and I'm loving them, they'll do everything thats advertised on their site and do it well. Also maxstream having online chat support is amazing, their technical support staff have been very helpful with the few issues I ran into. Just thought I'd share my experience with them.

I'm thinking about getting the 2.4ghz xstreams to see if they'll really do the advertised 10miles.

[jackc]

I bought 3 maxstream zbee-pro's (I'm also in nz and cant use any 900mhz units) for shorter range (1 mile) telemetry and I'm loving them, they'll do everything thats advertised on their site and do it well. Also maxstream having online chat support is amazing, their technical support staff have been very helpful with the few issues I ran into. Just thought I'd share my experience with them.

I'm thinking about getting the 2.4ghz xstreams to see if they'll really do the advertised 10miles.

I take that you will not be running any real time video downlink, on your UAV?
Keep us posted on your MaxStream experience.

[defy]

I take that you will not be running any real time video downlink, on your UAV?
Keep us posted on your MaxStream experience.

At 1 mile the maximum I can stream (1 way, as the modules are half duplex) is about 100kbps, not exactly video streaming speeds but way more than enough for telemetry and maybe some still photos. a tcp/ip link isn't as stable, but also isn't really needed. I'm thinking of using a stand alone transmitter for video.

I have noticed that if these modules get too close to the gps unit or its active antenna that the gps can stop getting a fix. Luckily too close is only about 3-4 inches, I keep the wireless module and gps gear about 6-8 inches apart and it all works fine.

Jack I think we spoke on the phone a few week ago about the aerocommm modules. Since its winter time here in nz and the weather isn't the best for flying, I've started a side project which will help me create my navigation software. I'm building a small boat which will navigate the harbour just outside my house via gps. Hopefully this will help me create a 2d navigation system which will evolve into full 3d once I get back onto the UAV.