aerocomm transceiver

[toxicmouse]

i am looking for comms over a few km (hence the PMR data question), and found the aerocomm 868MHz transceiver
<A href='http://www.aerocomm.com/rf_transceiver_modules/ac4868_868mhz_rf_transceiver.htm' Target=_Blank>External Web Link</a>

i was hoping that somebody had used these and can comment on it. failing which, has anybody got experience with other transceivers with range over a few km.

thanks.

 

[Dippy]

Looks nice.
Where do you buy them?
Ar you allowed to use Gain antennas in UK for this type of gear?
How much?

I've seen similar (but don't look so neat) options at radiometrix. No doubt there are a zillion others for different parts of the world.

Best you buy a couple and let us know. Be slightly wary of range claims. Sometimes you have to part with the cash to find the truth in the Real World.

If others here had used them I'm sure they'd crop up on a search.

 

[manuka]

Look nice, BUT given their high data rate specs.(&amp; intended industrial application) I'd say they'll be quite costly. Tell us more about the nature of your &quot;several km&quot; link. Data speeds ? LOS ? Power supply ? Cheap 433MHz ISM can work wonders, especially if a Yagi antenna <A href='http://www.picaxe.orcon.net.nz/yagi433.jpg' Target=_Blank>External Web Link</a>&amp;/or repeater used <A href='http://www.picaxe.orcon.net.nz/433rpt.jpg ' Target=_Blank>External Web Link</a> Stan

 

[toxicmouse]

AeroComm RF Transceiver Development Kits 868MHz cost &#163;115 from BFI Optilas, contact Kirsten on Tel: 01908 326 342 (UK). that is for two tranceivers + bits and pieces. currently there is a 6 week lead time though. the tranceivers sell on mouser.com for $79, &#163;41 each. sure its not cheap, but if it does what it says on the tin then its a bargain.

searches have not yielded much info on the use of the transceivers, other than a high altitude baloon project- they were not thrilled with it, and now use 434MHz. of course there is the 900MHz version used in the US which is succesfull. i doubt there is much difference in a few MHz.

on the plus side, there is a lot of literature and support, and the modules seem to be designed for people like me who don't realy know much about over the air problems.

Stan, i am just making projects to fill time, so there is not real application. i want to get comms to about 10km with a decent data rate and low power consumption. adding relay stations would be fun anyway, but i think i will try a long leap on this one. i intend to play with a some super-cheap 434MHz hardware in about a week, so i will probably try out that Yagi antenna too.
cheers.

 

[manuka]

TM - OK &amp; wish I had your &quot;to fill in time&quot;. Most Forum old hands I'm sure will agree that 433MHz ISM units are an absolute doodle to use with 08-Ms, &amp; you'll learn HEAPS about UHF comms &amp; simple antenna at the same time. Suggest you tell us what data rate &amp; the link terrain you intend over that 10km link (+ your budget!) as 2.4GHz ZigBee etc may do if line of sight (LOS). Cell data comms is very well established now too but of course it cots to use. Of course 470MHz PRM &quot;CB&quot; is the most tempting but regs. need considering. Here in Aus/Nz we're allowed 3 seconds an hour on a data channel &amp; ranges can be 10s of km thanks to the 1/2 W power. Stan

 

[toxicmouse]

stan, the terrain i will most likely use is rolling hills with lots of vegetation. the data rate is unlikely to comprise of a continuous stream, more like 10 bytes updated every 4 to 5 seconds. there is a very good chance of black spots due to the hills, and the thick vegetation is not going to help either, but there is not a lot i can do about that.

you are certainly right that i will learn a lot about antennas and UHF, that process has started already. am i right in thinking that the lower the frequency the longer range i will get, and the higher the frequency the better penetration (of vegetation) i will get?

any help or suggestions welcome.

 

[Dippy]

You've really opened the 'opinion' can of worms there.
Your thoughts on F vs range and penetration are not necessarily true.

This whole radio thing is a mixture of experience, calulation and a bit of luck. But the greater the first two terms in that equation then the luck factor can be reduced.

Range can also be affected by your coding method. This is one of the charactersitics of Manchester coding (and similar) improving the response in many types of radio receiver and hence having a slight improvement on effective range.

Ultimately this is going to require you to part with the cash and experiment. People here can only give their best advice based on experience and knowledge.

By the way, do you have a size limit on your antennae? Do you want an antenna as big as a TV aerial? This may limit your frequency choice. Are there any other transmitters locally? Legal requirements?

If you have a website giving more detail than permissable here that would be very useful for others. I'm sure someone was fiddling with long range stuff last year. I've only dabbled up to 1 km with 434 stuff non-directional.

 

[andrewpro]

Whoa there. I have a feeling your not going to get 10km through heavy vegetation with a frequency that high. At least not with legal power limits.

You might be bale to pull it off with a gigantic dish, but then you wont have the ability to go &quot;through&quot; hills as it'll be very unidirectional.

It's seeming that Stans repeater at 434mhz is looking like a much better option. The lower the frequency, the more &quot;stuff&quot; you can go through. Given that vegetation is mostly water, it's pretty good at soaking up just about everything. Especially that high in the bands. Get into microwaves, and it's even worse.

So theres my vote. 434mhz (at the most! less would be nicer) and repeaters. That or ridiculously illegal power levels. But..since that's illegal...I'd go with repeaters and a much lower frequency <img src="wink.gif" width=15 height=15 align=middle>

--Andy P

 

[manuka]

Modest blush- that simple 433MHz data repeater worked a real treat,&amp; would be near ideal given you've only a handful of bytes every 5 secs or so. Consider even several repeaters?! Of course powering them may then be an issue, with PV solar most tempting but open to theft/damage if up a tree etc.

Higher RF freqs generally have lower penetration, behaving essentially as does light. Even powerful 470MHz UHF CB &quot;PRM&quot; sets will struggle over 10km of rolling hills. Here in bushy NZ I find the 1/2W types are only good for ~2km in such terrain, although LOS (across Wellington Harbour) I readily manage 10km, &amp; ~20-30km LOS with &quot;cotanga&quot; antenna each end. Borrow a couple of these sets &amp; do a wandering site voice audit with a mate back at your base. &quot;I'm speaking to you from the big oak tree on the ridge-can you still hear me?&quot;

You still haven't said just what the nature of your data is ( or budget!),which could naturally be important. Do you need real time reception or would store &amp; forward do? Cellular? Radio hams have all manner of legal comms. avenues &amp; high power, so it may even be worth getting your ham ticket ?

Suggest you specify exactly where you are as well- rural/urban? Boring things like interference can ruin any number of wireless possibilities... Stan

 

[toxicmouse]

thanks a lot for your suggestions. i would be silly not to be swayed to the 433MHz brotherhood, so an order is <i>en route </i> !

andypro, illegal comms is not an option, so i think i may have to dabble in antennas.

stan, rural- so cellular is not an option. i am after real time or as close to it, so if comms break down then data would be stored and sent when when comms have been re-established. perhaps i am being a little ambitious. as Dippy said, a little experimentation is needed and then when i get a feel for things, then i should venture into more complex tasks. at least i have established what frequency i will be working with, that narrows down the options considerably. as for budget: as little as necessary. i will spend up to about &#163;70 for a transceiver, but if i am going to have to experiment (thus wasteage), then a lot less. so if there is a lot of support and literature then i am prepared to spend a bit more- which 434MHz appears to have.

thanks again for your help.

 

[manuka]

Thought: Good ols 26-27MHz CB may be available for data? I'm not up with UK regs on this, but voice comms penetration is great in your sort of terrain! Stan

 

[hippy]

Just to throw a spanner in the 433MHz works - To be licence exempt LPD, Low Power Device / SRD, Short Range Device, with MPT1340 type approval, it's 10mW.

www.radiometrix.com/pdf/MPT1340.pdf

RF Solutions sell a range of modules, but the only licence exempt (MPT1329) high power stuff is on 458MHz and not cheap ...

http://www.rfsolutions.co.uk/acatalog/FM_Radio_Modules.html

They also sell even more expensive Radio Modems which are probably better suited to long range telemetry.

 

[hippy]

If you're going for repeaters, what about Zigbee ? XBee Pro's are 100mW; that's about 1 mile, but earlier comments on shrubery attenuation at higher frequencies noted.

The advantage of Zigbee ( XBee particularly ) is that optimised over-air signalling, auto-forwarding, error detection and lost packet re-transmission is included and automatic, making it a standalone bi-directional repeater - program it up, attach a battery, leave it to do its job.

One other issue that hasn't been mentioned - How are you going to power these repeaters which will have quite a significant battery drain ?

 

[toxicmouse]

hippy, the 457MHz modules are a little too pricey for me. as for Xbee Pro, the 868MHz modules earlier were up to 250mW and advertised up to 15km (even though i doubt i will ever reach this). perhaps what makes this a difficult topic is the lack of set parameters and constraints, but then i don't have these. this is just for education, so what is important is that i learn- which i feel i will do irrespective of the actual device.

thanks for your advice.

 

[andrewpro]

I think what you should do right now is think of it as more of a mechanical problem than an electronic one.

If you haven't already, try to do a detailed (as much as possible) site survey. This should include distances, elevations, direction, interfering factors (such as the above mentioned vegetation, power lines, things like that).

Things you should be looking for are how far can a straight line be maintained, how far &quot;up&quot; then &quot;down&quot; needs to be traveled to make it over the hills, possibly get a detailed map and see if you can take a different route than originally thought to make the job easier.

Once you can answer all of these things in detail, then start looking at the technologies you need to pull it off. You may be surprised that by looking at something from a different angle can change the entire outlook on how it should be approached.

It seems like we're trying to provide an answer for a question that doesn't exist. Or possibly the wrong question. The more detail you can provide, the better answer we can give.

--Andy P

 

[manuka]

TM- 3rd request. Can you PLEASE tell us more about the nature of the data. Is it &quot;hush hush&quot; ? What are the implications of corruption by noise etc? Will you need error detection? This may seem incidental,as it could well be if temps. etc are being noted &amp; you get a one off high reading, BUT may be crucial. STRONGLY SUGGEST that you drop everything &amp; do a site survey with a couple of hand held 470MHz voice sets.

&quot;Somewhere in rural UK&quot; is much too hazy these days &amp; reminfds me of a Goon Show script extract. Hence also please give Google Earth location refs for our collective brain power to ponder.

 

[toxicmouse]

Stan, i am extremely fortunate in that i currently have a lot of spare time. i choose to use that spare time tinkering with electronics, with the hope one day that i may use some parts of the projects i assemble. so i really cannot give you exact coordinates or surveys because i simply havent got any.

this transmitter project started when a hiker friend of mine mentioned that it may be safer if we had trackers on us that automatically relayed our location to a base camp. now as i see it, this is totaly impossible because we hike up to 30km a day and often in extremely mountanous regions, even jungle (30km flat, considerably less in jungle). thus relay station are out of the question, the hikers and the base camp are mobile, and in the next six months i will be in the Yorkshire moors, Maluti mountains in Lesotho and in the thickest jungle of Brunei.

i could just buy an Iridium phone and that would solve that issue (and i probably will), but this got my imagination going and i would like to try out some wireless comms. in my original post i enquired if anybody had experience with the aerocomm AC4868 tranceivers because they looked flexible, reliable and relatively cheap. i want to get some hands on, but i didnt want to waste money buying a lemon. perhaps my original post should have asked what devices should i buy to get experience with comms and the answer seems to be cheap 434MHz devices.

so i am not after a specific solution, there is no application, i just hope to develop comms and then maybe use it to improve other projects in the future, and if i can get 10km i will be happy. so the nature of the data: it is not &quot;hush hush&quot;, there must be error detection; and i am most likely to test it in my back yard which has excellent LOS but the application may be anywhere- so doing a survey would be futile. implications of corruption by noise: no point in receiving the wrong information, assume that the application is not life critical.

i do appreciate your comments and if there is any info i can provide to help you, then i will be glad to do so. although, i would rather not be associated with Goon Shows.

 

[manuka]

Right- NOW you're talking! Simple &quot;our man in the field&quot; location is really right out of the question in dense terrain, &amp; has of course been an ancient military and S&amp;R nightmare ever since people ventured out of their caves. At a radio level just stepping behind/under a tree/rock or sitting down for a rest may block even powerful signals. Short of voice reporting back to base, the only viable method uses GPS that auto-sends back co-ords. In places like Borneo (&amp; even here in NZ) the tree canopy can be so dense that satellite GPS signals will be blocked however. It's hard enough to even get daylight at ground level in such jungle.

Over just a few km however the near century old technique of &quot;fox hunt&quot; radio direction finding(RDF) can be a little winner. At UHF/VHF this uses directional Yagi style antenna, or SW/MW cross referencing from several tracking sites. Orientating the inbuilt ferrite loop on an AM pocket radio is also well known. Although infamous for WW2 style aircraft navigation &amp; spy hunts, or 1960s unpaid TV licences, it's also been a great outdoor hobby for decades - see =&gt; <A href='http://www.ussc.com/~uarc/rptr/UARC_RDF1.html ' Target=_Blank>External Web Link</a> etc. A serious application relates to locating crashed aircraft, since although most now use emergency UHF satellite sensed beacons, these may be masked by terrain. Nearby endangered animal tracking in dense bush is popular in NZ using this technique too.

Aside from Picaxe friendly low power 433MHz Tx/Rx, I assume you've grabbed a couple of cheap &#189;W 470MHz PRM UHF CB handhelds by now? <b>If not then DO SO &amp; ASAP! </b> These have suprising range (~3-5km), features &amp; quality, but are are dirt cheap- as low as ~&#163;10 each. Get a pair that are easy to use, as IMHO some are excessively complex &amp; an ergonomic nightmare to operate. Ensure they come with rechargeable batteries too, as being &#189;W their current drain can be heavy on transmit. You'll legally learn heaps about RF propagation with them, &amp; can rustle up simple &quot;cotanga&quot; antenna as well.

But given your interest I'd say <b>use your current time to study &amp; pass your radio ham licence !! </b> . Hams enjoy all manner of powerful gear &amp; techniques (+ even their own satellites- OSCARs) barred to the rest of us, &amp; they've great comradeship. Check RSGB etc (Radio Soc. of Great Britain)=&gt; <A href='http://www.rsgb.org ' Target=_Blank>External Web Link</a>. Stan - ZL2AJZ (40 years a ham!)

EXTRA: What are you actually doing in these far flung regions? Scientific? Adventure ?Missionary? (The only heathens I encountered last year in the Yorkshire moors were my kids screaming in the back seat of our car-&quot;He's breathing my air&quot; ! These little darlings gave a similar performance when in Brunei 1998.) If the latter role then cheap store &amp; forward &quot;flying mailbox&quot; LEO (low earth orbital) sat. comms exist to help keep you civilised when jungle clearing based.



Edited by - manuka on 10/03/2007 22:12:38

 

[wmerrin]

What you are describing is well implemented in amateur radio's APRS - Automatic Position Reporting System. http://en.wikipedia.org/wiki/APRS
In the US it is typically implemented in the 2 meter band (144 - 148 MHz) on standard frequencies. In real life two meters is not strictly limited to line of sight as badly as the 4xx MHz systems.

For your application you would use a base station consisting of a radio and a laptop computer running APRS software. The antenna could be hoisted up into a tree for some height advantage. You would carry a GPS receiver and beacon transmitter on your person. At preset time intervals your GPS coordinates would be transmitted and when received by the base station would be recorded and plotted by the APRS software. If you don't need two-way comms with the base station then you don't need complete transceivers - just a beacon transmitter and a receiver to feed the laptop.

In the US search and rescue groups are making good use of this technique, even to the extent of putting miniature beacon transmitters on tracking dogs.

I'm not familiar with licensing issues in the locations you are talking about, but some quality internet time should give insight into reciprocal operating priviledges that are fairly common these days. As Stan noted, the RSGB is a good place to start your research.

Wally

 

[toxicmouse]

thanks for that, hiking is just for fun. i have a couple PMRs but sending data over them in the UK is illegal. having said that, they have little buttons so that i can send morse code on them, which i would have thought is data of sorts. i'll check out the sites. excuse the ignorance here, &quot;cotanga&quot; = coat hanger? is this another example of colonial improvisation?

 

[Dippy]

Stan has produced a full range of antennae based on domestic equipment. Thank goodness he doesn't work in the kitchen section of Walmart as he'd discover that the Kenwood pasta maker resonates perfectly at 434MHz.

 

[manuka]

Mmm- 434? Walmart you say? I'll try that one...

Cotanga is indeed a corruption of &quot;coat hanger&quot; &amp; the term arose from their improvised use to replace broken car telescopic antenna. The galvanised wire however is near perfect for engineering UHF Yagi elements =&gt; <A href='http://www.picaxe.orcon.net.nz/yagi433.jpg ' Target=_Blank>External Web Link</a>

Guilty as charged for cookware antenna ideas, as witnessed by my now near infamous 2004 &quot;WokFi&quot; site <A href='http://www.usbwifi.orcon.net.nz' Target=_Blank>External Web Link</a> that still pulls in ~1500 visitors daily. Stan

Edited by - manuka on 12/03/2007 11:08:24