RF module suggestions?

R&C

New Member
I searched the forum to get an idea of the various RF modules out there, but there are so many, I don't know which to get.
So my question is, what modules have worked for you guys?

Please bear in mind that I've never used radio, and am a beginner in electronics, so the simpler the better! ;)
I would like it to be relatively cheap, range is not vital (the max I'll use is 50m), and preferably a transceiver.
I found a transceiver here: http://www.maplin.co.uk/media/pdfs/A60JN Datasheet.pdf but I can't make heads or tails of the datasheeet (in particular, the pin connections to PICAXE), and don't even know if it would work with PICAXE.

Thanks for your input.
R&C
 

manuka

Senior Member
The key to success with PICAXEd wireless is indeed to start VERY SIMPLY, & build up your skills as you tame the basics. You really can't beat cheapie ASK modules for this, but some are very low power,have "deaf" receivers, may overload when too close & annoyingly insist on a 5V supply. My present recommendation is for the Chinese Dorji TX/RX pair reviewed here => http://www.picaxe.orconhosting.net.nz/dorji434.pdf,as these have been free of such strife and "always work".

Note- I highly recommend making a simple 433 MHz monitoring receiver from a Dorji Rx too, as many 433 MHz data woes arise from interference by other services. In built up regions these can be back yard wireless weather stations, garage door openers, car remotes, energy meters,wireless doorbells,toys & even legally high power ham radio operators. The resulting beeps,buzzes,tones & chirps can make the 433 MHz spectrum slot sound like an African dawn chorus as a result! Stan (ham ZL2APS since 1967)
 

Dippy

Moderator
Stan, maybe you should produce a webpage of RF devices that you have tried (and trusted) with a line or 3 describing pros & cons of each.
And advice on responsible use maybe?

A question (as I'm only thinking out loud)...

Do you think that a lot of the interference is down to:-

a) People (hobbysists and manufacturers) using excessive power for the application and/or surroundings?
e.g. if blokey down the road has a doorbell with 500m range he'll interfere with me but if only 25m then he won't.
Does this also apply to some hobbyists who simply judge RF preformance on range?

b) Poor quality RF gear (usually cheap and often made in a shed).

c) Excessively long transmission bursts. A doorbell is very occasional, ditto car fobs.
I've lost my UK regs file but there are duty limits - and they're specified for good reason.
Little Johnny doing near continuous data from his weather station with a 500m range RF in a built-up area is going to pi55 off a lot of people.
 

manuka

Senior Member
-produce a webpage of RF devices that you have tried (and trusted)-
Nice thought,but it's a near moving target & -sigh- an emotive one with vested interests often at work... Quieter & higher power 900 MHz spectrum slots are looking increasingly tempting as well too. In any case my skills,slant & setup techniques may differ hugely from folks elsewhere!

-a lot of the interference is down to-
UHF interference varies greatly with location. Even here in the expansive South Seas I'm bombarded at 433 MHz with signals from my own & suburban neighbourhood devices,along with those from Wellington city (~10km away cross harbour). Sure - suitable data massaging can usually still get the message thru', but if my 70cm ham transmitting gear is in operation then most basic 433 MHz receivers can become swamped or desensitised. All manner of similar mischief can lurk nearby,especially in high density urban set locations.

But aside from interference insights, a significant PICAXE 433 MHz data issue often relates to folks not even knowing if their transmitter is working as intended. Woes may be hardware &/or software of course! Few tinkerers will have a UHF scanner handy (or know how to use it!), & this is where a simple 433 MHz band monitor can be extremely valuable.

Et voila -I've surely mentioned this surely a zillion times before, but (for those who've just come in) check the Dorji & Keymark hacks below. Both have undocumented RSSI (received signal strength indicator) tap points that've been very handy for tracking,tweaking & (antenna) trimming. Refer my Dorji Instructable. Stan.
 

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srnet

Senior Member
Even here in the expansive South Seas I'm bombarded at 433 MHz with signals from my own & suburban neighbourhood devices,along with those from Wellington city (~10km away cross harbour).
Sure - suitable data massaging can usually still get the message thru', but if my 70cm ham transmitting gear is in operation then most basic 433 MHz receivers can become swamped or desensitised. All manner of similar mischief can lurk nearby,especially in high density urban set locations.
Its much the same here, I live in the middle of a city, close to a very large Hospital, it borders on the park I use for a lot of testing. At standard module frequencies, 434.100Mhz there is so much activity that you only get short range. In the amateur 70cm bands it is a lot quieter .............

But then is then interference (other users) restricting range a real problem, after all the modules being used are supposed to short range devices, its just good fortune that some of them are capable of long distances, in the right conditions or location.

Few tinkerers will have a UHF scanner handy (or know how to use it!), & this is where a simple 433 MHz band monitor can be extremely valuable.
Over in the RC Model forums there are a few open source implementations of long range RC control using the Hope RFM22 and RFM23, its scary how little the users of these things know about the very basics of RF. Harmonics ? What are they ? No means or ideas as to why its useful to check how much power (field strength) their DIY RC control systems are actually putting out. Scary because these DIY systems are being used for flying models beyond visual range (FPV) over populated areas etc.

Whats real silly is that there is open source software out there which turns one of these RFM22 receivers (around £12 each) into a handy scanner;

http://www.rcgroups.com/forums/showthread.php?t=1617297
 

Dippy

Moderator
That's useful Stan and srnet, thank you both.
Gosh, srnet that is a worry with RC control.

Up until this Forum I really hadn't been aware of the cheapies from China.
I had always used Radiometrix, RFSolutions and similar which were made and tested to certain standards.
And all my designs were low power and trying to do a duty based circuit without pukka RSSI is tricky.

Proper yield and harmonic measurements are simply beyond Cheapo manufacturer's budget. And i doubt many care at all.
And this Forum 'competition' to see who can buy the cheapest is, in my opinion, asking for trouble and promotes crap to the detriment of proper makers (regardless of COM)..
Who knows what a $3 Ch Special chucks out; little Johnny loves it because his digits get 20m but can simultaneously blat the neighbours' terrestrial DTV.

I live in the sticks so the 434 band interference isn't such a big deal, but after twiddling at 868 I can really see the benefit for SRD work.
I experimented with the lovely little CC1101 (with a Stan recommended scanner) and got great results.

I was just hoping that someone (trying to be unbiased regardless of Chinese freebies) could list what has found to be good with honest figures where possible.


In UK we have a lot of younger car drivers using HID headlight kits and blinding everyone else because of spread and intensity.... there's almost a Hippy analogy there ;) Sadly, there's no MOT Test for RF stuff.


(Perhaps there should be another Forum section where we can discuss this sort of thing. Crownhill has "The Lounge". It can go alongside the "Tutorial" section perhaps....)
 

russbow

Senior Member
(Perhaps there should be another Forum section where we can discuss this sort of thing. Crownhill has "The Lounge". It can go alongside the "Tutorial" section perhaps....)
I await with great alacrity. :D
 

Dippy

Moderator
"Fancy some bang for buck gold plated "900 MHz" performance then? "
- they always seem 'gold plated' when free eh Stan ;)
Let us know if it is really is Gold Plated AFTER evaluating when novelty has worn off.


I'm not sure if 900MHz is actually legal for exempt SRDs in UK (please verify).
Isn't the 900Mhz band (or part of) been allocated to Vodafone or some PWN?
There may have been changes as my documents are a little old.

It's interesting reading ETSI EN300 220 "Technical Characteristics and test methods" - I wonder how many manuf's have bothered?

Also, just in case the UK user has a guilty feeling, it's good to read "UK Interface Requirement 2030 Licence Exempt Short Range Devices".
It lists Frequencies, ERPs and DUTY cycles to comply with the Ofcom regs.
 

manuka

Senior Member
Dippy et.al: 868MHz you say? Fancy some bang for buck gold plated "900 MHz" performance then? Check this Australian designed 1 Watt, high data rate & sensitive RFD900 telemetry modem. Default settings are 57600 baud, N, 8, 1, and 64k air data rate,but they'll go down to 2400bps. The radio control model crowd LOVE them, with one poster calling them an "XBee killer". I'm presently evaluating a loaned pair for an article.

Although legal 900 MHz spectrum slots are globally fragmented, this sub 1GHz band is far quieter than 433 MHz. Much higher power (~a few Watts) is legal too. Path losses are of course greater than at 433 MHz, but high gain antenna (even parabolas) become feasible at 900 MHz. These can more than compensate -point to point links of 10s of km at decent data rates are quite achievable. The "Serval Mesh" project is using them for smart phone links.

Retro-edited for Dippy to indicate "loaned"
 

Dippy

Moderator
"Fancy some bang for buck gold plated "900 MHz" performance then? "
- they always seem 'gold plated' when free (on loan but I bet you might get to keep them) eh Stan ;)
Let us know if it is really is Gold Plated AFTER evaluating when novelty has worn off.


I'm not sure if 900MHz is actually legal for exempt SRDs in UK (please verify).
Isn't the 900Mhz band (or part of) been allocated to Vodafone or some PWN?
There may have been changes as my documents are a little old.

It's interesting reading ETSI EN300 220 "Technical Characteristics and test methods" - I wonder how many manuf's have bothered?

Also, just in case the UK user has a guilty feeling, it's good to read "UK Interface Requirement 2030 Licence Exempt Short Range Devices".
It lists Frequencies, ERPs and DUTY cycles to comply with the Ofcom regs.


PS. Here's a snippet out of my old doc - does this still apply for exempts SRDs in UK?
Ofct1_srd.JPG

Retro-edited for Stan who retro-edited his first post :)
 

manuka

Senior Member
Dippy: You may well be right - we're in a different ITU region down here! I did say that 900 MHz was fragmented of course - refer a simplified (!) bandplan below (thought to date from ~2009). The RDF900 units are nominally >900 MHz, so I'll check lower tuning (868 MHz?) when they arrive.

Globally however the sub 1GHz "digital division" is a big player lolly scramble,as the closure of UHF analogue TV is freeing up spectrum,especially ~700-800MHz. Advances in electronics are further making <1GHz almost a DC band as well.

Phew- when I started in radio some -mumble- 50 years back even 144 MHz ("2m") VHF was considered only for the brave,with most activity/circuitry/antenna/propagation well below 30MHz. I recall as a teen using Clive Sinclair's MAT101 transistors (imported at $$ from the UK) to proudly design a 455 kHz BFO (Beat Frequency Oscillator) for SSB (Single Side Band) resolution.

But back in 2013, best console yourself with 242 pages of fine print on this Feb. 2013 EU document . Stan.
 

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srnet

Senior Member
First post and an advert ?

For anyone interested the RF4463PRO wirelss transceiver module, which uses the Si4463 device, is an absolute pig to drive, very much more difficult than the Si4432.

I cant get PICAXE code to work.

So not recommended at all.
 

srnet

Senior Member
Dorji's version may be more user friendly =>http://www.dorji.com/docs/data/DRF4463D20.pdf
The advert was for the basic Dorji module, its a nightmare, even after you work out the Dorji Data sheet is wrong, and that the Si4463 datasheet has quite a few important omissions.

I have mede it transmit carrier, but cant get it into direct modulation or packet transmit modes. Silicon Labs support's view of the problem was;

'I checked your configuration and the modulation seems to be working correctly. I attach the spectrum figure.'

What they really mean is that it works on their WDS development system, not helpful.

That higher power one may well be more user friendly however, it has a user interface in front of the Si4463 which really is needed.
 

manuka

Senior Member
That higher power one may well be more user friendly however, it has a user interface in front of the Si4463 which really is needed.
Aren't they both 20dB (100mW)? Tx power is a tad incidental of course as the limit is normally 25mW. I assume you mean the one below is the friendlier? My past PC setup experiences with Dorji's UI have been pretty positive in fact. Stan.
 

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srnet

Senior Member
Aren't they both 20dB (100mW)?
I think so.

My past PC setup experiences with Dorji's UI have been pretty positive in fact
Maybe so but the DRF4463 in native form really is an exception.

Its not Dorji's fault, but Silicon Labs.

Maybe someone with better skills that I can make it work, but I just cant seen the point as the the Si4432 is way easier to program.
 

Axel87

Senior Member
Following in R & C's footsteps here, and playing with the idea of using RF to activate my new door locks. Ill probably purchase the RF kits you mentioned, but were does one go from here?
I am wondering about range, I would like to be able to reach at least 40 ft.
'Transmit range up to 50m" - 50m=164 ft.
Lets say I wanted a 1/4 mile? or half mile?
 

srnet

Senior Member
Lets say I wanted a 1/4 mile? or half mile?
Long range is possible, just use better modules.

There is a variety of RF modules out there some easy to use, some harder to use but with better performance.

The ERF\URF modules that Rev Ed sell are capable of long distance performance;

http://www.techsupplies.co.uk/epages/Store.sf/en_GB/?ObjectPath=/Shops/Store.TechSupplies/Categories/PICAXE/PICAXEConnect

The range you get in practice depends to a great extent on the location and antennas used. The range you will get in an urban setting (lots of buildings) can be only 1% of what the pure line of sight (LOS) range might be, such are the vagaries of UHF propagation.
 

Axel87

Senior Member
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