Interesting new 433 MHz ASK modules

manuka

Senior Member
In spite of my preference for more sophisticated wireless approaches, Chinese firm Dorji have just sent me some new 433 MHz Amplitude Shift Keying (ASK) data modules to evaluate. You'd think this entry end of the market would have been quite done to death by now,BUT bravely Dorji have rustled up new modules that (it transpires) may just cut the mustard for simple needs.

We'll no doubt see, but compared with other offerings these are not only cheap (~US$5-$10 a matched pair) but are compact,dead easy to use, have a much more powerful (but legal)TX, significantly more sensitive RX, µA level snooze capable and are supply voltage tolerant.As every 6dB gain doubles range I estimate maybe up to an order of magnitude range boost over regular 433 MHz cheapies may result. Links of perhaps a km could be feasible, and a trio of AA cells may be good for near shelf life on the receiver when suitably PICAXE controlled. Australian PICAXE outlet MicroZed intends handling them down under (along with Dorji's regular GFSK transceiver & swish new mesh networking & sensor modules).

A glaring data blunder has been revealed however. Unless St.Pat's Day mischief is at work with my vision,then it seems that the Dorji web site & .pdf images for these new modules are shown mirror imaged! Rest easy lads-the Irish in me has risen to the challenge & I've now flipped them correctly. Refer the attached for these and a feature summary. Module testing to follow. Stan.
 

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Goeytex

Senior Member
I got mine last Friday and have tested around the the house with the DRA887TX with the DRA886RX. They work fine with Pixaxe rfout and rfin.
 

manuka

Senior Member
Great- were your modules direct from Dorji too? Any US outlets? Care to share your circuitry & code (which presumably is running on a higher PICAXE)? Stan.
 

srnet

Senior Member
On the topic of RF modules, apart from the Hope RF ones, are there any other modules out there where you can configure the frequency directly ?

That is swap the devices between the standard short range remote control bands (434Mhz) and the amateur bannds on 432Mhz ?
 

manuka

Senior Member
davehouston: Agreed! The market has long been awash with them. However many have weak transmitters (~a few mW) & "deaf" receivers(~-100dBm) that also insist on tighter supply values. Jaycar's popular & reliable (but ~US$20 a pair) Keymark/SpiritOn modules are typical.

srnet: Certainly- check the likes of these Dorji GFSK transceivers at ~US$25. However hams are allowed high power on 70cm of course,so it's debateable that a mere 10s of mW would have much appeal. Full featured UHF "shirt pocket" transceivers abound at bargain prices (< US$50) of course too - typical being the Puxing PX-2R. (FWIW my only UHF ham gear is a reliable $$$ Kenwood dating from the mid '90s!)

EXTRA: Have just Googled & spotted a "Nice Tech" RX lookalike- see below. Synoxo's SYN470R "engine" seems quite an appealing RF IC. Stan. (ZL2APS)
 

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srnet

Senior Member
Thanks Manuka.

Do you know of any similar (cheap, very small) modules that can be programed for the 2M/144Mhz band ?

The Hope modules go down to 240Mhz only.

(GW7HPW)
 

SAborn

Senior Member
On the topic of RF modules, apart from the Hope RF ones, are there any other modules out there where you can configure the frequency directly ?

That is swap the devices between the standard short range remote control bands (434Mhz) and the amateur bannds on 432Mhz ?
Yes these you can...
http://www.diytrade.com/china/pd/10174841/RS232_RS485_data_radio_modem.html
http://www.diytrade.com/china/pd/5608347/20_dBm_SI4432_transceiver_module.html

As Stan has said in the past they are excellent modules and easy to use, to be honest i would not touch the cheaper ones that Stan is testing in this thread after using these transceiver ones.
Will also comment Dorji is very good to deal with and have been very prompt to answer questions.

I think Dorji must have Stan on speed dial as they had quoted him to me in a email. :)

(too slow Stan got in first)
 

srnet

Senior Member
Ah, IC.

These Dorji modules appear to use the same RF IC as the Hope Modules (SI4432) but front end it with a micro of some sort, which I can see would make the frequency setting a heap easier.
 

manuka

Senior Member
-I would not touch the cheaper ones that Stan is testing in this thread after using these transceiver ones.
Much my initial feeling too,BUT these ASK modules do seem appealing for skinflint budgets & new users (who may be daunted by configuration issues). Folks after a bit more punch than other 433 MHz offerings may be tempted too, especially given the handy RX snooze feature,low RX drain & more flexible supply. This latter feature alone may be appealing,as numerous cheapie 433 MHz RX insist on a tight 5V supply,which hence requires extra circuitry or more batteries- or both...

Disclaimer: I have no financial involvement with Dorji or any of their agents,and although open to product samples (!), my reviews of wireless modules (especially 433 MHz) are usually posted for a "heads up" to suit the wider (PICAXE) community. Predictably - given my lengthy educational background - I've a slant towards wireless products that are reliable, easy on batteries, cost effective and easily configurable!

Stan.
 

Goeytex

Senior Member
Great- were your modules direct from Dorji too? Any US outlets? Care to share your circuitry & code (which presumably is running on a higher PICAXE)? Stan.
Be glad to share the circuitry and code. And pointers for getting increased range without breaking any rules ... Later today ..
 

davehouston

New Member
davehouston: Agreed! The market has long been awash with them. However many have weak transmitters (~a few mW) & "deaf" receivers(~-100dBm) that also insist on tighter supply values.
In N. America we are limited to about an order of magnitude less power tha most of the world so I cannot comment on wheter they are weak or not As fr the receivers, most are -103 to -110dBm and I get more than adequate range with a decent receiving antenna and a wideband preamp. The transmitters I've used typically work with 3-12V.
 

SAborn

Senior Member
Stan,

One test i would be interested in while you have wet weather is the range they work at in heavy rain, as my past use of the Jaycar ones proved they would become unreliable over 20m in the rain, they simple just dropped out, i see Dorji quote 10-90% humidity reliability for most of their range.

I dont mean placing the circuit in the rain, just transmitting through the rain.
 

manuka

Senior Member
I've just put these new Dorji ASK modules to work (under PICAXE-08M2 control), & can report very pleasing trials so far. The handy PICAXE "RFIN/RFOUT" commands need 14M2, 20M2, 28X2 & 40X2, so I've stuck with classic "SERIN/SEROUT" on the basis that folks would have 08M2s on hand. The attached picture shows my simple 08M2 driven setup- note the low current RX drain (~20 µA level) achieved by suitable PICAXE pin switching! The Synoxo SYN470R RF IC apparently has Wake On Radio (WOR) features (pin 12), but this is not brought out to the DORJI module control pins. Those with a keen eye & steady hand may find it worth exploring -data sheet below!

The beefy TX draws ~30mA on ~4½ Volts however, which exceeds a PICAXE pin source current. Switching has hence been done with a small NPN transistor via a ~4.7k -10k base resistor from the PICAXE pin2. In fact a quick bare TX module test shows ~1 µA drain with no data input. Sourcing this data from PICAXE pin4 however showed ~30mA drain irrespective of a data signal being supplied. This may well relate to a PICAXE sink/source issue, which such suitable code setting as "REVERSE" could thwart. Can someone perhaps explore this ?

N.B.After years of struggling with just a few piddling 433 MHz mW, we may now be in TX overkill. It's apparent that using a regular portable PICAXE 3 x AA supply may mean the TX (quoted as 17dBm = 50mW at 5 V) may be running above the usual legal max of 13dBm (25mW) permitted in most countries! Fresh alkaline AAs of course have voltages ~1.6V (so 3 x 1.6 =4.8V). Running off 2 X AA may be too low for the TX or PICAXE as batteries age, so ( to avoid using a regulator) perhaps use a dropping Si diode in the TX supply line? Using NPN switching on the TX supply (as I've shown) drops just the TX voltage by ~0.7V of course,ensuring regs. are nominally respected. This could be a particularly important issue, as overpowered 433 MHz TX modules may be become banned imports... It may be mere 10s of piddling mW, but radio regulations need respecting to prevent such incidents as this "dog collar" saga.

At the data level a particularly crucial need is to use the likes of several 85,85,85,85 ( 01010101 = ASCII "U" of course) preceeding the outgoing serial data to ensure the receiver is suitably responsive. PICAXE fans know this is a classic need for similar 433 MHz modules, and it was found essential here as well.

The example just endlessly counts to 100 - the appeal of this relates to lost or corrupted data reception being readily spotted on an attached (F8) reception terminal screen. I've made no great effort to match the RX/TX alert spells, and although no data was lost it's possible TX SLEEP and RX module snoozing (& serial wait) times may require adjusting for more demanding needs. All manner of tweaking can naturally be done- Andrew "BrightSpark"should receive some samples too, and will no doubt refine layouts even further! Due to our extremely wet weather today range testing so far has been just around the house & yard- I'll check ranges when it clears.

As mentioned earlier, I'd normally not now bother with ASK modules,as swish GFSK transceiver types in the ~US$25-$30 range are far superior. However such GFSK types often need significant configuration, & (with SMA antenna) a pair may set you back ~US$60. For those new to wireless data work, or for simplex needs, I'd say the ease of use & LOW PRICE (under US$10 a matched TX/RX pair) of the ASK offerings may appeal. They're certainly likely to carve out a "down under" niche (via Australian PICAXE distributor MicroZed), as Jaycar's traditional Keymark/SpiritOn 433 MHz modules cost ~twice as much,are less sensitive,are supply picky & have low TX power.
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EXTRA: One rain lashed trial later! The 3 X (fresh) AA powered setups used antenna approximating a ¼ wave (~165mm) whip at both ends, TX & RX units both ~waist high above the ground,with signals travelling thru' timber buildings & urban vegetation obstructions (+ stray reflections from garage doors & vehicles). Both 08M2 driven modules were ASK & 1200bps was used. My rough verifications of viable range under such conditions were -

Keymark/SpiritOn (Sourced via Jaycar as TX ZW3100 and RX ZW3102) totalling Aust$25.90 ) ~30 metres

Dorji (Sourced via MicroZed as TX WM4603 and RX WM4601 totalling Aust$9.70) ~150 metres

This is consistent with Dorji's superior RX (by ~3 dB) & more powerful TX (by ~10dB), giving a system gain of say 13dB. As each 6dB gain doubles range, then approx a good 2x2 = 4-5 times the range would be expected. Hence the verified 150/30 (=5) is a good confirmation!

Right -over to you guys- my work here is done. Stan.
 

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Goeytex

Senior Member
Nice ...

I just got off the phone with USA FCC officials. Unfortunately the 433 Mhz Band is not legal for use here except for:

1. Licensed Amateur Radio
2. RFID ...only for use at Airports and commercial warehouses and only for special use.

§ 15.240 Operation in the band 433.5&#8211;434.5 MHz.

(a) Operation under the provisions of this section is restricted to devices that use radio frequency energy to identify the contents of commercial shipping containers. Operations must be limited to commercial and industrial areas such as ports, rail terminals and warehouses. Two-way operation is permitted to interrogate and to load data into devices. Devices operated pursuant to the provisions of this section shall not be used for voice communications.

Goey
 

lbenson

Senior Member
Here is a link to a guide by Linx Technologies concerning operations in the 260mHz to 470mHz range (I found this on Sparkfun, which sells 433mHz modules):

http://www.linxtechnologies.com/resources/documents/an-00125.pdf

Included as an appendix is FCC CFR 47 Section 15.231, "Periodic operation in the band 40.66 - 40.70 mHz and above 70 mHz".

A flow chart is provided as guidance on legal operation.

This is what paragraph (e) (the exceptions paragraph) says in part: "Intentional radiators may operate at a periodic rate exceeding that specified in paragraph (a) of this section and may be employed for any type of operation, including operation prohibited in paragraph (a) of this section, provided the intentional radiator complies with the provisions of paragraphs (b) through (d) except the field strength table in paragraph (b) of this section is replaced by the following:" [... frequency 260-470 - Field Strength of Fundamental (microvolts/meter) 1,500 to 5,000].

I don't know much of anything about RF, so don't know exactly how 1,500-5,000 microvolts/meter of Field Strength of Fundamental applies to the Dorji and other 433mHz units.

I think the interpretation of this has been that short transmissions containing measurements, such as temperature, and control codes are permitted if the levels are acceptable and gaps between transmissions are at least 30 times the length of transmissions.

Anything can, of course be subject to interpretation by the FCC.

Thoughts by more knowledgeable folk on the implications for power rates in the U.S. would be appreciated.
 

Goeytex

Senior Member
That is very interesting as I spoke directly with an FCC bureaucrat in the equipment / device division that told me I could not 433 mHz to send temperature / humidity or control data. Seems like Linx may understand the rules better than the regulators. I will need to investigate further as I really like the 433 mhz devices. particularly the smart transceivers.
 

srnet

Senior Member
If you want to use fixed frequency modules that are cheap and simple to use, then it seems inevitable that they will be illegal (to use) in large areas of the world.
 

ciseco

Senior Member
"On the topic of RF modules, apart from the Hope RF ones, are there any other modules out there where you can configure the frequency directly ?"

The XRF / URF / ERF and SRF all can be set in software between 315-433 & 868-915

We are working on a 70Km booster for 868-900
 

ciseco

Senior Member
Why that specifically? not being an ISM band I doubt it would attract inetrest from major manufacturers, so with only a small potential market I'd expect solutions to be rather expensive and usually very slow at moving data. Moving to another more popular band will see a decrease in price.
 

srnet

Senior Member
Why that specifically? not being an ISM band I doubt it would attract inetrest from major manufacturers, so with only a small potential market I'd expect solutions to be rather expensive and usually very slow at moving data. Moving to another more popular band will see a decrease in price.
Thanks for the prompt reply.

It has to do with remote telemetry control of RF beacons as are used in weather balloons and the like. On the transmit side the Hope modules do a credible job at 434Mhz, but on the uplink (receiver side) they are very insensitive.

144Mhz is the common choice for an uplink (command) interface which you can use assuming you have the required Amateur licence.

As you say, the market is small, and apart from relativly expensive fixed frequency modules, I have yet to find a (cheap) frequency configuarable module covering the 144Mhz region.
 

Goeytex

Senior Member
"On the topic of RF modules, apart from the Hope RF ones, are there any other modules out there where you can configure the frequency directly ?"
I believe there are some Nordic NRF905 based modules that can be software configured for either 433/ 868/ 915. These are usually front end modules with the registers addressed via SPI and need a microprocessor to add UART support. You may find some on Ebay.
 

ciseco

Senior Member
"As you say, the market is small, and apart from relativly expensive fixed frequency modules, I have yet to find a (cheap) frequency configuarable module covering the 144Mhz region. "

I think you'll always find that to be the case as demand wont dramatically increase, it's I guess pay the money or move band are really your only choices

This summer we are planning with a UK High Altitude Society member to do a 37Km data link at 868Mhz to what I understand is the outskirts of space, is this not enough range?

The power amp we are using is being used by a client of ours who does 10,000's of water meters, they are proven and reliable
 
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ciseco

Senior Member
"These are usually front end modules with the registers addressed via SPI and need a microprocessor to add UART support"

This is what we insulate the user from with our radios as they have a built in micro, you pay about £5 over the parts cost for build and software (2 yrs of work), instead of weeks of frustation trying to get something going (or giving up) you can get them running in less than a minute. The cost of an aditional micro is easily £2, for most people an easy life is worth an additional £3.
 
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Goeytex

Senior Member
I hear you.

It took me about 25 hours to write & test the code for a micro used with Nordic NRF24LF01+ to make it "Picaxe Friendly" I imagine it would be a similar process with the 905, which I may do and then post the code here for others to use and improve upon.
 

ciseco

Senior Member
I have some experience of them too (not on AXE) but on an internet gateway that I designed. Did you also find a well folded paper plane would go further. I thought the RFM12B was poor till meeting the NRF. It's cheap but so is tesco cola, I would not buy either ever again :)
 

manuka

Senior Member
Quick Dorji ASK range tests just run (refer pix) indicate they'll typically be good for up to a 500 metres "semi line of sight" link with simple whip antenna,stretching to maybe 1km if clear LOS. In built up areas (timber frame buildings & urban vegetation) expect ~150 metres, falling to maybe 50-100 m with significant obstructions. Hope this helps - it's well ahead of the ASK/OOK competition ! Stan.
 

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SAborn

Senior Member
It took me about 25 hours to write & test the code for a micro used with Nordic NRF24LF01+ to make it "Picaxe Friendly" I
Goeytex,
Did you post your work on these public, or can i get a copy of your program, as i have a pair of them sitting here waiting to be tested. (no point in reinventing the wheel)
 

lbenson

Senior Member
Can someone explain how Stan's assessment of the potential power of the Dorji devices ("using a regular portable PICAXE 3 x AA supply may mean the TX (quoted as 17dBm = 50mW at 5 V) may be running above the usual legal max of 13dBm (25mW) permitted in most countries") relates to the U.S. FCC restriction of 1,500-5,000 microvolts/meter of Field Strength of Fundamental?
 

Goeytex

Senior Member
Goeytex,
Did you post your work on these public, or can i get a copy of your program, as i have a pair of them sitting here waiting to be tested. (no point in reinventing the wheel)
I posted code in complete projects using the INHAOS modules that use an Asian knockoff of the Nordic NRF24L01+. This Picaxe code was based upon my initial code done with the actual Nordic Chip. There are some minor but important differences between the two on a couple of registers. I have the code on a thumb drive. Let me dig it up and I can post it in completed projects. In the mean time take a look at the code for the INHAOS modules. If I recall, I commented it pretty well.

As a side note ... I found that the Nordic Modules and INHAOS Modules were compatible with each other.

Goey
 
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Goeytex

Senior Member
Can someone explain how Stan's assessment of the potential power of the Dorji devices ("using a regular portable PICAXE 3 x AA supply may mean the TX (quoted as 17dBm = 50mW at 5 V) may be running above the usual legal max of 13dBm (25mW) permitted in most countries") relates to the U.S. FCC restriction of 1,500-5,000 microvolts/meter of Field Strength of Fundamental?
I found this doing a Google search on microvolts per meter vs dBa . Maybe it can help.

http://www.microvolt.com/table.html
 

davehouston

New Member
Can someone explain how Stan's assessment of the potential power of the Dorji devices ("using a regular portable PICAXE 3 x AA supply may mean the TX (quoted as 17dBm = 50mW at 5 V) may be running above the usual legal max of 13dBm (25mW) permitted in most countries") relates to the U.S. FCC restriction of 1,500-5,000 microvolts/meter of Field Strength of Fundamental?
Radiometrix in the UK used to have an app note with a chart showing the relationship between allowable European and FCC power but the link I had no longer works. An email to their tech support has gone unanswered.

For a rough approximation, RemoteTech's TM20-1 which they say is FCC compliant has 20m range according to the datasheet. IOW, FCC power limits are miniscule.
 

Goeytex

Senior Member
My Dorji DRA886RX ASK Receiver setup for testing.

14M2 is dedicated to RFIN / Decoding. The 08M2 gets data from 14M2 via serin with a timeout.
The timeout is 1 second longer than the TX interval, so a timeout means a packet was missed.
A missed packet increments a word value written to EEPROM. So that I can power up later and
read the data. Total packets are also recorded to EEPROM and incremented every 100 packets
Packets are sent at an interval of every 15 seconds

The antenna was copied from a dissected commercial 433 Mhz SMA antenna.
It is 22 ga solid copper hookup wire. There are 22 turns ..With the OD (including insulation)
being .250". The insulation provides the space between loops. Total length of the antenna
is 3.20". Below that is a "ground plane" made from scrap aluminum sheet 1.85" in diameter.
The pins were bent 90 degree on the rx module so it could be mounted horizontally. The
header pin for the antenna was removed and the antenna end was soldered in its place.

The DRA887TX transmitter uses a similar antenna and ground plane

With this setup I can receive 8 byte packets from the DRA887TX at 200 meters with less than
1 missed packet per 2000 packets. The power level of the Transmitter is very likely beyond
legal limits in the US, but can be reduced to legal limits using a series resistor from the 5V supply
or by operating at a lower voltage.

Edit: I forgot to note that I was getting about 1 missed packet per 100 with a straight 1/4 wavelength
wire antenna and no ground plane.
 

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srnet

Senior Member
This summer we are planning with a UK High Altitude Society member to do a 37Km data link at 868Mhz to what I understand is the outskirts of space, is this not enough range?
Could be, can you say which particular module you are using (in a balloon I presume) and how much power and antenna gain you need on the ground station to get that far ?
 

manuka

Senior Member
Ibenson: Other things being equal,field strength (FS) relates mostly to distance away from the transmitting source. Google shows diverse formula, with P = 0.3 E^2 (P = transmitter power (EIRP) in Watts and E = field strength in Volts/meter) applying at a distance of just 3 metres = ~an "across the room" distance.

If FCC restricts FS to 5,000 microvolts/meter = 5mV/m = 0.005 V/m
Then TX power is = 0.3 x (0.005)^2 = (3x10^-1) x (25x10^-6) = 7.5x10^-6 Watts = 7.5µW

Such a tiny power output is hardly going to blister any paint work,although it's several orders of magnitude stronger than a typical 50 nanowatt in car MP3 style FM transmitter!

Goeytex: Good work, with findings akin to mine - RFIN/RFOUT are certainly worth using. An old ham trick for a quick ground plane is to position the transmitting antenna on a car roof top. Due to the slight elevation this also gives good RF take off. Stan (ZL2APS)
 

lbenson

Senior Member
Thank you, Stan. So the Dorji transmitters at 25mW are on the order of 3,000 times more powerful than is permitted by FCC rules under the exceptions in paragraph (e). So perhaps 315mHz or 2400mHz setups would generally be more appropriate in the U.S.
 

manuka

Senior Member
That seems the case- although (being "offshore") your FCC regs & their cussed fine print are not of similar concern!

The myriad of long US marketed 433 MHz gear however indicates there must be some local loophole,witness all manner of wireless key fobs,door chimes,back yard weather stations & energy meters etc. I note the likes of this La Crosse wireless thermometer use 915 MHz, but many others use 433 MHz - ranges are usually quoted as good to 100's of feet (indicating their TX is of 10s of mW).

Lower frequencies of course will have better punch thru' obstructions, meaning (for modest data rates) 315 MHz would be preferred over 2.4GHz. At this higher freq. however significant power is allowed & -when combined with high gain compact antenna-LOS ranges can be quite amazing. Stan.
 

davehouston

New Member
315MHz is subject to even lower FCC power limits than 433.92Hz. And there are no loopholes - while transmitter modules are sold w/o restriction, all finished transmitters sold in the US must undergo FCC certification testing with the antenna and the final product will have an FCC ID number on the label. Antenna connectors must be of a type that make it tough for Joe Sixpack to find a replacement antenna (although since nearly all use a lefthand thread of the same size, this is nice on paper but of has little deterence in practice). The 330ft range claimed by LaCrosse is about 10x what it will actually do out-of-the-box. (I've had them.)

However, I get about the same range as Stan by using a good receiving antenna and a wideband preamp between antenna and receiver.
 
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