The product page for the 3DR radios is full of bogus specs! Could you please post the REAL specs?
For example, the page claims "Receiver sensitivity to -121 dBm". That is the spec for the SiLabs chip radio. HopeRF lists the specs for their radio module as significantly less sensitive, and obviously you can't obtain the spec of the module when used within another product, like the 3DR radio.
Also, what's with the range claims? I see you've changed it at least once, but why not make a realistic range claim. These radios should do around 8 km. So why only say one or a few? Have you really not properly tested them over a few km?
Also saying "with Si1000 8051 micro-controller and Si4432 radio module" sounds like the product page writer may not have a good grasp of the hardware. It has one Si 1000 radio chip in it. I guess you can argue that statement is sort of true, but it certainly could cause someone to misunderstand and think it has two chips on board.
Don't take this as a rip. I just see a lot of radio retailers out there that either flat out lie about the specs or have such a poor understanding of the technology that they mistakenly put wrong specs. I don't think DIYdrones is either of these, so I thought I'd offer some constructive criticism to help you guys get going.
I also kind of feel responsible since I recommended using these chips in a radio design in several posts last Sept.. So if you need any help, just ask.
Replies
Hi Tridge,
Could the 8W V6 Pro Booster for 433MHz Digital Systems be a viable amplifier for the 3DR Radio (433Mhz ver.)
Cheers
Chris
has anyone found a good antenna combo thanks
@ Tridge, quick question if I may.
The amp used in the test on the wiki, are they commonly available, or it is it tester / beta that your using? I'm asking as I am unable to find a bi-directional amp on their (Shireen) site or store that matches the spec of the one your using. I'm also guessing it was direct from them and not Aust. distributor (Rojone?)
Cheers mate, thanks
George
PS Congrats to you and team for a great, and much needed product!
I wonder if I may add a little information into this discussion of receiver sensitivity.
Receiver sensitivity on its own is not a particularly meaningful measurement. In order to become a meaningful measurement (i.e. one that will allow comparisons between different radio receivers) some additional information is necessary. This additional information is bit error rate and data rate. Without these two quantities it is impossible to make comparisons between different receivers.
Most inexpensive radios only quote one or two out the the required 3 quantities, making comparisons impossible.
Whether error correction is included in the measurement is entirely up to the manufacturer, but in my view it makes more sense to use the configuration most likely to be used by the end user. Sometimes this adds latency, and this should also be stated.
Cheers,
Andrew (Dunlop)
The radio guide claims 7.4km x 4 range with the Spireen amplifier.
http://code.google.com/p/ardupilot-mega/wiki/3DRadio
Does that mean I can almost double that range with a set of higher gain antennas with a patch antenna on ground station and omni in air and achieve around 30 miles??
Any description of proper antennas made of a piece RG179 ? - the provided antennas are too bulky and heavy - I'd like to make my own.
Jake,
I can assure you that I do try to make the docs as accurate as possible. Yes, I have really done range testing, but as I explain in the docs, range varies depending on a lot of factors. I say "a few kilometers" because that is about as precise as you can get with a radio. The radio doesn't suddenly stop working at X kilometers and what absolute range you get varies a lot between tests.
Secondly, the receive sensitivity numbers are not just based on the Si docs, they are based on real lab tests. We found that the chip does actually exceed the spec sensitivity. The sensitivity also varies a lot with air data rate. The highest sensitivity is at very low data rates. The radio can be configured for 2 kbps if you like, in which case you will get a great receive sensitivity result, but you will also not be able to send much data.
At some future time we hope to publish lab results to make it easier for people working on compliance.
yes, I've really properly tested them. With the supplied antennas you can get some packets through at 8km, but not many. The packet loss at that range is usually quite high, mostly dependent on what the local noise floor is. In practice I expect people will need high gain antennas to achieve 8km with these radios without amplification.
Cheers, Tridge
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