Hello all,

I am working on some unmanned vehicles and it is required to have both video and telemetry transmissions. I would first want to look for some modules that are capable of sending both of telemetry data and video link. Do you have any suggestions for this? By the way it is necessary to have these modules ranges to be at least 10km in LOS (preferably better).

Best regards,

Fatih

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Hi!

I'm also looking for a similar solution, alltough I have already found my target frequency of 5.8GHZ as I will be using 2.4Ghz for my RC radio.

theoretically, sending both should be perfectly doable, thinking of using TBM (Time multiplexing) as telemetry will only need small duty cycles and leave most of the transmitting time for the video. However I wasn't able to find any module that was capable of doing so.

You said that you need 10km range, may i ask what region you live in? E.g. in Europe it will be nearly impossible to achieve those ranges without going over the limitations.

As frequency goes up, watt for watt range goes down.  As frequency goes up, penetration goes down = less range.  As frequency goes up, multipath problems increase = less range.

The only advantage to higher frequencies is smaller antennas.

When you go from 900 mhz to 2.4g you loose about half your range.  When you go from 2.4g to 5.8g you loose about half your range again.  

Add in the multipath interference and the LOS issues and it makes 5.8g a very poor choice for transmission at any decent range.

Unfortunately I don't have the choice of using 2.4GHz or 900MHz for receiving Video / Telemetry data, because there will be nearly always some 2.4GHz disturbance nearby (e.g. because of another pilot standing next to me who i don't always want to force to turn off his radio) and because 900MHz is simply completely illegal to use in Region 1.

The only two other choices are 433 MHz and 868 MHz. 433MHz is quite polluted already and its power is limited to 25mw.

868MHz seems to be the better solution, max. power is set to 500mW with a max. duty cycle of 10%. However i Don't know whether 10% duty cycle is sufficient for any serious transmission and I haven't seen any propper 868 Transmitters either.

5.8GHz sure has it's limitations but as my flight times will be between 8 - 10 min only, I can't even fly that far away so i'll loose eye contact.

You might try 1.2g.  I use one that has 12 channels ranging from in the 900's to around 1600.  I've posted links in other posts, they're available on ebay.

I guess things are different across the pond, but here in the US people use whatever gear they want and I've never heard of anyone getting fined for it.  The laws are so poorly written here that it's nearly impossible to understand what's legal anyways.

The rules are different for just about every variation on every type of device and frequency range.  Since they don't bother to enforce import regulations on the devices they obviously don't care what the end users do either.

Hi,

well yea, using 900Mhz with high power output would disturb the air communication here and as I live near a real airport maybe not the best idea to do :D

I think 1.2Ghz will disturb my GPS module too much, won't it?

ATM I'm looking into sending telemetry over the audio channel of a ImmersionRC 5.8Ghz module using a modem, which seems to be the best solution for me for now.

Well, it uses 12 channels.  They range from the low 900's to around 1600.  The beauty of this is that you can easily find a channel that doesn't bother your other gear.  The downside is that because of this range of channels it probably doesn't have the tightest filtering.  I've had good results with it though.

Hi!

Okay i have looked through your posts but couldn't find the ebay link and on ebay i just found some CCTV transmitters which are def. to big for my UAV. Could you please post or send me the link?

Cheers

Yeah, the search is kinda weak here.

I use one of these systems...

http://www.ebay.com/sch/i.html?_sacat=0&_kw=15CH+700mW

At one point I had a list of the frequencies each channel used, but I've lost it.  Maybe I'll figure them out again when I play with my new SDR.

If you look around enough you can probably find at least the range of frequencies it runs on.

Looking through them they mostly just say 1.2g, but one listing says:

Output Frequency/ Channel Number 0.9G/1.2G /1.3G 8CH

 

So they do have a pretty big range of frequencies.  Should be easy to find a clear channel on a legal frequency no matter where you are.

I think I have the 8ch TX with the 15ch RX, but it looks like there are 15ch TXes available.

Of course, YMMV with Chinese gear like this, but I'm happy with mine and it's hard to beat the price.

Hi,

thanks for the link, i found out that this product is made by a chinese company named Shenzen Clairvoyance but I couldn't find out any further specs yet. But I'll maybe buy one from china :P

However do you as well send telemetry data over the audio channel or do you use a different method. What method would you recommend for transmitting telemetry over the audio channel?

Hmm, sending 57K baud down the audio channel?

I think that's the wrong answer.The current method is to either put the OSD in the airframe and send overlayed telemetry information over the video link, or much more recommended to use a set of 3DR telemetry radios and thus have a secondary control channel. You want to have bidirectional coms on the data side for a number of reasons.

Even if you could, sending 57K baud down the audio channel is only a downlink connection. It's probably not capable even if you used an old pair of 56K phone modems(what a crazy hack that would be), the bandwidth of the video TX audio circuit probably cannot support that kind of rate.

So what I'm saying is, forget about the audio channel. It analog and in no way can support telemetry.

So to answer the question, I don't know of any radio natively that does analog video and then 57k or more data rate. You must run to separate radio systems and further, you want the data to be bi-directional. Best choices today are the 3DR radios for data and then whatever analog video setup.

Also, just to recap another thread, lower frequency goes further range on the same TX power. IF you are allowed in your country, 433Mhz radios hands down have the longest range. The next best thing going is 900Mhz and there are tons of both data and video radios systems in the frequency. Much higher frequency like 2.4GHz is going to max out the legal TX power and STILL require you to use directional antennas just to reach your target range. This extremely complicates the entire system with antenna tracking.

Sorry, needed to link to this thread http://diydrones.com/forum/topics/question-on-frequency-interferenc...

 

Point being, you need to know your available frequencies legally and the max power. Plug those into some RF link budgets (A term you need to be very familiar with) and figure out what the minimum setup that will reach 10K realistically. Then work form those figures and start looking at radios that meet the spec. This is the "correct" way to build a professional setup.

This link is a must read http://www.afar.net/tutorials/how-far/ 

 

Hi,

thanks for the replys so far, you guys are incredibly helpful!

What I'm basically trying to achieve is to get a UAV / FPV Quadrocopter that i can control using std. 2.4GHz (because receiving on this frequency wouldn't make any sense due to other 2.4GHz radios nearby) and getting Video AND Telemetry from the Quadrocopter using only one extra module. I'm not quite sure yet why I would need an extra uplink as well as i could just use the 2.4GHz for that, couldn't I?

433MHz surely would give the best range but i fear that with a max. of 25mW legal ERP it will get too much penetration from nearby radio thermometers etc.

Also I would need to convert the analog signal of the FPV camera to a digital MPEG stream to be able to transmit it over the 3DR Radios, right?

@Vernon, thats exactly what I'm doing all the time :P

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