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fallenangel3k

My dual A/V and diversity receiver

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hecko Everyone!

Currently I am developing my own DIY dual AV and diversity receiver based on a PIC16F88, airwave awm623 rx_modules, MAX7461 LOS alarm chips and MAX4310 high bandwidth AV switches.

The PIC16F88 is running on the internal 8Mhz osc.

The both Airwave AWM623 2.4Ghz receiver modules are soldered each to aPCB which also includes the power supply for the module, the MAX7461 LOS-alarm chip and the Antenna of course.

The dual AV switch is consisting of 4x MAX4310. It is 2:2 switching with 2 inputs and 2 outputs. The outputs can modus "A_Only" (both outputs have signal A then), "B_Only", "DUAL" AB (uses rx_a for AVoutput1 and rx_b for AVoutput2 -> use with two transmitters/cameras on the plane/heli) and diversity "AUTO"switching which then let the RSSI and LOS decide which rx we going to use.

The code for the PIC16F88 is written in Picbasic Pro:

SEE NEW FILE ATTACHMENT

Feel free to use this code for your own project or ask/give any questions/comments...

Greets,

Marcus

diversity_rx.pbp

Edited by fallenangel3k

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Hi Marcus I'm doing a simular thing with four AWM608 modules. The main difference is that mine will probably switch more slowly than yours but fast switching for diversity is not my main aim. I just want auto switching between four patches mounted pointing North,South,East and West, any diversity action will be a bonus.

I will be intererested to see how the MAX7461 performs as I have not used them in my design.

How long do you think it will be before you are at the testing stage ?

Regards, Terry

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Hi Terry!

one initial stage test was sending a carrier signal only (tx turned on with no camera attached)... the LOS chip pulled the line low as expected/hoped.

Next test will be how it reacts to missing/corrupt frames during transmission. I expect/hope it to work as fine as in the first case, too.

So as you can see, I am already on the testing stage.... still need to do some boards and soldering, need a project case, etc... progress will be reported here of course.

BTW: Your system switching between N, E, S, W is already a diversity system if you switch the receivers accordingly to their RSSI signal.

Best Greets,

Marcus

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Thanks for your update, I will watch with interest.

Yes my system is a diversity system but I was just pointing out that perfect video is not the main aim but it would be a nice bonus.

So far I have the LOS code working for my pic and the video switch. The next stage is to write the code for the switching/diversity pic.

Terry

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hecko everyone,

finally the project is build/done in a nice projectbox.

I also added power/signal status led and a switching negative voltage source which I probably won't need since I use direct DC-coupling of all modulboards. But this way I also gained some first experiences at negative voltages... ;c)

A word about how it performs in real life.... I only have done some minor indoor tests but the diversity switching already works super fast and fine (without any notice).

The power LED also tells me now if I have a valid signal at all (it blinks/is off when you have no correct signal) and the receiver-status LEDs tells me which receiver is active.

I maybe will also install a small LCD which then gives me info about signalstr., channels and receivers used and a display of the supply voltage. And speaking of voltage, the last thing will be a undervoltage cutoff to safe the batteries with an accoustical alarm some time before the cutoff (I have some free ADC channel and additional switch pin left).

So finally this is going to be a fully-featured diversity or dual a/v receiver for an very low price which is was worth the DIY apporach instead of buying a commercial unit for 200 or even more Euros...

If there is any interest, I will make the Schematics and/or PCB layouts available...

Outdoor test will be done once the weather is a bit more friendly... ;c)

Greets,

Marcus

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Thats good news! Glad to hear you got it done and working! Can't wait to see how your outdoor tests perform. Man I wish I knew how to do this kind of building... :(

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Phil and all,

at first I had not even a clue about that all, too.... so I simply taught it all myself...

Some first outdoor tests were performed today. I am totally stunned, the system performed super well, showed many times less dropouts in video (and that with my 0815 thrown together and unmatched diy Lambda/2 (6.5cm) Antennas) and best of all the quallity/fidelity of the video improved by a magnitude, too.

Both, The quallity/fidelity and range of those cheap HONGKONG SYSTEMS CAN NOT COMPETE in any way...

I will put up some sample videos shortly....

Greets,

Marcus

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Thats great news, Im just debugging my code at the moment so the end is in sight for me too. Can't wait to see how it performs with 4 RX's, I have my fingers crossed it works as well as yours.

Terry

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That is a terrific report. It would be interesting to see videos at the same site with and without the diversity feature enabled.

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I was bench testing my four AWM608 modules and I am seeing a big difference in performance between them. One seems to pull the video from almost nothing, two seem ok and one is very poor. Has anyone else noticed this with the Airwave modules ?

Terry

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I was bench testing my four AWM608 modules and I am seeing a big difference in performance between them.

Is there any chance it is an issue with the module's RF input layout? At microwave freq's, that is a critical area; even if construction looks nearly the same, RF losses can vary. But beyond that, I have seen varying part-to-part performance on other video rx brands, so that is certainly possible in this case too.

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Is there any chance it is an issue with the module's RF input layout?

No, each rx is on its own board with separate input and I have tryed swapping them about but it make no difference. Its on a test board at the moment, when I get it working ok I will build it on to a smaller board. Sorry for the rubbish picture but you should get the idea.

Terry

post-6-1163092930_thumb.jpg

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Hi fallenangel3k

Thanks for the details of your project.

I'm just wondinering of you are timing the switching to occur during a blanking period and if so how?

Thanks again and be assured there is interest!

Cheers

B.

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Boris,

no, currently the switching is untimed and happens almost instantly once either RSSI is only a bit higher or the LOS-alarm is low on one.

In my room test this brought up some funny results. when I put my hands halfway between (close together) tx and my diversity rx, then on some times the switching was continously and I could see both status leds go bright and dark that fast, that it seemed as both were one. Yet, there were only little interference produced by the fast switching... mainly on the audiochannels, the video almost showed no sign of switching. In normal conditions you probably wont even recognize the switch besides the fact that one rx puts out a slightly brighter image than the other one.

I am very happy with my design, I just need to put up the videos to show and satisfy you, too (at least in compare to HOW cheap the design was against a commercial kit). Unfortunately I only own a 320x240 mpeg4 recorder with a lousy quallity and even worse it is defect somehow, I can not record anything, only view live... anyone a cheap 640x480 recorder on sale? :c(

Greets,

Marcus

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Hi Fallenangel3k,

Further to your

If there is any interest, I will make the Schematics and/or PCB layouts available...
on 7th November 2006, I think many, not just I would be interested in more info on your project, so yes, please do.

Regards

B.

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Terry,

I have enjoyed reading many of your posts and in particular your description of your tracking antenna project. I'm just wondering if you are planning to share this new diversity project? I certainly hope so. (Please?)

B. :ph34r:

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-AT-Boris & Mark

Thanks for your additional interests. Since all my documentation and schematics are handdrawn (and you probably wont decipher a single line..hehe) I will have to redo them in some schematic program.

The layout files are already available... but only in ABACOM SPRINT LAYOUT format... can you make use of this format? (*.lay)

Greets,

Marcus

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Boris, I have no intension at this moment to share any more than I am doing now. That is to say I will post info that may help guys decide what they want to make themselves but I will not post full details as with Mr RC-CAM projects. The main reason for this is I build to satisfy my own needs and I dont develope projects to the point where they are commersial. If I were to do this for instance with my diversity receiver then I would probably work on it and test it for another year and I have too many other things waiting to get designed and built ;)

That said I am happy to help with others projects on a personal basis if asked.

If Matt comes through with his diversity receivers you may not bother buiding your own, Im not sure when he expects them to be availible though.

Terry

Edited by Terry

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Hi Marcus,

Can you send me the code? Does not download from here.

I am doing a LOS and RSSI diversity for a video project and appreciate

anything you can share.

Senor

///////////

The code for the PIC16F88 is written in Picbasic Pro:

SEE NEW FILE ATTACHMENT

Feel free to use this code for your own project or ask/give any questions/comments...

Greets,

Marcus

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Guys I know this thread is old, but after searching the internet for a wiring diagram for the awm623 I only get several older hits. This thread seems my best chance of working out which pins are used for what. Can anyone help?

 

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