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mklarich

Klarich Electronics/BlackWidow Diversity Receiver

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This system uses 2 receivers from BlackWidow's 2.4Ghz line of transmitters and receivers (Frequency Set 1) to virtually eliminate multi-path interference.

Multi-path interference occurs when a signal originating from a video transmitter is received by a receiver that also receives the exact same signal a split second later because the 2nd signal has bounced off of an object and arrives a split second after the original signal. Sounds kind of confusing but it is the source of much of our troubles with video systems. I have been trying out different antenna configurations for 4 years trying to get amazing video, believe it or not a simple rubber duck antenna and small patch antennas have given me the best results. Many patch antennas that have higher gains to increase receive sensitivity also narrow their beam width which reduces the area that an airplane can fly in without having the antenna pointed at it.

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The system works as such. My circuit board is designed to switch between 2 video receivers that are set to the same channel. My circuit decides which receiver is getting the better signal and then switches to that receiver in-between frames. You don't see the switch!!!

This video shows exactly how the diversity receiver works, to allow the viewer to know when the diversity receiver has actually switched we disabled the audio channel on one of the receivers. This allows the viewer to hear when the switching occurs.

Please email us with any questions or post them here.

Thank you,

Matthew Klarich

Klarich Electronics, LLC

www.klarichelectronics.com/videos/ke_bw_diversity1.wmv

mklarich-AT-klarichelectronics.com or Bill Strong [ williamhstrong-AT-yahoo.com ]

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Looks like it works well, do you have any pictures of the setup ?

Terry

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You can see a proto of it in this picture. This picture is posted in another thread. Bill Strong will have a shot of the new unit up on here later today.

The new unit is all black to match the receivers. I am still surprised no one asked me what the heck that thing was on the tripod, but then again my airplane was in the shot...along with my wife..... Probably should have put her first :huh:

Matt

ccrcc1.jpg

Edited by mklarich

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Those aerials look very close together, dose it improve the dropped frame rate at long range by much ?

Terry

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mklarich

How much is one of them there diversity receiver things any way?

That sure is a nice looking airplane you got there how dose it fly and where can I get one?

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Those aerials look very close together, dose it improve the dropped frame rate at long range by much ?

Terry

I'll jump in with my comment since Matt and I differ on our choices of antennas. He's happy with the standard whips and I like to fly with high gain patches.

The 14dbi patch antennas I'm using now are linear polarized, so when I set them up I orient them so the polarization axis's (axees?) are 90 degrees from each other. That way I'm effectively getting both horizontal and vertical polarization.

In my situation, spacial diversity is playing second fiddle to polarization diversity. As you suspect Terry, spacial diversity becomes less critical at longer ranges due to good-ol' geometry.

*** Dave, the units will start at $299 and will include the same antennas Matt pictures. I'll try to get some pictures done today but I am fast running out of hours in the day.

Bill

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Great, finally someone made an affordable diversity receiver! And judging by the video the quality is great. Can the frequency of the recevier be tuned to match my TXs (I have few already) or do I have to buy BW TX's to go with it?

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I am getting my website updated this weekend. Val, the unit is using frequencies compatible with blackwidow A/Vs frequency set 1. I am working on the older lawmate receiver version this week. Its output is a little different then what I am working with right now.

I will have info and pics up shortly.

Regarding antenna distance. A wavelength at 2.4ghz is 30cm long. It doesn't take much distance between antennas to make a huge difference. Just look at wireless routers for computers, their frequency is only 50mhz away from us and their antennas are closer together then mine.

More info will be up later this weekend, please ask any questions you have. I need to get a faqs list setup for the unit.

Thanks,

Matt Klarich

Matt

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What TX are you using on the video?

It really looks good!

Are you comparing RSSI outputs to decide which receiver to switch to?

The problem to be able to use other RXs would then be calibration to output levels if I understand correctly?

And maybe it's stupid, but what about using 1 whip antenna and 1 patch? So when you are close to you the whip will grant you omnidirectionality, and when flying far away (where angle is reduced according to the good old geometry you were talking about) the gain of the patch, which of course is pointed roughly in the good direction, will give you the needed range...

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Matt and I are riding a fine line on the forums when it comes to talking about technical details.

On the one hand, as contributing members, we are chomping at the bit to tell you every detail of how the units work. But as vendors, we have a responsibility to our companies not to get to detailed.

Where appropriate we are happy to share details that we gleaned from public domain. But our individual inspirations must remain secret :rolleyes:

Ok, now to your question. Yes, the circuit compares RSSI voltages between the receivers. Matt's experiments have shown that of the samples tested, the RSSI ranges are surprisingly well matched. The receivers used are identical so we had hoped this would be the case.

Regarding antenna selection, I'm really excited to see what people end up doing. Your idea sounds plausible, now we just need to get some units in the field for everyone to try out their own theories.

Someone asked on another thread about indoor use. This is perhaps the most challenging environment to work in and theoretically, a diversity receiver should help these situations. I expect that once we get the units in the field we'll have a better of idea of where the diversity switch will shine. I also expect to hear about some creative antenna placements to help with indoor apps... As we learn how people use the units we'll post on our respective websites with tips and tricks that we learn.

Regards,

Bill

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The video demo is outstanding. Looks like an awesome product. Way to go!

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Much thanks rc-cam, I took a long time to develop this unit to be an amazing product. This is my 4th board revision and 3rd case revision.

Below is a picture of an almost completed unit. The labels are arriving early this coming week and units should be available for sale at the end of the week. If all goes well they will be ready to ship friday.

Matthew Klarich

m1klarich-AT-klarichelectronics.com

diversityrx1.jpg

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Nice construction Matt, well done. Can your switching box work with Felsweb receivers? Does it require high voltage RSSI to correspond to weak signal?

Kilrah, using one omni and one patch is the right combination - it's exactly how I end up setting up my antennas. Except that I run my tracking bi-quad instead of patch.

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Felsweb frequency set:

CH1: 2414 - CH2: 2432 - CH3: 2450 - CH4: 2468MHz

Do you think it is possible to retune BW receivers to a slightly different frequency?

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Use channel 3 ;) no retuning required. Are you using audio channel for anything val? Need to see if audio offset is the same.

Matt Klarich

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Matt, I run two different channels from my heli, so I need to match two channels :(.

I do use audio to send telemetry data, but audio carrier offset can be adjusted from Felsweb TX (they have a pot for subcarrier offset), I don't think audio will be a problem to match.

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You might be a good tester for this val, we have been wondering if the switching would corrupt audio data. This system was designed primarily for video, audio was an afterthought.

If needed I can add a switch to the current model that the user can turn the audio channel switching capability off, so you will always be listening to audio from one of the receivers while the video still switches.

How many receivers are you running in your diversity receiver?

Matt Klarich

Edited by mklarich

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My diversity receiver is switching between two receivers, just like your model.

Audio switching wasn't a problem for me. A frame may be dropped during switch, I never looked - the overall performance is not affected. Video quality is more sensitive to switching, especially when I fly in the dark when any noise in the picture adds to confusion.

If you need a tester, I volunteer.

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Kilrah, using one omni and one patch is the right combination - it's exactly how I end up setting up my antennas. Except that I run my tracking bi-quad instead of patch.

Okay, that's cool :)

audio carrier offset can be adjusted from Felsweb TX (they have a pot for subcarrier offset)

Aha interesting!

I had not noticed this... unfortunately it's not with the felsweb ones thatI'm having this problem :(

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Ok, I finished up the second batch of receivers and they are on the way to Bill Strong of Blackwidow A/V along with stickers and related material.

He will have enough units in stock by monday to feel ready to start selling units.

If you have any questions please ask, I am still working on my website trying to get everyones questions answered.

Matt Klarich

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I'm still working on the documentation for the unit, hope to have it done by Monday....

Bill

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Val, I need to get a hold of a couple of felsweb receivers and a transmitter. Can you post a link to their website please? What is my lead time on an order generally?

Thanks,

Matt

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http://www.felsweb.com/p3/500mw.htm

They used to be pretty quick with delivery - takes a week or so to get here from Hong-Kong. Their RSSI signal is inverse - the higher voltage will correspond to lower signal.

Edited by cyber-flyer

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