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mieczotronix

Airwave 612 Tx and 608 Rx compatibility

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I am about to buy a video Rx Tx set.

I would like to buy Airwave 612 RF Transmitter (500 mW) with Airwave 623 RF Receiver sold by Active-Robots. Unfortunatelly they sold out these receivers.

I mailed them twice but they haven't responeded. Has anyone been buying stuff from them recently? What's up with them?

Since they still have in stock Airwave 608 RF Receiver (which is normally sold in pair with 609 transmitter) I wonder whether the 608 Rx would work with the 612 Tx

I know they work in the same band, but I am not sure as to channel spacing / modulation stuff.

What do you think?

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Their customer support is horrible. I couldn't get a response from them (after at least three e-mails from me) until I threatened to give them bad reviews on the forums, then they still didn't help with my problems as they promised. They did offer for me to send my RX back to them for analysis, but that means I have to ship the thing back to the UK. I wound up buying a ready made system from another online vendor that didn't cost much more that works just fine.

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Well I must say I have had no problems with Active Robots, always fast delivery. As for the 608 being ok to use, I seem to remember it is but I would check the data sheets first.

Terry

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I just checked the latest data sheets and they dont tell you the frequencys anymore !

I just tryed it and I get all 4 channels.

Terry

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Sorry if that was not clear ( I was running a bath at the time ), yes they will. I find the 608 not very sensitive but as long as you are not using the 10mW TX I would not worry.

Terry

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11 days passed, so I hope should be getting my tx/rx soon.

Active Robots, I must say behaves very strange. They responded to none of my three e-mails. In the last one I asked them about my order status, since I haven't received any confirmation from them (only from PayPal, which makes me hope that I will get my money back if something goes wrong). They haven't responded to it either. Their marketing is almost non-existing, at least for overseas customers.

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I can only say again that I have not had problems with them but I do live in the UK so that may make a difference <>?

Terry

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I got the stuff today, but

the transmitter has those tiny little 1,54 mm pins. I am unable to find those tiny sockets at any local parts shop, so I guess I will end up etching my custom pcb to act as an adapter (still have to buy pens, pcb, chloride, 0.8 mm drills, driller head - that's a lot of stuff).

It surprised me that Tx and Rx have no SMA sockets for antenna, just bare pcb (Rx) and those tiny pins (Tx). Also the two units came completely unmarked. Just two shiny metal boxes. I just hope I got what I wanted.

Yet I am pretty amazed with the transmitter size, it's almost the size of a large post stamp.

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I sold my wire directly on the pins at 90 deg. and add a drop of epoxy to retain wire on the case. No SMA connector on mine too. I buy one from Digikey.

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Thanks Terry for the photo

What are these yellow blocks? Decoupling caps before and after 5V reg (the black block I suppose) and are they 100 nF? Do you think I should feed P/S through 10 uH choke? I can't see clearly - have you attached the Tx case to power ground?

Edited by mieczotronix

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Thasts odd my post disapered when I pushed the button, so I try again.

The yellow blocks are 47uF caps but only because thats what I had laying around. I dont use a choke but I am using a separate battery. I would not use a choke unless I found it nessasary. The TX is attached to ground only inside the case, I have not added one.

Kasper, the 608 works well.

Terry

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Ok. I etched pcbs, drilled them, soldered everything. Checked for short-circuits and I hooked everything up. And as expected no image. Then I started checking things. I checked that the transmiter draws 400 mA. Then I was about to check whether the voltage doesn't drop too much with this load and instead of connecting voltmeter to +5V line I connected +12V to it. And then this gentle sweet-smelling smoke told me I was holding the wrong cable. And now due to my stupid error the tx is now baked. I'm mad as h*ll. arrrrrgh (grizzly sounds).

I took the Tx box apart and noticed one of the SMD elements (rather big black plastic box) is molten on one edge. It has no labels whatsoever on it so, I won't be able to fix it myself. Sendit in back and forth to active robots does not seem to make sense. I think I 'm going to buy a new Tx. I am really really mad at myself.

And before I baked the transmitter I think I discovered the cause of the missing image - one GND lead was unsoldered. Da*n!

Edited by mieczotronix

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I ordered another Tx on Sunday (three days ago) and it arrived today. What a surprise! Only three days!

Now I will have to be very very careful with the new Tx.

Could someone tell me:

If I test Tx and Rx side by side on a bench - will they work or I have to place them a couple of meters apart?

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Could someone tell me:

If I test Tx and Rx side by side on a bench - will they work or I have to place them a couple of meters apart?

You don't need to put them apart, they will work well side by side on our table, take care with your new tx, send a photo to us before plugging it, we will verify it if you want :) Smelleing smoke, It happens to me too many time :) You learn the hard way.

Terry, I'm sorry, I miss your post... You have make very good job, you can start business with that :) Only one thing is wrong and must be correct to have the best transmission( I think, by experience). Ground is very important when we play with RF signal. You must have a very good ground everywhere, normally the PCB ground is weld at many point with the metal case(minimum the four corner), also the ground lead input is weld to the case (it also add strenght to the lead, in a crash it will not broke your pcb by pulling on it).

I don't use PCB, I weld the regulator directly on the tx case, and I glue with epoxy the components in place. The two green can are 100 uf electrolytic capacitor,16Volt. The microphone is from Supercircuit.

post-5-1154567528_thumb.jpg

Edited by Vrflyer

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I weld the cover with a weller gun, I place the tx in a ...... to dissipate heat while welding.

post-5-1154569146_thumb.jpg

Edited by Vrflyer

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Thankx VRflyer. I think this time I won't be so careless and won't blow up the module.

I also got some experience regarding ground. What I learned is that you shouldn't make any loops with ground, as instead of shielding it will pick RF noise. I learned this many years ago when I made a pcb for graphic Eq. I made a nice ground patch all around the PCB as I thought then It will eliminate noises. When I soldered everything it turned out that the op amps are picking a lot of noise, almost like an FM radio in between stations. I fixed it when I cut the ground loop at one spot and connected it in start topology.

I checked with ohmmeter that Tx metal case is connected with all its ground leads, so there isn't realy any point in soldering it to ground on pcb apart for mechanical considerations.

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ok, this time all worked fine.

Now I got some questions.

Since I have a 12V camera I supply the transmitter through two regulators 7809 and 7805. These are those large regulators with metal heatsinks and I soldered them to the back of the PCB to a ground plate just underneath the Tx module.

txbot.jpg

The transmitter draws 390 mA and both regulators and the transmitter itself heat up considerably. Whereas I can still touch the transmitter (so it must be around 40deg Celcius) but I regulators seem to be hotter (I guess about 50 deg C or so).

Do you think I will have to mount the transmitter somewhere outside the plane where the air flow will cool it? Like there:

plane.jpg

Or shall I put just the regulators outside plane on a piece of heatsink and leave the tx inside the plane.

Another thing I noticed watching the feed on TV is that the video is a little bit jaggy on vertical edges of the screen. So far I haven't used any capacitors, chokes or anything neither in transmiter nor in the receiver I just used 7809+7805 in transmitter (which is supplied from battery) and 7805 in receiver (which has been supplied from a p/s unit). Camera is connected to the Tx with just a pair of twisted bare cables 10 cm long. I thought that video signal is quite resistant to interference, but maybe I am wrong.

So I guess caps will be needed, but what kind of ? 100 nF / 100 uF and where in Tx or Rx.

The documentation for Ariwave receiver suggests I should feed the video out signal through 470uF/10V cap. I haven't done that. But what's this supposed to be for anyway?

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So far I haven't used any capacitors, chokes or anything neither in transmiter nor in the receiver

78xx series regulators must use the stability caps that are shown on the data sheet. Otherwise they are well known to oscillate without warning. This may not be your problem now, but not having the recommended caps will give you grief sooner or later.

The documentation for Ariwave receiver suggests I should feed the video out signal through 470uF/10V cap. I haven't done that.

The cap is needed when the attached video monitor or recorder (or whatever is attached) does not include protection from DC offset of the video signal. It is considered good practice to include it.

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