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When you say "lose video", do you mean that you get a black picture or that the same "snow" appears than when you watch the receiver output without any TX operating?

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I get no video, like when the transmitter is off. At home, where I can have the transmitter and receiver only 15 feet apart, I get a snowy picture. At much greater distances the receiver's squelch operates and I don't get anything.

When I bought the video system I mounted the camera and tx on a rc car and my 9 year-old friend and I had a blast driving it in and around the house, so I am familiar with the deadspots in the house due to large metal objects like stoves, refrigerators, and furnaces.

I now get not much of anything at all, not like I had up until a couple of weeks ago. There haven't been any crashes or other traumatic events....

--bluegill

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Hello again

I am building my PCB for the Air waves module.

Has anyone had any experience on the PTN78000WAS DC-DC switching regulator?

http://focus.ti.com/docs/prod/folders/prin...hnicaldocuments.

The input will be 12volt constant from a DC-DC switching boost regulator because some of my gear runs on 12volts but I have to step down for the TX module.

The PTN78000WAS will be install about 3mm away from the antenna connection were the antenna screws in and I'm concerned about noise interference.

Is this a good idea ?

The rest of my camera setup in still being created.

Many Thanks

Crash Pilot 1

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The PTN78000WAS will be install about 3mm away from the antenna connection were the antenna screws in and I'm concerned about noise interference.

Beyond the coax connector, if the antenna elements are substantially further away (several cm's), and the VReg is being used with the Tx (rather than the Rx), then it will probably be fine.

Regardless, this is an RF application, so the RF construction/layout precautions should be followed. For sure, decouple per the data sheet using low ESR caps, and keep your wire leads short.

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  • 2 weeks later...

Hi All,

Great to hear that these Airwave modules are working out. Looks like there's some great setups being put together - and cheap!

Crash Pilot 1, how is the PTN78000WAS performing? I'm having trouble finding a decent Vreg in Australia. Did you have to order the PTN78000WAS from overseas?

Cheers,

-TheOtherRob

Edited by TheOtherRob
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-TheOtherRob

I have not completed the TX as of yet because I wanted to make sure it worked without the PTN78000WAS and just off a separate 5 volt power supply. I am waiting on a receiver so I can test the TX and then I will add the PTN78000WAS.

I received the PTN78000WAS from Texas Instruments as a Sample. It came from overseas and arrived in about 3 days. Hopefully I will have the receiver this weekend.

Crash Pilot1

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Guys

Just incase anyone is interested. These module appear to run the same frequencies that are used in Australian sold receivers. Wired up my camera and took it down to the local JAYCAR store and tested it on their receivers. It worked so I bought a receiver and in the specs in the manual it lists all 4 frequencies to be exactly the same as the airwave module. The funny thing is on one channel I can pick up a FOX SPORTS pay TV channel clearly. I think one of the neigbours must have a wireless setup on the TV.

Crash pilot1

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Also have one neighbour using something like this... noticed it once I had the receiver on without the transmitter being powered. the signal was very very weak, but I took my 30dB RX antenna and with it could locate relatively precisely where he was, around 300m across a field :P

I wonder if he has noticed something as it happens that i've been flying quite a number of times over that field and on the same channel with a 50mW TX :lol:

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  • 8 months later...
  • 5 months later...

I have bought the Airwave 612 RF Transmitter (500mW) and Airwave 623 RF Receiver and completed the circuits. I have tested the circuits and the video link works but I get dropouts when I move the transmitter around in certain places. The worst thing is if I move the transmitter about 30 metres away or more, from the reciever, the video becomes completely fuzzy.

From what I've heard, I should get over 2 Kilometers of transmittion range from this transmitter.

Are these two modules compatible or did I get the wrong reciever?

Could it simply be an antenna problem?

Could it be a problem with my circuit?

Thanks for any help,

Matt

Here are the parts for the transmitter:

cimg32301ud8.jpg

Here's the camera:

cimg32531eu0.jpg

Here's the completed transmitter and reciever

cimg32481nt6.jpg

cimg32501nc6.jpg

cimg32571vf9.jpg

Here's my downlink setup: (Eventually it will be in a case)

cimg3273qi3.jpg

Edited by AXI Motor Models
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I have tested the circuits and the video link works but I get dropouts when I move the transmitter around in certain places.

If the dropouts are seen as brief loss of sync or video, and come and go as the Tx is moved about, then I would say that you are experiencing multipathing. That will be a problem if you operate near structures. For example, around the house it will be horrible. At a open field with nearby metal fabric fence (e.g. cyclone), or parked cars, it can occur too. Also, I see you are using an omni whip antenna on the Rx. That will surely invite multipathing.

The worst thing is if I move the transmitter about 30 metres away or more, from the receiver, the video becomes completely fuzzy.

Now that is a problem. With 500mW, you should get hundreds of feet in an open field. Your testing will not be valid unless it is performed in a wide open space, far from reflective surfaces. It that what you have done?

BTW, how did you route the copper trace on the Rx and Tx paths that goes to the antenna? This is a very critical area that needs to support a 50 ohm microwave RF signal. Definitely requires extreme care. The exact layout will depend of fiberglass dielectric characteristics, trace width, and its ground plane.

BTW, although it is really hard to tell, but in the photo it looks to me like the ground plane is a bit meager around the SMA's. FWIW, the usual solution is to solder the chassis SMA directly to the sardine can in order to eliminate the PCB's critical RF layout issues.

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Hi, thanks for the help.

The place I've been testing is inside my house and outside along my street where there are many houses, but it was line of sight.

Here's a picture of the SMA connector and the copper traces:

It was really hard to solder the connector to the 3 module pins (To the middle/right of the photo)because they were 1.27mm apart. The two outside pins coming through the cut in the circuit board are Ground and the middle pin is the antenna pin.

cimg32421ct5.jpg

Edited by AXI Motor Models
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The place I've been testing is inside my house and outside along my street where there are many houses, but it was line of sight.

Neighborhood environments are horrible places for wireless video system evaluation. With microwave RF, you need a wide open area in order to make effective performance judgements.

Here's a picture of the SMA connector and the copper traces:

The construction I see at the SMA is not an effective layout for 2.4Ghz RF. The grounds cannot be simple traces and the RF signal trace must be designed for 50 ohms impedance. For lowest loss, I suggest you mount the RF connector directly on the sardine can and eliminate all interconnect wiring. There are some photos floating around the forum that show how others have done this. Although this change may not fix your short range issue, it will ensure you have a fighting chance.

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1) Yes. With the SMA chassis mount method, the body of the SMA should be soldered so it has substantial surface contact with the grounded tin on the Tx's sardine can. The center pin is connected without any extra wires.

2) From what I can see on the PC layout of the other board, RF-wise, is vastly different. The SMA is soldered to a substantial ground plane.

The issue is that RF behaves differently than what is found in basic DC circuits. Especially microwave RF. "Short circuits" can easily behave as open circuits (due to inductance) and open circuits can be act as direct shorts (due to capacitance). With microwave RF, everything matters. Or so I've heard. :)

There is no telling if you will notice an immediate improvement. But, it should eliminate a probable source of RF loss, which will help things later on.

Edit: Terry posted a photo of his SMA mounting in this thread: http://www.rc-cam.com/forum/index.php?showtopic=1159

Edited by Mr.RC-Cam
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Be sure to clean all the flux residue from the SMA surroundings. It needs to be fastidiously clean.

Before you chop up the SMA connection, it would be worthwhile to benchmark the existing performance. Just test the range in an open field, far away from ALL buildings cars, and metal fences. Ignore the intermittent sync or video loss; end of range is seen as video that starts to show snow. Then go back to the shop and remount the SMA's. Return to the test site and repeat the range test. The test setup must be duplicated exactly since any deviation in the setup will skew the results.

If the changes you make do not improve things, then there is something wrong with the system. At that point I would suspect the Airwave modules or the antennas. It would be good to bring along a DiY GP Patch Rx antenna to see if that sweetens the deal for you.

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I'm late a little bit, I got a busy week :)

Here how I do, your lucky I have these photos, but not knowing what to do with it :)

I removed the three pins, and with an x-acto I removed the two pads on each side of the center pins on the PCB. I put a lot of solder while using a Weller heat gun to solder the ground and put very few solder an using 25 watt iron for the center pin. All the flux was clean with alcool buyed at Drugstore. I cut the center pin a little bit.

post-5-1160360186_thumb.jpg

Edited by Vrflyer
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