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Please help..2.4GHz antenna/reception issues


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#1 dznf0g

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Posted 17 October 2011 - 10:47 AM

I hope you folks can help. This isn't an RC issue, but it seems to me that the forum members here understand the little 2.4 GHz systems better than some other places. I've been lurking and TRYING to keep up. I have very little understanding in this area, so be gentle, please!

I have a 30' Airstream travel trailer on which I am mounting a backup wireless camera. It is about 45' from camera to monitor. I pass through a lot of aluminum, wood and glass between. This is the system I have.

http://www.4ucam.com...ght-Vision.html

The picture quality isn't HORRIBLE most of the time and I get quite a bit of interference in more populated areas. And of course the bluetooth in the truck really messes it up while on a call only.

I am thinking I can improve the picture quality and maybe reduce the effect of some the interference with better antennas. I tried moving the antenna forward in the trailer with the extension cables on the webpage, but I think I am losing more dBs than any gain in reducing distance and losing one wall.
The website doesn't tell me much, especially about the stock antennas as well as the 2M antennas at the bottom of the web page. I would like the Tx antenna to be inside the rear of the trailer, so I am missing a lot of metal and have a relatively clear shot through the front glass and into the truck cab.

What is the 2M antenna? Does the fact that it has an extension hurt more than the 2M antenna helps (over the rubber ducky)?

As you can tell, I don't know much about this stuff. Your help is greatly appreciated.

#2 Terry

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Posted 17 October 2011 - 11:00 PM

In many ways this is bad for 2.4Ghz, the 2.4Ghz signal will reflect off all metal surfaces and cause the signal to drop out. The best way round this is to aim the TX and the RX arials at each other, this means using patch type aerials. Clear line of sight between both aerials is important at 2.4Ghz for a good signal.

The 2m aerial you talk of is just a higher gain aerial and will not solve most of the problem.

Matching circular polarized aerials would be the best choice.


Terry

Edited by Terry, 17 October 2011 - 11:06 PM.


#3 dznf0g

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Posted 18 October 2011 - 05:14 AM

In many ways this is bad for 2.4Ghz, the 2.4Ghz signal will reflect off all metal surfaces and cause the signal to drop out. The best way round this is to aim the TX and the RX arials at each other, this means using patch type aerials. Clear line of sight between both aerials is important at 2.4Ghz for a good signal.

The 2m aerial you talk of is just a higher gain aerial and will not solve most of the problem.

Matching circular polarized aerials would be the best choice.


Terry


Thanks, Terry,
I thought that might be the response I got.

I did read up quite a bit about directional patch antennas. (Not that I understand too much of what I read) When I go shopping online, all I see are pretty big ones designed for long distances or large areas.

I also found forums where RC'ers made their own small ones for airplanes and the like, but the parts list and construction directions assumed the reader knew A LOT more than I certainly do.

Since I only need to send the signal 45', what is commercially available that is small, not unattractive and unobtrusive? Obviously, the monitor is on the vehicle dash and the camera is mounted to the rear of the trailer (caravan, for your, Terry :) )

What would you experts suggest for my need?

Edited by dznf0g, 18 October 2011 - 05:15 AM.


#4 dznf0g

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Posted 18 October 2011 - 05:19 AM

In many ways this is bad for 2.4Ghz, the 2.4Ghz signal will reflect off all metal surfaces and cause the signal to drop out. The best way round this is to aim the TX and the RX arials at each other, this means using patch type aerials. Clear line of sight between both aerials is important at 2.4Ghz for a good signal.

The 2m aerial you talk of is just a higher gain aerial and will not solve most of the problem.

Matching circular polarized aerials would be the best choice.


Terry



What are circular polarized aerials? Can you point me to some online? Any small ones for my particular need?

#5 dznf0g

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Posted 18 October 2011 - 06:12 AM

Is 2 of these this what I need?

http://www.l-com.com...m.aspx?id=21787

What's the difference between right hand and left hand? Which do I need?

Are there any smaller units available?

This is the correct connector right? (based on the receiver and transmitter in the first post link)

Is there a problem if I use an additional 10 foot extension to get the camera antenna routed inside the trailer, thus eliminating two aluminum skins and aluminum framework? This would give the signal a path through one wood cabinet face, two panes of glass and one pane of plexiglass.

Edited by dznf0g, 18 October 2011 - 06:20 AM.


#6 Terry

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Posted 18 October 2011 - 07:56 AM

The patches you found are fine, the connectors look ok too.
Extending the camera aerial lead should be avoided if at all possable as it will eat the signal at 2.4Ghz, its always best to extend the camera video lead but this may not be possable with your camera. That said if extending the aerial lead is the only way to avoid metal panels then it may still be better than nothing. Trying it is the only way to be sure.


Terry

#7 Mr.RC-Cam

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Posted 18 October 2011 - 10:17 AM

What's the difference between right hand and left hand? Which do I need?


You'll need a pair with identical polarization. That is, both need to be right or left polarization (not a mixed set that is one of each type). You choose which one, left or right. In your application they both will work the same; it is simply a coin toss on which type to purchase.

Heed Terry's advice, minimize the coax length when practical. However, sometimes longer coax improves performance if it can help avoid LOS obstacles, even with the enormous RF cable losses it causes. In the end, the best solution is the one that works best for you. So continue to experiment.

By the way, you might try the windsurfer WiFi type antenna mod on your video system's two antennas. If this 15-minute modification increases performance then it would provide some hope that the patch antennas will help out.
- Thomas

#8 dznf0g

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Posted 18 October 2011 - 12:42 PM

Ok, I made up two of the windsurfers and I do note a marked improvement. I now have no bouncing (cutting out?) of the picture and no bands of snowy white noise. I still have occasional white horizontal lines (frequency interference?), but even that is lessened. This is with the 10" antenna extension cable attached and the stock, what, maybe 1dB - 2 dB gain short antennae???

There was a difference whether I installed neither, one or the other, or both windsurfers, with obviously both installed being the best.

So what is your advice?

Two of these 8 dB gain? http://www.l-com.com...m.aspx?id=22306

Or two of these 8 dB gain? http://www.l-com.com...m.aspx?id=21787

WHAT DOES THE POLARIZATION DO?

Does anyone know what the angle, or effective width of strong signal is, at 45 feet distance from the 2 antennae? (I don't know the correct terminology here, sorry) When I am backing with the trailer on and in a jacknifed position, will I still be in the "window"?

Thanks, again.

Edited by dznf0g, 18 October 2011 - 01:01 PM.


#9 dznf0g

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Posted 18 October 2011 - 12:56 PM

I see now thr polarized one is 65* both horizontal and vertical....that should be plenty wide enough.

#10 Mr.RC-Cam

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Posted 18 October 2011 - 01:32 PM

So what is your advice?


The only practical advice is to encourage you to experiment and determine for yourself what works best in YOUR unique installation. Regarding linear versus circular patch antennas, the circular polarization should help reduced common interference problems. But in the end, the best antenna solution is the one that solves your RF installation's problems.
- Thomas

#11 dznf0g

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Posted 19 October 2011 - 01:47 PM

Thanks to all. I have ordered up 2 of these:

http://www.l-com.com...m.aspx?id=21787

One more really basic question. Do I use 50 ohm cable if I must use an extension?

I lied....one more basic question....for my application, do I mount them horizontally or vertically?

Edited by dznf0g, 19 October 2011 - 01:49 PM.


#12 Terry

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Posted 19 October 2011 - 10:58 PM

Yes 50R cable, as they are CP in should not matter if they are mounted H or V.


Terry

#13 Mr.RC-Cam

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Posted 20 October 2011 - 10:19 AM

one more basic question....for my application, do I mount them horizontally or vertically?

Maybe it would be wise to ask what you mean. I've seen a variety of installations that did not work well because the installer thought "horizontal" meant laying the antenna flat, pointed skyward. That is not the same thing. :)

Also, some antennas that are advertised as CP are actually partially CP and partially linear (sadly, some are barely CP and mostly linear). So to squeeze every ounce of performance I recommend installing them so their mounting orientations match (like you would do if they were linear designs). There's no downside to this, so no reason to skip doing it that way.
- Thomas

#14 dznf0g

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Posted 20 October 2011 - 11:28 AM

The install manual says for vertical polarization cable should be exiting from bottom or top. For horizontal polarization cable should be exiting from left or right of the antenna. I will be mounting it, of couse "on edge" not laying flat or flat against a ceiling.

In my application, does it matter how it is oriented?

Edited by dznf0g, 20 October 2011 - 12:37 PM.


#15 Mr.RC-Cam

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Posted 20 October 2011 - 12:36 PM

The install manual says for vertical polarization cable should be exiting from bottom or top. For horizontal polarization cable should be exiting from left or right of the antenna.
In my application, does it matter?

With an authentic CP antenna the polarization (and related antenna orientation) issues don't matter. But if their manual is stating information about polarization, then either the manual's author was confused, or the antenna is not fully CP (see my previous post).

Per my prior recommendation, just assume it might matter with this antenna design. So regarding which polarization orientation to use, the best choice for your travel trailer installation will depend on what you find works best in YOUR installation. We won't know the answer, you have to experiment and see what you like best.
- Thomas

#16 dznf0g

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Posted 21 October 2011 - 04:42 AM

Maybe it would be wise to ask what you mean. I've seen a variety of installations that did not work well because the installer thought "horizontal" meant laying the antenna flat, pointed skyward. That is not the same thing. :)

Also, some antennas that are advertised as CP are actually partially CP and partially linear (sadly, some are barely CP and mostly linear). So to squeeze every ounce of performance I recommend installing them so their mounting orientations match (like you would do if they were linear designs). There's no downside to this, so no reason to skip doing it that way.


Here's what they say, They do use the term "vertical" and "Horizontal" polarization, but also say it doesn't matter?????

http://www.l-com.com...G2409PCR-SM.PDF

#17 Terry

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Posted 21 October 2011 - 06:05 AM

To be on the safe side I would mount them both the same V or H.


Terry