How do I measure the output of an antenna plug?

[uhcoog1]

I've got a wireless video transmitter/receiver (2.4ghz), and it's got wayyy less range than advertised. Before I return it to China (and deal with that hassle), I want to check a few things out. I've measured the draw, but I wasn't able to measure the output at the antenna jack. Can I measure this with a multimeter?

I'm guessing I don't understand the way antenna's are wired, because when I checked for current going from the inside of the jack to the threads, it wouldn't register any current or even light a simple test light.

The antenna's are large- look like a 9dB onmi or similar?

 

[rfradioconsult]

You need a wattmeter and a suitable terminating load (50 Ohm), this type of device probably puts out about 10 mW or less, that is 10/1000 of one Watt. Don't expect any long range, maybe 100' or less, no antenna will really make much difference.

 

[uhcoog1]

Thanks

Thanks for the answer. It was sold to me as a 2watt, 2,000 meter capable unit (I need something to cover 1000 yards minimum).

Discount 2.4G Wireless AV Audio Video Sender + Receiver 2000m 2W

I figured I'd give it a go for the price. They verified by email that if it did not perform as advertised, they would refund the full amount. Time to get my money back...

I tested the draw of the unit - .3 amps, on my 12v battery. That's drawing 3.6 watts, right?! Is it that inefficient?

I don't have a wattmeter. Is there anything I can test with my multimeter? I tried testing the amp output, but I still don't know how the current flows in this jack! I tried putting my multimeter (on the lowest amp setting) between the two insides, and connected the outsides with a wire.

So, quit trying and get my money back? Or is there anything I can test with my multimeter beforehand?

 

[kb0nly]

Is that one of the units they claim to be 100mW or 1000mW? I have seen a lot of them on ebay. I know most of them put out around 10-50mW at best from what i have seen real world with a meter, but it takes a very sensitive meter to detect the output at these levels. I used a micro/milliwatt meter i borrowed from a friend to test one that i used to have, was putting out about 15mW.

It's 2.4Ghz so its like wifi, too many object to go through etc and you lose signal fast. Also it actually shares channels with some of the wifi channels, the unlicensed frequencies that all these 2.4 devices are on. Try different channels and see if it helps range at all, you might be sharing the channel with another strong signal nearby and wiping it out at the receiver.

If you can run a cable, looks like your camera has a siamese cable coming out of it with BNC for video and a coaxial plug for power, you can buy a siamese camera cable cheap. I just bought a 150 foot cable for my camera for $30. Sure its not as convenient as wireless but a lot better picture and less hassle.

 

[kb0nly]

Ok, they claim its a 2w, doubt it as that would be illegal anyway but who knows what they are making and shipping out these days from overseas.

Nothing you can do with a voltmeter, you need to measure RF not voltage or current or anything like that. If you built a simple RF detector probe then you could measure the RF as a voltage on your meter, but you would need a calibrated reference to know what voltage is what wattage, etc.

I have built a few RF probes for tuning and adjusting stuff over the years, and it takes a lot of effort to get it right when your talking 2.4Ghz.

 

[uhcoog1]

kbOnly-

Thanks for the data points. This one claims 2watts, but the box it came in said 1 watt. So, I'm sure it's everything you say it is.

Looks like I'll be sending it back.

The purpose is for 1,000 yard target shooting, with a secondary purpose of remote feral hog activity viewing (feral hogs are a real problem here in texas). The 1,000 yard range is a public range, so whatever system I have I need to be able to keep in the truck.

What suggestions do ya'll have for a wireless transmitter/receiver for my purposes? I've had a difficult time finding appropriate transmitters/receivers. Long range transmitters don't seem to be very popular!

 

[RadioDaze]

I wonder if the lack of power could be overcome by using some directional antennas (Yagis)?

 

[davidgcet]

you need directional yagis for long distance like that. keep in mind that your laptop wireless adapter is going to have WAY less power than the AP does, so even if you can "hear" the AP you may not be able to talk back and thus have no link. if this unit supports it, maybe you cna setup 2 of them as a wireless bridge and just point a yagi from each to the other.

BTW, an averaging power meter might read something on that unit but a regular one won't. the pulses are just too fast to trip the meter. more than likely you would need something like an anritsu sitemaster with a power meter adapter, only cost you about 5,000.00 for a used one!

 

[RadioDaze]

...you would need something like an anritsu sitemaster with a power meter adapter, only cost you about 5,000.00 for a used one!

Great. You just told a guy with guns that he needs to quickly raise five grand.

 

[davidgcet]

lol, well he won't need the meter if he uses the guns to get the money!

 

[kb0nly]

LOL...

Regarding the yagi's... For about $10-15 you can get a 20-25dB yagi for 2.4 on eBay. I have bought and used some for setting up wireless networks now and they work great. So that would be my best suggestion. Since the operation is meant to be portable you could easily take a cheap camera tripod and mount the antenna and the camera on it with a bracket, so the camera points one way and the antenna the opposite, then you put a yagi on your receiver as well, of course another tripod would work good there also.

Here is an example of one of the yagis i have. Got it for $15 on eBay, took a couple weeks to ship because it came from Hong Kong, mounted it to an old tripod i found in a thrift store with a bracket i made.

 

[uhcoog1]

Hahaha!

LOL LOL!

You guys are cracking me up! I'll avoid using the guns to raise money for now! haha

I'll look into the yagis and I'll see what better transmitter and receiver I can get.

Thanks for all the help!

 

[davidgcet]

assuming the terrain is flat and both antenna bases will be at the same height above sea level, your antennas will need to be 10-15 feet above ground to clear the 1st fresnel zone. if you don't clear it, part of the signal bounces back up from the earth and obstructions and can kill the signal. online calculators don't go under a 1 mile link, which requires about 14' height above the highest obsctrution or ground level on each end, your actual results may vary but this is a starting point.