Frequency question

Frequency question
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Frequency question - 8/27/2003 7:20:44 PM

Posts: 194
Joined: 9/3/2002
From: Toronto, ON, CANADA
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Hi there!

Can you guys explain to me what differences can I expect in RANGE and QUALITY OF SIGNAL from 900mhz, 1.2 ghz, and 2.4 ghz systems. After reading some posts here, I realize that 1.2 is illegal, but would still like to know, how frequency difference relates to above 2 factors.

I undertand that a higher frequecy penetrates objects less, and has a higher bandwidth.. but why some people choose 900mhz, and others 2.4 ghz?

I'm sure each one has it's benefits... I'm looking for a system my self.. and from all the research i've done, it looks like the black widow av system is the most feasable option. But then again.. they also have both 900 and 2.4 systems..

-eugn

Frequency question - 8/29/2003 12:23:06 AM

Posts: 92
Joined: 3/18/2003
From: None, OR, USA
Status: offline

watt for watt, lower frequency travels better in air than higher frequency.

higher frequency use antennas that are smaller... not too big a deal with stock dipole, but when you look at high gain antennas, 900mhz antenna start becoming lot bigger than 2.4ghz antenna real quick!

Last is how much work you want to do to get in air. Black Widow only offers 2.4ghz "ready-to-fly" system. Rest of equipment is solder,test, and fly.

Let us know decision and how it turns out!

David

(in reply to ebeygin)

Frequency question - 8/29/2003 6:18:01 PM

Posts: 194
Joined: 9/3/2002
From: Toronto, ON, CANADA
Status: offline

thanks for your answer...

so basically a 600mw 900mhz system will have a better range than a 600mw 2.4 ghz system?

I plan to buy a non ready-to-fly system from blackwidow...

I either want a 600mw 2.4hz system or the 500mw 900Mhz system...

I will purchase either, by buying bare components.

To me, it seems that the 900mhz systems are more bulky and require more voltage. Which one of these would you guys choose and why?

-eugn

(in reply to ebeygin)

Frequency question - 8/29/2003 10:14:22 PM

Posts: 305
Joined: 8/29/2003
From: Whiting, IA, USA
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Your thinking is correct ebeygin.
But keep in mind, the receiver sensitivity and antenna attached will make a bigger difference than kicking up the power on an inefficient system. Not two many companies advertise the quality of their equipment (or the ratings of their antenna), just the power and cost. (quality is harder to sell)

I read an article where someone set up a 27 mile 2.4 GHz network using 50mw hardware and 24 dBi antenna.
I have a 200mw 1.1 GHz spy-cam that won�t make it 200 yards and 50mw 2.4 GHz that will go over 1.5 miles.

I would check the price on antenna for the freq you are thinking about before you buy, Remember if you go with an omni or sector antenna you need to place it upside down, they have down tilt. One benefit of 2.4 is the range of antenna available, and the price!

Whatever you do have fun doing it!
Jim

(in reply to ebeygin)

Frequency question - 8/30/2003 12:34:08 AM

Posts: 572
Joined: 1/27/2003
From: Deep in the Heart Of, TX,
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Also keep in mind that with either system, you need a license to operate the transmitter.

Later;

D.W.

(in reply to ebeygin)

Frequency question - 8/30/2003 8:38:21 AM

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Joined: 9/3/2002
From: Toronto, ON, CANADA
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Actually, I'm lucky.. I live in canada, and here we don't need any licence for anything below 1w.

As all of you, I too was looking for the "best" wireless system, both money and quality/range wise.

From looking all over the web, with my mediocre experience in rf electronics, it seems that blackwidow av is the best system. Their 200mw ready to fly system has shown some amazing results from users. So considering that, I wanna swap the 200mw transmitter for a 600mw (2.4) one...the size is a bit larger, but still extremely small and light. This should boost the range significantly also.

The only thing left, is to experiment with antennas, and if I find the right configuration, long range and good quality is expected. Even with the stock version, you can get amazing quality video within a 1/2 mile range.

I was set to buy that system, but then noticed people talking a lot about 900mhz systems. So that's when I wondered, that there are other feasible solutions out there. But I still think that the 2.4ghz systems are the best for our applications.

sorry for such a long post

-eugn

(in reply to ebeygin)

Frequency question - 8/30/2003 8:50:34 AM

Posts: 536
Joined: 6/6/2002
From: West Coast, CA, USA
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quote:

but why some people choose 900mhz, and others 2.4 ghz?[/QUOTE]Although this is just a generalization, the 2.4Ghz systems tend to be more modern designs. From my experience (and others), the high quality 2.4Ghz systems are providing better performance than the existing 900Mhz device designs. Not much new stuff is using the 900 Mhz RF band, so what is out there is often a bit toothy. Also, the compact size of the 2.4Ghz antennas is a plus.

quote:

Actually, I'm lucky.. I live in canada, and here we don't need any licence for anything below 1w.
You should re-review the Canadian RSS210 docs. For license free 900MHz and 2.4GHz applications in your country, you are limited to 50mV per meter @ 3 meters. This is less than 1mW of RF power. However, spread spectrum is allowed up to 1W. These are the same power restrictions as the good ol' USA imposes.

_____________________________

Best Regards,
Mr. RC-CAM

(in reply to ebeygin)

Frequency question - 8/30/2003 12:32:03 PM

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Joined: 8/29/2003
From: Whiting, IA, USA
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Looking at the rating of the US store bought video sender I am using, it is rated at 50,000mV/m @3m.

By replacing the stock TX antenna (probably 3dBi or higher) with a 2.2 dBi omni and the RX antenna with a 12 dBi 90-degree panel I am getting a good signal on the ground at 1.5 miles.

Did Radio Shack sell me illegal equipment?

(in reply to ebeygin)

Frequency question - 8/30/2003 9:03:08 PM

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From: West Coast, CA, USA
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[QUOTE]Looking at the rating of the US store bought video sender I am using, it is rated at 50,000mV/m @3m.[/QUOTE] There is a typo in that spec sheet. It should read 50,000uV/m @ 3 meters. That is the same as 50mV/m @ 3 meters. Well under 1mW.

If you post the FCC number that is listed on the Tx (on or near the serial number) I will try to locate the FCC test data to see what its real measured power is. It is amazing how little RF power is required to get long range when a good Rx and antennas are used.

_____________________________

Best Regards,
Mr. RC-CAM

(in reply to ebeygin)

Frequency question - 8/31/2003 5:48:35 AM

Posts: 194
Joined: 9/3/2002
From: Toronto, ON, CANADA
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IA-Flyer: Can you describe briefly what kind of system are you using, with which u get 1.5 miles? What are it's power specifications?

and just in case, if I'm not familiar with the technical data you post, if you would modify the 200mw black widow av system with the same technique that you used on yours, what range would you expect?

-eugn

(in reply to ebeygin)

Frequency question - 8/31/2003 1:30:11 PM

Posts: 305
Joined: 8/29/2003
From: Whiting, IA, USA
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FCC ID:
AAO1501972-T
307001H10046A

Sorry I didn�t get back quicker, but I am busy trying to get the system ready to fly tomorrow.

I�m not sure how much power the transmitter puts out? At the time I purchased them I recall 50 mW but that was just something I found on the Internet. The transmitter running on 2 9-volt batteries draws 125 mA, so even driving the camera from one of the 9 volt batteries I should get close to 4 hour run time. I will do some more searching on the FCC site for the exact power output when I have a chance, unless mr.rc-cam finds it first.
I�m not too worried about the signal strength because they were a store bought item and I actually dropped the transmitter strength with a slightly smaller omni antenna.

10+ miles is not a problem for a 50mW 2.4 GHz network and they have more things to worry about than just receiving some kind of video signal. I would expect a 400mW system with a good TX antenna and as �big as you can get� receive antenna to get video until the dust in the atmosphere, trees or the curvature of the earth get you. There are a few power / antenna dBi calculators online and I have a few on drive that could give a pretty good estimate, but I�m sure if the receiver has good sensitivity the system would give far more range than you or anyone else would need.

When I get time I will send a few pictures of the TX and RX with everything installed and flying. But for now I need to get back to building so I can (hopefully) fly the system tomorrow.

If the picture comes through, it is a transmitter wired and ready to be mounted in the wing center section of my video plane, and a stock TX with an omni installed.
The lower part of the picture is when we were testing the range, it was sent through the system.

I don�t plan on flying much over � mile until we do some good range tests. But If I have any success I will post a few pix. Here in Iowa most roads are spaced 1 mile apart, so anything I need to shoot from the air should be within � mile. I was surprised to see the system get 1.5 miles on the ground, they had been lying in a closet because they (and my microwave oven) mess up my wireless network.

Jim

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< Message edited by IA-Flyer -- Aug 31 2003 12:21PM >

(in reply to ebeygin)

Frequency question - 9/2/2003 4:19:24 AM

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Joined: 9/3/2002
From: Toronto, ON, CANADA
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impressive, IA-Flyer!

Let us know how your flight went!

I would never imagine, that such long ranges can be possible, just with the right antenna setups... looking forward in purchasing my 600mw black widow...now that you mentioned it.. might as well go for the 200mw.. it's 3 times smaller.. and I don't need a range further than 1 mile.. (at least for now that is)

-eugn

(in reply to ebeygin)

Frequency question - 9/2/2003 9:51:53 AM

Posts: 305
Joined: 8/29/2003
From: Whiting, IA, USA
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The rain quit just before dark last night and I got in a short test flight. It worked great! Had it hooked to my DV camcorder and slowly worked my way out to around � mile then called it a night.
Today the weather was beautiful and we went to the airport and I flew the plane 2 20-minute flights. On the last one we went over 7 tents of a mile, no problems.

The antenna worked as I expected, I just taped it to the back of my car for these flights so there will be some improvement when I get it on a stand and find the best angle to place it. One thing about these types of antennas, they have a narrow vertical beam width. You can get tremendous range when you are in the beam, but if you fly directly over the antenna at 50 foot altitude you get breakups or loose video.

It was kind of funny but expected, to fly back from almost a mile and watch the video start breaking up as I got close but above the antennas working area.

Here is the antenna I�m using and its patterns think of the pattern as your flying area.
There are some big antennas on the market, I have a 20 dBi panel on my roof (maybe not tomorrow:-).

http://www.cushcraft.com/comm/support/E-Plane/S2401290P12NF/2400%20E.jpg

http://www.cushcraft.com/comm/support/H-Plane/S2401290P12NF/2400%20H.jpg

There is a picture of the antenna I am using on the right side of the page, it�s the tall one.
http://www.cushcraft.com/details.asp?style_id=6&catid=201&group_id=1

I have a yagi also; the problem with them is the narrow horizontal beam width. With the wide antenna I am using, I can fly a wide area with out moving the antenna.

I�ll take a few screen shots and post them here when I get a chance.
You were talking about increasing the antenna on the receiver on the black widow system. You should be able to find a radio shop or some electronic shop that can hook it up for you. With my small system I did not use any connectors, I soldered everything direct to avoid connector loss. With the higher power TX you are getting have the shop put an �N� connector on the receiver so you can switch between a panel and omni antenna.
I�ll probably put a big omni on my other receiver for close in flying.

Overall I�m very happy with the results of my low power system. My ultimate goal is to mount my digital camera (5 ounces with video out and 3 power optical zoom) on a tilt pan mount and use a detached color view finder from a old camcorder as a head set viewer. I plan to use a gimble on the back of the headset to control the tilt and pan, so when I move my head the camera moves. Or just use it as it is, depends on when the fun wears off!

This is a picture of my 2 pound video plane. 2.5 with the video gear.

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Frequency question - 9/2/2003 10:03:17 AM

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From: Canyon Country, CA, USA
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Cool looking plane!
How much did the antenna run you? I am looking at getting a patch antenna for 900mhz in the near future since a yagi isnt really that practical for our uses. The dipole whip aint cutting it.

_____________________________

"B Positive to ground, over..."

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Frequency question - 9/2/2003 12:35:20 PM

Posts: 305
Joined: 8/29/2003
From: Whiting, IA, USA
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Thanks Fubar-One.
I designed this one as a park flyer type airplane with about a 1.5-pound load capacity.

I hate to say it, but I think I gave around $25.00 each for 2 of those antennas on ebay. :-)

I have a pile of 2.4 GHz antennas that I bought a few years ago when I was playing with 802.11b, in-fact the internet I'm using now is over 1/4 mile away, trees, tractor trailer, trees... Damn I hate trees, wish they would all go back to the rain forest where they belong! Every time I see one on TV when I�m flying I start shaking.

The cool 2.4 gig stuff has really thinned down on ebay, I think the prices got so low that most companies quit putting the high end stuff for sale there. I'm not sure how much the antenna would cost from cushcraft but my 20 dBi antenna retailed for over $800 and I bought it on ebay for $100. Best to find this stuff on an auction!
I�ll try to find the name of the company that dealt in the surplus antennas I bought back then, they were great to work with and may have some 900 MHz stuff.

BTW, I loved your crash videos! O S#%T, I couldn�t stop laughing!

(in reply to ebeygin)