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Mr.Pibb

Amplifying a Spektrum Signal Possible?

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I've been wondering about something:

I believe the DX-7 (US version) runs at 100mW. Is it possible to use a 2.4GHz amplifier to increase that power level for longer range flights? I realize that it no longer makes it FCC compliant, but is it possible? I would think one could operate at higher power levels if an amateur licence were aquired, am I right?

Will something like this work?

http://cgi.ebay.com/RF-Amplifier-2-4GHz-1-...1QQcmdZViewItem

Also, can you just attach a patch antenna in place of the standard whip antenna? I think I read somewhere that there's a standard compact connector inside the DX7 that allows for the antenna to be switched out.

Feel free to shoot down my thought of an easy way to add some range....

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I would think one could operate at higher power levels if an amateur licence were aquired, am I right?

What you want to do is possible. Unfortunately, the Spektrum R/C system uses some frequencies that are not allowed under the ham rules.

I think I read somewhere that there's a standard compact connector inside the DX7 that allows for the antenna to be switched out.

The Unigen module's antenna jack is a U.FL connector.

Edit: I just looked at your link. I'm not sure the Unigen module would like the bi-directional amp. Driving RF *into* it might be an issue.

Edited by Mr.RC-Cam

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Not legal but you could always put a patch on the top of your TX.

Terry

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OK, so it sounds like an amplifier on the ground (not two way) or switching to a higher gain more directional antenna may help but may not be "legal". Well...I may go the patch antenna route anyway. :D

I've also considered something like this that could be easily removed or placed on the antenna depending on the flight conditions (long range verses "normal")

http://www.freeantennas.com/projects/template2/

Does anyone have any experience with the performance of these things? Do they really yield 9db gain? I suppose testing it out by using the bind button and finding the maximum distance without loss of signal with and without the reflector would be a good experiment.

What's the conversion for db gain vs increased range? Does 9db give me a 25% increased range in a particular direction? 100%? 2%?

I'm too lazy to try to add an amplifier at the receiver side. The spektrum already uses two receivers with some sort of diversity setup. Based on what I've seen, I wouldn't put it past you Mark to try it though! :D

Edited by Mr.Pibb

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What's the conversion for db gain vs increased range?

In a perfect world, every +6dB doubles range.

Antenna gain comes at a price. Its beamwidth becomes narrower as the gain increases.

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I built the small version of the parabolic reflector mentioned in the link above. I just used a piece of aluminized Mylar a the reflector, not sure how conductive it is but it should be pretty good since it is thick enough to be totally opaque.

I didn't use it while the plane was in the air, I only tested it on the ground using the bind button to see the relative change in range.

Standard antenna:

58 paces to start seeing loss of control

With reflector:

88 paces

So, an additional 50% added to the range...not bad for something you can build from things you have sitting around the house. Supposedly you get more gain by building a scaled up antenna, but it would be harder to mount on the small antenna. As it is this one fit perfectly.

I may just keep it handy in case I go trying to push the range on my DX-7 again...

http://www.rcgroups.com/forums/showthread.php?t=757406

I'd only use it as a backup since it can be slipped on quickly and easily.

I bet it would work pretty well on the video systems as well. I could try this on my 900Mhz video system, but I think I'll scale it up since I'd probably see negligible gain since it is so small relative to the wavelength. Maybe it can work as a patch antenna alternative...

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Any Wireless amplifier should work :D You can get a two watt 2.4 GHZ amp from hyperlink that only requires 30 mw drive, that should extend your range beyond your wildest dreams :D You can get one for less than 400 bucks ! An amp with a patch antenna, and you should be able to send your plane into space..

JettPilot

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