BEC + FPV transmitter = problem! - RC Groups
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Jul 06, 2010, 05:53 PM
"Where are the shovels?"
wise guy's Avatar

BEC + FPV transmitter = problem!

I'm having some trouble with figuring out how to run a powersupply on the plane. The kit came with two transformers; one 1.25amp, and one 3amp. Because the instruction manual is written in Chinglish, God knows which one goes to which. Logically the 3amp would connect to the transmitter, however it could easily be the other way around. Perhaps it doesn't matter.

My biggest concern is frying the transmitter on the plane. I definitally don't want to just wire in a 3S lipo to the transmitter. My initial thinking was to have a pair of new 6v 5A UBECs I have connected in seris powering from the flight battery, but this may as well fry the tx just as easily. I have an "adjustable" BEC from Dimension Engineering (at the ripoff price of $15 ) a year ago for my former transmitter, however I'll have to connect it to a multimeter and use the guess-and-forget approach on the potentiometer on the BEC... probably won't be very accurate, and because the BEC is capable of 10 watts, I'll probably still fry the tx.

Any help/ideas would be greatly appreciated!
Last edited by wise guy; Jan 22, 2011 at 11:14 AM.
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Jul 06, 2010, 05:56 PM
"Where are the shovels?"
wise guy's Avatar

Info about where I bought the transmitter (not necessary to my BEC/FPV problem)

I've bought a couple of 2.4ghz video transmitters directly from manufactures over the last two years... being that Hobby Lobby sells grossly overpriced FPV equipment, and the others (such as nitroplanes and Hobbyking) sell pitty 50mw-100mw transmitters, there are simply no retail video stores that interest me. Range Video, aside from their alleged spotty customer service, sell 500mw transmitters for $50, which is not bad, so longs as they have quick processing. When I emailed Range Video to ask how long processing time takes, I never got a response. The with them... for all I know he's an undergraduate running a shop out of his dorm room.

Enough said about that... I bought a brand new 2 watt 2.4ghz from a guy (runs an electronics dealer) in California for a fair price of $165 with free shipping. I figured it didn't matter that I was paying $50-$100 more than buying from a manufacture directly, however given that it would be expensive to pay EMS shipping for a small item, I would spend allot of time researching and contacting a distributor, I opted for a US dealer. Plus, I know I get a for-sure working product with a dealer warranty, and I got it in 3 days from the time I ordered it. $165 for a 1-3 mile range transmitter versus $545 for a Hobby-Lobbyitized 200mw FPV kit? I'm not doing too bad... Gotta love small business.
Jul 06, 2010, 06:06 PM
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If that transformer from Dimension Engineering is an "Any Volt" you'll be fine. Once you set it, it stays set regardless of the input voltage. I've used it as well as using just a 3s pack and I've never had an issue. The "3 amp" power supply is most likely for your receiver. In any case it's overkill for either one. The power consumption should in the milliamps, not amps for either tx or rx.
Jul 06, 2010, 06:10 PM
Staying Frosty
Hellsiege's Avatar
I have Rangevideo gear - but I use a 3s lipo directly powering my downlink, and then another 3s lipo on the receiver. Not sure what the tolerances are on your specific gear but with a full charged 3s lipo at 12.6v figured it could handle the .6v extra. I don't have issues until I get to the low 11 volt range, then it's just not enough and you get more static / vid cut outs...

Good Luck

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Jul 06, 2010, 06:37 PM
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On a 1500 ma 3s lipo you should get at least three hours of use before the voltage becomes an issue. I really wonder if your 2 to 3 mile tx is all they said it is. I too, fell for that sort of thing and once I took all the cabinet off the tx to lighten it, the inside was no bigger than any of the chinese cheap tx's. Anything over 500 milliwatt is overkill anyway. Use a patch antenna and 200 milliwatts will transmitt farther than your rc tx will fly the plane. Try black widow. first class products and first class service. They also use what they sell so you have the benefit of their experience.
Last edited by randall1959; Jul 06, 2010 at 06:42 PM.
Jul 06, 2010, 08:02 PM
"Where are the shovels?"
wise guy's Avatar
I have my doubts on the range too, however I feel much better that I bought from a solid dealer. Like I said, I got a great deal (compared to the hobby stores) and I'm not going on the manufacture's word. The system is very well built, especially the transmitter, with warranty flags on the screws (in case you try to crack it open yourself, they void the warranty), a large heat sink and fair enough antenna. So there is no doubt in my mind that the system transmits a perfect 2,000mw. I ordered a 18dbi antenna (around 15" long) to go with the tx. Maybe a dish for the rx. Besides, without an amplifier on my tx, there is simply no way I'll loose video range.

CBs and the FRS radios are almost never within their stated transmission abilities. CBs are suppose to be 5 mile radios, however they are in fact around 1/2 mile in a typical suburb. On the highway, maybe 3 miles. I bought a "18 mile" FRS at Costco last year that only worked at 3,300 feet in a suburb. On a ski slope or farm I'm sure this would be different.

I can always hook my Optic 6 to a 100 watt Guitar amp and get 40+ mile range on the flight controls then again I'll probably get a call from both the FAA and FCC when they find a 70oz 4 meter sailplane littered with my thumb prints and address label on it crashed into a class B airport.
Jul 06, 2010, 08:09 PM
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I'd get a patch for the rx. Lots less direstional than a dish. Much wider angle. They also aren't very large. With a patch antenna you won't need a large tx antenna.
Jul 06, 2010, 08:18 PM
"Where are the shovels?"
wise guy's Avatar
So I won't have a problem connecting a 3S 20C 1500mah lipo directly to the tx? i.e. won't fry anything? (including the camera)

I'm thinking on connecting the lipo directly to the tx, and then use the variable BEC from Dimension Engineering to power the 9v camera (connected to the same lipo)...
Jul 06, 2010, 08:26 PM
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Your tx probably has a built in regulator so you should be fine. Then you can use the variable dimension regulator to power your camera. I have an fpv setup that has a 5 volt camera and a 12 volt tx. I run both off the same 1200 ma 3s lipo. I just use a radio shack 5 volt regulator on the wire that runs the camera.
Jul 07, 2010, 10:49 PM
Flying with the eagles
etman's Avatar
I use the balance plug of my 3s lipo for powering my 12V video TX and 12V camera.
Jul 08, 2010, 02:01 AM
Registered User
When I was using a single pack (2s lipo) to power everything I did the same. I used the balance plugs. Power fom the balance plugs were going to voltage regulator and then it would power the Rx. And main wires of the lipo were powering the downlink Tx that I got from Range video. The Tx was rated for 12volts (3s lipo) but I was using only 2s lipo just to have single pack on board. Then I started using 3s lipo for the downlink Tx as recommended. However, I really didn't see much difference after switching to 3s from 2s. With 3s, downlink Tx heats up alot though...
Jul 08, 2010, 05:10 PM
Registered User
Kmart's Avatar
Originally Posted by etman
I use the balance plug of my 3s lipo for powering my 12V video TX and 12V camera.

A fully charged LiPo works fine.
Jul 12, 2010, 10:39 AM
Its all fun
Tonystott's Avatar
Wise Guy, I have used at least 4 of these cheap downlinks, without any problems. I hook them straight up with a 3S LiPo without any issues. All three currently in use are great.
Jul 19, 2010, 11:59 PM
"Where are the shovels?"
wise guy's Avatar
My 18dbi antenna came in today. It is a heck of allot bigger than the thing that came with the tx, but the weight is still reasonable. I'm wondering if I need a similar antenna on the rx to get proper performance. I was thinking of a dish on the rx, but some folks said that was a bad idea. Is it necessary to have a beefy antenna on the rx, even though this is a one way system?

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