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Old Jan 22, 2013, 11:53 AM
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United States, PA, Pittsburgh
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can you sort of speak "overclock" Frsky output power

Hi guys im a spektrum user and recently began to try FPV, According to lots of user Frsky is the way to go and spektrum (according to them is not so "good" for FPV purposes)
Well i began to search an according to Vendors Frsky is only 50 mw output, compared with 200mw output of my current spektrum transmitter (according to specs in pdf file)

Before somebody starts explaining me output power does not have so much importance as compared with a Good antenna or double power is just 1/4 increase in range, or that Frsky even with 50mw on paper it gets 1 mile out with a strong link, i know that (or at least the little i have research about radio frequencys and a little in ham license books)

what i understand so far is that frsky decided to go with 50mw because theres different rules in different european countries limiting the output power, BUT here in the US we can use a higher output power than 50 mw and still be legal.

I dont want to use an amplifier, for that i prefer to go back to 72mhz. So my question is in theory (at least just as proof of concept) would be possible to increase output power??( i have read on FPV forums that some vtx units of 400mw are the same as 200mw its just the vendors make them output more power thats why there not so good, so theres some proof it can be done )

any input is appreciated

thxs in advance guys,

jose
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Old Jan 22, 2013, 12:53 PM
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United States, CA, Novato
Joined Sep 2003
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Sure - Very easy - Just load up some V1 firmware for more power.

50mw is rated at the module. The antenna then boosts that rating, I think that is the rating that Spektrum and some other companies give you.

I'm sure someone with better electronics knowledge will pipe up better details for you.

-Wayne
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Old Jan 22, 2013, 12:57 PM
Radio? Screwdriver!
United Kingdom, England, Bristol
Joined Aug 2011
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The actual output power all depends on antennas. Put a high gain antenna on, then the EIRP increases. Hence FrSky probably had to reduce the output to meet the regs. Also Spectrum is only 200mW output power on DSM2, DSMX is less. Probably to meet spectral density regs maybe? Or just not necessary to have such a high output power for LOS flying? I'm not too clued up on FCC regs.

I don't know where you got 50mW output power from, but from my own research using a calibrated spectrum analyser at a Type Approval laboratory showed that the conducted output power at room temperature is 18.53dBm (around 70mW). Conducted output power measurement point was from the connector on the back of the module. As it was tested in a thermal test chamber (a test chamber that you can alter the temperature of), there was a couple of RF cables between the FrSky module and Spectrum Analyser which will have lost a bit - at most a couple of dB.
Here is a camera photo of it - the power output of the peak marker is shown in the top left hand corner in blue.


Now if you want more power output there are a couple of options. Firstly there are WiFi power boosters you could connect up. These commonly go up to 1W off the shelf. This is likely to bring you to illegal output powers (unless you have a HAM licence, etc).

Alternatively, a bit more novel and completely legal way of boosting output power would be to use the same trick that Computer overclockers use - freeze the module ICs! I'm serious!

Transmission output power is increased when the temperature is decreased as the resistance on the board/in the ICs is reduced. Now my measurements in the calibrated lab showed that at -16C you can get 20.43dBm - around 110mW. I haven't tried it, but I bet -16C is possible using simple Peltier cooling modules. Would be fun thing to try and play around with.

This was done at around -16C:


Si.
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Old Jan 22, 2013, 01:02 PM
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Romania, Dolj, Craiova
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Sure, load V1 firmware and lose FCC compliance

That power was reduced during tests for FCC certification, and Frsky wasn't the only, many companies found there are spurious out of band receiver transmissions on the back channel (telemetry), requiring power reduction.
The power reduction is not related at all with EU countries standards, which are more permissive, there is no such test authority as FCC, you declare on your own the conformity with laws, and that's all... until someone find you lied and report

Want maximum range you can achieve with a Frsky system: one way is the solution, the legal one I mean.
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Old Jan 22, 2013, 01:17 PM
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Or wait for the long range system from FrSky.
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Old Jan 22, 2013, 02:19 PM
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United States, PA, Pittsburgh
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Quote:
Originally Posted by SimonChambers View Post

I don't know where you got 50mW output power from, but from my own research using a calibrated spectrum analyser at a Type Approval laboratory showed that the conducted output power at room temperature is 18.53dBm (around 70mW). Conducted output power measurement point was from the connector on the back of the module. As it was tested in a thermal test chamber (a test chamber that you can alter the temperature of), there was a couple of RF cables between the FrSky module and Spectrum Analyser which will have lost a bit - at most a couple of dB.
thxs si for the clarification but if you chk the modules specs in aloft or hk youll notice it says 60mw (before it used to say 50mw in the HK page)

Rotozuk,i didnt know frsky was planning a long range setup, thats great news. (by the looks frsky is gonna get part of my income this year , with the 12xd and long range system good times)
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Last edited by jaas75; Jan 22, 2013 at 02:36 PM.
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