Electronics > RF, Microwave, Ham Radio

homemade VTX 5.8GHz signal booster

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LaserSteve:
I just looked at a European weather map.  You have beautiful weather  today in Spain. There are many well placed, beautiful Doppler Weather Radars, as well.  All 14 of them.

http://www.aemet.es/en/eltiempo/observacion/radar?w=1

We would have to know the characteristics of your antennas to work the Friis Equation and determine just how far you need to be away from the radar... Most likely 20-30 Kilometers for a high power system on a drone.
~

Perhaps move to 2.45 Ghz where no one cares,  and near field propagation is better from drones because of the longer wavelength...

Steve

hendorog:
5.8GHz at those power levels isn't illegal here, but read up on your on regulations.

There are plenty of people who have flown long distances on 25mW, easily several kms. Just google 25mW FPV record and you will find something.

The rest has already been said, but it might help to clarify:
The secret to FPV is the antennas, not high power. Go to fpvlab.com DIY section and read up on how to build and test them.
Long range means you can use a highly directional (high gain) receive antenna - which is perfectly legal. You don't need to adjust its direction much if at all. Long range FPV has its own rules and laws you need to research and abide by of course.

If you just want to fly close range reliably but through foliage then 2.4GHz should be better. I've only used 5.8 so would need to ask someone who has direct experience.

energy_hunter:

--- Quote from: mayonesa on March 28, 2016, 01:51:35 pm ---
--- Quote from: energy_hunter on March 28, 2016, 12:15:58 pm ---I would recommend the RF5616 power amp at 5V for your application along with a 150um thick RF layer. This amplifier has better input and output return losses, comes prematched and the RF caps look like they are integrated on the chip already which will make it easier to use.  You may be able to just use the evaluation board out of the box.  KISS!
http://www.rfmd.com/store/downloads/dl/file/id/27928/rf5616_data_sheet.pdf

I agree with the previous poster about transmitting. You need to be careful you're not radiating harmonics and jamming some other application. It looks like harmonics are low for this part but as you increase the transmit power the harmonics will increase and you may be over the allowable limits.

--- End quote ---

Reading the datasheet if my imput power is 25mW (14 dbm aprox) the output at 5805 MHz will be gain+dbm input? or allways 22 dbm (max output) Attached the img

Thank you

--- End quote ---

The plot you show is for displaying gain compression of the PA and you can calculate the input power to get 22dBm from the plot. Input Power (dBm)= 22dBm - Power Gain at 22dBm (~29dB) = -7dBm.  Please note that at compression you will have more harmonics and worse linearity which may or may not affect you with your signal's modulation. Most WLAN amplifiers are designed to handle 10dB Peak to Average signals so if you have much less then you can use this amp at a higher output power than you can for WLAN.  At +14dBm input power you may kill this part so check the datasheet for max input power levels.   

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