Electronics > RF, Microwave, Ham Radio

homemade VTX 5.8GHz signal booster

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mayonesa:
Hi,

I have a video transmitter VTX 5.8G 32CH that operates between frequencies 5645 MHz and 5945 MHz. It has 25 mW's power output (mean signal strength). I want to build a circuit that increase the power from 25mW to 500mW, I live inside a valley surrounded by trees and mountains, and the radio signal behave awful.

My question is, ¿what approach should i used to achieve the goal of clear visibility? i have two paths in front of me:

1- Using a RF amplifier like SST11LP12
   http://www.farnell.com/datasheets/1669517.pdf

2- Using a RF transistor like BFU768F
   http://www.nxp.com/documents/data_sheet/BFU768F.pdf

I have a lots of doubts about db gain, power input, power output, impedance matching... What i am sure is I'll go to 4 layer's PCB, with 50 Ohm traces for RF to match my 50 Ohm VTX otput and 50 Ohm of my Antenna input.

Of course i will pay more if the chip makes easy the circuit (KISS principle :)
I'll really  appreciate all the help. Thanks a lot!!!

PS: ¿Is it possible to simulate this behavior with spice software?

tggzzz:

--- Quote from: mayonesa on March 28, 2016, 11:21:04 am ---Hi,

I have a video transmitter VTX 5.8G 32CH that operates between frequencies 5645 MHz and 5945 MHz. It has 25 mW's power output (mean signal strength). I want to build a circuit that increase the power from 25mW to 500mW, I live inside a valley surrounded by trees and mountains, and the radio signal behave awful.

My question is, ¿what approach should i used to achieve the goal of clear visibility? i have two paths in front of me:

1- Using a RF amplifier like SST11LP12
   http://www.farnell.com/datasheets/1669517.pdf

2- Using a RF transistor like BFU768F
   http://www.nxp.com/documents/data_sheet/BFU768F.pdf

I have a lots of doubts about db gain, power input, power output, impedance matching... What i am sure is I'll go to 4 layer's PCB, with 50 Ohm traces for RF to match my 50 Ohm VTX otput and 50 Ohm of my Antenna input.

Of course i will pay more if the chip makes easy the circuit (KISS principle :)
I'll really  appreciate all the help. Thanks a lot!!!

PS: ¿Is it possible to simulate this behavior with spice software?

--- End quote ---

Don't forget to bribe your local law enforcement officers to overlook your transmitter's interference with other users, both in-band and in entirely different bands. Unless you know what you are doing (which you clearly don't), there's a good chance you will stomp over other people.

I suggest you join your local radio amateur group and don't think of transmitting until you can answer the question "given my modulation and the IP3 of these components, what is the power spectrum of the output". And even then, you should probably measure the output before connecting it to an antenna.

Alternatively, buy equipment that is specifically designed and certified/licenced for your specific requirement.

Psi:

--- Quote from: mayonesa on March 28, 2016, 11:21:04 am ---I have a video transmitter VTX 5.8G 32CH that operates between frequencies 5645 MHz and 5945 MHz. It has 25 mW's power output (mean signal strength). I want to build a circuit that increase the power from 25mW to 500mW

Of course i will pay more if the chip makes easy the circuit (KISS principle :)
I'll really  appreciate all the help. Thanks a lot!!!


--- End quote ---

You could buy the parts to make a RF amp for $35
Or just buy a new 5.8Ghz 600mW transmitter for $27

KISS says you should do that latter

energy_hunter:
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.

mayonesa:

--- Quote from: tggzzz on March 28, 2016, 11:32:23 am ---
--- Quote from: mayonesa on March 28, 2016, 11:21:04 am ---Hi,

I have a video transmitter VTX 5.8G 32CH that operates between frequencies 5645 MHz and 5945 MHz. It has 25 mW's power output (mean signal strength). I want to build a circuit that increase the power from 25mW to 500mW, I live inside a valley surrounded by trees and mountains, and the radio signal behave awful.

My question is, ¿what approach should i used to achieve the goal of clear visibility? i have two paths in front of me:

1- Using a RF amplifier like SST11LP12
   http://www.farnell.com/datasheets/1669517.pdf

2- Using a RF transistor like BFU768F
   http://www.nxp.com/documents/data_sheet/BFU768F.pdf

I have a lots of doubts about db gain, power input, power output, impedance matching... What i am sure is I'll go to 4 layer's PCB, with 50 Ohm traces for RF to match my 50 Ohm VTX otput and 50 Ohm of my Antenna input.

Of course i will pay more if the chip makes easy the circuit (KISS principle :)
I'll really  appreciate all the help. Thanks a lot!!!

PS: ¿Is it possible to simulate this behavior with spice software?

--- End quote ---

Don't forget to bribe your local law enforcement officers to overlook your transmitter's interference with other users, both in-band and in entirely different bands. Unless you know what you are doing (which you clearly don't), there's a good chance you will stomp over other people.

I suggest you join your local radio amateur group and don't think of transmitting until you can answer the question "given my modulation and the IP3 of these components, what is the power spectrum of the output". And even then, you should probably measure the output before connecting it to an antenna.

Alternatively, buy equipment that is specifically designed and certified/licenced for your specific requirement.

--- End quote ---
Yes before the brainstorming I made a research and 500 mW is allowed by law in my country. I will study more in order to answer those questions  :-+ Thank you

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