Power Amplifier for LimeSDR mini

Dear All,
I could not figure out what is the power output of LimeSDR Mini on different frequencies - 900Mhz - 2 Ghz range (if anyone knows pls advise)… therefore i thought to use power amplifier…
I am a relatively new in electronic and please advise would it be possible kind of just remove transmitter antenna from LimeSDR mini, attach power amplifier to antenna slot and hence having more powerful radio transmission ?
If so what cheap power amplifiers would you recommend and if you know any links for further info or how that should be done - would you be so kind to advise me please…

Thank you so much.

Amplifiers tend to be band-specific and so a good starting point is to know which band(s) you’d like to use. Following which the next question would be what power output you’d like to achieve. Then next what waveform/modulation type you will be using. The last question is important because the amplifier specification for a given band + power output may be wildly different if you were using it with Morse code vs. something like QAM256.

In addition to an amplifier you should really have filtering too and this is band specific also.

You don’t really get power amplifiers that are good for a wide variety of bands, which is why we made the LimeRFE, which also integrates band-specific filtering.

But this is a very complex solution and hence why it is not cheap.

andrewback thank you for your valuable response…
In fact i d like to learn GSM networks therefore would need amplifier for that specific type of signals…
I read about LimeRFE but it is a bit costly i can not afford it at the moment…
Would you be so kind and advise if there is a cheap solution PA / filter etc etc for limeSDR mini…range may be some 20 meters …?
Also can you advise me a link where i can read and learn how to select PA depending what task (band, modulation etc etc ) i want to do ?

GSM operates on numerous bands, so you would need to pick one :slight_smile:

sysmocom are a good source of components for GSM. E.g. they provide duplexers, which allow you to connect one antenna and transmit + receive at the same time. Using these also typically gives better performance.

http://shop.sysmocom.de/t/gsm-related/duplexers

They also sell an LNA for DCS1800 band, which will amplify the uplink (mobile to base station) signal.

eBay may be a good source for cheap surplus power amplifiers. New they can be quite expensive.

Note that you may also need more than one PA, e.g. one that acts as a “driver” and amplifies the signal to a level suitable to properly drive the input of the main power amplifier. Without which you may not get anything like the full rated output of the PA. But on rating, this will be less for a modulated GSM signal than it would be CW.

andrewback you definitely are very helpful thank you so much…
Let me ask further questions - so back to the duplexers as you mentioned …

  1. Can i attach a sysmocom duplexer (provided that i will select one for particular band) to limeSDR mini and eventually duplexer will transmit more powerful GSM signal ?
  2. Where and what should i read to be able to answer the question above myself ?
  3. What do you recommend me how to measure LimeSDR Mini transmitted signal power (FM AM GSM (GMSK modulation)? I want to measure signal on different distances from LimeSDR mini…

Thank you so much

Without a power amplifier as well, the signal will not be more powerful and may be slightly lower, because of the duplexer introducing a small loss. However, range is not just a function of base station power and it also has to be able to hear mobiles well. What a duplexer may help to do is stop your transmit signal being received by the SDR and in turn making it less able to hear mobiles.

One possibility would be to look at the LimeRFE block diagram or schematics and follow the Tx branch for the cellular band you’re interested in and then note down the devices used in the predriver/driver/PA chain in that path, then look up their datasheets. The LimeRFE has been designed to take the output from a LimeSDR and amplify it to the stated power output for that band, i.e. cellular bands 24dBm.

Use an RF power meter or a spectrum analyser connected to the SDR Tx port.

That is not how you measure power output. You can measure received signal strength with a receiver, or signal level with test equipment, but this is not the same as measuring the power output at the SDR Tx port and in this case antennas, objects in the room and reflections etc. would all affect the measurement.