Regarding low LimeRFE RF Output Power

Currently I already received a new LimeRFE after waiting almost 1 year. I hook up my new LimeSDR mini with LimeRFE and I run my python program with GNU Radio components at 144MHz, sadly I only got around 2.4dBm output from LimeRFE itself. But I noticed that my new LimeSDR mini version 2 at 144MHz, it’s can only deliver around -40dBm output. How I want to solve this problems? And what is the minimum RF input for LimeRFE in order to get the RF output power as its claim in their measurements documentation?

Hi Bahari,

I can answer only about LimeRFE board which, in my opinion, didn’t cause problem in your setup.

Here is my explanation:
Please find a pdf file in a link bellow

There, you can see that, for TX at 144 MHz, gain is about 33 dB and its OP1dB is of about 34 dBm (this is
shown on page 7, figures 12 and 13). Moreover, at around 190 MHz this gain is going even higher, above 40 dB.

Following the numbers you claim, it turns out that you have more than 40 dB gain which indicates that LimeRFE board is probably OK.

Regarding these results from the link, our prototype board gain was measured with -30 dBm input signal (Figure 12). To achieve 34 dBm output power at output of the LimeRFE board, the input signal should be roughly around 0 dBm, or even a few dB higher.

If you can give us the board number (board number is on sticker on acrylic case), we can check measured results of that particular board. We did measurements of every board which was sent for selling.


Hi Branko, very thanks to you for instant reply. I already resolve this issues via updating and compiling LimeSuite to the latest one directly from github. Now I’m getting 3.78W RF output power via LimeRFE. It seems the existing version of LimeSuite was not compatible with LimeSDR mini version 2.0.

Before this I’m testing with the LimeSDR mini version 1.0 with the older version of LimeSuite to double confirm the RF output power from LimeRFE, and It works - So I conclude that the low RF output power was due to the older version of LimeSuite. Thanks again Branko


One last question Branko, can I powered up LimeRFE with 13.8VDC power supply?. From schematics the PSU IC seems can tolerate wide input voltage

My board number: #7

Hi Bahari,

TPS62136RGXT (DC-DC converter) can have 14V at its input without any problem.

Problem can happen (I do not claim that is for sure and always) at amplifiers which are supplied with that very same voltage. When these amplifiers have a little bit higher voltage than nominal 12V, and when you push these amplifiers too high (if you bring them input signal to take them out from “the small signal region”) then they can be damaged.

I have checked critical transistors datasheets (RD16HHF1 and RD01MUS2B).
General rule of thumb that maximum allowed drain-source voltage (collector-emitter voltage) should be at least 2.5-3.0 times higher than DC supply voltage for that transistor.

For RD16HHF1 maximum allowed drain-source voltage is 50V, so this one should be supplied with 14V, without any problem.
This transistor is in “HAM30” and “HAM50-70” bands.

For RD01MUS2B maximum allowed drain-source voltage is 25V only. If you have high input signal, you will plush transistor out from “small signal regime” and this transistor can be damaged!
This transistor can be found in “HAM30”, “HAM50-70” bands as driver amplifier, “Wideband1-1000” band as power amplifier, in “HAM920” band as driver and in “HAM1280” band one of these transistors is in driver and one is in power amplifier. Power amplifier is always more critical than driver amplifier, because this one gets higher input power.

We tested all our boards on 12V, so I can guarantee only for 12V. If you are going to 14V (or 13.8V) power supply, please be careful.