Extend SDR Transmit Range - LimeSDR - HackRF - Adalm Pluto Amplifier

[Music] hi and welcome back to another tech minds video so a question i get asked quite a lot is how can we increase the power output from our sdr transmitter now not all sdr receivers have the ability to transmit as well as receive but three of the most common sdrs with transmit capabilities are the lime sdr mini the hack rf1 and the add-on pluto now if you've played around with the transmitting side of these sdrs then you'll know that they do not output much rf power maybe a few milliwatts depending on the band so if you want to extend the transmit range of one of these it's not as hard as you might think and it doesn't have to cost a fortune either so what you also have to understand is that these transmit capable scr receivers cover such a wide bandwidth you'll most likely see a variation in power levels as you change its transmit frequency for example the lime sdr mini has been measured to output 15 milliwatts at 437 megahertz whereas if we set the lime sdr many to transmit on say 2.4 gigahertz the output power would be as low as one to two milliwatts the hack rf1 is also rated to output at least one milliwatt up to 30 milliwatts depending on the band the adam pluto outputs around 1.5 milliwatts at 2.4 gigahertz now all of these power levels are pretty much estimates and will also change due to the cables being used the power meter calibration and even the power supply to the transmit capable sdr rf amplifiers work in such a way that you input a small signal and then the output side of the amplifier has that same signal amplified with more power now big power amplifiers like those that we see at ham radio stations would have some form of tuning and specifications for certain bands that means we couldn't use an amplifier that's designed c for 50 megahertz only with a transmitter that only transmits on 144 megahertz but what if we just want a small amount of gain from an amplifier that could cover a large frequency range well you would most likely want to look at something like the widely used spf 5189z these have a great frequency range of between 50 megahertz right up to 4 gigahertz the specifications for these radius gain are around 12.8 db but it's highly unlikely you'll get 12.8 db gain across all of the bandwidth but you will get some sort of gain now the good thing about the spf 5189z is that they are extremely cheap we're talking less than ten dollars the other good thing is that if your input signal is extremely low then you could potentially cascade two of these together in line to provide a higher final output now when i was testing various options for my q0100 uplink transmitter for 2.4 gigs i used the lime sdr many as your transmitter and then i had two of these spf 5189 zs as a preamplifier to my final amplifier now it's also worth pointing out that the drawback of using very broadband amplifiers is that they will also amplify rf harmonics coming from your transmitter to get around this you should use an rf bandpass filter for the frequency that you're transmitting on the middle amplifier there the analog devices cn0417 is a device specifically designed for use between 2.4 and 2.5 gigahertz with a 20 db gain and a maximum input of 100 milliwatts we could potentially see around 1 watt rf output from this device now the cn0417 has a built-in filter for between 2.4 and 2.5 gigahertz so it would be no use outside of these frequencies in fact i use one of these in my qo100 preamp circuit the cn0417 is a professional piece of equipment and works extremely well however it does have a price tag of around 50 euros depending on where you purchase it from you'd only really want to use a con417 if you're going to be targeting 2.4 to 2.5 gigahertz the amplifier there on the right the rf2126 is another broadband amplifier ranging from megahertz up to 2.7 gigahertz with a rated 12 db gain at 2.4 gigs now notice how the 12 db gain has been specified only for 2.4 gigs this is because the game will be a lot less on other frequencies but it will still work now i'm going to show you the effect of using one of these amplifiers in line i'm going to be using my hack rf mounted in a porter pack as the transmitter and we have an immersion rc power meter to measure the results but because the power meter has a maximum input of 1 watt and i want to protect it from overpower i'm also going to use a 10 db attenuator in line we can set this offset within the power meter so it displays the correct power reading to us so we don't have to work it out so first off i'm going to set the hack rf to transmit an fm carrier on 2.4 gigahertz and then we're going to measure the power output directly with no amplifier in line now by pressing the right button on the porter pack it starts to transmit and you can see this by the screen going black on the porter pack this means it's in transmit mode now if we take a closer look at the power meter we can see that we're measuring an output power of around 3.8 milliwatts it's fluctuating slightly there so let's do the same test but with the analog devices cn0417 in line and powered up so here we have the cn0417 connected in line and the con0417 is easily powered from a usb hub and that's what the black cable there is so if we turn the port pack to transmit mode we should see a massive jump in power output and there we go as you can see we are now around 430 milliwatts quite impressive if you ask me so let's go ahead and take a look at how well the spf 5189z works so the spf 5189z actually comes metal canned and with sma connectors on both ends now mine looks like this because i've been performing quite a lot of experiments with it and i've removed one of the sma connectors on the can so we know that the hack ref was outputting around 3.8 milliwatts at 2.4 gigs without any amplification so let's see how well the spf amplifier works and there we go we have around 13.2 milliwatts at 2.4 gigahertz now as the spf is a wideband amplifier let's also take a look at how well it performs on 433 megahertz so with the hack rf1 changed to 433.5 megahertz and the spf in line we're seeing around 6.6 milliwatts if we then take the spf out of line and check the power output of the hack rf at 433 megahertz we can see that it's not even one milliwatt in fact it's minus 4.35 dbm now i don't own one of the amps that i showed you earlier but i hope this demonstration shows you how these broadband amplifiers work in comparison to a dedicated frequency amplifier for those wondering the spf amplifier only requires 5 volts to operate i actually run mine from a 12 volt supply but it goes through a step down converter to provide me the 5 volts that i need to power the spf amplifier i'll leave a link down in the description below of where you can purchase these if you want to and if you've got any questions about this or you've used this or another type of amplifier with your sdr transmitter then please feel free leave a comment below and we'll be interested to hear your experience until the next video guys take care stay safe thanks for watching and i'll see you in the next one [Music] you

Channel: Tech Minds

Views: 52,714

Keywords: ham, radio, software, defined, digital, dstar, dmr, fusion, ysf, nxdn, antenna, resonant, nanoVNA, how to make, how to, tutorial, waterfall, signal, transmission, qo-100, eshail2, tech minds, amplifier, hackrf, limesdr, mini, power, rf, spf5189Z, cn0417, rf2126, extend range

Id: yOkdg1lGfes

Length: 8min 37sec (517 seconds)

Published: Wed Aug 19 2020