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Using Cheap Asian Electronic Modules By Jim Rowe Three low-noise HF-UHF Amplifiers Left-to-right: module one (1MHz-3GHz), module two (5MHz-6GHz), module three (50MHz-4GHz) All three of these low-cost wideband HF-UHF amplifier modules claim to provide 20dB of gain, over frequency ranges of 1MHz to 3GHz, 5MHz to 6GHz and 50MHz to 4GHz. They vary mainly in terms of size, shielding, supply voltage and price. T he 1MHz to 3GHz module is the largest, with a PCB measuring 50 x 50mm. It has SMA input and output connectors at each end and a mini 2-way terminal block for the power connections at the rear. The amplifier circuitry is inside a 32 x 30 x 6.5mm shielding box in the centre of the PCB, visible in the photos. There’s also a small power indicator LED at upper right (D2). This module is currently available online from Banggood (code 1238137; siliconchip.com.au/link/ab8q) for around $15, plus $7.50 for postage. That makes it the cheapest of the three modules we’re describing. It has been designed to run from a 12V DC supply, with a stated current drain of 75mA. It has a maximum input level of 0dBm, and the maximum output power is said to be +19.5dBm (approximately 100mW). While it’s described on the PCB as a low-noise amplifier (LNA), no noise figure (NF) is given. I could find no information regarding its internal circuit, or the active devices inside. But when I powered it up and checked its gain with my Signal Hound SA44B spectrum analyser and TG44A tracking generator (controlled using their Spike software), the results were quite impressive, as you can see from the red trace in Fig.1. The gain measured about 21dB at the low end, drooping fairly smoothly siliconchip.com.au to 13.5dB at 3GHz, and then wobbling up and down a bit before falling to 3dB at about 4GHz. That’s not bad for a lowcost module with a rated frequency range of 1MHz to 3GHz. I don’t have the equipment to measure the NF, but I was able to use the SA44B with Spike to measure the module’s DANL (distortion & noise level) at 1GHz and 3GHz with a 50W input termination. I then compared these measurements with the DANL of the SA44B alone (50W input termination) at the same frequencies. The results showed a rise in the DANL from -153dBm to -138dBm at 1GHz (+15dB), and a rise in DANL from -149dBm to -139dBm at 3GHz (+10dB). This is perhaps not good enough to qualify the module as an LNA, but quite acceptable for many applications. I also checked the module’s current drain from the 12V supply, and it measured precisely 75mA. So overall, this module is a good choice if you only need to amplify signals at frequencies up to about 3GHz, and would be happy with the gain curve shown in red in Fig.1, the maximum output of 100mW and the modest noise performance. It would likely provide a good way to boost the output from a drone control transmitter, for example. The second module The next amplifier module is physically smaller, with a PCB measuring 33 x 24.5mm and again with SMA input and output connectors at each end. This module doesn’t come with a mini two-way terminal block fitted to the PCB for power, but there are two Module one is the largest of the three measuring 50 x 50mm, it uses a twoway screw terminal block for the power connection. Australia's electronics magazine February 2022  41 Fig.1: the gain curve for the three modules – red (1MHz-3GHz), blue (5MHz6GHz), green (50MHz-4GHz). pads at top centre ready to mount such a block (on either side of the PCB). The amplifier circuitry is again inside a shielding box in the centre of the PCB, measuring 18.5 x 14.5 x 3.5mm. There is no power indicator LED. This module is available from Banggood (code 1119141; siliconchip.com. au/link/ab8s) for around $21.50, plus $7.50 for direct mail shipping from China. It is designed to operate from a 5V DC supply, with a nominal current drain of 85mA, so it can be powered from a standard USB power pack. Again, it is claimed to provide a nominal gain of 20dB, this time from 5MHz to 6GHz, with a maximum input level of 0dBm. The maximum output power is stated to be +21dBm (around 120mW) at the 1dB compression point. This module isn’t claimed to be an LNA. I could find very little information regarding this module’s internal circuitry, apart from the suggestion that it’s based on a Qorvo SBB5089Z InGaP MMIC (monolithic microwave integrated circuit) amplifier device. This comes in a 3- or 4-pin SOT-89 package, and in the data sheet, Qorvo gives the circuit for an evaluation board which I have redrawn in Fig.2. That is a pretty standard MMIC circuit, and probably close to what is inside this module. When I powered it up, the first thing I checked was its current drain from a 5V power pack. This turned out to be 36mA, less than half the claimed nominal value of 85mA. However, the current might increase when the module is delivering its maximum output power of +21dBm. Next, I checked its gain with my Spike test setup. This combination only goes up to 4.4GHz, but the result is shown in blue in Fig.1. As you can see, it was pretty respectable over this range, varying between about 13.5dB and 16.5dB with an average value of around 15dB. The Qorvo data sheet for the SBB5089Z suggests that it probably extends to provide at least 14.5dB of gain at 6.0GHz, but I can’t confirm that. After this, I used the SA44B with Spike to measure this module’s DANL at 1GHz and 4GHz with a 50W input termination, and again compare them with the figures for the SA44B alone, at the same frequencies. The results this time showed a rise in the DANL from -153dBm to -140dBm at 1GHz (+13dB), and a rise from -140dBm to -132dBm at 4.0GHz (+8dB). The second module is the smallest and most sparse of the three. It only has two unused pads for the power connection. 42 Silicon Chip Australia's electronics magazine This is a little better than the results for the first module, but still perhaps not good enough to be regarded as an LNA, even though it would be quite acceptable for many applications. So this module would probably be a good choice if you want to amplify signals at frequencies above 3GHz, up to about 6GHz, and would be happy with the gain curve shown in Fig.1 (blue trace) and its ability to deliver up to approximately 120mW. The noise performance is not too bad, either. On the down side, this module will cost you about $6 more than the first one, and doesn’t come with a terminal block already fitted. But its smaller size might make it easier to fit into equipment like a drone control transmitter. The third module The final amplifier module we’re looking at differs from the other two as it is completely housed in a cast aluminium case, so it’s fully shielded. The case measures 42 x 32 x 12mm, with the SMA input and output connectors at each end and an insulated feed-through pin fitted to the rear of the case for its power input. A small solder lug held by the feedthrough pin’s external body allows for the connection of the negative power lead. This module is available from Banggood (code 1443559; siliconchip.com. au/link/ab8t) for around $31 plus $7.50 for shipping from China, which makes it the dearest of the three. Like the second module, this one operates from a 5V DC, with a nominal current drain of 90mA. So again, it can be powered from a standard USB power pack. The nominal bandwidth is 50MHz to 4.0GHz, with a typical gain of 19dB and a maximum output power of +22dBm (about 150mW) for 1dB compression at 2GHz. The maximum input signal level is stated as less than +10dBm, or 10mW. The noise figure is quoted as typically 0.6dB, suggesting that this module is intended for use as an LNA to boost the sensitivity of receivers and test equipment like spectrum analysers. I measured its current draw at 82mA, just a little lower than the claimed value, but as before, this was when the module’s input was terminated with 50W. It will likely rise when the module is handling an RF signal. siliconchip.com.au Fig.2: little information is given on the 5MHz-6GHz module, so the circuit shown is based on a Qorvo SBB5089Z-based evaluation board. It should be close to what the module is comprised of. Next, I checked its gain, as before with the SA44B/TG44A/Spike test setup. The result is shown in green in Fig.1. The gain is highest at around 50MHz (27dB), drooping down to around 15dB at 1.32GHz, 10dB at 2.2GHz and 2dB at around 4.0GHz. This is a little disappointing, considering the amplifier is claimed to have a gain of 18dB and a bandwidth of 50MHz to 4.0GHz, but it would still be quite useful if you are mainly dealing with signals below 1.8GHz. As noted earlier, I don’t have the equipment to measure the NF directly. But when I used the SA44B spectrum analyser with Spike to compare the amplifier’s DANL at 1GHz and 4GHz against that of the SA44B alone (in each case with a 50W input termination), the results were noticeably better than for the other two modules. At 1GHz, the DANL rose from -153dBm to -143dBm (+10dB), while at 4GHz the DANL rose from -140dBm to -135dBm; a rise of only 5dB. So it might be a bit lacking in terms of gain and bandwidth, but it probably does qualify as an LNA. The bottom line Based on these test results, each module has strengths and weaknesses. The best choice depends on the gain and bandwidth you need, the kind of application you want to use the amplifier for and how much you can pay. For example, the second module offers the best gain/bandwidth performance, coupled with a reasonable noise performance and the ability to provide an output of around 100mW. It’s also not that much more expensive than the cheapest (first) module, so it is probably the best choice for applications like boosting the output of a drone control transmitter. But the first module provides much the same performance at frequencies below 3GHz, so with its lower price, it is an attractive choice for the same kind of application. siliconchip.com.au Suppose you are mainly interested in signals below about 1.8GHz and noise performance is critical, such as boosting the signals going into a receiver or spectrum analyser. In that case, the third module is probably the best choice, despite its significantly higher price. Using these amps with the LTDZ V5.0 spectrum analyser You might recall that towards the end of my review of the low-cost LTDZ V5.0 spectrum analyser (January 2022; siliconchip.com.au/Article/15178), I mentioned that I would be testing this type of amplifier module to see whether they could be used to improve that device’s sensitivity. That’s because the LTDZ analyser has a relatively high noise floor of about -77dBm, meaning that any signals lower than this (or possibly even slightly higher) would essentially be ‘lost in the noise’. An LNA could be used to boost these signals well above the noise floor, allowing them to be distinguished and measured. After checking out the three modules reviewed here, I decided that the second and third (LNA) modules would be the best candidates for this job, so I tested both. First, I inserted the amplifier modules in front of the LTDZ analyser, with their inputs terminated with 50W, and ran some plots to see if their noise affected its noise floor. They did not; the noise floor measured -77dBm with or without both amplifiers. The next set of tests involved feeding a -80dBm CW signal from my signal generator through the relevant amplifier module and into the LTDZ analyser at four frequencies: 1GHz, 2GHz, 3GHz and 4GHz. Without the amplifier, I would expect a flat line at -77dBm. Any peaks above this would mean that the amplifier was providing some benefit. With the second (cheaper) module, I saw two bumps of about 7.5dB on either side of 1GHz in the first test, about 7dB on either side of 2GHz, about 4dB on either side of 3GHz, and about 2.5dB on either side of 4GHz. So this module does give the LTDZ analyser a modest increase in sensitivity up to 4GHz, without affecting its noise floor. The reason why there were two bumps rather than one peak is explained in the main body of the article linked above. It’s a property of the analyser’s unnecessarily broad resolution bandwidth, not a failing of the amplifier module. I also tested the more expensive LNA and got two bumps about 8dB high on either side of 1GHz, two much smaller bumps (<1dB) on either side of 2GHz, two similarly small bumps on either side of 3GHz, and no discernible bumps at all around 4GHz. I must conclude then that the second, less-expensive amplifier module with a stated frequency range of 5MHz to 6GHz is the best option for improving the sensitivity of the LTDZ analyser, and does give a helpful improvement in sensitivity, of about 10.5dB at 1GHz, 10dB at 2GHz, 7dB at 3GHz SC and 6.5dB at 4GHz. The last amplifier module is housed inside a cast aluminium case. There’s an insulated pin fitted to the edge of the case which is used for power, along with a solder lug adjacent for the negative power lead. Australia's electronics magazine February 2022  43