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 photo below.
There’s also a small power indicator
LED at upper right (D2).
This module is currently available
online from Amazon UK (and others)
for around £9 and up, including delivery – search for ‘1-3000MHz 2.4GHz
20dB RF Broadband Low Noise Amplifier Module UHF HF VHF’. It’s the
cheapest of the three amplifier 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
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.
42
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 and 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
possible 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.
terminal block fitted to the PCB for
power, but there are two 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) – https://bit.ly/
pe-apr23-amp2 – for around $16, plus
shipping from China (free for orders
over $50).
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
doesn’t claim to be an LNA.
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 Module one is the largest of the three, measuring
end. This module doesn’t 50 x 50mm, it uses a two-way screw terminal
come with a mini two-way block for the power connection.
Practical Electronics | April | 2023
Fig.1: the gain curve for the three modules – red (1MHz-3GHz), blue (5MHz6GHz), green (50MHz-4GHz).
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).
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 a little 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
The second module
is the smallest and
most sparse of
the three. It only
has two unused
pads for the power
connection.
Practical Electronics | April | 2023
for the connection of the negative
power lead.
This module is available from Amazon UK (and others) for around £19
and up, including delivery – search
for ‘50M-4GHz Low Noise Amplifier
0.6dB RF LNA Amplifier’.
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.
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
43
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.
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.
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 (PE, February 2022),
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
44
The third and 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.
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 and 6.5dB at 4GHz.
Reproduced by arrangement with
SILICON CHIP magazine 2023.
www.siliconchip.com.au
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