SPF5189Z modules as LNA

[fasleitung3]

Hi,
Some time ago I published a comparison of various amplifier modules as
part of a series of articles about hydrogen reception. At that time, an
module based on the SPF5189Z which can be bought on ebay at a low price
point turned out to be a good low cost solution. The noise figure
measured at 1420 MHz were in the 0.6 to 0.7 dB range. While not great,
this is still good enough to get some decent results. Over the time, we
have purchased a number of these devices for various applications. A
recent purchase, however, was a mixed experience. There were 6 units,
three of them were cleary underperforming. We measured 2.1, 2.4 and 1.8
dB noise figures. The other three were at 0.57 dB, equivalent to what
we had before. So if you are planning to use these, be aware that you
may not receive what you are expecting. There is an easy way to tell
the good ones from the bad ones even if you cannot measure noise
figures: We noted that the good ones had a typical current drain of
around 80 mA, whereas the bad ones were in the range of 130 to 180 mA.
So the bad performance seems to be clearly correlated with power
consumption. The gain of the devices was between 12.7 dB and 13.0 dB
for the bad ones and 13.9 to 14.2 dB for the good ones.

We also measured three Noolec SAWbird H+, they had a noise figure of
0.52 dB. The gain was 40.2 to 41.5 dB. So these had very consistent
results.

Happy observing!
Wolfgang