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LNA designs
Category: EME Equipment, Created: 2001-11-02 22:45:47

Preamplifiers are an essential device for serious EME operation. Lot has been built, written and tested and - still there is the desire to push NoiseFigure down even more - without giving up stability.

For most measurments relative NoiseFigure data is good enough. In most case it is interesting, whether one device is worse or hopefully better than another one of which you have an idea how good it does the job.
Nevertheless, the luxury of reliable absolute NoiseFigure is related to professionally calibrated testequipment, properly used.

All preamps in this article have been measured (Nf and Gain) with these fine testequipment:

Agilent (hp) 8973B 10MHz - 3GHz
Agilent N4000A NoiseSource
10MHz to 3GHz, sweeps NF and GAIN. This precious toy helps to win the EMEers fight against noise... Noise Source with ENR of approx. 6dB, fits to  Agilent 8973A Noise Figure meter

The new HB9BBD preamplifier:
This device offers >40dB gain at very low Noise Figure at 1296 MHz. A SETI
version at 1420 MHz is available with the same specifications.
The new preamp has a very high Q and thus minimal noise. The silver plated body with ceramic printed board
The silver plated body with ceramic printed board The body is silver plated aluminum, the print Teflon/ceramic.

If you are interested to learn more about this cavity LNA for 1296mc or if you might want to buy one click here:

There are other very good designs:

This beutifully built preamplifier will be described in more detail later W7CNK has developed this beautiful preamp.

it is improving the NF to 0.18dB! SM0PYP built this two stage device.
Removing ATF35076 and replacing by ATF36077 results in significant NF improvement!

Here you find the datasheet of theATF36077 for very low noise preamplifiers.
PHEMT for low noise preamplifiers

NEC offers some interesting HEMTs for Amateur applications -
Replacing the ATF36077 by NE32484A pulled the NF another notch down. Due to the relatively small gain of the first stage, the match between the first and second stage (MGF1304) is critical. Optimizing the transformation between the two stages, gain increased significantly above 50dB and the NoiseFigure improved from 0.17 dB to 0.15dB.
NE3210S01 was expected to offer better NF. This did not prove to be right.

Here is the two stage 23cm version of a high Q preamp with the
: Please note that the plot represents the arithmetic average of 10 measurments which makes the NF reliable.Testequipment: Agilent 8973B and N4000A

typically NF is 0.2-0.23dB, Gain 38-42dB This is an SM0PYP/WA6PY design

This is the best hemt I ever measured The little red coil is the match to the second stage and is critical for NF and Gain The red coil is critical!

On February 9 2002,Dave, G4HUP/DL4MUP visited me and we had an interesting preamp session:

Dave's Cavity Preamplifier
The body of such device has to be tightly closed.. It helps to select the best matching transistor This device will receive some technical attention by Dave..
and here is the plot after changing to NE32484: We removed the FHX35 but this is not the main topic here..

Dave had built this preamp by DB6NT
This device belongs to DL4MUP This device belongs to DL4MUP/G4HUP

and this one by DJ9BV

A new design by W7CNK, ATF36077 and Stanford SPF-2086 in the second stage.

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