144, 432 and 1296MHZ Low Noise Amlifier

A few years go I also made a LNA using a MGF1302 FET , and it always worked flawlessly. Although it sometime gave up and was distroyed again because I forgot to take it out of the transmission line when going to transmit, then I had to renew the fet again,..

A lot of times you read a LNA will make your station receive better,..it doesn`t, what a antenna doesn`t receive can`t go to the receiver so it also can`b be amplfified by a LNA. It`s a usefull tool to overcome the losses in your transmission/receive line. Those signal would be lost in the line and now it is amplified so it will come through towards the other end at your receiver.

Well,, time to get started, looked around on the internet for some designs I could use. Stumbled across the design of PA3BIY, using a ATF54134 EPHEMT fet, and other sites with circuit board layouts and parts. So the choise was made very fast. I re-drew the print design using "sprint layout" so I could print it out on transparent foil.
At the radiomarket "de Lichtmis" I bought some PTFE circuit board to create some better quality boards,..always better as FR4,..also more expensive.


I ordered the parts at www.rfmicrowave.it , capacitors used are ATC-100B SMD. Trimmer cap a Johanson 5476 Hi-Q one. These parts are more expensive as regular ones, but hopefully I the LNA will be better as the last one.
Housing  also has to be made,..I will see what it will be, a tiined rectangular can or massive milled alluminium one.
(it`s going to be a tinned can)

You can find a  good description at the site of OZ1PIF, for the 144 and 432Mhz version. Here my "sprint-layout" file of the circuit board.

I `ve build the LNA and adjusted it on frequency/maximum gain. So let`s see what is the difference between the old one and this one connected it between my antenna and my TS790 listening the dutch beacon on 144.416Mhz. I can say, a big improvement, if I connect the old one (MGF1302) the noise level increases with about 4 S-point toghether with signal. When I connect the ATF54143 LNA only the signal increases, the noise level increases only one S-point. So the signal/noise ratio is much better with this Low Noise Amplifier. This is just what I needed for weak signal communication using WSJT.
Good thing is I made two circuit boards,..so the next one can be made for 70cm.







Beside the LNA there are coming a few things extra. This will be two integrated RF relays. Wired so I can switch the LNA on or off again in by-pass modus. Switched by hand on the PA by a switch or switched off in by-pass by the sequencer in the PA when it going to TX.
This option can be usefull when receiving strong stations when the LNA is not needed. And the LNA is switched off during TX of the PA. The extra shielding from the "outside" to the LNA will be even bigger to protect the sensitive ATF54143.

This board with the extra relays will also be made for the 432Mhz LNA.






The changed circuit board with the relays is seen at the right. With two extra  PIN diodes to secure the ATF54143 for static. And the two relays to switch the LNA in by-pass. The board used is 0,75mm thick PTFE board. Bought at a HAM-fest.
Most RF carrying lines are now designed in 50Ω stripline, and "mitered bends".

Here the excel file to calculate the "mitered bends".



The board has been changed again. Version 3.0 has an extra filtered output. This filter will be three pass helical filter. These are made by TOKO. Adjustable from 140-180Mhz with a bandwide of approx 8Mhz. While the LNA has enough gain, the losses of about 4˝dB through the filter will be compensated enough by the LNA. The board also has a little change, more 50Ω stripline and mitered bends towards the ATF54143. The two PIN diodes are now changed to just one at the input in front of the input relay.

The helical filters are:
For 2 meter band it is the 
TOKO FE-7H3-160.
For 70cm band it is the TOKO 5CHT-493S-1072A.
For 23cm band it is the TOKO 5HW-125055F-1305.

Available at:  www.rfmicrowave.it


144Mhz LNA. Version 3.0 with relays and helical filters.

Screenshot of the SA with LNA under test. -3dB point bandwide is 8.05Mhz.
After adjusting the gain is 25dB. A bit more as seen above. (completely closed tinned box)

432Mhz LNA, V3 with relais and helical filters.
approx. 12dB gain inclusive filter/relais losses.


For the 23cm LNA (1296Mhz) a new board will be designed. Also with switching relais and helical filter on the output. Also with the ATF54143 EPHEMT FET.
For the board I used the design of OK1DFC.  I made a few changes to it to incorporate the relays and helical filters and the by-pass stripline. Also looking at the Agilent datasheet for it.

V1.0  orginele uitvoering nagebouwde print. 2009
V2.0 Print met opgesoldeerde relais. 2013           
V3.0 Print met relais en bandpass filter. 2013   


renewed on  10the August 2014