Cette page était sur le site de PE1PZN; mais le lien ayant disparu, j'ai reproduit ici l'article que j'avais conservé. (F5AD)
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ATV 23cm PreAmplifier

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From the Electron of July 1990 I once rebuild the preamplifier for 23cm.
When I started testing the preamplifier, by attaching it to my satellite receiver and tuning to the local ATV transponder at Soest I was confronted with all kinds of rubbish, much oscillation tendencies and a lot of noise amplification.
At my QTH (JO22MG) I received the ATV transponder of Soest (PI6ATS 1280Mhz) with signal strength of 8 but with a lot of noise (B1).
Soon it appeared to me that the MF-signal was far too big, caused by the consecutive MSA0685's (MAR8). Most wideband satellite receivers get overmodulated due to this and all starts mixing in the receiver casing.

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In this schematic I replaced both MSA0685's with the BF65 that is easily obtainable at local stores. I also added two rings so the amplifier has a smaller bandwidth resulting in less mobile phone interferences.

The result was satisfying, very low noise and enough gain to receive weak signals. (over 29dB between 1240Mhz and 1300Mhz within 2.5dB)

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I now receive Soest with signal strength 1 on the S-meter but without noise (B5) !
This preamplifier is tested, and has a maximum gain of 29.66dB on 23cm, and the 900Mhz (GSM) signal is reduced by 10dB.

I have made a new layout and schematic. Notice that you should place and solder the last SMD condensator C12 straigt up from print to BNC connector. The print is double-sided, the bottom-side is ground so the components should be placed on the top-side. Dimensions of the print is 3,5 x 11 cm (WxH) exactly.

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Parts list:
R1 = 100 Ohm resonator
R2 = 270 Ohm resonator
R3, R4 = 56 Ohm resonators
R5, R6 = 330 Ohm resonators
1 X MGF1302 fet
1 x 78L08 regulator
2 x BFG65
FK = Ferritekrale 3mm
C2,C3,C5,C8,C11 = Sky trimmers SPF green (or equal ones 0.8 till 5pf)
C1,C6,C7,C9,C10,C12 = 10pf SMD
C4 = 1,8pf SMD
C13,C14 = 47Pf keramic
C15 t/m C20 = 1nf keramic
C21,C22 = 1nf trapezium condensator
L1,L2 = 1 coil of 0,5mm zilverwire, inside diameter 3mm
L3 = 10µh coil
D1 = 1n4003

Good luck with building this preamplifier.
PE1PZN

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