PA4FP 70cm EME

My Amateur Radio Station PA4FP (1990-2003)
(Not active anymore on 70cm EME)

INTRODUCTION.
How I built a small, simple and medium power 432MHz station & hope to work Moon Bounce.
A burning ambition of mine for many years was to build an amateur radio station that was capable of Moon Bounce operation. (to transmit a signal from earth, bounce it off the moon and have it received back on earth). My antennas had to be limited in a small back garden, but I also want it to use for normal operation on 70cm (Tropo). The power had to be limited to 400Watts or less as specified by the terms of the Dutch license. And a second wish is that I also want to be QRV on 1296MHz and up with EME in the future.

How I built the station.
I decided to make 4 x 26el DJ9BV-OPT70 (8,5wl) This is possible to put in my Versatower with in the future 6 x 38el DJ9BV-OPT70. Controlling the position of the antenna was provided by Yaesu G-1000SDX azimuth rotor and for elevation i' am using a actuator who's normaly used by TV-Sat dishes. With this elevation system must it be possible to move the 4 x 26el DJ9BV yagi's up and down.(or 6 x 38el DJ9BV in the future)

Building the Yagi's.
First I started with building the dipole's, I want them all have the same measure, so i decided to make a mould, I was sure then all the dipole's where made with high precision. After that I made a mould for the boom and was ready to produce a lot of antennas. The Yagi elements from 5mm dia did I made on the lathe, to get also high precision.

4x 26Ele. DJ9BV-OPTII 8,5 Lambda length

A 4 way antenna power splitter.
The material of the power spitter is brass and then you have the possibillty to solder direct the N-connector on the housing, so this is waterproof.

The Question which I often here is: What is the best length for the phasing lines?
If all antennas are equal it does not matter at all. The impedance is perhaps not precisely 50 ohms but that does not matter at all. if the cable is not exactly 1/2 wl (or multiples) the impedance seen by the power divider will not be the antenna impedance. it will be some impedance with exactly the same WSVR as the antenna. The reflected power you can measure at the main feed point will be the same you only change the phase angle between the forward and the backward waves in the cable wich makes no difference at all. Personally I never sould stack more than 4 antennas and then they are all identical so I always cut the cables to fit mechanically without any concern at all of the elctrical length in wavelengths, they just have to be EQUAL.

Building the Power Amplifier.
The amplifier I built has a EIMAC 2x 3CX800/A7 and can produce more output than specified by the terms of the dutch license. So this is not the problem anymore

Pre-amplifier.
I contructed a GaAs Fet preamp based on the BJ9BV design in the DUBUS manual IV. I used the MGF-1302 single gate GaAs Fet. This preamp has a very low noise figure (0,5 dB) and good gain (18 dB) and also a unconditional stability, even without a antenna.
But after a while i had the idea that some thing was't right working with the preamp. So after a lot of work and new MGF-1302's i decided to buy a preamp from DB6NT, who's has a nice gain and noise figure. (Gain-20,5 / NF-0,29dB) This one is working now very well.