144MHz EME antenna by PA3FXO


Following photo's give an impression about the new Yagi setup I have build for 144 MHz EME (earth-moon-earth) qso's.


In the beginning I purchased a second hand 10 element Cue Dee Yagi. This type of antenna works fine and is matched to 50 Ohm by a Gamma Match.
Regarding to a 300 Ohm folded dipole the matching is easier because there is a shorting clamp which can be adjusted in stead of fooling around making a coaxial balun.
The tuning of a coaxial balun takes some time because you have to cut it to size and eventually it will be too short :-)
A Gamma Match can also be made by hand and info is on the antenna link in the left column.

Anyway, to get on with the story ...... the 10 element Cue Dee was old and had signs of weather attacking it during the past years.
The SWR was not to be tuned beneath 1:1:4 and on a analyser it had two SWR dips on 143 and 147 MHz ....mmmmm..... also when elevating form horizontal to 50 degrees or more there was no difference in received noise !!
With this antenna I made my best Es qso ever in 2007 when working EA8TJ over 3167 km's. But if I wanted to work EME the antenna had to be exchanged by another version, which was the 15 element Cue Dee. This was also a second hand version and had to be restored because some elements were broken and also some plastic element stand-offs were broken.
Specs: 12.9 dBi and 7.5 meters long.
This antenna had good matching to 1:1 meaning a minimal loss in the 50 Ohm matching.
Former coax was Aircell-7 but this was also replaced by 1/2 inch Cellwave. (tnx to PE1RDP and PC2A for the delivery).
The elevation rotator used is a Kenpro KR-500 which easilly elevates the long Yagi to the moon ..... ahhh what ease.
Now the band noise goes from S7 to S0 at 50 degrees even with preamp.
At first I thought the preamp was broken but I was fooled and all was fine ! The preamp is home made with a MGF1302 and a gain of 24dB / noise figure of 0,22 dB. See more info on this website.
The used power is 200 Watts from a modified 150 MHz power amplifier.
Because I use a home made secquencer I can turn off the preamp and switch antenna relais before I apply RF power.
This is done to save the relais contacts because with high RF power you could burn them out.



The first step was to take down all the former antenna's which I used for 23cm & 13cm ATV, FB-13 dipole for HF, and the 70 cm Yagi. Only the single dipole for 6m was allowed to stay.

The mast I use is a 4m steel pole with in the top a 1,5m thinner section. It passes through a roof tile into the house and no grounding is made.

I don't beleave in grounding low antenna setups because it makes the whole setup almost zero Ohms and therefore attractive for lightning strikes.

If I was living in a single house out in the country side the situation would be different, but I have higher buildings around my house and also a powerline nearby.

Step 1: assembly of the 15 elements and boom and putting it together.


Step 2: putting the elevation rotor in the mast and preamp / relaisbox below.
.....grrrr.... see the moon and no antenna in the mast .... great stuff.


Step 3: testing the elevation ....when will the reflector hit the roof :-(


Step 4: testing SWR and preamp at sky noise ... all working fine. Also added the 70cm Yagi.


Eye-ball QSO at the QTH of Arno PE1RDP in Veldhoven ...he is the one to blame for my EME "madness" and i'm thankfull for it. Lets do some realDX !



The temporary step was to rebuild the former 10 element CueDee to a 8 element DK7ZB Yagi. I had to shorten most of the elements (6mm diameter) and had to make a new dipole and 28 Ohm match.
This was done with TV coax-6 which is 75 Ohms and delivered by Arno PE1RDP.
In the pictures you can see the green TV coax but before putting it on the roof I covered it with black tape to protect it against sun uv-light.

The test setup was done in our garden on a small ladder and wood pole. The SWR was 1:1.02 on 145 MHz .....without tuning. Great stuff already. I put the 8-ZB on the roof but comparison against the 15 CueeDee was not fair.
The 8-ZB was lower in the pole, also fe with cheap aircell-7 coax and most of all the antenna was looking into the elevation frame and elevation rotator.
The difference was noticable on audio level but further tests will be done.





Some history of the first steps ....testing in the field:

The 15 element Cue Dee was tested in a field to see if we could receive EME signals outside of the city area and we actually recieved our first station OE3FVU, Franz who was happy to transmit a signal for us. In the pictures below you can see an impression of our first test, with help of PE1MYH and PE1PCJ . Equipment was put in the back of my car and we did not use a preamp that day.



Here are some pictures of my prevoius setups when I was still active on 23 & 13cm ATV and also 70cm and 6m with at the bottom a FB13 HF dipole. To make sure all these antenna's would not distroy the antenna pattern of my new Cue Dee I took them all out and have only a dipole for 6m to monitor this band for conditions.





This is the setup put up march 2008 with a Kenpro elevation rotator (modified with digital read-out).
A screen shot of my first EME qso with KB8RQ:


The water proof box for preamp and coax relais. I use Spinner 7/16 connectors and 1/2 inch coax on 144 MHz.



So far the impression of the aluminium I am growing on my roof. No neighbour complaints yet .... but they don't know how crazy I am with this hobby.
What to do next ......well..................I am thinking of a 2x 10 elements DK7ZB as replacement ....let the show begin.

73's Cees PA3FXO

updated on 8-9-2009



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