After many QSO's on 6M, usually via ES or Tep, I wanted to try 6m eme.
My first point was to receive some signals with my current setup.
So I started monitoring the moon, and yes I could receive some stations,
the strength of the signals were between the value of-27dB and-30dB
and this with my 4 element yagi. After this montitoring I was ready
for a sked with W7GJ.
My setup was a 4 element Yagi without elevation system
and like I think without any profit of ground gain.
During two days with good moon conditions we tried to make a complete QSO unfortunately without success. The day after our test I started monitoring W7GJ qso's with other stations. Surprisingly quickly I discovered the following: W7GJ eme signals were received when the moon was between 60 and 30 degrees. With this new experience, we decided to make a new sked. And yes, this time successfully, after a few minutes the QSO was complete. The first 6M eme qso between The United states and The Gambia was a fact. The signal strength of the received signals were -28db and with the moon at 56 degrees. An incredible qso knowing that thanks to the reflection of the roof this was possible, never seen. After this particular qso I decided that there were maybe even more possibilities with a better antenna system.
After some research and with the of resource of materials that could find here in C5,
I decided to build myself a long boom 6 element yagi.(model of DK7ZB)
To build this antenna is fairly simple. For the balun I used 75ohm foam (black tv coax) coaxial cable. Detailed information for building this antenna can be found on this website : Longboom antennas for 6meter.
My setup for 6 meter EME:
- 6 Element long Boom yayi with 10.4 dBi gain.
- TS2000 + home brew pre-amp.
- coax loss 0.7 db
- Amplifier: 600 Watt on JT65A mode
With this setup, I started again looking for EME stations. Several stations were received and that with a signal strength between -22db and -29db . W7GJ and G8BCG where received with-22db between 30 and 20 degrees and I think there was some small ground gain . A sked was made with Peter, G8BCG, and after a few minutes the QSO was complete with my best reception signal -27db and the moon was at 4 degrees. I was very hopeful to work more EME stations, but .... However, after several sked with other stations, it was not possible to make a complete QSO. I received in many cases their calls with values between: -27 en -29 db, but usually the did not receive any signal from my.
The only way to find out for more successfull EME QSO : building an elevation system for my long boom yagi antenna or change my 6 elem yagi. So I decide to start first with a elevation system.
I build myself a low cost elevation system :
- Aluminum plate, a few screws, four heavy door hinges and some U-brackets.
- A satellite moter with controlunit : actuator and GBox V-3000
With this setup I have an elevation from 0 to 45 degrees and these are all stored in the memory buttons. In this way you can navigate quickly.
So after setup the hole system I found out that there was no improvement . There is more than one reason for this problem , one of this : I lost the small ground gain when I elevated my antenna . Secondly the 6 Elem , with a 75 ohm match (Foam-PE, V=0,82 CATV 1,23m ). It looks like that I lost a lot of power in this match, I make a test : my 4 elem Zx Yagi with gamma math handle my 700 Watt without any problem compared with my 6 Elem , the amplifier switch himself to protection mode in full power mode.
So conclusion: Either I must change the match ,using a better coax cable, like RG11, or mabye a better solution , building a new long boom yagi , such as a 8 elem without a coax match but using something like a Pawsey stub, as example G0KSC Antenna Balun . This balun is not limited in power handling, is easy to make and simple to install. So up to the next step ...in the spring of 2014.
After the above discription from my expierience at home, I dismantle my 6 elem yagi and install
the hole system include my elevation system on my car on the beach. Just one think, there was no power
on the beach from where I will operated with my portable station , so I rent myself a African generator !!!!!!!
A sked was in progress with N7NW and K7CW. Like you can see
the two stations are well receive starting from 28 degrees till 4 degrees with best signal around
10 degrees . A big difference, at home not one single trace from both stations and here on the beach
these amazing JT65A signals. So I was verry optimistic to complete this two contacts however,
again a small problem, the generator was not able to handle the amplifier.
In spite of that fact, I wil go back to the beach , and thry to find a place where I have a normal power line . But that's another story.
I decide to build my own yagi for several reasons. One of this ,the hole antenna must be with me in the plaine to The Gambia and the maximun alowed lenght of lugage is 1.50 meter.
The 30mm profile are set to 12,5 Meter length with the 25mm profile ,this profile is 400mm long ,so on each side we put 200mm in de 30mm profile en drill on both sides 2x 6mm holes . With the 1mm alu plate, I make very small strips and put those between the 30 and 25mm profile so that there is no space between, and connect each lenght with 4x6mm inox bolts.
Drill 8 holes 6mm for the elements .
Make 2 x L profiles 60mm long for the drive element .
The same work for the elements , elements 10mmx1mm iside with a 100mm of 8mmx1mm, 1 drive element 13mmx1,5mm iside with a 100mm of 10mm the other with a 10mmx100mm of nylon rod . (I found this very cheap in a local store , a stick from 1000mm used for protect a grazing cattle with electric kabel to keep there horses inside . ) For all other isolators for the elements have a loock on G0KSC online shop .
The mast plate is 3mm thick and 150mmx150mm on the mast side and 150mmx60mm on the boom side and connected with 4x6mm bolts . The boom is between this two mast profiles.
To keep the boom horizontal en straight I used 4 ropes, connected from the mast point in V-form to the boom . This is the only way for this 12,5 Meter long boom .
The balun is just a flat Alu bar with a length of (300 / 50.150MHz) / 4 = 1495mm . I chose 50.150 as a compromise between 50.100 and 50.200. The balun is screwed on one side to the DE1 4mm bolts connect one end at the feedpoint (inner core) . The other side is srewed to the boom . (Don't forget to use anti-corrosion paste on the joint!)
I read now some negative comments about this Pawsey balun, but here he is working gud .
I dont buy a pipe bender ,just buy this 2 loops on G0ksc online schop . Very Easy !! And ready .
Assembling and testing :
Putting up just a bit and connect the Ecoflex 15 coax . On the MFJ-259B you can see my first the result .
A special thanks to Justin , G0KSC and Chris , G3WOS for they exellent information on there websites. With there info you can build your own 6 Meter antenna very easy. Also many thanks to Peter, G8BCG for his support.
To build yourself a good 6 meter antenna is not difficult , only here in C5 land it is not easy to find materials .
|EME INITIALS .|
|Initial||Date and Time||Info||Callsign||EME DXCC||New DXCC|
|1||11 May 2011||Qso screen||W7GJ||Y||Y|
|2||04 May 2012||Qso screen||G8BCG||Y|