STARTING OUT
My first setup on 4M was a 2M to 4M Howes transverter driven from an IC-275H and a 3 element Moonraker yagi. In choosing the 4M antenna I had 2 considerations :
1) Size (limitied due to small secondary mast for the yagi)
2) Cost (small - cheap ?) I was uncertain what 4M could offer me so expenditure was limited in case of disappointment, however I was not disappointed at all ! ;-) |
 |
| WEAKEST LINK |
| I enjoyed my first few months on 4M (2005), working a number of countries via Es prop. However I noticed that locally
generated qrm was more prolific on 4M than 6M but this didn't deter me. |
| I decided to change the transverter and obtained one from Spectrum
Communications and used the transverter output of my IC 756 Pro to drive it. This turned out
to be a good combination, the 756spectrum scope giving useful indication to activity across parts
of the band and a rig whose operation I was very accustomed to. The weak link though was the
antenna. The construction of the termination (SO239 socket) box was very poor, allowing water
ingress which is probably why the SWR was way off on quite a few occasions. |
 |
| GROW YOUR OWN |
| I had seen a lot of positive comments about Pop YU7EF yagi designs over the past few months and I decided to
investigate. I had a few old antennas lying around including an old 6M 3 element yagi with a 25mm square boom, 1.73M long and I thought I could possibly make
use of these bits to make a new antenna. I had seen a short 4 element design on Pop's website so I contacted Pop and after an exchange of data, Pop came up with a suitable design using available materials (almost) - the ef0404st. |
| After removing the reflector from the Moonraker antenna and adding to the elements from the 6M antenna, they were
resized to Pop's dimensions. The boom/element mounting pieces from the 2 yagis are the same and can be seen on Nige G7CNF's website along with the method used to insulate the elements from the boom. The only missing part was the RFC
(radio frequency choke) and after I scrounged a piece of 60mm plastic pipe from local builders merchant, I wound the RFC and connected it to the driven element. |
The final result being a 4M 4 element yagi which is performing very well despite its small size/gain - a much better antenna
than the Moonraker !
I have left out the "outtakes" in the assembly process to save my embarrassment, enough to say I made a few mistakes during construction
phase. However Pop patiently guided me through them and the result was as he expected. Big thanks Pop !!!
|
| UPGRADE |
| The ef404st has now been replaced wit a YU7EF ef0504-che ! This is basically the ef0504 but slightly adjusted to cater
for my differing materials. This has only been in use since 3rd April 2009 and as yet no pictures to show. However it has been successfully used to work EA6SX and EA5EF (MS)
and inter G (tropo). More to follow.... |
| |
| |
|
4M Antenna