I’ve been quite busy the past few weeks trying to finish some station improvements before the CQWW DX SSB weekend. SSB is my least favorite mode, but if conditions are good, you can have sky high rates which makes up somewhat for all the QRM. My station works much better on CW, but the WW SSB is one of the greatest contests of the year.
First of all, I had to repair my 80/160m mast. The bamboo was a good idea, but when I pulled a little too hard to try to clear the vertical wire from a branch, it snapped off about 2ft from the top. Down it came and in it’s place I put up 70ft of aluminum mast – somewhat flimsy but fine for the 20-30mph trade winds we get here. Before I pulled the antenna up, I hoisted up my GoPro camera and got some bird’s eye view photos from the 70ft level.
As you can see, the takeoff is not spectacular but is not bad either. The biggest advantage is that this location is pretty quiet most of the time. There are moments when I have power line noise to my south, but there is nothing but jungle to the north.
Once I got the 80/160m antenna back up, I finished building my new remote coax switch. My soldering turned out to be a total mess, partially because I was pressed for time and because I used mostly parts on hand, but it works very well.
Essentially, I took my original Beverage switch box built in 2006, and modified it. This switch box uses momentary push buttons to select and latch an antenna, which makes it easy to switch directions quickly. Inside this box is a LM317 with set resistors for R2 to vary the voltage output depending on which antenna is selected. This voltage is then “injected” into the RG-6 feed line through a RF choke and HV capacitor.
At the far end, the DC voltage is “extracted” from the feed line with another RFC, and there a LM3914 chip senses the voltage, selecting an output depending on the value. This output drives a PNP transistor which activates a relay with a 5V coil, selecting that particular antenna. The chip and the relays are driven by a 7805 regulator at the far end. I only use it to switch between 4 different antenna, but it is capable of selecting up to 10. Thus – I am now able to remotely switch between four different antennas on this particular feed line without any additional wires. I do have a second feed line running to the jungle which I still use my standard two-position switch to feed two additional Beverages.
I now can listen in 5 directions: 240 (Africa/SE Asia), 330 (EU/JA), 030 (NA – longer feed line but quieter RX toward NA on 160), 050 (NA – shorter feed line so it performs better on 40/30m), and 110 (SA). I still am planning on installing a Beverage toward VK/ZL before the CQWW DX CW weekend.