Monthly Archives: September 2009 - Page 2

160m almost finished

This weekend we managed to get a lot of work done on the 160m vertical. I (SM2WMV) started on Friday evening to build the ginpole which we were gonna use to put up the tower sections. It’s made out of steel which makes it heavy but at the same time I trust it to 100% even though I have welded it myself. It wasn’t that extremely hard either to get it up in the tower, even though SM2LIY complained a bit about his hands hurting 😉

We started on Saturday to raise up the first 6m by hand with the ginpole attached to the top. After that we pulled up the second tower section so at the end of day 1 the tower was 12m high. On Sunday SE2T showed up to help, except cutting down trees he did help putting up the sections for the 160m vertical. After Sunday was over we had pulled up one more section and after feeling that the tower was very wobbly I climbed up on Sunday evening to attach a few steel guy wires to secure it. After that I had run out of fuel, probably since I had to lift the last tower section the last 5cm by hand, since I had attached the ginpole too low and I got to pissed off to hoist it back down and up again so I did some power lifting instead 😉 The attached guy wires did make it easier to climb (mentally) on Monday when we put up the last 6m of tower section. Now next weekend we will put up the pipe in top of the vertical, which will make the vertical pretty much full size. We will probably make it a little shorter so that we can use a coil to ground, making the antenna DC-grounded.

Here are some pictures!

4×8 beverage switch tested

I made a cable to temporarily set up the beverage switching to two radios before the openASC control system is implemented into the station. I decided to use the LPT port of the linux server running at the SJ2W site and I did an easy to handle web interface to switch between the different beverages, just 8 click buttons which each select a different beverage antenna.

The 4×8 switch which can be seen below can route eight different antennas to four different radios. One can select one beverage at the time on each radio and by adding bandpass filters to each radio one can listen to the same beverage without any 3dB drop. That is still to do though but a prototype has been tested and it seem to work, based on slightly modified OH2U filter design.

I did some measurements on the beverage box to see what kind of cross coupling there is between the different channels. Since I am limited to two layer boards the routing is not easy to do in a optimal way RF-wise but considering it’s meant to be used on lowbands it is not as big problem as on the other 6×2 switches I have designed.

The insertion loss on 40m was typically around 0.17dB while on 160m the insertion loss was around 0.06dB which is just fine for RX antennas (even for TX…). The cross coupling between different antennas were as worst -45dB while using radio 1 was using ant 1 and radio 2 was using ant 2. When radio 1 was using antenna 8 and radio 2 was using antenna 1 the coupling was -63dB which is just fine. When radio 1 was using ant 8 and radio 2 using ant 4 the cross coupling was -65dB. So it varies a little depending on ports but the “bad” combination seem to be channels right beside each other. One could maybe improve this by soldering copper planes between the relays but that is too much work with 32 relays. The cross coupling between radios were typically around -50dB on 40m. All values listed above if not noted otherwise was measured on 40m. On 160m the cross coupling was typically -90dB or better except when having a port right beside each other, which reduced the coupling to around -60dB.

This weekend we’ll hopefully hook the switch up at the radio QTH so stay tuned for the end result.

Cable support

Today I felt like doing some digging so I started with filling the hole around the tower foundation for the 60m tower. After that I felt like mixing some concrete so I decided to fix the post which will support the cables for the 60m tower and also hold a cabinet with various electronics and connections for the tower. I first thought about using regular lumber but decided to use a steel pipe instead, this made it a lot easier. I just took a pipe which was around 4.5-5m long and put it about 60cm down into the ground. The hole size is about 120l which means around 250kg weight when it’s filled with concrete. I also added a frame around it to make it look a bit nicer.

To get the tubing straight before pouring the concrete I used a steel tube which I connected with help of a boom to mast plate for a 10m yagi and to the vertical post I used a CUE DEE special clamp which is a very neat thing. After I had it straight I started the concrete mixer and mixed around 130l of concrete to fill the hole. I sure don’t think that the post will buckle to the weight and tension of a few 7/8″ cables 🙂

Here are the pictures

Beverages “finished”

Now all 8 beverages are pulled out to the planned length. We have still not connected the coaxes or baluns. I have a roll of 500m RG-58 on the way so hopefully by next weekend we’ll have them all connected. Now I need to finish up the 8-port beverage switch which is able to route any beverage to 4 radios. It will be very interesting to compare the noise levels on the different ones and also how well they work on 160 and 80m.

These are the finals:

Beverage, 580m (1900 feet) long towards West Coast US (330 degrees)
Beverage, 550m (1800 feet) long towards East Coast US (300 degrees)
Beverage, 320m (1050 feet) long towards South America (260 degrees)
Beverage, 220m (720 feet) long towards EU/Africa (180 degrees)
Beverage, 320m (1050 feet) long towards South East (120 degrees)
Beverage, 450m (1480 feet) long towards Australia (80 degrees)
Beverage, 700m (2300 feet) long towards Japan (45 degrees)
Beverage, 800m (2620 feet) long towards North (5 degrees)

Tomorrow work will continue with the beams.