Monthly Archives: April 2012

A shitty welcome

Posted by sm2wmv on April 29, 2012 1 comment

When me and Teemu (SM0W) arrived at SJ2W today after a nice weekend in Umeå at an SSA ham meeting and I got down into the basement I was met with 10cm of water on the floor with poop floating around. Luckily it was about 2cm from the granger amplifier so we arrived just in time. After a few hours of work from a clean up crew they did emtpy the crap-well. So now we will see how much I get from the insurance company but luckily no radio gear was damaged. However one room in the basement has got a wooden floor which is now ruined. This kind of sucks the motivation out of me and we will see how much money I will have left after this for antenna projects, might need to put all the plans on hold (aaargh!).

Anyway, I showed a video tour of SJ2W during this ham meeting and I have published it on youtube. Currently it is in Swedish but I have plans to make a dubbed version in English.

Components placed

Posted by sm2wmv on April 22, 2012 Comments Off

Today I spent some time at work again. I felt like putting components to the in-band QSX system and now it is soon ready to be programmed and tested. I realized though that I had forgotten to put a driver chip for the external transfer relay which will be used to transfer the in-band radio to transmit with the run radios amplifier and antennas. However, it is an easy fix just putting a couple of FETs onto the transfer relay and use a couple of the AUX I/O I routed out to a header, in case I needed extra I/Os in the future.

Now I need to order some connectors and switches, so that I can finish up the maneuver boxes and start programming it. I will mount it in a 19″ rack box which will also contain the transfer relay and dummy load which will be used if the “wrong” radio transmits at the wrong time.

[Show as slideshow]

Stay tuned…

Milling PCBs and power splitters built

Posted by sm2wmv on April 21, 2012 Comments Off

Today I spent some time at work. I needed to mill a board for work, but mainly to test that the through hole plating system works properly, since the last time we used it some vias were broken. This time though it looks very promising, but we will see when I assemble and test the boards. I decided to add some own designs to fill the panel, so I did add a sound card interface I’ve designed with a Winkey 2 chip, audio isolators, FSK support via a FT2232 USB chip which creates two virtual COM-ports.

I also added the in-band QSX electronics to the panel, which will hopefully this summer make us able to work in-band QSOs for real. I also got a couple of transistors from a friend at work (from mini-circuits) that I will use to build a 25dB preamp to be used to compensate for the cable loss. We are going to put up a vertical about 400m from the house using RG-59 as coax as a start to test how well it works on 20-10m. We will later extend the system using a small loop with the NULL towards our TX antennas. More information on this when I am putting the system together.

I also built a couple of power splitters. Or actually one of them is for 160m and does not contain the option to power split, its a regular 2×1 switch but with an A/B output making it possible to route it to both 6×2 switches, which means to any of the four operating positions. The other box is for 10m to replace the one at SJ2W which has got some funny problem which I have not been able to find. So I will replace it and see if the problem goes away, if so I will fix that splitter and make a new UN-UN for it with 6 windings so its optimal for 80m. I use 4 windings on 10m. I put the 7/16″ connectors in the lathe to make them fit into the PCBs. The connectors were donated by SG3P, thanks Gunnar! He has probably donated 90% of all 7/16″ chassis female connectors at SJ2W. I did order a few from China, very cheap so we will see the quality if they are good enough to be used at the station.

I also removed some BNC-connectors from old research projects that I will use on the in-band QSX electronics.

[Show as slideshow]

SG3P visited, lots of electronics built

Posted by sm2wmv on April 16, 2012 Comments Off

Gunnar, SG3P made a visit up to us during the eastern holidays. The plan was to build openASC power meters for his station (SK3W) and to build some spare cards which we can use if something breaks at either of our stations. We built seven power meters for him and three meters for me but we use different pickups. I use regular couplers using FT140-61 or FT240-61 cores while he wanted to use 2-3 GHz stripline directional couplers which he had gotten hold of a bunch. They had about 53dB attenuation on 28 MHz and around 77dB attenuation on 160m. The attenuation for 10m is pretty good for the design looking at the signal levels, but unfortunately the level is a bit low on 160m, so the frequency counter does not work properly on 80 or 160m. However, since he was going to use the power meters on a single band this was not a problem.

Another problem is that since SK3W is primarily a M/M station, transmission will occur on 10m at the same time as for example 160m. Since this will result in any reflected power getting into the antennas on 160m from 10m will be shown as 24dB higher, thus if for example 1 watt is inserted into the pickup on 160m from 10m this will result in the 160m meter showing 250w of reflected power, which is quite a big error in the measurement and will for sure trigger a high VSWR reading. So to avoid this I very quickly designed a few 2-pole bandpass filters in Elsie which were just optimized to give lots of attenuation higher in frequency and insertion loss was not an important factor. It took a couple of hours to make the filters and the result was superb when we calibrated the units. Even when transmitting with 100w in the reflected direction through the couplers they as most indicated 0.1w in the 160m pickup.

We did not build any BPF for 10m since I felt this was not needed. Only measurement error will be from harmonics which should be at such a low signal level that the measurement error will be very low.

After calibrating the units Gunnar seemed to be very happy and hopefully it will work well at SK3W. I think he will be very happy for the high VSWR protection feature in openASC, a step of making the stations safe for “The Tord”.