Monthly Archives: December 2012

Shack makeover

The radio shack has gotten so messy lately, that it felt like it was time to redo everything properly. Now when all equipment pretty much is the same regardless of contest it is easier to put cables etc more permanent. Priority #1 will be getting the remote up and running and the rest will have to take as long as it takes before everything is working to 100%. Position #1 and #2 (SO2R position) will be done when I have the support op fixed which will be a high priority now so its done before WPX SSB.

SM2XJP helped me all day so it went pretty well and part of the stuff is now done but still lots more to be done.

I also went out to remove some snow which had stuck to some guy wires.

Some winter pictures

I have been playing around getting rotators to be controlled by the openASC system. Right now I have installed it on two antennas (5el 15m, 5el 20m) and hopefully before the Christmas break is over I will have it installed also on the 60m tower and the 10m stack. I rotate it either with the openASC box or with the openASC Controller software which communicates with the box over ethernet and can be used remotely. By just selecting which antenna I wish to rotate and clicking in the map the rotation of the antenna(s) start.

openASC Controller run in Windows 7

openASC Controllerr run in Linux

Here are some winter pictures,

W7IUV preamp and rotator boards

I’ve been in the mood for building so I built a W7IUV preamp that I am going to test if it works better than the MMIC version I tried earlier. That one works too but I am hoping to get even better IMD performance from this one, we will see.

I also assembled two rotator boards for the openASC system. I intend to get the rotating working via the openASC system during the Christmas break which would make remote operating even more fun! Now I have four boards so I can convert all rotators and the easiest one is the alfa spid where I only needed to mount the bus interface, uC and the RS232 converter since its a serial controllable rotator. The other ones are the 3-phase motor of the 60m tower (24v relays), the YAESU G-1000SDX and an old EMOTATOR 1103MMX where I will just interface it against the push buttons and the potentiometer for indication. SM0SVX has written a great piece of software for the rotor control @SK3W and I have written the interface so it works against my hardware as well now.

I have decided to remove the pulse sensor on the 60m tower and put a 3-turn 1k potentiometer that I got from SM2O. This will make the system more safe even if the rotator board has got a big super cap which makes it possible to save the current position before turning off. However it can still lose pulses because of RF etc, so the non-volatile behavior of the pot will be more reliable.

And even more filters…

People might think I am crazy building all these filters all the time. But I think it’s really fun and I learn a lot by doing it. Now I think as I wrote in the previous post figured out how to do the filtering at the station. These RX filters will sit in the RX-path of the transceivers and I might do so that they are switched in depending on which bands the other radios are on. For example if the run station is on 20m then the 20m filter will be switched in on the mult stations and if one mult station is on 15m then that filter is switched in on the other mult plus also the run station. That way I will have the least amount of insertion loss possible, since it’s no need to use filters on bands which does not have any radio transmitting on them. Not that the insertion loss is high, but every 10th of a dB counts, at least in my opinion.

I first tried to build the filter on a PCB that I milled but it was extremely hard to tune it and I could only blame it on coupling between the filter nodes and I did not get near the performance that I expected from simulations. The filters are 5-pole chebyshev notch filters. So to test my theory I built a box with chambers and added pole for pole into it and measured and already with three poles I beat the old result and a lot better insertion loss as well. When adding two more poles the result was close to the simulations and I am very pleased with the performance.

Now I need to figure out if I should be pleased with just three poles or if I should go for 5 poles, we will see. I think I will make a bunch of filters in a big box and make chambers for it, will be a lot of work but I think it will be a great result and totally worth it. But I will make another test first, and that is to use toroids on all five inductors and that way maybe the coupling will be so low that I don’t need to use chambers, it’s worth a try because it would make it A LOT easier to build them.

I also put a Webswitch which we got sponsored from Microbit 2.0 AB into a box, that will be used at the station to be able to switch gear on and off over ethernet. That way I can reboot stuff if needed and not needing to have power on to the openASC system the whole time etc.