Saturday, 7 January 2017

Laserbeam delights - Audio DSP filter for CW

Last Monday I had a bit of free time and I have been planning to help Keith G0RQQ put his new audio CW filter into a box for some time. It made sense to use the bench in the workshop here because everything is set up and read to go, Keith preferred that option to destroying the dining table at his place. He has a Laserbeam dual band filter module from Sotabeams and I have to say it is a great bit of kit for something so small. Well worth the money to add a new level to older or wider receivers.

In the classic QRP style Keith wanted to fit the board into an Altoids tin to be the ideal companion to his Frog sounds QRP single band 40m rig. Keith did add on the additional filter integration kit from Sotabeams for an additional £5.50.

VK3YE has done a great look at this and has a video demonstrating its use on home-brew kit. Have a look at the video to get a really good idea of how this works.

We really were blown away by the performance of this little box of tricks when we tried it on the big rigs in the shack. The filter is a brick wall when switching between wide and narrow and it is excellent to listen to. I think this filter may well be on the cards for me to pick one up very soon to play with the rigs here at M0TEF towers.

Sunday, 1 January 2017

Some QRP fun, 40m QRM and the Virgin Media TIVO box

I have been enjoying my festive break from my work and spending a couple of weeks sorting out some projects and radio related experiments. I have fired up the little QRP rigs to work a handful of stations on CW. I never managed to work anything on the SW-20 rig with 2.5w into the butternut HF-9v antenna so moved onto the 40m band using the doublet antenna. It always seem more fun to me to work with the basic kit than with the big station and I seem to get a bigger kick out of working stations from the simple rigs, battery power and wire antennas.

I did work a few stations around Europe but it was at this stage I felt the need to seek out the noise on the 40m band. You can see below the SW-20 with my spare HyMound Key and world map on the bench in the shack.

I promised myself I would get to the bottom of some QRM that I was experiencing on 40m and causing issues to RX of weak signals on the 40m Band. I used my trusty little HB1B with a small telescopic antenna to check where the RFI was coming from, it turned out that the issue was from the TV set.

With lots of fiddling, messing about with ferrite and two angry children who couldn't watch TV one afternoon I tracked the QRM to the Virgin Media Set top Box TiVo that was radiating RFI into all connecting cables and coupling the noise to everything with a connection to the TV and mains.

I managed to solve the issue with many many windings of all cables and the power supplies onto ferrite cores and the S-meter now reads no noise where as before it was S9+ when near the TV set.

All I need to do now is locate all of the TiVo boxes in and around my neighbourhood to do the same. I hope it makes a substantial difference to the DX receiving potential of my station on the 40m band.

HNY for 2017 and may the Sun Spots keep coming to allow us just a little longer for QRP contacts to remain possible, 73 DE M0TEF.