Tuesday, 23 June 2015

Notes from the Shack - ARRL June VHF Contest

June is a great time for 6m, with Sporadic E openings occurring from time to time. So far this year, despite spending a good deal of time listening - or in the case of JT65 mode, watching, I've had very few contacts. Getting Guadeloupe, a new country for me on 6, out of the blue was a nice surprise though. New countries don't come too often for me on 6, and this one was my fifth, although one of them has not confirmed yet.

This being my first VHF contest, I didn't know what to expect. I was hoping that there'd be plenty of stations to choose from, although my home-made loop antenna at 20' isn't exactly world class. Before the contest I decided to resurrect my Softrock IF Lite SDR receiver to drive a spectrogram - or panadaptor if you prefer that term. This goes into a newly acquired 192KHz bandwidth USB audio interface for display using the SDR Sharp software. The Softrock is now in a project box purchased at Dayton, with a 1/4" stereo phone plug for the audio interface, a BNC connector for the IF cable, Power Poles for the 13.8 VDC input and a power switch. The receiver draws very little current but now that the station has battery backup it's best to eliminate even small current drains.

Initially, SDR Sharp showed many spikes in the signal of up to about 25db, and also a hump of about 25db for 3KHz on either side of DC. Neither of these are desirable. A clip-on ferrite on the cable between the receiver and the audio interface reduced the spikes to less than 10db which is a lot better, but the DC hump was still there when the contest started. That will have to be investigated another day, and hopefully it will be solved in time for Field Day. Even with these limitations, though, the spectrum display proved to be very useful in the contest.



The above photo is before the choke was installed. Below is how it looks after installation. As you can see it made quite a difference.



Only one contact was made on Friday evening, which was with John VA3JI, at a distance of about 10km. I heard C6AT in the Bahamas as well, and he copied part of my call before fading away forever. That was the only Sporadic E activity heard the entire weekend.

In the end, there were 5 Canadian stations and 3 US stations in the log, all but one using CW, including Mike VE3FGU up in Keswick. The 3 US stations were all in New York, which surprisingly is a new state for me, most likely courtesy of tropospheric scatter. One of the New York stations was in my own grid square, and all the Canadians were there or in FN04, but the other two New York State stations were new. So in total my log showed 8 stations worked with 4 multipliers for a whopping 32 points. The great thing about a low score is that I have a very good chance of beating it next year!

VE3UBL/B, our local 6m beacon, was a constant companion on the spectrogram. The morse code could be read directly from the display. All the contacts were found using it. I found it to be about as sensitive as my ears, but searching the band was way faster visually. The next thing I need to work on after getting rid of the hump is calibration of the display against the K3 so I can read the frequency directly instead of just having a relative indication. At $25 for the kit and $10 or so for parts to mount it is a much less expensive option that the $1,500 or so for the Elecraft P3 (yes, it's cheaper than that, but with US dollars, shipping, HST and the fact that I'd be compelled to buy the external monitor option, it would be about $1,500 by the time it was installed in the shack, plus another $200 for a dedicated monitor).

No comments:

Post a comment