amended 11/23/2009, noon
This year’s SSB contest was great motivation to become a better CW OP.
It should have been obvious when the RigBlaster turned up dead Tuesday evening that Murphy had decided to grace the KazShack with his exuberant best during the SSB portion of Sweepstakes. Or maybe the K.I.S.S.(Keep It Simple, Stupid!) rule should have been followed when working around the hole the absent RigBlaster introduced into the scheme. The audio check test runs Thursday evening would have helped identify the problems, but the work-around was not prepared by then. Such is Life.
The long and short is that I really lidded up the bands with RF infested audio. The problem was much worse with the FT-920 for some reason, but the K2 was not a whole lot better. And yet, people still dug it out. The one curiosity in the entire thing is that the FT-920 monitor sounds pristine. It seems like I read somewhere the monitor on that radio is before the RF sections – but not sure why RF on the line is not causing the audio monitor to be distorted as well.
The DVK audio from the computer was the worst. The pipes suffered from that, since the voice is still not 100 percent from an issue over the holidays in 2008.
My intent was to enjoy the contest, and play with SO2R. As it turned out, it was more like SO(0.33)R – except the audio was crap from both radios. The nasty audio didn’t do much to encourage answers to CQ’s, so most of the activity came down to S&P. Even if I had planned to operate class “A”, I’d probably have ditched that and turned on the packet system anyway – even if it had resulted in a checklog.
Watching the spots was probably the highlight. I spent a lot of time spotting as much as I could find that was not already on the band map, as well as any stations that seemed to be having a slow period when we crossed paths.
I had better luck on 15m than on 20m. 20m is tough sledding with a dipole and low power compared to the other bands. Probably did not spend enough time on 40m. The resurrected 15m/10m rectangular loop paid off with a few mults I think I would have otherwise missed.
Since I had time to toy with the second radio(in rx anyway), I came to the conclusion that SO2R on SSB is going to be several orders of magnitude more difficult than on CW. It seems it will be a whole lot simpler to mentally filter out CW signals on either ear than with SSB.
With CW it’s just a stereo pile-up. With SSB it is more like Donald Duck talking with Peanuts’/Charlie Brown adults at a Van Halen concert, all played to the background melody of RTTY and slow scan tuner-uppers.
Quoth Snoopy…”Bleh”.
It is always curious to see which sections will be left on the table. No Quebec? That’s not normally one that goes missing. Rhode Island is a bit easier to miss from the QTH. The other three, MB, BC, NT, are sections that are “the usual suspects”, so missing those is no big surprise. AK and PAC turned out to be easier than normal when I stumbled upon stations from both before they were spotted. I picked up the first AB station in a similar manner, but later worked a couple more. I had an OK station call me during my one 40m run, but I was not able to copy him through the “donald duck” QRM. The 6’s were all tough with the poor audio.
Almost zero time was spent in packet pile-ups. Three calls then move along. That was probably necessary with Murph’s bad audio on top of the low power crappy antennas. No one trying to manage a pile up is going to waste time on a weak station with bad audio. Thats not to hard too understand, and it sure makes sense. So there is even less point in wasting time that way than normal.
Missed:
RI QC MB BC NT
The Good:
- The SO2R switching performed flawlessly. I made a lot of use of the “follow active radio” feature when S&P.
- The momentary contact buttons on the SO2R control are a great feature. It is really easy to jab a button to concentrate on one radio. This is especially true in SSB, because SSB is harder to separate mentally than with CW.
- Need to implement foot switches for that momentary audio switching, as K4QPL suggested. That’s a great idea.
- Lots of fun spotting folks otherwise lost in the cracks.
- If his serial number reflected actual Q’s KA1ARB’s station was kicking butts and taking callsigns. Nice to see somebody was having a good contest.
The Bad:
- Murphy. ’nuff said.
The Ugly:
- Missed Thursday evening “test” contest, which may have helped fix the problems.
- OK – maybe not quite ’nuff said. Initial cables for SSB audio seem susceptible to RFI. Need to solve that. Prefer to have the RF at the end of the coax and on the antennas rather than floating around the shack!
- Computer DVK – crappy audio. WHY? Just another RFI problem?
The Final Damage:
Summary: Band QSOs ------------ 160: 0 80: 191 40: 93 20: 35 15: 42 10: 0 ------------ Total: 361 Sections = 75 Total Score = 54,150
Let me know what you find out concenring the RF issue. Same problem here on 75m. I had two antennas on the band – inverted v and windom. The windom would totally knock out my voice macros above 3800 and distort them below 3800. Never had this problem on cw or rtty, but did have wavy lines on monitor. I’ve got over 20 ferrite chokes snapped on everything, but no match for ssb rf!
73
Bob – K3MQ
Hi Bob,
Some background on the problem set up here.
I brought some of the problem on myself. When the Rigblaster turned up dead, I did a quick operation on my mike/DVK switch box to add an isolation transformer for the DVK input. In the process of re-routing the audio cables, I had to make them longer. It is a combination of shielded audio cable and cat-5 twisted pairs.
I expected the DVK to be the worst. It was. The surprise was the audio in the FT-920 monitor sounded pristine, but the actual transmit audio was reported to be the worst of the lot.
Late in the contest, I realized the box of ferrites I had just got in the shack ‘just might’ help. After wrapping the cat5 through a couple of them, and wrapping about five turns of one of the shielded cables through another pair, the mic input on the K2 seemed to be much better. Maybe I should add some beads inside the switch box and the SO2R box too.
I expect I need to choke the feedlines outside the shack somewhere, but I have pretty good matches on all of the antennas. Time to re-examine all of the inside connections too, and try to re-route cables/interface boxes from everything that might be hot with RF. The 80m antenna is as far away from the shack as is physically possible, but it is broadside to the house. I expect choking the feedline at the Sixpack and again at the shack entrance might help.
If I figure out the real problem, I’ll follow up. My approach is that ferrites treat the symptoms. That is better than nothing, but I want to eventually figure out the real source of the problem.
I have had problems with RF in my audio as well. First with my dipole on 80m, and no amount of ferrites in the shack would cure it. When I finally wound 20 turns of coax on a 5″ PVC pipe as a balun at the dipole feed point, all problems went away. This year I put up a 40m dipole with no balun, and of course my audio problems are back…
Kaz, thanks for all your write ups. I really enjoy them!
Thanks Rob,
I’m hoping that I can insert the baluns at the A and B terminals of the SixPack. I have the switch centrally located, and it would simplify things to put chokes in two places. If thats not sufficient, I think I’ll also try choking at the shack entrance in addition to at the SixPack.
I think it would be best to add them at the antenna feedpoints, but it’s a real chore snaking some of the antennas throught the forrest. As they get knocked down and need repair, I’ll probably insert individual chokes on each antenna.
BTW – Thats one nice score from KA1ARB! I tried to freshen up your spot when I ran across you guys. 80m was funny. The first time I heard you, the signal was weak. I didn’t call then, figuring my LP would not be heard(like last year). A couple hours later you were !!much!! louder. We’re so close, I didn’t expect there to be that much difference as propagation changed – I figured it was always ground wave.
Must have been wrong about that! Very interesting.
Great writeup. I didn’t notice any problems at all with your audio.
Of course, I was 8,000 miles away in ZS-land with no radio. That could have something to do with it.
Hmmmm. Now that you mention it, I didn’t get any complaints from any of the others who did not operate. I was limited just to the small group that actually found me on the air. Whiners. 😉
Here’s what I finally did to end the RFI issues.
Problem #1:
Power supply – One source of RFI problems was sharing the radio power supply with the SO2R box. I put the SO2R box on a separate wall wart, and that helped a lot.
Problem #2:
SO2R box cabling. Because of the shack layout, the SO2R cables are all pretty long. Putting ferrites on all cables more or less solved the problem with the FT-920. Still had RFI on the K2.
Problem #3:
.01 bypass caps on all of the relays and DC connections in all switch boxes.
Problem #4:
Didn’t really have ferrites on ALL of the cables. I really didn’t expect the PTT line to be an RFI issue, but solving the RFI problem on the K2 required ferrites on both ends of the PTT line(at the radio mike jack, and at the relay output in the SO2R box), as well as on the foot switch itself(at the SO2R box). While I was at it I added ferrites to the DC power cords too. It took three ferrites right at the mike jack on the radio end, so that may have been the source of ingress.
It is possible I also did something else which inadvertently helped solve the problem, but after a couple of weeks of head scratching and trial and error, I can say that UNdoing any one of #1 thru #4 will re-introduce RFI.
The problem with the PTT line really has me perplexed, but I guess it is in close proxinity to the audio cable at the radio mike jack, so any RF on the PTT line is probably getting into the audio there.
After all of the trial and error, my impulse is to add ferrites on all control cables on both ends, and immediately after they enter/exit each device.