[CQ-Contest] Dirty signals

K3BU at aol.com K3BU at aol.com
Wed Dec 15 12:16:58 EST 1999

There seemed to be quite a few of them in 10m contest. The better the 
propagation, the worse they look. If one's signal is a picture of the 
operator, then it is not a pretty one.
    We should really check our signals before firing up into the heat of the 
contests. The reasons are obvious, unnecessary interference (unless one wants 
"dirty" elbow room and clear frequency - illegally), risking disqualification 
and reflection of the operator's ability. Also, things happen during the 
contest or operation that can make good signal rotten, without us knowing it.
    Definitely, the "offender" should be told. You don't always know what is 
getting out of the antenna. You might hear it OK on the rigs monitor, but 
amplifiers and bad connections can add nasty things to the quality of signals 
and harmonics. If told, especially by the few stations, one should seriously 
check it out and take corrective action. Some have thick skin or do it on 
purpose, they will not correct the problem and keep going, offending the rest 
of us.
    Way to check the own signal is first to listen on built in monitor, to 
check the audio and the amount of compression. Too much compression might 
look "good" on the output meter, but can actually take away from the 
legibility. There are some "champs" that are louder when they are not talking 
into the mike, rather when talking. Negative compression? It can happen with 
some ALC circuits. Do the final check with some distant station (with good 
radio) and ask for signal quality report. That should do for preparation 
before the contest. The same goes for clix on CW. Know your signal. 
    There are also problematic "reporters" like I experienced during WW SSB 
on 80m. Bunch of next door old timers on the QRU weather net with Eico 753 
"latest" model, complaining that "you are too wide and running too much 
power". Subsequent checks with known contesters confirmed that there is 
nothing wrong with my signal (besides being loud locally with 3 el wire 
beam). I also got some reports that my signal audio or CW tone was raspy. At 
the times I was feeding two antennas simultaneously and phase shifts due to 
propagation would cause beating and aurora like sounding signals. Again 
switching to one antenna and check with reputable station confirmed no 
    But then AFTER the WW CW contest I was told that while on 80m I had 
harmonic on 40m and even small pileup going there. I wish I was told about 
this DURING the contest. I could have made quick checks and see if the 
harmonic disappeared and what caused it. I will investigate it. At the time I 
was using IC781 on transmit and also used split RX feature. I have read that 
IC775 had similar problem when using dual VFO for receive. Normally, 
synthesized rig and linear amp that is not overdriven should not generate 
appreciable harmonics. Anyone else had similar experience? 
    So when "inspecting" signals, first check that your RX is OK and not 
being overloaded (TS870 before filter mods used to do that), use the 
attenuator, bring the signal to about S9 and see how it sounds. Make sure you 
have noise blanker (!) off, DSP off, notch off. Then if signals sound rotten 
do not hesitate to inform the "proud" owner. When few reports are received 
and verified, the corrective action would and should be taken. Perhaps those 
persisting on driving "garbage truck" on our radio highways chould be put on 
the "dirty signal honor roll", maybe it would help to clean up the act. 
    Beware of small and low drive amplifiers, they can be overdriven by 
simply line voltage going up after midnight (or down) and working condition 
being changed by the fluctuation in the line voltage. 
    To check compression level on SSB, the best thing is to step on the foot 
switch and keep quiet. Watch the power meter. If you get deflection more than 
just a hair above zero, then you are transmitting background noise and QRMing 
yourself. Turn the mike gain down untill you see just a hair increase, then 
adjust amount of compression while saying 'ooooola. Some ALC systems (like 
TS870) can actually cut the average power down if too much compression and 
drive is applied.
    Lets keep it clean and make more room for new little pistols.

73, MX & HNY2K

Yuri, K3BU, VC1A

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