DIGITAL MODE AUDIO AND OTHER AUDIO RELATED PROBLEMS
When speaking about audio going into a radio remeber that is what modulates your radio and garbage in is garbage out.
First thing to do like in BPSK31 is setting up the audio were it does not over drive the rig and make it flat top or create audio harmonics. This can be achieved by using the Windows Mixing program, (little speaker icon on bottom right of desktop or control panel sound devices)
You need to find the wave out or main output slider also by keeping the audio levels down you will not over heat the finals as much as well.
Now keeping that other window open bring up your software and use BPSK31 now dial your RF output to 100watts, ( I know we do not need 100watts on bpsk31) After dialing in 100watts key up for a time period and take note of the power level is it sticking around 100watts? Well your audio level is probbaly too high, start lowering the out going audio till maybe around 75 watts or so, now type something, Is the power meter bouncing up towards 100watts? If so, well you probably got it very close now. now turn on your ALC meter does it have no reading at all? If so then your audio is almost perfect, You might want to check with a few on the air contacts too see what they are seeing , I mean someone that will tell you the truth and also someone on a steady path to you as well, because weaker signals and QSB will hide problems in the noise levels. (as reminder you can dial down the RF power knob to what ever PEP you want it set for, I would recommend a fairly low wattage setting especially if you are a ragchewer and plus you should always use the smallest amount of power required in the first place. MYTH: RF POWER EFFECTS SPLATTER etc.. NOT true except when the rig actually has a problem , but remeber garbage in is garbage out. It doesn't matter if it is 1 watt or 1kw.
Ok what if I did set the audio correctly and some one complains to me I have a buzz in the audio or have harmonics from my audio on the waterfall, This could be due to a ground loop.. Ground loop get introduced when two or more ground points are not the same quality of a ground, there potentials are different. One way to solve this is tie all grounds to one common ground ( not daisy chained) .ie. atu,s.w.r. meter,radio etc.
What if someone complains I have a very wide and spread out type of QRM and or maybe have some extra noises in the actual audio heard by human ears that just do not sound right at all, This could be from RFI, RF energy can get onto the chassis of equipment or ride on the audio lines etc, It is a good idea to use isolation transformers to keep RFI off the audio lines and optoisolators on the PTT line to keep RFI off the PTT line
After you have nailed down your audio levels and such make note of these settings to always put them back in the same positions, Using a accessories ports make it easier not to accidently bump a knob etc.. In some software such as MixW it can remeber the audio level you set inside of the software itself and keeping the sound card set to fullblast all the time, makes life easier that way you could say.
It is always good practice to use ferrite beads on all the audio lines and also the PTT line if you have one..make sure you use a good earth ground for your equipment. Also grounding the case of the computer to the radio ground might even help with CPU type of noises in the RX of the radio.
Using a good quality sound card is always helpful as well, I have owned about 5 sound cards and there has only been one I was impressed with, while viewing the signal in full duplex on the watterfall, no side bands, harmonics etc compared to some other sound cards I have used before. It was a Turtle Beach Santa Cruz , but now they do not support the card anymore (. Having a card that has very high SNR is helpful 100>SNR and having a low THD%(Total Harmonic Distortion) is helpful <.05% on how clean the signal will be on transmit
An example of a slightly over driven signal marginal signal strength
An example of a over driven signal with strong signal strength