On 2-1-2013 3:41, Steve W3AHL wrote: Here's my "top 10" things to look into:
If you have your digital audio going into the ACC connector, I would try unplugging it (and all other cables going to your computer, such as CI-V, etc.) when you get a bad report. The ACC audio input is very sensitive to RFI and ground loops. And RFI can be fairly sensitive to frequency, which may explain why it is intermittent. And this is what caused the bad audio! Thanks! The other problem with the 7K is that when you use the ACC audio input for digital, any noise in the room gets picked up by the mic and mixed with the digital audio, unless you remember to unplug the mic cable.
The DATA port is better for digital modes since it requires a higher drive level, but maybe that's what you're using already. When I use the ACC port, I put a 65K resistor in series with the audio input, connected inside the shell of the DIN-13 connector at the radio. That increase the audio level on the line to about 400 millivolts. Will using a Signalink USB or Microkeyer help in this situation? Or is using the Data port the solution, regardless of what interface I use? Since the 7000 came with a Data port connector, I could replace the big Acc conector with the smaller Data connector. You didn't mention what your mic gain setting was. I normally use about 30%, with the mic about 1-2" from my lips and off to the side a little. Compression will greatly increase any soft background noise in the room (making my big scope's fan sound like a "howling vacuum cleaner"), but you said that turning off compression didn't make much difference.
The ALC meter shouldn't be peaking at more than half of the green bars, although the noise you describe doesn't sound typical of overdriving things.
The next thing to try is adding common-mode chokes to the feed lines. Depending on what type of antenna and feed arrangement you have, you should add a common-mode choke (either a current balun or HF-rated ferrite chokes) at the antenna's feed point. If that isn't practical, then before the feed line enters the house and again on the output of the tuner.
Do you have a good single-point RF ground for the shack, with each part of the radio system (radio, tuner, computer, etc.) grounded directly to it with a relatively short, heavy (#6-8 AWG) wire?
Another common cause of RFI (especially intermittent) is loose feed line connectors. On PL-259's the point needs to be seated in the notch and the shell screwed down tight. Also, a poor solder joint on the braid (or broken braid where it was nicked when the outer jacket was stripped) to the connector shell will leak a lot of RF to cables near the radio back panel.
Your TBW settings could probably use some tweaking. I would suggest wide=200-2800, mid=300-2700. I don't use narrow, but having 500 for the low cut is too high, in my opinion, so perhaps 300 or 400-2600, depending on your voice. But that isn't causing your noise problem.
Without knowing more about your antennas, feed lines, grounding and their layout relative to the shack, its hard to be more specific.
Steve, W3AHL
--- In ic7000@..., Robert Elsinga <robert@...> wrote:
Hi all,
I mostly do digimode on HF (and FM via repeaters on VHF/UHF), but on
occasion I do some phone on HF. It has happened to me a couple of times
that I get a comment on my audio (without asking), that it sounds "bad".
One user described it as "like a howling vacuumcleaner". Today I did
some test with a nearby HAM on 80m (an simultaneously via a repeater on
FM) and he didn't notice it being bad. Okay, speaking directly into the
mike revealed some plopping sounds and the digimode audio cable produces
some hiss from the computer (cheap USB sound dongle and direct couples
audio cables, no money for a Signalink USB or Microkeyer yet), but
nothing more.
At first I thought (and was suggested) that it could be RFI, but I also
got bad audio reports on 40W or less. And, moving the MFJ926B from 5
feet to 25 feet away from the IC700 didn't make a difference.
Then I suspected the Compressor and TBW settings. And okay, Wide
(100-2900) sounds better than Mid (300-2900) or Narrow (500-2900), but
neither sounded "bad". Even the compressor had just a minor influence on
the "badness" of the audio.
Until now I got a handfull of spontaneous bad audio reports, one from 15
miles away on 80m and the rest from DX stations (Lebanon, Egypt,
Switzerland, to name a couple). IIRC I used Wide/Compressor on all
QSO's, but switched off the Compressor on all occasions and that didn;t
help that much.
In digimode I get an occasional QRZ/AGN, but most QSO's are 100% copy
(unless the remote station is on the edge for me, but even them I get
mostly solid reports).
So, do any of you recognise this bad sounding audio phenomenon? If so,
any suggestions on how to avoid it? I'd like suggestion that don't
involve buying other microphones though. ;)
--
Robert Elsinga =8-)
PC5E - www.pc5e.nl
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