K3/0-mini poor audio

[SM5PHU]

Does anyone here have experience in the K3/0-mini?

When I connect the supplied cable from the K3/0-mini to the AUX/MIC input at the control RRC and put the radio in TX, a high level of noise is introduced. This noise almost entirely masks my modulation in SSB.

I don't experience the same noise level if I disconnect the K3/0-mini from the AUX/MIC input, and connect my microphone directly to the RRC instead.

I have changed power supplies around, to eliminate that possible error source. Also there's no problem running my remote K3 locally.

I notice a previous post about similar problems, but that thread didn't end in any conclusion.

73,
Jonas/SM5PHU

[dj0qn]

Jonas,

You may wish to put this on the Elecraft main reflector instead, since this is likely an Elecraft problem.
Brandon at Elecraft can otherwise help you if no one answers right away there.
http://mailman.qth.net/mailman/listinfo/elecraft

73,
Mitch DJ0QN / K7DX

[SM5PHU]

Thanks Mitch,

You're right, this is most likely an Elecraft problem, rather than a Remoterig problem. Or (less likely, but still) a configuration error on my part.

Since my K3/0-mini is under warranty, I sent a mail to Elecraft support already last week, but they have still not responded.

I will consider to make an entry on the Elecraft reflector.

73,
Jonas/SM5PHU

[dj0qn]

Jonas,

I have seen a few mails about audio problems oin that reflector, so you have a good chance of getting help.
Brandon's direct mail is brandon@elecraft.com and he designed the K3/0 mini.

73,
Mitch DJ0QN / K7DX

[SM5PHU]

Elecraft sent me another cable (the one that connects the K3/0-mini to the Control RRC).
But this did not improve anything.

I borrowed another K3/0-mini from a friend, but this also did not make any difference.

I tried new RRC settings that Elecraft suggested, but also this made no difference.

So I'm still looking for a solution.

73,
Jonas/SM5PHU

[dj0qn]

Speak to Brandon please!!!! He designed everything.

Good luck and 73,
Mitch DJ0QN / K7DX

[SM5PHU]

I realize Brandon is the designer. Elecraft support has assigned Craig W6WL to this task. I perfectly trust him, I'm confident he's capable to ask Brandon if he needs to and I see no reason yet to bypass him :-)

73,
Jonas/SM5PHU

[dj0qn]

Jonas,

Basically I mean that you need to contact Elecraft to solve this problem, Brandon would be best. The K3/0
mini support is done by them and not by Microbit.

73,
Mitch DJ0QN / K7DX

[K3TN]

Jonas - I have the same problem and Elecraft's solution was to send me a replacement audio board, which didn't seem to change the problem. My solution was simply to plug my headset (both mic audio and headphone audio) into the RRC and not the Mini. If I had it to do over again, I would have bought a used low end K3 rather than the K3 Mini.

73 John K3TN

[SM5PHU]

Yes, if the Mini doesn't work as intended, a bare-bones K3/10 could have been an interesting option instead.

Even though it looks like this is a problem in the (Elecraft) K3/0-mini, I know of some people who have had issues with ground-loops in the (Microbit) RRCs, causing noise on the modulation. So it is not yet completely ruled out that the root cause is in the RRCs.

The reason I'm posting here is that other people with the same problem may come here and look for a solution. So if I find the root cause, I will post information here.

I'll continue to trouble-shoot. Next step is to establish if the problem really originates on the control side, and then to have a closer look at the DC supply.

73,
Jonas/SM5PHU

[SM5PHU]

I've done some more testing. Both the K3/0-mini and the control RRC add noise.

• Replacing the cable between the K3/0-mini and the control RRC AUX/MIC port does not improve the situation.
• Replacing the K3/0-mini does not improve the situation.
• Replacing the remote RRC does not improve the situation.
• Replacing the remote K3 radio does not improve the situation.
• Tweaking the codec gain settings in the RRC does not (significantly) improve the situation.
• The only component that I have not replaced is the control RRC. I'll borrow one and make a last test next week.

The noise modulated onto the RF SSB signal increases with increased mic gain setting on the remote radio.
So a high-output condenser microphone reduces the problem, but does not eliminate it completely.

My conclusion is that the mic port on the K3/0-mini cannot be used at all.
A dynamic microphone should also not be used, due to its low output level.

The best result is achieved with a condenser microphone connected to the AUX/MIC input on the control RRC.
But there is still far too much noise in my opinion.

When listening over the air in a separate (KX3) receiver, the noise level reaches S9 when I hit the PTT, even with no microphone plugged into the AUX/MIC port on the control RRC. (OK, maybe this doesn't say so much, since the RX is very close to the TX.)

When plugging the cable from the K3/0-mini into the AUX/MIC port on the control RRC, the nose level increases from S9 to S9+20 dB, even with no microphone connected to the K3/0-mini. This tells me that the K3/0-mini adds a whole lot of noise on top of what is already introduced by the RRC.

The following are the settings that I have been recommended by Elecraft:

Remote K3:

MIC SEL: rP:L (no BIAS)
MIC LVL: 42
MIC CMP: 5

Radio RRC:

Codec out gain: 250
Codec inp gain: 32
Codec inp HPF Hz: 163
Codec inp attenuation: Yes

Control RRC:

Codec out gain: 250
Codec inp gain: 18
Codec inp HPF Hz: 82
Codec inp preamp: Yes

I've tried some other settings too, but have made no systematic testing.
Does anyone have other recommendations for parameter settings to reduce noise from the RRC?

73,
Jonas/SM5PHU

[sm2o]

mic level 42 låter orimligt, brukar ligga på 20-23 nånting

/micke

[dj0qn]

What did Elecraft tell you?

73,
Mitch DJ0QN/K7DX

[SM5PHU]

Yes, 42 seems very aggresive. When I run locally with a dynamic mic, I usually set mic gain to 25. When using a condenser mic, I set mic gain far lower, maybe around 5 or 7.

Elecraft told me their settings worked OK for them, that I should plug the microphone directly into the RRC, or that I should use a condenser mic.
To be fair, the only settings they really gave me were the ones in bold:

Remote K3:

MIC SEL: rP:L (no BIAS)
MIC LVL: 42
MIC CMP: 5

Radio RRC:

Codec out gain: 250
Codec inp gain: 32
Codec inp HPF Hz: 163
Codec inp attenuation: Yes

Control RRC:

Codec out gain: 250
Codec inp gain: 18
Codec inp HPF Hz: 82
Codec inp preamp: Yes

The other ones I picked from their screen dump.

I've played around with the codec inp gain settings on the control RRC, but they don't seem to make any difference on the noise.
(The RRC user manual says codec inp gain should be set to 0 in the control RRC, not to 18 as I had set.)

I tried to disable the codec inp preamp in the control RRC, but this only affected the voice level, not the noise.

I'll try to do some over the air testing during the weekend, with a golden-eared friend of mine.

73,
Jonas/SM5PHU