Date
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QCX-mini constant 700Hz tone #qcxmini
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Mont Pierce KM6WT
Well, got my QCX-mini built today.
I had one cap missing (that I know of), C32. I stole a .1uF SMD from another kit to replace it. The one I found was the next size bigger, so didn't fit great, but solder seems to be holding it in place. BPF tuning went well. Tuning I-Q Balance, Phase Lo, and Phase Hi all went well. Audio, does seem fairly low. Turned all the way up, it's just loud enough. One weird thing, there is a constant 700Hz tone in the audio. It sounds almost like a spotting tone, except there's no way to turn it off. Also, when turning the rotary dial, it makes a scratchy noise on every click. Band is dead right now so haven't tried listening to any stations yet, but, I have a feeling that 700Hz tone is going to make it difficult to copy signals... Anyone else have this 700Hz tone in their audio? Any ideas on what's causing it, or how to get rid of it ?? 73 Mont |
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Mont Pierce KM6WT
On Sun, Dec 27, 2020 at 10:27 PM, Mont Pierce KM6WT wrote:
One weird thing, there is a constant 700Hz tone in the audio. It soundsFound out something interesting about the 700Hz tone... When I change config setting 3.8 CW offset the tone changes to whatever it is set to. So I guess Clk2 is on all the time, and is getting into my receiver audio. km6wt |
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Richard - N1RBD
I heard the same thing. Haven't done anything with it, as I'm waiting on a new BSS123 ro replace a cracked Q5.
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You normally hear this tone when you are in the menu mode because alignment functions use it, but when you exit out, then it won't be there. I'm hearing the encoder scratching too, and I think it's related to something being too high in gain, which may he why I can't adjust the IQ, low and high, and why the sidetone is so loud. Still investigating...
-- 73, Dan - W2DLC |
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Mont Pierce KM6WT
On Mon, Dec 28, 2020 at 06:12 AM, Daniel Conklin wrote:
You normally hear this tone when you are in the menu mode because alignment functions use it, but when you exit out, then it won't be there.Thanks. But that's not it. The Tone I'm hearing is there ALL the time. This is not the same tone you hear when you are in Alignment menus. Actually at power on, it's not there until after the Splash screen goes away, and the VFO frequency is displayed, which is likely when the first time the si5351a's clocks are initially programmed at power on. Besides alignment, Clk2 is also used for transmit. It's frequency is offset by the value configured in config setting 3.8 cw offset plus the current receive frequency. Clk2 + offset tracks with Clk0/Clk1 so it's always at the right frequency when you press the key. When I change the "3.8 CW offset" and then exit the menus, then the tone changes to the new CW offset value. In normal CW mode, Clk2 is running all the time and set to the receive frequency plus/minus the configured CW offset. When keying the transmitter, you are actually keying circuit path between Clk2 and the RF Amp via IC3. So what I am hearing is Clk2 bleeding through to the receiver section. It's probably crosstalk between some of the traces, probably affected by a missing or defective cap somewhere, or a short somewhere, or ? km6wt |
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Gregg Myers
Hi Mont, You should not have to have the volume control all the way up, not even close. If you have the volume maxed out, it suggests your audio amplifier is at max gain (and therefore very sensitive to microphonic noise and the amplification of spurious signals). IMO, I would focus first on why the volume needs to be turned up all the way, and once that is fixed I think your other symptoms may also disappear as a result. 73, Gregg On Mon, Dec 28, 2020 at 8:11 AM Mont Pierce KM6WT <de.km6wt@...> wrote: On Mon, Dec 28, 2020 at 06:12 AM, Daniel Conklin wrote: |
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Richard - N1RBD
On Mon, Dec 28, 2020 at 01:27 AM, Mont Pierce KM6WT wrote:
Is this what you're hearing? https://drive.google.com/file/d/1HMU5mBZwH4ku-Uhb1xclVSU2pRCUx1vt/view?usp=sharing |
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Mont Pierce KM6WT
On Mon, Dec 28, 2020 at 07:24 AM, Gregg Myers wrote:
You should not have to have the volume control all the way up, not even close. If you have the volume maxed out, it suggests your audio amplifier is at max gain (and therefore very sensitive to microphonic noise and the amplification of spurious signals). IMO, I would focus first on why the volume needs to be turned up all the way, and once that is fixed I think your other symptoms may also disappear as a result.Actually, the audio is quite loud. When I do I-Q, Hi, Lo alignment, turning the volume all the way up is very loud, and I can hear it overloading the amp. I think when in receive mode, background noise is so low, I can turn it up full volume. With freq generator near by, volume is loud as expected. But if I move it away, to simulate a weak signal on receive, then I can hear to two tones beat together... km6wt |
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Mont Pierce KM6WT
On Mon, Dec 28, 2020 at 08:13 AM, Richard wrote:
Is this what you're hearing?Yes, the tone in the background. If you change your 3.8 CW offset, does the tone also change with it? km6wt |
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Richard - N1RBD
I'll check when I get home. My volume is fine at half way so the issue appears to be independent of low audio.
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Richard - N1RBD
Yes, the background tone is directly related to the CW Offset frequency, although it definitely doesn't sound like a 1:1 correlation. I changed both the CW Offset and sidetone frequency to 600hz. The background tone went down by a few Hz (<30?) and the sidetone was generated at a clearly lower frequency than the background tone.
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Mont: In normal CW mode, Clk2 is running all the time and set to the receive frequency plus/minus the configured CW offset. This is not true. In normal CW receive mode, CLK2 is off. It is actually off at the output of IC1. It is turned on for transmit and for the alignment functions but is not on all the time. It is on the display frequency. In receive mode clk0 and clk1 are both on displaced from the display frequency by the amount of the offset and out of phase with each other by 90 degrees. On transmit one of them stays on frequency and the other jumps to the reference frequency (27 MHz in my case). If you are truly seeing CLK2 on all the time then you have an issue. It’s easy to check with a scope on pin 4 of IC3. If you haven’t already done so, try a factory reset and see if that fixes it. Good luck ... Ron On Mon, Dec 28, 2020 at 14:09 Richard <groups.io@...> wrote: Yes, the background tone is directly related to the CW Offset frequency, although it definitely doesn't sound like a 1:1 correlation. I changed both the CW Offset and sidetone frequency to 600hz. The background tone went down by a few Hz (<30?) and the sidetone was generated at a clearly lower frequency than the background tone. |
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This may or may not be related to this thread,but I accidently discovered that in receive, my 40m QCX-mini is generating a signal at 700 Hz (sidetone freq and CW offset) below the VFO freq that is being picked up on my other receivers, connected to different antennas. The signal disappears if I disconnect the antenna from either the -mini or from the other receiver, so it is being radiated from the antenna connected to the -mini. Does this indicate a problem with the -mini? This signal registers S9 on my K3.
73, Randy, KS4L |
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Richard - N1RBD
On Mon, Dec 28, 2020 at 05:31 PM, Ronald Taylor wrote:
I don't have a scope, but I see 26mV at Pin 4 when in receive mode. |
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Steve Z
Randy:
This is normal behavior for a direct conversion receiver like the QCX. Steve N9SZ |
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That calculates out to about +10 dBm if I can assume roughly 50 ohms. Probably close enough to the roughly +7 dBm the chip is rated to put out so you are seeing output on CLK2 during receive and that shouldn’t be happening. Did you try the factory reset? Ron On Mon, Dec 28, 2020 at 16:12 Richard <groups.io@...> wrote: On Mon, Dec 28, 2020 at 05:31 PM, Ronald Taylor wrote: |
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Mont Pierce KM6WT
On Mon, Dec 28, 2020 at 02:31 PM, Ronald Taylor wrote:
In normal CW receive mode, CLK2 is off. It is actually off at the output of IC1. It is turned on for transmit and for the alignment functions but is not on all the time.Thanks for that info. I have to admit, I don't know how it works... For some reason, I didn't think it could actually send the I2C commands to Si5351a fast enough to turn Clk2 on/off like that. thanks, mont |
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geoff M0ORE
What was the 26mV at pin 4 measured with? On 28/12/2020 23:30, Ronald Taylor
wrote:
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Mont Pierce KM6WT
On Mon, Dec 28, 2020 at 03:30 PM, Ronald Taylor wrote:
Did you try the factory reset?No. Just attached the scope to IC1 pin 6. No Clk2 output on RX, only on TX. Interesting.... So, how is the sidetone generated? Could it be the sidetone I'm hearing? When I key the rig, in live or practice mode, I am hearing the same tone. Loud when keying, but attenuated when not keying? I'll start tracing through the sidetone circuitry and see what I can find. Thanks Guys!! km6wt |
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Mont Pierce KM6WT
On Mon, Dec 28, 2020 at 01:09 PM, Richard wrote:
Yes, the background tone is directly related to the CW Offset frequency, although it definitely doesn't sound like a 1:1 correlation. I changed both the CW Offset and sidetone frequency to 600hz. The background tone went down by a few Hz (<30?) and the sidetone was generated at a clearly lower frequency than the background tone.Mine is identical to the sidetone. I turned my sidetone volume down to 1. Now when I key, the background tone and sidetone are at the same level. The background static goes on/off with TX Muting. Interesting... thanks, mont |
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