Title: IQ calibration problem
Post by: F5AGL on 27. February 2021, 06:50:37
Hello,
I am bored with the IQ calibration phase of my mcHF (M0NKA kit version 0.6.3).
I am having trouble reducing the carrier to 3.600 MHz LSB (mcHF to 3.624 MHz USB). The problem is the same on the other tapes.
I installed the latest firmware and bootloader:
- Firmware: D2.11.95
- Bootloader: 5.0.4
The problem remains the same.
Do you have any indication of the possible origin of this problem?
73 qro
Gilles, F5AGL |
Title: Re:IQ calibration problem
Post by: DF8OE on 27. February 2021, 09:14:12
Hi Gilles,
if the suppression is very poor there is a hardware issue in the IQ chain. So it is important to know if the suppression is very bad or not. IQ calibration only works if hardware chain is not defective.
vy 73
Andreas |
Title: Re:IQ calibration problem
Post by: F5AGL on 27. February 2021, 09:33:02
| yes, i think i can say the suppression is very bad. |
Title: Re:IQ calibration problem
Post by: DF8OE on 27. February 2021, 10:26:37
If it is very bad check the following signals:- i and q local oscillator signal at mixer
- solderings at the input transformer
- (audio) signal from output of the mixer over the op-amp to the input of the audio codec. I think one of these signals is lost. If it is so you will have bad suppression and correction does not work at all.
Good luck
vy 73
Andreas
|
Title: Re:IQ calibration problem
Post by: F5AGL on 27. February 2021, 16:41:40
Thanks for your help.
I follow signal from IQ oscillator to mixer, solderings at input transformer (T4), audio signal from UI board to RF bard, all links seems ok with ohmmeter. :(
Could it be a configuration problem ?
Gilles F5AGL
|
Title: Re:IQ calibration problem
Post by: DF8OE on 27. February 2021, 17:16:53
No. It is a hardware problem. You must use a scope for bug hunting.
vy 73
Andreas |
Title: Re:IQ calibration problem
Post by: F5AGL on 27. February 2021, 19:33:09
| At the first power up, i had a problem with C105 (10 uF PA part). Fuse blow up. I replaced C105 and after that mcHF was OK. RX is all ok. TX seems to be quite ok (5-10W). But i have this pb of IQ calibration. If I put 127 for TX Phase on 80m for example, side carrier reduce a little bit. But i can't cancel it as it could be. I test all links around TX Mixer, LO, etc... I have no scope at this moment... I tried with +6kHz translation in place of -12, it's the same... |
Title: Re:IQ calibration problem
Post by: DF8OE on 28. February 2021, 08:07:10
You need a scope for tracing the signals.
vy 73
Andreas |
Title: Re:IQ calibration problem
Post by: F5AGL on 28. February 2021, 10:07:54
| yes, that's right, i'm going to test this with a scope. |
Title: Re:IQ calibration problem
Post by: peter_77 on 28. February 2021, 15:02:58
| IQ calibration only works if hardware chain is defective. |
|
Is that sentence really true or is there a "not" missing before defective ?! ??? |
Title: Re:IQ calibration problem
Post by: DF8OE on 28. February 2021, 16:35:24
Hi Peter,
thank you for reading this thread. Of course there is a "not" missing. I have read my own post many times but my brain always automatically placed it where it is missing ;D :o
vy 73
Andreas |
Title: Re:IQ calibration problem
Post by: F5AGL on 28. February 2021, 16:49:19
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