The toroid windings can't cause a frequency error like that. The
output frequency is directly generated by the Si5351A and is just
amplified from there. Incorrect toroid windings can increase the
losses in the circuit, reducing receiver sensitivity or causing low
transmitter output, but won't change the transmitter frequency. The
toroids are all used in filters and transformers; there are no LC
oscillators in the design.

What is strange is that the error is nearly 40 KHz. The QCX master
oscillator uses a low cost and low precision crystal and all generated
frequencies will be inaccurate to whatever extent that crystal is
inaccurate, but the error is not normally anywhere near that large. It
would have to off by more than 5000 parts per million.

If you have a frequency counter available, measure the frequency of
the oscillator at pin 2 or 3 of the Si5351A. It will change a bit
because of loading from the counter, but it shouldn't cause that large
a change. It should be exactly 27.000000 MHz though it usually is not.
Whatever percentage it is NOT 27 MHz will also be the percentage that
7.030 MHz is not accurate; the absolute difference will be smaller.

The calibration procedure stores a correction factor in the firmware,
so that the calculations are done from the actual frequency of the
master oscillator.

I seem to remember something about a bug in one version of the
firmware that can cause a large frequency error. You may need to
reflash your microcontroller.

Unsure of how to do that. I don't see it in the manual.

Nice job.

You might want to consider adding ?some air vent holes around the 7805 regulator and also the three final amp transistors.
--
73, Bernie, VE3FWF

I just finished by 40m QCX and looking at the reverse beacon network, when I transmit my callsign on 7030.00 I am picked up on RBN at 7069.3.
I have tried the factory reset and re aligning the radio. Do I need to mess with the windings on the toroids?

KN4FAW

Pat,
Thanks for the info.? Mine is in the second batch. Ordered 5/31.?
Vern

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Pat , Do you remember how long ago your ordered your QCX case.? Did they provide a tracking number?

I only have a PO box and check my mail once a week.?? I would hate for it to arrive and sit there , plus hate? to check mail everyday.?
Mostly junk mail , but I can hardly wait for the enclosure to arrive!.

Thanks,
?Vern

I mounted the GPS board within the U3S enclosure but brought out the antenna connection to an SMA and used a packaged GPS magnetic mount patch antenna (did not use the component patch antenna supplied with the GPS kit).

73,

Robert, WA2T

My idea to keep the gps with the U3S without adding heat to the U3S enclosure.?

Hammond transparent blue box. Advantage: no display window is required.

Would be nice if this can work with a LO of 9.667MHz to receive 2m band
Or is a substantially reduced sensitivity to be expected?

Erik

The detector will receive on all odd multiples of the LO.
However, as it is a sampling detector it means samples are missed.
Even at 3 times the LO sensitivity is down by almost 9dB.

73 Alan G4ZFQ

Thank you.? I'm working on your suggestions.? I appreciate the help, and I'm going to look closely at all of them.??

When experimenting with BPF I noticed the receiver module will receive a station transmitting at 15.4MHz when tuned to an LO of 1.03MHz. Of course only when using a well tuned BPF to get rid of the noise or transmissions at lower frequencies and at a 20 dB lower level. Seems to be the 15th harmonic. Its seems also possible to receive at the 5th harmonic of the LO
Is this to be expected?
Could that also work on higher frequencies? I did not yet try BPF above 15MHz.
Would be nice if this can work with a LO of 9.667MHz to receive 2m band
Or is a substantially reduced sensitivity to be expected?
I will give it a try anyway
--
Erik@Home

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Tony, N0PBA, no, you need to lower the value of C21 and C22 so paralleling additional caps with the originals will not get you there.? I also suspect that DC leakage that are a characteristic of electrolytic capacitors may be playing a part here as well, so the original C21 and C22 capacitors need to go.

73,

Robert, WA2T

If you perform a RESET and follow Hans directions in DIAGNOSTIC mode there is a procedure to follow to fault find this.

73 Ken G4APB