Spurs at 14mhz

[Nazim]

Hello Everyone,
I'm at step 20. Got receiver working and was able to tune in to ham stations in a 3000 km radius on a 20 and 40m using just two Petlowany coils sticked behind the window as antenna.
Quite an achievement!
The only thing which bothers me is a spurious screen on 14mhz. On 7 and 10 mhz there is only a smalish spike in the middle of the screen, but 14 mhz looks like a hacksaw (screenhost attached)
Could it be result of a bad assembly (bad transformer winding, grounding problems?) or a software misconfiguration?
I'm using Linrad 03.46 on GNU/Linux x64. Will try to setup a Quisk and check if there are spikes on a Quisk screen.

All the Best,
Nazim

[Nazim]

Checked with Quisk, spurs are still there

[DJ&OA]

Hi Nazim,

Check your switching power supply, or try to use a battery.

73, Rainer

[AE9RB]

Nazim, these seem excessive. 1kHz can be from USB. I've attached what my 40-30-20 radio looks like on 20m with a dummy load. It could be anything: filters (T2), antenna, tuner, power supply, USB cable.

[Nazim]

Hi David and Rainer,

Thank you for advise. I'll check with a dummy load, another power supply/battery and shortened cables.

All the Best,
Nazim

[AE9RB]

I accidentally reproduced this in my lab because I forgot to check the power supply voltage after working on another project. Make sure you are testing with 13.8VDC.

[Nazim]

Rewinding transformers, changing power supplies and USB cables gave no results.
Finally, I've applied a liquid rosine flux to U10 and U11 pads and re- heated them.
Magically, spurs almost disappeared. Now my Linrad screen looks beautifull.
Thanks for your suggestions! Hoping my experience will be useful to others.