BATC Forum

I am a bit of an LF fan and use 136kHz a lot. Since building a MiniTiouner (that works very well) I am seeing hundreds of spikes on LF and top band. Powering down the MiniTiouner, or disconnecting the coax to the dish, at the receiver end, kills it. I am suspecting the buck regulator board from Ebay, but thought I'd ask if anyone here has seen a similar issue and if you attempted a fix? Thanks.

That will be down to the DC switched mode regulator proving the 4 volts to the regulator ICs.

The cure is to turn the Minitioune off!

Clive

I don't see this myself but the little regulators can be noisy and they are not all the same quality. Usually these signals are transmitted through the power supply but perhaps not in your case. If disconnecting the coax fixes it, this implies there is noise being transmitted on the coax and picked up by your LF antenna, Therefore you ought to be able to reduce it with a suitable ferrite choke over the cable.

It might not be the regulator, it could be coming from the USB connection, but you don't have to use the specified one, you could use a 3A linear regulator instead but be aware it will dissipate a lot of power from a 13.8V supply. Alternatively add some filtering to the input side, e.g. a choke and capacitor. Don't ask me for the values, I don't know.

Mike

OK gents, thanks for the ideas, I THINK unplugging the USB cable made no difference, but I will get hands on again tonight.

I think the eBay buck converter board is faulty, since turning it off (it ran 24 hours, seven days a week like the PC before I started investigating the noise) it has started shutting itself down. There's no power LED showing when it shuts down, but power is still getting to the power input.

As the LED is powered directly from the buck converter I have to assume the converter is stopping. And probably noisy when it is working. I should have socketed it...

I always fit a DC filter after a buck converter.
A choke followed by a 100uF.
Choke not critical I used common ones found on eBay
Put a scope on DC O/P from buck converter and see the difference.

73's
Martin
G8KOE

Thanks again for the advice, I had time today to mess with this and I had a stack of three FT240-77 ferrite rings in my stash so tried winding the MiniTiouner end of the LNB coax around them about ten times and the interference has now gone and I am back, (for now, touching wood) to my nice and quiet LF environment!

EDIT: The shutting down was due to a bad solder joint on the LM* semiconductor, one was obviously poor and re-flowing all the pins fixed that, but not the noise. Not sure if the noise is from the MiniTiouner or from the other direction, from the LNB and it's power supply outside in the box, but at least it has gone now

G8KOE wrote: ↑

Fri Oct 15, 2021 8:22 am

I always fit a DC filter after a buck converter.
A choke followed by a 100uF.
Choke not critical I used common ones found on eBay
Put a scope on DC O/P from buck converter and see the difference.

73's
Martin
G8KOE

A ferrite ring choke on the LNB coax has worked, but next time I am inside the MiniTiouner I will add this filter, too and remember it for other projects, thank you Martin.

Please correct me if I am wrong, but as per the picture isn't the solution....
+ve should pass through the inductor to a capacitor across 0 and +ve???
Gareth

You might find a filter on the input side quietens down a switching regulator - that's why there is one in front of each regulator on the Winterhill board.

https://www.analog.com/en/technical-art ... ilter.html

Mike