MiniTiouner LF and HF interference

Discussion about the MiniTiouner board and the MiniTiouner Digital ATV Receive Software. See also http://www.vivadatv.org/index.php
Basil
Posts: 103
Joined: Tue Sep 10, 2013 7:28 pm

MiniTiouner LF and HF interference

Post by Basil » Tue Oct 12, 2021 10:35 am

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.


Image

G3GJA
Posts: 179
Joined: Sun Nov 20, 2011 3:44 pm

Re: MiniTiouner LF and HF interference

Post by G3GJA » Tue Oct 12, 2021 10:47 am

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

g0mjw
Posts: 1747
Joined: Sat Sep 20, 2014 9:15 am

Re: MiniTiouner LF and HF interference

Post by g0mjw » Tue Oct 12, 2021 11:59 am

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

Basil
Posts: 103
Joined: Tue Sep 10, 2013 7:28 pm

Re: MiniTiouner LF and HF interference

Post by Basil » Tue Oct 12, 2021 12:32 pm

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

Basil
Posts: 103
Joined: Tue Sep 10, 2013 7:28 pm

Re: MiniTiouner LF and HF interference

Post by Basil » Thu Oct 14, 2021 7:35 am

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...

G8KOE
Posts: 59
Joined: Fri Aug 09, 2019 8:14 am

Re: MiniTiouner LF and HF interference

Post by G8KOE » 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
Attachments
Choke Filter.jpg
Choke Filter.jpg (239.63 KiB) Viewed 874 times

Basil
Posts: 103
Joined: Tue Sep 10, 2013 7:28 pm

Re: MiniTiouner LF and HF interference

Post by Basil » Sat Oct 30, 2021 11:35 am

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 :)
Last edited by Basil on Sat Oct 30, 2021 3:42 pm, edited 2 times in total.

Basil
Posts: 103
Joined: Tue Sep 10, 2013 7:28 pm

Re: MiniTiouner LF and HF interference

Post by Basil » Sat Oct 30, 2021 11:37 am

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.

radiogareth
Posts: 830
Joined: Wed Jan 06, 2016 9:46 am

Re: MiniTiouner LF and HF interference

Post by radiogareth » Sat Oct 30, 2021 3:13 pm

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
Lowpass_Filter_LC.svg.png
Lowpass_Filter_LC.svg.png (17.25 KiB) Viewed 408 times

g0mjw
Posts: 1747
Joined: Sat Sep 20, 2014 9:15 am

Re: MiniTiouner LF and HF interference

Post by g0mjw » Sat Oct 30, 2021 5:18 pm

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

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