Topic: Interferance from Bliz on AM - RESOLVED

[Ian.]

Hi,

I have had a Blitzortung for a little while and recently have taken up radio ham as a hobby, I have been trying to track down a strong pulsating noise source and today I found the main culprit, it's the Blizortung controller, turning the LED display of makes a great difference, unplugging the whole unit even more so!

I like have the lightning detector, I even mounted in a frame because it looks cool, but me thinks it's time it moved into a screened enclosure, has anyone experience of a similar issue and how did you solve it?

Many thanks

Ian

[miraculon]

The PWM controller for the display backlight is a known issue. Was it the illumination that you disabled, or the entire display?

I have mine set to 100%, since that stops the PWM signal and the LED is completely "on".

The controller isn't optimized for EMC. I am sure that the ST Micro Discovery "mezzanine" board makes things worse than an integrated solution would. I think that the BO team is working towards integrating the STM32 onto the single board.

Also, two-layer PCBs are difficult to get EMC (or signal integrity) right. It should be multi-layer with ground planes. Of course this would result in a more expensive board.

Can you determine if the noise is radiating from the board, or is conducting down the wires then radiating (more likely at lower frequencies)? Ferrite clamps won't help at low frequencies that much. (I bought some special lower frequency clamp-on ferrites and was disappointed in the results)

Shielding (screening) the housing may or may not help depending on what the radiation mechanism is (board or cables). Have you eliminated the 5V power supply as a culprit? Some switching supplies are notoriously noisy. What Ham band are you experiencing the problems at (what frequency?). There might be some countermeasures that you can take, but knowing the culprit frequency is a good starting point.

Maybe some of the Hams can chime in.

Greg H.

[Ian.]

Hi Greg,

I turned the display completely off which helped, the 5v wall wart was checked and was very quite with regards to interference (checked with the Blitz unplugged).

The interference spread is strongest on a number of spot frequencies (350Mhz, 521.5Mhz, 924.7 Mhz, 990.3Mhz, 1.802Mhz, 145.537Mhz) and does cause slight interference patterns on the waterfall display when using PSK31 at 7.040Mhz (40m band).

I haven't fitted any ferrite clamps yet, a radio rally is coming up at the end of January and I was going to get some from there, as a first step I might wrap the board in cling film and put it in an anti static bag, see what that does

[W3DRM]

Hi Ian,

I have not experienced the same interference you mention on any of the ham bands (HF,VHF or UHF). However, my rig is in my garage and the Blitz equipment sits in my home office. That is about 30 feet away. The Blitz antennas are outside and within 25 feet or so of my HF vertical and about 50 feet from my VHF vertical. I have several other loops and inverted-V's for 10-Meters and have no interference on any of the antennas.

I do have my Blitz display set to time-out after 30 seconds to help reduce any noise it may be creating.

Here are some questions that will help us to work through this issue:

• What kind of Blitz setup do you have?
  
  • i.e., Is it a RED with both H and E-field boards?
• How do you have your system setup relative to channels gains, etc?
• What kind of Blitz antenna are you using?
• How is your Blitz equipment located in relation to your ham gear?
  
  • i.e., both the Blitz boards and their respective antennas

Sorry for all the questions but, without any knowledge of your setup, it is really hard to do any troubleshooting.

[Ian.]

Hi Don,

Really appreciate the help here, so no probs with the questions.

The details of the build I documented here - http://www.chatteris.biz/blitzortung_build.html -

- The build is a RED with Revision 7.4 firmware, only 200mm ferrite antennas are in use.

- The gain has been set to automatic, but one channel always seems to perform better than the other, I've attached screen shots of the typical gain setting and the signal display showing the normal interference I get (its never been a particularly quite setup, hence poor detection performance, I've put this down to a lot of powered electrical equipment in the loft, I have placed the antennas as far always as I could , I suppose the next step would be weatherizing the unit and mounting the assembly outside)

- 200mm ferrite inside a tube with an earth copper outer with 1mm break down the full length.

- The Blitz antenna is 7m away from the receiver, but only  3m away from the external ham antenna, the Blitz antenna is in the loft, a height of 4m from the office desk.

- The controller is mounted on the office wall 1.5m from the rig.

The cable from the controller to the antennas is shielded cat 5 and I've put a separate earth to a ground rod independent of the house earth.

If I hadn't got the ham radio I would have blissfully unaware!

[Cutty Sark Sailor]

Ian, this is probably a very dumb question... but have you grounded the controller ONLY to 'cold water' or equivalent?  And you only have the one ground on the system?   It should be ONLY at the lug provided on the controller.. no where else. Your H field ferrites should be connected right to the antenna inputs on the amp, as short of leads as possible.
I've no E or H radiation to speak of out of my controller...  You may have a ground issue on the controller, or amp... those boards have substrates...  There should be no emission from the Blitz antennas...

[Ian.]

Hi Cutty,

The ferrite leads have not been extended, they are clamped in the terminal block on the amplifier, I cleaned the varnish off, crimped bootlace ferrules on the ends and soldered for good measure.

 These questions have me thinking- the earth rod was for the controller, TV pre amp and Boltec LD-250, so do go to multiple devices and I've not thought about it before, but the braid of the tv cable connecting to the tv could cause multiple earth paths.

My plan today is to have another look at my amplifier and directly solder the wires from the ferrites onto the board, not related to the interference issue, but to see if that changes anything regards why the green trace is always better than the red trace, the second job is to earth the controller directly to the copper water pipes and see what happens.

I'll post up results later today.

[W3DRM]

Ian,

What happens with the noise levels when you remove the ground from the controller board? Does it get stronger or weaker? Have you checked your 5V DC power supply for a clean DC output? Some of the switching type USB supplies are notorious for excessive DC ripple.

Keep at it we'll figure this one out, eventually... 

BTW, your build looks really nice and neat. Much better than mine, for sure. Great job! 

[Ian.]

Hi Don,

I turned the AM radio on and was greeted with the normal crackle - loud buzz - crackle -loud buzz, dropped the earth lead from the controller and the noise was significantly reduced, the buzzing is exactly in step with the flashing red LED on the ST board (led is the one nearest to the gps socket).

Adjusting the LCD to 100% didn't make a difference, turning the LCD off reduced the background buzz somewhat, but the predominant buzzing is in step with whatever function the LED is indicating is being performed.

I'll redo the earth wire to a copper pipe when I get back in later today.

[Cutty Sark Sailor]

Seems like you had several issues getting online... display, etc.. is that right?  I'd go back and recheck those issue mediation procedures....
anyway, another thing to check would be for crystallized or poor solder connections, loose pins on display, discovery board, etc. Also check on the ground block on controller.. there have been a few instances, (I'm one) where the torque of tightening the screw has broken the pin going into the board, resulting in an intermittent or no ground connection.   Make sure the 25mhz crystal is installed well, with no solder touching or close proximity to case... also check the Discovery board for any loose connections that may have developed when you installed those big lytics vertically instead of bent over.  Something similar may be affecting the 'amplitude' of the channel you are concerned about gain differences. When I installed E field, I'd an intermittent issues with Channel A... thought I'd found the culprit several times... finally
located a faulty "through" on L6 (I think it was, in the E amp, ...made sure the solder bled through to the top connection on the board.

[Ian.]

Looks like I might have led us all on a merry dance  quality of the power supply has come up a number of times and under no load the PSU was radio quiet, on load the noise seemed to come from the controller, hence it got the blame.

I decided to power the controller on battery to discount the PSU once and for all and its quiet! Looks like the noise was the PSU and I was convinced it was OK, thanks for all your help guys, you all really came up trumps for me and its appreciated.

The controller is currently plugged in to the USB outlet of a CCTV DVR to power it with no problems, I will start looking round for a linear PSU now.

I will take the advice and connect the controller to a single earth point and also I'll check my soldered connections to see if I can get the antenna to perform with similar gain. (I'll swop the antennas over to see if the problem moves before I do anything else).

When its all back together, I'll post an update.

Cheers

Ian

[miraculon]

Looks like I might have led us all on a merry dance  quality of the power supply has come up a number of times and under no load the PSU was radio quiet, on load the noise seemed to come from the controller, hence it got the blame.

I decided to power the controller on battery to discount the PSU once and for all and its quiet! Looks like the noise was the PSU and I was convinced it was OK, thanks for all your help guys, you all really came up trumps for me and its appreciated.

The controller is currently plugged in to the USB outlet of a CCTV DVR to power it with no problems, I will start looking round for a linear PSU now.

I will take the advice and connect the controller to a single earth point and also I'll check my soldered connections to see if I can get the antenna to perform with similar gain. (I'll swop the antennas over to see if the problem moves before I do anything else).

When its all back together, I'll post an update.

Cheers

Ian

Ian,

I have had good luck with the linear power supply described in this old thread:

http://www.wxforum.net/index.php?topic=20043.msg193085#msg193085



TeraDak U9VA Linear Low noise Power Supply

Greg H.

[Ian.]

Hi Greg,

I do remember your post about this some time back, thanks for reminding me, I'll have look around for one.

Cheers

Ian

[W3DRM]

Cutty also suggested another power supply. I had high noise levels from my original supply and when I bought the one that Cutty suggested, the noise simply disappeared. It's also listed in one of the threads on the RED kit.

Glad to hear you've found the source of your problems! 

Now you can get on with the fun side of the project.

[Cutty Sark Sailor]

http://www.powerstream.com/AC-1898.htm

[Ian.]

Thanks again everyone, I went in the loft to retrieve the amplifier and check over the solder joints, I reflowed a few which looked dodgy and reassembling I realized yet another school-boy error, the setup, before I took it apart to work on, had the +ve from each ferrite connected to the two inner terminals, with the -ve on the outside terminals of the amplifier board, not only that but I had the ground on the wrong terminal, instead of the end terminal nearest the capacitor, it was on the furthest, boy I couldn't have got this worse, if it wasn't for the radio issues, none of my fundamental errors would have come to light and my stations performance onto the network would have remained very poor.

The gain is now up to 4000 on each channel and the signal is looking a whole lot better.

Hopefully this saga will help others and also show that as a community were not to proud to own up to mistakes.

Thanks for the link Cutty, shipping to the UK is $88.76, 5x the price of the unit , off to Google.

Cheers Guys have a great 2015

Ian

[Cutty Sark Sailor]

Thanks again everyone, I went in the loft to retrieve the amplifier and check over the solder joints, I reflowed a few which looked dodgy and reassembling I realized yet another school-boy error, the setup, before I took it apart to work on, had the +ve from each ferrite connected to the two inner terminals, with the -ve on the outside terminals of the amplifier board, not only that but I had the ground on the wrong terminal, instead of the end terminal nearest the capacitor, it was on the furthest, boy I couldn't have got this worse, if it wasn't for the radio issues, none of my fundamental errors would have come to light and my stations performance onto the network would have remained very poor.

The gain is now up to 4000 on each channel and the signal is looking a whole lot better.

Hopefully this saga will help others and also show that as a community were not to proud to own up to mistakes.

Thanks for the link Cutty, shipping to the UK is $88.76, 5x the price of the unit , off to Google.

Cheers Guys have a great 2015

Ian

Yeah, I was afraid the shipping would be outrageous, but at least Powerstream was willing to ship!  Now, if you'll look for the specs on that little jewel, and get one somewhere with similar specs, you'll have no issues.

A few of us have built REDs and some "Trailblazing Green" builders, and got lucky, and had no real issues.  I suspect it's very few, however, Others, like me learned quickly how noisy our environment could be, and the importance of using a 'quality' 5 V source. We learned a lot with Greens and REDS.... and
that has led to a great deal of experience, and issues like yours, and ours, are feeding the design of the next generation system, that's moving right along. It looks like it will knock the socks off some folks...
So your 'issues' and willingness to pursue and mediate them don't go un-noticed, and have a great value to our hobby!

Well done, Ian, and Congratulations!!!

Mike

[Ian.]

I ordered the TeraDak from ebay http://www.ebay.com/itm/TeraDak-TeraLink-X1-X2-DC8-5V-1A-USB-DC5V-port-Linear-Power-Supply-/181467993450?
on the 5th Jan, dispatched e-mail on the 7th Jan, arrived here in the UK from Honk Kong today 10th Jan!, brilliant, plugged it in and I couldn't believe the difference in quality.

I've got back on the mailing list as I want to get an E field unit when they become available.

[DaleReid]

Ian,
Glad you are stomping out the bugs.

For me, at least, without the unfailing support of the more experienced members here, I would have been wandering aimlessly about and even put some of the problems on the back burner or even languished longer.  It is nice to know you are not alone, and that's what makes this group so much fun.

I know the feeling of making some of the fundamental errors, and then overlooking them as one 'thinks' all the basic stuff has been done right and ignoring the obvious.  Glad you found the errors in the ferrite hook ups. Sort of like when a program that is simple 'should' work and didn't until you found a mis-named variable or some such.

Now with the polarity corrected, all those strikes mysteriously appearing on the other side of the globe will be gone and the Mediterranean storms will be back again.

Dale

[Ian.]

Hi Dale,

I agree, the help and support on here is incredible, people freely giving their time, knowledge and expertise in order to advance the hobby and help other do the same (even putting up with me asking noddy questions) is so refreshing.

Sometimes I just wish I could contribute more, rather than take all the time, without doubt, not only my Blitzortung but my whole site wouldn't be anywhere it is today without the people who make up this forum.

Weather folk are a rare breed

Ian

[Cutty Sark Sailor]

Hi Dale,

I agree, the help and support on here is incredible, people freely giving their time, knowledge and expertise in order to advance the hobby and help other do the same (even putting up with me asking noddy questions) is so refreshing.

Sometimes I just wish I could contribute more, rather than take all the time, without doubt, not only my Blitzortung but my whole site wouldn't be anywhere it is today without the people who make up this forum.

Weather folk are a rare breed

Ian

'S Ok.. Ian... we all started out taking... now we give back... and so will you.

[Ian.]

Hi Mike,

I sure hope so, I am building a Blitzortung for a Weather Enthusiast in Ireland who got in touch with me, that will be another one coming on line when the bits get to me, so I'm trying give a bit back that way.

The TeraDak I received today made me smile when I looked at the front panel.

Cheers

Ian