Help with HF RFI

[justinbowser]

Howdy!  I have quite a bit of RFI coming from my Classic 200SL.  It is present on 40M and 20M but worse on 40.  It almost sounds like a carrier with some staccato mixed in with it.  It occurs about every 25-26 KHz (7.169, 7.143, 7.118, 7.092, etc) and hits my meter at +20.  It is much worse now that I erected a 40/20 M inverted V antenna up about 35'.  Can anybody suggest filtering/choking to help drop this down?  I have clipped ferrite beads on the wires going into and out of the CC as well as on the +12VDC lead to the radio.  I have wrapped the RG6X coax 12 turns around a 4" form and also have a string of 5 clip-on beads right before the radio on the coax.

Thanks!

Justin B.
KI5GKD

[Vic]

Hi Justin,

Please read the following Thread,    and check out the Links in Reply 1:
http://midniteftp.com/forum/index.php?topic=4922.0

Separation of antennas from PVs and the power system,   and using Mix 31 ferrites for HF frequencies,  on the PV leads into the Classic,   and often on the leads from the CC to the battery,
is a good place to begin.

Later,   73  GL,   Vic

[justinbowser]

Vic,

Thanks for the reply.  I had no idea that the panels radiated RF and have one end of the inverted V actually tied off to the panel rack so maybe this is why my noise problem got worse after the new antenna went up.  I will try to move them away a bit and see what happens.

73,

[boB]

Yes, I believe the PV wires and panels  are a BIG contributor  of EMI radiation if high frequency noise is not stopped at the controller end.

[justinbowser]

Should I attach some clip-on beads on each string out at the combiner box?

[boB]

Should I attach some clip-on beads on each string out at the combiner box?

No, these need to be added as close to the electronics that the PV wires are going in to as possible.

You can ALSO put something up at the combiner as well of course.   But you will need to put common mode ferrites around both wires, not just one each at a time.

You CAN put beads around each wire individually as well but they must be rated to not saturate and give some EMI reduction while passing DC current.

[ClassicCrazy]

Should I attach some clip-on beads on each string out at the combiner box?

No, these need to be added as close to the electronics that the PV wires are going in to as possible.

You can ALSO put something up at the combiner as well of course.   But you will need to put common mode ferrites around both wires, not just one each at a time.

You CAN put beads around each wire individually as well but they must be rated to not saturate and give some EMI reduction while passing DC current.

Bob - how would one calculate those saturation levels ?
Or is there just some easy way to make a good guess at it  ?
Larry

[Vic]

Ideally,   one would want a toroidal core,  or clamp-on bead that can accept several turns of BOTH of the PV cables  (and,  if needed both battery leads at the CC).   This causes a DC current cancellation,  because  the DC current is going in one direction in one of the cables,  and the opposite direction in the other cable of that pair.   The only current that the ferrite "sees",   is the difference,  which is only the NOISE current.    Very little chance that this current will saturate any reasonable sized core that will accept several turns of both cables.

FWIW,   Vic

[boB]

No or VERY little chance of saturation when used for common mode filtering because the DC current cancels out.

It is only when using a differential mode choke (toroid or whatever on ONE wire at a time) that you may have a chance of saturation or reduction in the wanted insertion loss of the RFI trying to be reduced/tamed.

Some kind of lower permeability (mu) core would be used for differention.  Powdered iron sometimes for that.  There are other alloys that can also be used for that.

For common mode chokes, the permeability can be very high like, 5,000 to 10,000 or so.  The graph to look at for common mode chokes is the insertion loss vs. frequency.

  You want as HIGH of insertion loss as possible for a particular range of frequencies.

[justinbowser]

I have ordered one of the "Monster"  mix 31 toroids from https://www.kf7p.com/ as noted in the thread Vic pointed me to.  I will wrap the PV in and CC out wires through the toroid a couple of turns right before they go into the Classic housing.  I have 8 ga coming in from the panels and 4 ga from the Classic to the battery bus bars.

[Vic]

OK Justin,

Please let us know how that works.   73   GL,   Vic

[justinbowser]

I got my monster 31 mix toroid today so I shut off the array and batteries and wrapped my PV in and out wires through it.  I wrapped them as pairs two turns around the core right before they go into the CC.  Tomorrow, once the Classic is breathing hard I will see if my RFI levels have decreased.  I have also determined that my DC refrigerator is putting out RFI as well so I will order another 31 mix toroid to run the 12V leads through.  All I have is type 43...

[justinbowser]

OK, moment of truth time!  CC is putting out about 1800 W so I turned on the Yaesu and the noise is still there~!    As far as I can tell there was no reduction in the level.  I also drove a T-post into the ground about 10-12 ft away from the solar array and attached the antenna ends of the inverted V that had previously been tied to the solar panel mounting rails.  I do not have the panels grounded, could this be a contributing factor?

[Vic]

Hi Justin,

The description in the first Post  does strongly imply that the Classic is the most likely noise generator.

So,   as far as you can tell,  the noise level  has not been reduced after choking the PV leads?

Assume that your HF radio runs on 12 V DC.   Have you shut off the inverter  to try to eliminate it as a cause?  Have not re-read this Thread,  you may have tried that ...

You could try doubling the number of PV wire passes through that core,  to see if there is any difference.  The noise intensity should vary in proportion to the power being produced by the Classic.

You could also try to more that toroid to the battery cables,  close to the Classic to see   ...   assume that the second toroid has not yet arrived.

Thanks,   73,   Vic

[justinbowser]

Vic,

I have eliminated the inverter from consideration for this particular RFI issue and since these repeating "carrier" tones go away after the CC goes into rest I'm pretty sure it's the culprit. 

I'm not sure if I have enough slack to get even one more turn around the core so I might have to relocate CC to do that.  Both cables from CC to battery bank and input from panels are wound through the toroid.  Attached is a pic.  It looks pretty ugly so don't laugh too hard...

Radio is about 10' away from the CC on it's own voltage converter.  I run 24VDC to the radio location and then use a 24VDC to 12VDC converter to power radio.