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
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
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,
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.
Should I attach some clip-on beads on each string out at the combiner box?
Quote from: justinbowser on July 06, 2020, 12:29:25 AM
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.
Quote from: boB on July 06, 2020, 01:07:13 AM
Quote from: justinbowser on July 06, 2020, 12:29:25 AM
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
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
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.
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.
OK Justin,
Please let us know how that works. 73 GL, Vic
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...
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?
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
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.
Hi Justin,
Thanks for the info, and pic.
YES, sorry for the mistake on how your radio is powered. 12 V radios do not usually do well, connected to a 24 V battery.
Your cables and core look fine.
It is probably not worth it to try getting some more turns through that core.
Did refer that other Thread of Tobit's, and do not know how much isolation you tried, but, when you disconnect the antenna from the radio, does all of the RFI cease?
Do you think that adding the toroid with the PV and batt cables through it diminished the RFI at all?
The level of the RFI should vary, based on how much power the CC is producing.
Am quite distracted, finishing income TAXes, and paying, so more later. Thanks, Vic
Well, those results suck.
Next I think is to remove the Classic from its mount and see if its chassis grounding is part of this issue.
I do not know how the Classic is mounted. Maybe a picture of that ?
Bob, classic is just screwed to the wall with a ground wire to the breaker box which is grounded to external ground rod. Sorry about the huge pics but I am at our cabin and Photoshop is on my home PC so I have nothing to resize them with...
Should I put in a ground rod for the panels?
Hi Justin, Thanks for the pic.
It is a good idea to connect all of the metal enclosures together with a grounding wire (Eauipment Grounding Conductor - EGC), this is mostly for personnel safety.
Would suggest doing the same with the PV module frames. Typically, this cable is NOT brought inside structures, buy would connect to your Ground Electrode/s. There are specialized clamps for this. Some of the PV frame grounding is for personnel safety, and some to try to protect connected electronics/electricals, from nearby lightning strikes.
Is there a ground conductor in the AC cable twix the breaker panel and the inverter? Does this ground connect to the inverter case?
It seems that if adding the toroid did any good, that is was only a slight improvement, which is surprising.
Is the battery negative connected to your ground?
We have used metal conduit (EMT) for all cable runs that are above ground, including control and communication, BTS, etc.
We are going to make some changes to our RFI suppression gear, soon. This should be a interesting. Will be using several of those "monster" toroids.
Later, Vic
Thanks for the pic.
Did you turn the inverter OFF also when measuring the RFI ?
Did you remove the antenna connector from the radio to see if it still receives controller noise ?
Some ideas.......
Try disconnecting the green ground wire from the Classic.
Move those wires away from the inverter.
Twist the cables together.
Run the PV through metal grounded metal conduit.
Run the battery cable from controller through metal conduit.
Try running the radio off of a second small 12V battery that is disconnected from the big battery and see if the noise level comes down.
Disconnect the ground to the radio if it has it. Add a small ferrite around the radio +/- power lines.
Add a metal plate behind the controller and inverter that are grounded together.
You can try grounding the PV frames but that may not do anything. But it might !
I will think of more stuff.... Lots of things to try.
Vic,
I have Romex w/ground between inverter and panel. I will check with a meter tomorrow to see if inverter case is tied to ground and if not I will do that. I will also physically ground the battery negative to the ground point in the breaker panel, didn't really see a need for that since I "assumed" battery negative would be grounded through all of the stuff hooked up to the bank!
Next trip to "The Power Store" I will pick up the grounding hardware for the racks and ground them to the same ground rod the cabin is hooked to.
I have ordered a couple of smaller mix 31 toroids and will put one on the DC leads running to the refrigerator and one on the DC input to the radio. It probably doesn't help that my radio is probably almost 40 years old and technology has came a long way since then.
I also have to find some LED bulbs that don't produce RF "hash" as during the day with the refrigerator, lights, and Classic breathing hard I have a +20 noise level! Without the lights on I have about an S7 level with the 'fridge and Classic only seeming to produce RFI on specific frequencies. But, at those FX it is very strong. If I have time tomorrow I'll try to record the noise the Classic is producing tomorrow and attach it to this thread.
73,
Good deal Justin.
The grounding of the negative battery leg will be interesting. Can't assume everything grounds it but I can certainly understand why it might. Capacitors connecting everything to everything. Well, sometimes.
I don't know if newer technology radios are any better because RF is RF and it gets into stuff. I can't do much here at my house because of all the neighborhood noise as I think I mentioned before... Today I tried connecting back up my vertical in the back yard thinking that I remember it worked OK 20 years ago. But, doesn't seem to be any lower noise and W1AW code practice on 40 meters sounded exactly the same on single wire antenna or the vertical. I thought that the noise came down slightly when I moved the horizontal wire antenna (offset feed dipole) over about 40 degrees but now I'm not so sure it is much, if any better. I can hear strong signals though through the S9 background noise on HF.
OK, had a chance to play a little between Honey-Dos. Strange that I still have a pretty good Honey-Do list even out in the wilderness, but I digress...
With the inverter turned off and the 'fridge not running I have a background noise level of about S7-S8 on 40M which in my case being a mile from the nearest neighbor and power line seems a bit high. When I tune (on 40M) to one of the "hetrodynes" put out by the Classic it is about +20. If I disconnect the antenna I can still hear it but there is no meter indication. I would guess that means the noise I am getting is radiated?
If I ground the negative battery bus bar the noise actually sounds stronger!
I recorded a couple of audio clips of the noise. One on 40M and the other on 20M. The noise on 20M is not as strong as on 40M but still pronounced and repeats at regular freq. intervals. The CC output during the recordings was about 30 A as it is slightly overcast right now.
I think you said you are using a dipole antenna ?
I made a loop antenna and it helped with noise .
Larry
Ouch ! That is AWFUL !!
Oh man. So, has this Classic always radiated this badly ?
Are there any wires coming out besides the power lines ? Battery temperature sensor or maybe Ethernet cable ?
Bob - No it hasn't. I had not been on much in the past month and during that period of down-time I took down the MFJ-2240 portable dipole I had up about 25' and in it's place stuck up a 40/20 fan dipole with the apex at 35'. It's a homebrew job using an MFJ 1:1 balun at the top and fed with RG6x.
Your mention of ethernet made me remember that during that time period Larry was helping me out with trying to monitor the Classic (it's a 200SL) and I have a cable coming out attached to a serial I/O board feeding a WIFI module. Could this little cable be the cause of my grief? I will disconnect it and see what happens.
I might use the two FT240-31 toroids I have ordered to make a common-mode choke at the receiver end of the coax instead of the DC conductores to radio and 'fridge as I had originally planned. This may have to wait for a few weeks as I will be going back to "civilization" this weekend to catch up on a couple weeks worth of work that has been stacking up while I have been in the mountains hiding out from the bug.
Larry - I currently have a 2 band inverted Vee
I removed the cable for the wifi adapter with no change.
Oh, also a WBJr wire...
Hi Justin,
YES that is very loud RFI !!
Isolating the antennas from the PVs, power room, and cables that connect to them is quite often a large help. If you could possibly move your aerial one hundred, or more feet from the PVs, power room and AC cables it might be a win for you.
The CM choke on the coax cable at your radio is a good next step.
Am certain that this is conducted RF energy that is radiated from connected cables. t is surprising that your monster CM Choke appears to have done nothing, at all.
Good Luck, 73, Vic
Temporarily remove the WB Jr. wire just to make sure.
Actually, I heard some sort of periodic sound in that recording you uploaded. Could have been the 10 Hz from the WB Jr. !!
boB
Hi boB,
If you are referring to the tick tick tick tice, several times per second, that is the Classic itself. We DO hear that here, but it is much subdued, compared to the signal level @ Justin's.
Due to voltage drop in the battery cable, which was made longer by making 3 - 4 turns through some Mix 31 cores, long ago, replaced that cable with a short, direct one with no cores. Made a little difference in the V drop. And the 75 M birdies now sing a bit louder ... but it is OK.
Will be trying to move one Classic here, to be about four feet closer to the Classic battery breaker, and add a few turns of #2 Ga cable through a monster mix 31 core, to try to get lowest V drop, and some more suppression ...
73, CU boB, GL Justin
I have to finish up my battery cabinet before leaving back to the big city this weekend so won't be able to try any of these other tips until I get back. Before leaving, however, if I get some time I may remove the monster toroid from the in/out wires to the Classic and use this to wrap 10-12 turns of coax through it for a common mode-choke right before the radio.
After a trip back to civilization and considerable amount of procrastination I finally moved the Samlex inverter into the battery enclosure and ran the AC wires to the breaker pane through rigid steel conduit. I also wrapped the hot and neutral wires three turns through an oval shaped mix 43 core right after exiting the conduit. On 40M the background noise dropped from +20 to S9 and on 20M is pretty much quiet! I then ran my coax (right before radio) through a mix 31 toroid about 12 wraps in hopes of choking down some of the Classic noise but struck out on that account. It's looking like I might have to live with the 25 KHz interval "howl" coming from the CC whiole operting in the cabin. On a brighter note I have finally hooked up the 9 "old" Renogy 100 W panels to the barn through our original 40 A MPPT CC, AGM batteries, and inverter so will try moving the radio out there to see what the change will be.
+20 to S9 is certainly better. I have to live with S8 S9 ALL the time with NO relief from my neighborhood noise. We had an outage recently when there was a large fire nearby. The background noise was S ZERO ! (12V battery) After the power came back on and the noise came back up, I turned off the power to my house. Still S8-S9 so it isn't me.
This is 40 meters also. 20 meters is better and 80 meters is totally unusable for me except in the mobile now.
An interesting fact about multiple wraps of wire on the toroids is that too many turns can start giving you more noise because of the capacitance from the start to finish of the turns of wire so keep that in mind.
You can also add common mode capacitors to help the noise. This would be small capacitors from negative and positive to ground on say, the external world side of the toroid.
Can also add caps to the Classic side. Ideally, two toroids in seires with one differential cap between plus and minus and two caps from minus and plus to ground should give an extra drop in noise, hopefully.
Not easy stuff unfortunately !
Bob - Your location sounds like mine in Texas. I have a power line running about 10' behind my shop which is where my radio is at. The noise is pretty miserable...
Instead of winding the CC output wires around a toroid coil, and possibly introducing capacitance, would running the + and - lines straight through a few of the "oval" shaped cores do anything? When I wound the output wires three turns through the toroid it didn't seem to make any difference.
Yes, running the wires through a ferrite tube will work also.
If running those wires around the toroid a few times is not doing ANYTHING then the problem may not be what we are thinking.
Maybe there is a differential signal somehow allowing the interfering ?
How about the battery temp sensor wire ? Or the Ethernet cable ? Could the issue be those ?
Have you tried removing the Classic from the metal backplate if it is on one ?
Might try those things. If there are only the 4 wires coming into the wiring compartment (battery and PV) then it's gotta be coming through those except for the chassis iteslf.
Bob - Right now the only wires going into the CC are WB Jr wire, PV in, and the output to the battery bank. The Classic SL did not come with a battery temp sensor so that has never been hooked up. I had a cable attached to the serial port for monitoring the CC but I have removed that as well. CC is mounted to the interior OSB wall in the cabin. If you can tell me what value caps to scrounge and where to put 'em I'll give that a try. Would it be like an .oo1 uf ceramic cap from each DC cable to earth ground?
Thanks for the help.
Yes ! 0.001 uF is perfect !
Might put a small ferrite on the WB Jr. purple wire next to the Classic as well if possible.
Will do that tomorrow.
Bob,
I put the WB Jr. wire three wraps around a clip-on ferrite with no change. So, I got really drastic and moved the radio out to the barn which is about 50' from the cabin and the Classic noise is just as bad as it was inside the cabin. The barn runs on it's own system, batteries, panels, CC, inverter, etc. I then shut off the breakers in the MN Combiner box and the noise went away so I am pretty sure that this interference is radiated. I have not tried the caps yet but will order some.
OK, so it sounds like the interference is coming from the solar panel array.
Might try some differential filtering. I will have to look into that.
Are your PV wires from Classic to the PV array either twisted, close together or in conduit ?
boB
My array is 3x3 with each string running into the combiner box with 10 Ga stranded. 8 ga stranded goes from the combiner box underground through 3/4" (I think) PVC conduit into the cabin where it goes up the wall into the CC. Wires were straight pulled through conduit with no twists.
I currently have no ground on the panels.
As an aside the system that powers my barn is a cheapo Chinese inverter, Chinese CC, etc. It is quiet as a mouse! Very discouraging...
Bob - My capacitors got here today and wanted to double-check placement. I will remove the MNGP from the CC and attach one .001 uf cap between all 4 wires and ground, 4 capacitors total correct?
Wow! Glad to find that others are grappling with this issue! To date my solution has been to turn off the breaker to the solar panels, turn off the inverter (the PWR for my rig is a dedicated battery bank), and turn off any other circuit causing RFI. Of course, the Classic is the biggest offender. This is a pretty radical solution, but it works.
When I'm operating I'm typically doing weak signal work such as SOTA chasing and can't tolerate any RFI. Sometimes the Classic's birdies are far enough away from my operating frequency to allow me to leave the Classic on, but I usually don't want to risk it.
I haven't finalized my Classic installation yet and am planning to experiment with Amidon's Ferrite Toroidal Cores. To start with, I'm planning to try 75 Material (suppresses 200 kHz - 30 MHz) beads and #43 beads (suppresses 25 MHz to 300 MHz). Instead of doing several turns (because of capacitance issues), I'll try to get beads that just fit over the wire and run as many of the longest beads they have (1.25") as I can, possibly through the conduit if I have to. I'm hoping to avoid using caps as that can get messy and takes up space, especially for 4ga wire.
Of course, different cap values suppress different ranges of frequency; capacitors are self-resonant at a certain frequency. For thorough bypassing, often different cap values are used in parallel. 10µF would attenuate audio frequencies, 0.1, 0.01 and 0.001µF higher frequencies. My 1986 ARRL Handbook has a chapter entitled "Radio Design Technique and Language" that covers bypassing and RF leakage well. If desperate enough, you can alternate between a bead and caps, in series until you've killed all the RFI (and then put the Classic and all this filtering in a Faraday cage -- help! :-\). Sounds like work.
(I'm adding more here:) Probably the most robust way of suppressing the RF coming from the Classic:
- Enclose the Classic in an RF-tight enclosure
- Provide adequate venting and airflow
- Bypass each cable exiting the enclosure appropriately for the signal with ferrite beads and/or caps using chassis-mounted feed-through caps where possible.
- For the connections from the solar panels and battery, create a series of RF-tight sub-enclosures attached to the Classic enclosure with feed-through caps between them.
- In each enclosure, run the line through a ferrite bead or two and bypass with caps.
- Keep adding these sub-enclosures in series until the RFI is adequately suppressed.
- Finally exit these lines through chassis-mount feed-through caps.
- You'll have to anticipate having limited access to the controls and display. Perhaps you could provide a RF-tight door for this area of the classic. Remote control would make this easier.
In the past, the ARRL Handbook provided great construction techniques for this type of project; the current ones probably do as well.
It would be nice if Midnite or a third-party could create an enclosure like this (or a limited-emissions version of the Classic) for RF-sensitive environments. The problem is the limited market. It would certainly worth the money.
73 everyone!
E=IR
The metal honeycomb air filters are going to be pricey. You might be able to heat sink the classic to the metal case and use the case as part of the heat sink. How often do your fans run ?
https://www.pcmag.com/how-to/how-to-make-your-own-faraday-cage
https://mdcreekmore.com/make-a-faraday-cage/
Hi Mike,
You're right. A Faraday cage is overkill for HF RFI. The wavelengths for HF are just too long, the shortest being 10 meters. Even 2m probably wouldn't be a problem, if you made the whole enclosure with perforated metal, like is used with tube transmitters. Maybe something like https://media.digikey.com/pdf/Data%20Sheets/LMB%20Heeger%20PDFs/PERF-135.pdf (https://media.digikey.com/pdf/Data%20Sheets/LMB%20Heeger%20PDFs/PERF-135.pdf). I haven't checked around much yet as I was going to try stringing beads first.
E=IR
Eequals,
The Ckassic's metal case is an effective shield for Radiated emissions.
In general, the largest emissions in the HF frequency range, are conducted (and then Radiated) on the cables that connect to the Classic.
Common-Mode chokes are usually the best bang for the buck/effort. Depending on your frequencies of interest, choosing snap-on or toroidal cores, often, Mix 31 for good coverage in the HF range, is a good place to start. Place these chokes on all cables that are connected to the Classic, or other MPPT CCs. Generally multiple turns of each cable through the cores will improve the attenuation, to a point. Three, four or, even five turns is worth trying. For toroids, if possible one can try to spread these multiple turns of cable around the core. Bi, or Trifilar windings of multiple cables is best (IMO).
It seems, that the cables connecting to the PVs have the largest emissions, so choking those first is a good place to start.
Metallic conduit (EMT is usually fine0, containing all of the cables connected to the Classic, but separate conduit runs for the PVs, battery, and even control (BTS, Aux, etc) separate from the former two.
Our power room is a Faraday shield -- a seagoing Cargo Container -- but this has little effect on the emissions that are Conducted, and then, Radiated, when they exit the container. FCC Part 15, Class B emissions tests for Line Conducted emissions, begin at 30.00 MHz, so the entire LF, MF, and HF frequencies are not measured, and therefore, usually NOT suppressed in devices, like CCs, which are not connected to the AC Mains.
Place the CM chokes as close to the emission source (the Classic, in this case), as possible, ideally in a metal box, with continuous EMT grounds, connecting the box and the EMT for the input, and output). Am getting a bit redundant, have mentioned this quite a few times before.
Try to separate the antennas from the PVs, and power electronics, as far as possible ... and so on, and on ... Distribute AC power underground, and use metal conduit, where these cables exit the ground, etc.
Inverters, of course, can have their own emissions.
FWIW, 73 GL, Vic
Thanks Vic,
Yes, I've been reviewing Tobit's thread regarding his Kid as well as this thread. Also K9YC's RFI article is very helpful. Just turning off the PV breaker seems the easy way out. ;D Like Tobit I also use a 7300 with the same results, but I'm also getting the same signals on other radios, shortwave and 2M, all powered by internal batteries. I've found your posts to be very helpful.
The problem with SOTA is that most activators are on mountains when the sun in shining. :(
E=IR
Quote from: justinbowser on September 12, 2020, 04:27:06 PM
Bob - My capacitors got here today and wanted to double-check placement. I will remove the MNGP from the CC and attach one .001 uf cap between all 4 wires and ground, 4 capacitors total correct?
Yes
TO ground. Chassis which should be grounded.
Hi Vic,
QuoteThe Ckassic's metal case is an effective shield for Radiated emissions.
There are four 1 3/8" holes at the bottom of the Classic; there is also the display. If I were designing an effective RF shield, I wouldn't include holes of this size. (BTW, does the screen metal in the included screen/plugs for these holes go all the way through the rubber or plastic to touch the chassis to effectively create a shield? I don't have one in front of me.) Regarding the display: is there a ground plane in one of the layers of the PC board behind the display that would effectively function as an RF shield?
Perhaps you meant that the RF being transmitted off the
antenna power leads is so strong that the RF coming from the case is inconsequential.
I didn't realize that FCC Part 15, Class B emissions tests for Line Conducted emissions starts outside the HF band. Gracious!
E=IR
Hi boB,
I hear you're on the design team! I miss those days. Regarding the caps, what is the maximum capacitance that the input and output lines can handle? What about going as high as 0.01 or even 0.1µF (I'm not really referring to bypassing, but rather the stability of the internal circuitry)?
73,
E=IR
Hi Eequals..,
Just my opinion:
Shielding of the Classic, to the first order of things, might help reduce Radiated Emissions. One would expect, that, essentially all of the emissions in the HF (and lower frequencies), are line Conducted. Meaning, that your first efforts would be toward choking, and perhaps LC filtering of the DC cables connecting to the Classic.
Shielding and individual capacitors, might be expected to have some effect on very high HF frequencies, and above.
The Classic's case is probably a fairly good shield for Radiated emissions. It could be made a bit better (finger-stock, or grounding fingers, etc), but why not try chokes on the DC leads first, metal conduit, moving antennas, et cetera, if your primary interests are in the HF range?
EDIT, to add: In fairness to the FCC and Part 15, for unintentional radiators, it is stated, somewhere, that these devices "shall not (or similar wording) cause Harmful Interference". This can be an ambiguous situation, and could even require a Court to make that determination.
AND, also should say, that I expect that MidNite Solar complies with Part 15 (as I understand it), as there is no prescribed method and interface to measure Conducted emissions, below 30.00 MHz, and no Limits specified (as far as I know)<.
FWIW, IMO, and so on, 73, Vic
Very good, Vic. I'm definitely not starting with a box and feed-through caps! My first approach has been the off switch. 8)
boB,
I've been thinking about the implications of running the bypass caps to earth ground. The idea behind the UL's requirements is that no current normally flows on the earth-ground conductor, which is what GFCI detects. Would bypassing affect the Classic's GFCI functionality? What's the current threshold? I guess I could look that up.
Bypassing to ground is common with RF equipment. Depending on the length of the ground wire or strap to the ground rod assembly, certain wavelengths will present an infinite impedance at the equipment being bypassed. With broad-spectrum emissions like this, certainly some wavelengths will not be suppressed. The MFJ-931 Artificial Ground comes to mind, but that only addresses a narrow range at a time (depending on the Q). Of course, you could use a wide strap for your ground to lower the Q, but that would involve some effort with a typical structure. You'd have to be aware of the single point ground requirement to avoid ground loops.
I have more questions, but they'll have to wait. Isn't RF fun?
Cheers and 73!
E=IR
There shouldn't be any limit to the size of cap you could use there but anything large wouldn't help at RF frequencies I don't think. So no need for big C.
For charge controllers there is no FCC line test below 30 MHz. This is because it does not connect to the AC line.
But you and I know that below 30MHz is really more important ! I still want to keep things good but it is difficult.
Will help the best as I can !
Where/when did you do design work ?
73
Bob - I have not had time to add the caps to the CC, busy winterizing cabin's water systems and back and forth between TX and OK. Any further messing around on my part will probably not happen until spring. On my last trip up there (last week) I took an old "antique" 30 MHz scope up and left it so I will try to use that to poke around on stuff to see what I can see.
With the CC interference being just as loud after moving the rig to the "barn" I'm pretty sure the RFI is being radiated from the actual panels. The fact that my level of interference increased dramatically after switching from the MFJ-2240 portable dipole to the dual band inverted Vee. The MFJ was in effect 30' completely away from the panels while the inverted Vee (although higher at the apex) has ends that are closer to the panels. Relocating the antenna would be a last resort for me but may come to that.
I thought it was going to be so nice to have an almost non-existent noise floor being off-grid out in the middle of nowhere! :o
Oh, Eequals, welcome to the thread - as they say, "misery loves company!" I was starting to think I was the only one having grief with this!
I found that the HF full wave loop antenna I put up cut down on the received noise from my inverter. It is fed with ladder line to 1 to 1 and 4 to 1 baluns to coax into hamshack.
Larry
I'm going back up to the cabin in a couple of weeks to take care of a few more winterizing things. I think I'm going to look for a place to relocate my antenna to to get it further from the array and maybe have a chance to put the scope on the DC lines at the CC and at the combiner box.
Made it up to the cabin and had time to put a scope on the DC Output lines. The attached CC Out pos scope traces are on the +24V line going to the battery bank and the PV IN Pos trace is the pos line in from the PV array. Things are a bit overcast today so the Classic is not working very hard. A lot of ringing going on and this same pattern is on the PV input lines as well. Horizontal scale 5 usec/div and vertical set to AC at .1 V w/ 10:1 probe which makes the noise right at 4V peak to peak on the CC + out and about 5 V on the PV + in.
I forgot my .01 uf capacitors so I will have to wait until next trip to try them out on both PV IN and OUT lines. I suppose that having 5V of noise on the array could be my RFI problem?
Here is the PV in trace...
Hi Justin,
Thanks for the pics.
Much of the ringing, is probably due to scope probe grounding issues.
The ground leads on the probes need to be short, and direct to the PV and battery terminals of the Classic. This can be difficult to do. You might be able to shut off the PV and battery breakers of the Classic, and add a bare ground lead to either the unused Classic ground at the blue terminals, or loosen one of these blue ground terminals, and add your scope probe ground to one of the two Cl grounds and retighten it well.
If you have Common Mode chokes on the PV and/or the battery leads, you would want to also look at the far side of these chokes, to see what is being conducted on the cables that connect to these chokes.
Am in transit today. Others will have more meaningful comments.
Thanks, later, 73 Vic
Vic may be right... But there is an easy way to see if all your is seeing is real or if some or most of it might be due to common mode noise.
Connect the probe's tip and ground together and then touch that combination to where you had the ground in your pictures.
If you see no noise on your scope, then what you were seeing was real differential noise.
I have to do this all the time in the lab.
Sometimes, running the scope probe cable through a ferrite a couple/few times can reduce the CM noise seen.
After reading Vic's reply I did a little experiment. The waveforms I posted were between the "choke" and PV array with probe ground hooked to the metal conduit. I measured at the attachment point inside the CC and the ringing was gone. Poking into the cable on the other side of the "choke" showed the noise was back. The "choke" is what I mentioned earlier in the thread which was just two turns through a mix 31 toroid. I went ahead and removed the toroid but the conduit ground is still noisy.
Now to Bob's test - I clipped the scope ground to probe tip and then touched this to the conduit and just a flat line. I hooked probe ground to ground wire coming from ground rod and touched probe tip to conduit and tons of noise. So, I guess there's not a bunch of noise radiating out from the panels.
I guess I'm back to square one! Next spring/summer I will maybe move the antenna farther from the panels and orient it N-S instead of E-W and see what happens.
Slight update here... I finally gave up on trying to squelch all of the RFI I have been plagued with and moved my antenna further away from the cabin. This appears to have all but eliminated the RFI from my inverter but the Classic's "birdies" remained. I bought a West Mountain Radio CLRdsp and am able to filter out the birdies so I can at least now operate.
I have recently put together a uBITX V6 QRP transceiver and so far have made 74 contacts from the cabin in a little over a month! If MidNite ever makes a newer CC that is a bit quieter on the HF bands I might be convinced to buy one. Other than that the Classic 200SL has performed flawlessly.
Quick question - Is "Chatty Cathy's" voice an off-the-shelf produce or does she work for MS? Just curious... ;D
Have you heard her calling CQ yet ?
Larry
Chatty Cathy who can be silenced if you want, came from MidNite Solar. She was a gal that actually worked for us who did the voice.
The Spanish version that will eventually be coming is also a gal who works for us still.
So, you DID try adding ferrites to all 3 (common negative) or 4 wires coming into the Classic wiring compartment ? Hard to remember. I suppose I could read the whole thread LOL :)
73
Bob - Thanks, I was just curious since my wife and I kinda think of her as part of the family, now!
Yeah, tried ferrites, etc., so I kind of gave up. Had to put antenna back up anyway since a storm snapped the mast I had it hanging from and I got a good deal on the CLRdsp off QRZ classifieds so all is good.
73,
Justin B.
KI5GKD