VHF interference

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AKremotes
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VHF interference

Post by AKremotes » Tue Aug 07, 2007 12:39 pm

Experiencing interference/noise in application near (about 5 feet) VHF transceiver. Was wondering if anyone has experience with this? Are caps on the output likely to help or do I need physical distance? What is the switching frequency of the PWM?
I have about 10 nearly identical installs thus far. Only 3 have noise, one of which is constant when controller is operating and fairly severe.
Noise is predominant at 156.8MHz, but at the worst site has been heard on other marine freqs. as well.
Thx.

rlongdon

Post by rlongdon » Tue Aug 07, 2007 1:00 pm

-MX60 bridge switches at about 24.1kHz
-MX aux supply switches at around 32kHz
-MX Processor clocked at 12.228MHz

Regards,

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Post by Jim L. » Tue Aug 07, 2007 2:35 pm

Could be a lot of things, but could you isolate down to either radiated or conducted interference? If you run the radio off a battery separate from the PV supply, does the interference change?

What grounds are seen by the FM radio, and what grounds does the PV system have?

Are any control lines (includes mic inputs or data line inputs) from or to the radio close to any power conductors?

Is the radio power directly from the PV system?

Are the PV componenets below the antenna ground plane? Does the antenna have a ground plane, or does it depend on earth?

Best regards
Jim L.

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Post by GreenerPower » Wed Aug 08, 2007 7:16 am

Hmm! must be grounding. My fish-bone antenna is 5-ft from the inverter and all TV channels are fine. Try ferrite cylinders (or toroids), loop a few loops (1 or 2) around it on the hot and neutral wires output of the inverter. Is it the inverter or the CC ? If it is the CC, loop a few loops around a transformer core for the DC wires (close to the source i.e. the terminal blocks).
Be greener and may the force be with you

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Post by AKremotes » Thu Aug 09, 2007 10:13 am

Good questions Jim!
The radios are top of the line Motorola Quantars, chokes are on the power leads within inches of the radio chassis, and I'm sure there's some beefy filtering. Antennas are earth ground.
There's 2 800Ah Absolyte strings in parallel. The output of the CC's runs to the batteries, radios fed on seperate "load" run. However, the controllers do happen to be mounted in the radio hut.
There are actually two buildings on each mountain, a radio hut and a generator/battery hut. Mounting the controllers in the gen hut to begin with would have been a much cleaner install, but we are working with the existing infrastructure. The original design was just the radio hut, with batteries in it, and TEGs mounted inside the solar panel frame to supplement the PV.
When generator huts were added, TEGs were removed, batteries were moved to gen hut, but solar still came to a simple controller in the radio hut, then over to the batteries. Looking to keep cost down, customer wanted us to just replace the existing controllers. Moving them to the generator hut will require new runs from the panels at most sites as the generator hut is further from the panels than the radio hut.
An old RF guy here had the same suggestion of isolating the radio on a different battery, and we may give that a try. Unfortunately, all these sites are mountaintop helicopter access, so when we go back I want to loaded for bear.
More on the mountaintop configuration-
The radios are normally tuned to the marine distress freq.- 156.8MHz, and this is the frequency that noises up. Other marine band frequencies are usually clean, but do occasionally noise up as well (I suspect when charging is at it's peak)
The controllers are about 5 feet from the radios
radios are 24v
pos gnd
controller cases are grounded
radio casess and everything else onsite grounded (quality of the ground on any mountaintop up here is questionable, but there are spec ground rings around each structure with multiple driven rods.)
2 controllers per site
24 Solarex 60W panels on each controller
panels wired 48v
telco circuits deliver digital to one radio, analog to the other. These are a good 6ft. from the controllers and it's in/out wiring.


Wanted to investigate as much as possible here on the ground, so...
My bench test ended up being a 12v in/12v out setup from someone else's demo project that was sitting in our storage yard. It was convenient.
Using an o'scope, I first looked at the leads with input panels disconnected (sleep mode)- input leads were quiet, output leads had a 50KHz blip, about .1v p/p.
I drained the batteries enough to get the controller going, disconnected my load so I knew it was not contributing to any noise, and flipped on the pv. Outback showed 11A in, 13A out. No longer a clean 50KHz, other components mixed in so I couldn't trigger on it, but spikes were up to .6v p/p on the output, and .8v p/p on the input! As the batteries charged back up, the amplitude began to come down.

Who knows how big they get if you've got depleted batteries and full sun. Remote sites can churn out 14x this much current. Today I play with caps and toroids.

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Post by GreenerPower » Thu Aug 09, 2007 12:01 pm

Wow ! I'm overwhelmed with info. If the DC cables from the CC to the battery are hanging in free air between the 2 huts, they act as antennas to radiate the PWM charging current (are they ? how long is the run ?). If this is the case, try to make them "twisted-pair" (so that the magnetic field would likely cancel out between the + and - cables). Next is to wrap them with aluminum foil and ground the foil (make them "shielded cable"). If these are not applicable, try big toroids (close to the CC) and large caps across +/- out of CC.
With ~1400W from PV, the charging current could be ~30A i.e. the PWM peak current could be ~ 60A (2X for the 2 CCs, practically a strong broadcast station on the harmonics of the 50KHz PWM), you would need fairly large toroid to keep it from magnetically saturated for it to work as an inductor @ ~ 50KHz
Be greener and may the force be with you

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Post by Jim L. » Thu Aug 09, 2007 2:06 pm

The reason for keeping the batteries close to the radio is to keep a low impedance at the power port. Adding a power capacitor in parallel with an RF capacitor at the power port will shunt noise, but at a cost of reduced reliability.

The analog telco I'm guessing comes in on a two-wire. That must be split out to microphone and rcvr out, along with push-to-talk line control. If the split is done with a transformer, that could be a pickup point for noise. That also raises the question of whether the noise is coming into the receiver circuit, the interface circuit, or the telco line.

Both the analog and digital are likely 600 ohm terminations. For noise, low impedance is better than high.

As has been mentioned, wire twisting is done for magnetic field pickup. Electric field pickup is blocked by shielding. If the analog and digital are not shielded, then either braid or conduit could be added.

The other clue is that the noise seems to be worse at a single frequency. Is there some wiring that is wavelength resonant at that single frequency? Not likely. Some interference that beats with the radio IF frequency?

I think that replicating the problem on the workbench is better than trying to beat a helo schedule. But it's possible that some of the sites have corrosion that ups the impedance and increases the noise.

Will be interested to hear what you find.

Best regards
Jim L.

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Post by Vic » Thu Aug 09, 2007 2:54 pm

Hi AK ..

Reading a bit into what you have said, Think that the noise problem is on receive only, and am thinking that the radios run on 24 VDC Pos Gnd system. Have no direct experience with positive ground, but guess that this feature of the system is not the origin of the noise prob.

I also assume that the CC is an MX-60, which is a 70 Amp output switching buck converter, which operates at approx 25 Khz. Here, my MX seems to have alternate harmonics of this freq. loud, and less loud (on HF alalog radios).

First it would be good to confirm where the noise is getting into the VHF RX -- conducted, radiated, or both. Disconnecting the antenna from the VHF radio might help isolate this. Assume that most or all of the noise is comeing through the power cables to the radios. Try Toroidal cores with a number of turns of wire thru the core. Normally, you would run BOTH of the DC conductors to the radio place these chokes very close to the point where the CC connects to the batteries,

I would also place another set of these chokes very close to the MX-60's output. If possible run the PV in and the conductors to/from the MX in conduit -- EMT for example. The MX has large input capacitors, but still some noise might be conducted to the PV array, and radiated from the PV wiring into the VHF antenna.

You might consider the possibility of ground loops created from the coax RF cable being grounded the a spot in the system which is away form the common ground point of the system. THink that the coax runs need to be common point grounded with all of the grounds at one point. Am sure that the system has a lightning protection ground (the ring ground). Just how the power system common and the lightning/earth ground are treated is important. You probably have lotta experience with this, and I do not.

Here, have set up an off-grid Ham Radio site, with largish Solar/inverter system. Have taken a number of steps to keep the noise generated by the power system from being conducted or radiated into the receivers. Essentially all of the PV wiring is in EMT,, as is all of the wiring to/from battery bank, MX and inverters. However, the battery box is not shielded, and the AC out is run underground in PVC conduit. Have used common mode chokes on PV in, MX in and out. Works quite well, still a lil noise from the MX and inverters, but still have ultra-isolation trnasformers to add to the AC output at the exit from the shipping-container (metal) power room.

Good luck, let us know how things are going. Vic
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Post by AKremotes » Fri Aug 10, 2007 12:08 pm

Will be sniffing around my bench test with spectrum analyzer today to try to find the offending emission either at VHF or IF. May not be able to pick it out as this system does not put out anywhere near as much current as the mountain sites.
Jim, I don't think the problem is on the telco circuits as it's only on the receive, and it actually breaks the radio squelch. I'm strongly suspecting the cables from the solar panels are radiating and the antennas on the tower are picking it up. These cables are direct burial type, just laid across the ground- no conduit. The run from the controllers over to the batteries in the other hut are in grounded conduit.
This theory also explains why we have trouble at some sites and not others. The layout of tower/gen hut/radio hut/PV array is different for every site. Physical distance and direction of these cables away from the antennas may make all the difference.
If I'm able to find an offending RF component, will attempt small caps- (470 pico has about 40dB of insertion loss at 150MHz) across input and output to see if I can knock it down. I've also ordered some ferrite cores to try.
If I'm still not getting anywhere, I'll consider putting the runs in grounded conduit.

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Post by Jim L. » Fri Aug 10, 2007 1:25 pm

Then another principle that may be of help: current-carrying conductor pairs should be physically close to each other. The best example is an open ladder feed line. As long as the conductors are close to each other, they act as a feedline. When they are separated they act as an antenna.

Given that each site is a different configuration, if the lines have been allowed to separate or to form loops, that would aggravate the situation.

Background noise does not have to be on frequency to break squelch. It will still affect the automatic gain control.

It might also be a good idea to swap antenna configuration to see if the noise is getting in through the antenna/RF amp. It's still possible that some noise is getting in on the control lines as a path to the inside of the radio chassis. You could also hook a probe into the radio ANT connector to sniff with. And disconnect the antenna to remove that as a receptor.

Best regards
Jim L.

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Post by AKremotes » Fri Aug 10, 2007 5:23 pm

Can't see anything with the spectrum analyzer in the marine band. Had a quarter wavelength wire laying right alongside the input wires, then the output. When I looked at a wider chunk, I could see the noise floor come up a couple dB in the 4 to 6MHz region. I don't think there's enough current on my mock up to see the VHF interference.
We did have somewhat of a speculation breakthrough today. I was telling my techs that a possible solution may be to put the PV feeder cables into a shielded conduit, when they suddenly realized a difference between the sites with/without noise-
At sites with noise problems, there's a third, uninsulated conductor in the DC cables from the PV array which was tied to the positive gnd bus near the controllers. Not tied to anything out at the panels. This is standard for drain wires to only be grounded at one end, but sure sounds like a big antenna to me. If it's length is just right, it could be resonant at our trouble frequency. This could explain why one site is much worse than others.
I won't bother to speculate why they used a drain conductor for a DC run, back when PV controllers were just on/off switches. Or why they did it at some sites and not at others. It's the government and I've learned not to try to make sense of what they do.
As I'm typing this it occurs to me I could simulate this by attaching a half or full wavelength wire to my mock up, then see if I can pick something up with the spec an/VHF antenna.

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Post by sparky » Fri Aug 10, 2007 5:24 pm

If yoou don't get anywhere with Jim's excellent advice and others I would try the brute force method. Assuming I did not miss a key point here but at HP we had a few Spectrum Analyzers that were giving us fits and it finally was solved by taking a good one to the bad site and vice versa. It was the same kind of thing about 9 units and one of the techs pulled boards until we found bad feedthru capacitors on one assembly.

How many hours of sun today?

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Post by sparky » Fri Aug 10, 2007 5:25 pm

If you don't get anywhere with Jim's excellent advice and others I would try the brute force method. Assuming I did not miss a key point here but at HP we had a few Spectrum Analyzers that were giving us fits and it finally was solved by taking a good one to the bad site and vice versa. It was the same kind of thing about 9 units and one of the techs pulled boards until we found bad feedthru capacitors on one assembly.

How many hours of sun today?

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Post by AKremotes » Fri Aug 10, 2007 5:30 pm

Still lots of daylight- 16 1/2 hours, but we lose almost 6 minutes every day.
Pop & swap/process of elimination is my favorite troubleshooting method. Unfortunately, it's not as practical with the logistics involved with remote sites. Instead it's more like- speculate, ruminate, speculate more, bring as much stuff as you can with you, then try as many things as you can before the weather closes in and pilot says "we gotta go". At that point you decide if you're going with him or staying and sleeping on the hut floor for an undetermined number of days waiting for the weather to clear.

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Post by Jim L. » Fri Aug 10, 2007 7:58 pm

AK

Could you clarify something? With a drain wire, there is usually a shield or conductive tape around the cable. Is the drain wire just by itself with no shield?

Could it be that there were leftover cables used with ground wire that were wired as a "drain"?

The inductance of that wire provides a storage for dI/dt energy, and is tied to the power circuit.

Best regards
Jim L.

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Post by AKremotes » Wed Aug 15, 2007 8:34 pm

Haven't gotten to any of the mountains with interference, but just got back from another mountain/install. Had the crew do the install just as they had at the other sites, but no interference. I then set out seeing if I could create some.
The wiring to the PV panels is actually in a flexible spiral steel conduit, and found the "drain" wire tied to the pos. gnd bus near the controllers and also tied to the PV structural steel. Tried lifting this wire off gnd at the panels to simulate the conditions we believe exist at the trouble site, but this did not cause noise. Then went on to remove everything on the site from earth ground (one at a time, testing each time) and even with the entire site floating free of ground, had no interference.
Sun was bright, controllers putting out max power, I disconnected the transmission line running out to the tower mounted antenna, and connected to a spare antenna leaning against the Outbacks/wiring. Nothing.
Measured a piece of wire to one wavelength, hooked it to spectrum analyzer, and stretched it out towards the radios, nothing. Towards the antenna, nothing.
Tried grounding just the PV panel structure and nothing else, no noise.
Tried grounding just the Outbacks and nothing else, no noise.
Was able to get a handheld to break squelch if I put it right up against the controller wiring, but not consistently.
Took the cover off the MX60 and still nothing.
Attached my one wavelength wire to the neg input to the MX60, then strung it out toward the radio, nothing. Tried the same thing on the pos input, and both outputs, nothing.
Looks like we may get to the worst site next week, weather permitting.

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Post by sparky » Thu Aug 16, 2007 6:33 am

If you still think it is the MX would not 500 bucks for a spare MX be worth your trouble. I even have one and I could drive to get a spare. Just .02 !

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Post by Jim L. » Thu Aug 16, 2007 11:47 am

These kinds of problems can be so tedious.

Expanding on Sparky's swap out. It sounds that if things are as they should be, then it works properly. So now the question might be: what is not as it should be? Could be wiring, unintentional loop (not necessarily ground), corrosion, or equipment failure.

Always the possibility of oxide causing a rectifier type situation. Also any lightning protectors that have decided to start semi-conducting.

Good hunting and let us know what you find, please.

Best regards
Jim L.

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Post by sparky » Thu Aug 16, 2007 2:08 pm

Even more expanding on Jim's post of "diode effect" I would loosen every wire I could get to and retorque. Same thing with all PCB's that get case grounds. At least your not on a steel boat and the fault is corroding the hull underneathe you 3,700 miles out at sea! Sympathy !

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Post by AKremotes » Tue Aug 21, 2007 2:50 pm

I will be bringing spare MX60's to the site. We're going to try putting the dc runs in conduit and playing with grounding. If all else fails we will relocate the controllers to the generator shack (steel skinned bldg, as opposed to the fiberglass walls/roof of the radio shack).

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My RE system: We have a solar charging system aboard our boat that is controlled by an Outback MX60 and has 4 Kyocera 130 watt panels run as two pairs in series at 44 volts. This charges six 2 volt 55T25 batteries as a single "house" 12 volt bank.

Re: VHF interference

Post by solar sapphire » Thu Nov 06, 2008 5:28 pm

I installed a 4 x 130 watt PV system with an MX60 controller on our boat and have intermittent VHF interference on VHF Ch-16 and some additional frequencies. This is not consistent but once it begins, it seems to persist. When the buzzzzz starts it can be suppressed with the squelch control near maximum; however, this diminishes the radio's sensitivity to weak signals and, as this is the emergency calling and distress channel, this is not appropriate. Turning off the PV source stops the noise but this defeats the purpose of an PV array.
The noise persists when the VHF is entirely independent (separate battery) or a hand-held portable unit within 10 feet of the MX60 indicating the noise is not carried over the common wires.
The noise is not always present but will 'appear suddenly" usually when the charge controller has significant output. Once it appears, I have not noticed it ever stopping. The next day, it may be there or not, and again, will suddenly appear if the sun shines.
Best guess is that heat generated in the MX60 is the trigger and that there is something that is heat sensitive within my MX60 and some of those in the remote VHF sites since it does not appear to be a problem with all MX60 units. I hope there is a solution that the engineers at Outback can work out that resides within the MX60 as it appears this is not universal. :-k

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Re: VHF interference

Post by Vic » Thu Nov 06, 2008 6:20 pm

Hi ,

A few things. Isa is very unlikely that the interference is radiated directly from the MX-60. IMHO is is line conducted, and these connecting wire are doing the radiating. Might look at my earlier post above.

Try to isolate the VHF transciever's antenna as FAR AWAY as possible from the PV, and battery system. If you are using an HT (Handheld Transciever), then this is prob a lot of the problem, as an HT's antenna usually is a real comporomise, and the selectivity of many HTs is very poor.

The variability of the noise probably does depend upon the Solar input, the current delivered by the MX, the mode that the MX is in etc. Also, other things may raise the noise floor that the VHF radio hears, and the MX may be only part of this.

If this condition happens at the dock, then the entire noise eivironment of the area can be a large factor. Docks with many moored boats on shore power are just about the highest ambient noise environments you could find. Even with shore power off, many boats close together creates a noisy environment.

Furthermore, knowing little about your situation, I would be surprised if heating in the MX would be a factor with 130 Watts input. The MX can deliver as much as 70 Amps, and a 12 V system with 130 Watts in is only about 7.5 Amps.

Try ferrite cores on the PV input of the MX. If the problem does not get better with this, try Ferrite cores on the output of the MX.

Please tell us more about your system -- if you placed this in your signature, you would only have to do it once, until your system changes. L
lAND et us know how you are doing. With a call for help in this area, we seldom hear ANYTHING back from the poster. This demotivates those trying to be a bit of help. Thanks .. Good Luck VIc
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My RE system: We have a solar charging system aboard our boat that is controlled by an Outback MX60 and has 4 Kyocera 130 watt panels run as two pairs in series at 44 volts. This charges six 2 volt 55T25 batteries as a single "house" 12 volt bank.

Re: VHF interference

Post by solar sapphire » Tue Nov 11, 2008 12:04 pm

Before making any changes I feel I need to understand the basis for the interference and several observations and readings on forum postings give me pause. They are (not in a particular order):
1. The interference is not constant. It suddenly appears. The VHF radio is on all the time (Channel 16) aboard our vessel when we are in remote locations as this is the emergency/calling frequency.If the squelch is turned down (often in the evening when the boat is quiet and sun is low or down) at some point the next day there will be a sudden appearance of the BUZZZZ which can be contained by bringing the squelch to near maximum. This is primarily on Ch 16(and close frequencies) but not on Ch 9 (and others). I compiled a list of those with/without interference and sent it to Outback Power systems with my original report of the problem. The interference is evident on 2 separate hard wired VHF radios with different antenna and the wires running on opposite sides of the pilothouse about 10 feet apart. One VHF antenna wire (shielded heavy duty marine coax) goes past the PV feed at right angles separated by 3 inches. The other is 3 feet away at the closest point. Also, a hand-held VHF detects the interference when within about 10 feet of the controller and it is not worse outside in the vacinity of the solar panels.
2. When the breakers on the PV inputs are opened, the BUZZZ stops The breaker is on the positive lead only and there is a solar panel frame ground wire running to the controller in the same cable as the PV positive and negative feeds
3. There is no correlation of the BUZZZ with any particular charge parameter of the MX60 screen readout
4. The forum posting on Alaska remotes indicates interference on SOME BUT NOT ALL SITES Although there may be wiring differences between sites, I could not determine that there was a specific reason for interference at one site VS another.
If the interference is 1. INTERMITTENT (my case) and 2. ON ONLY SOME ALASKA REMOTE SITES (posted here and on Solar Guppy etc), then I am led to the conclusion that there may be a diffefence between individual MX60 controllers. I have observed numerous instances where rising temperatures cause 1. solder joints to change conductance (so called cold solder joints) and 2. eletronic components to alter properties (resistance/capacitance etc) and cause failure or "noise". My MX60 unit is generating heat when the BUZZZ becomes evident on the VHF. The cooling fan IS NOT causing it.
I'm still looking for answers. :-k

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Re: VHF interference

Post by Vic » Fri Nov 14, 2008 12:26 pm

Hi solar sapphire,

Sorry for my delay, been away. Thanks for the additional info on your install. Note MY error about your solar input--4 ea 130 W panels.

I am assuming that the VHF antennas are not mounted on a tall mast, but rather near the pilot house, and perhaps at a similar elevation as the PV array. Seems to me that the interference breaks the squelch at a point where the MX-60 is producing significant charge current. Any noise generated by the MX's buck converter (which is the part of the CC which is soing the actual charging of batteries or providing current to any inverters etc ) should increase as the current supplied by the MX increases. When I have monitored some of the "birdies" output from the MX in the HF spectrum, they are quite stable in frequency, so seems that they do not move around very much in frequency, however, any small variation in freq is multiplied as the frequency is increased. Perhaps a small birdie moves onto CH 16 VHF due to some change in MX sperating condition.

Just to restate some of the previous regarding isolation of the source and mode of interference paopagation : It is good that you note that the BUZZZZ stops when the PV breaker is seitched off. Seems that the MX is implicated. Placing Ferrite cores on the PV wiring at the PV input wiring at the MX would my first choice to try. If you could find some "clamp-on" type 43 (the most common type avail) and just clamp them on the wires, when the BUZZX was noticed on CH 16. Any change ? Perhaps the level of the noise was reduced, but not eliminated. Perhaps try some clamp-ons at the PV array end of the wire run. Any better ? If it is possible, winding several turns of the wire run through the ferrite will increase the attenuation that the ferrite offers (this is often difficult without adding additional wire) . This is the simplest thing to try.

Another important thing to try is to move the VHF antenna as far away from the PV and PV wiring as possible. Next, you might consider running the PV wiring in metal conduit. EMT is good, but in a marine environment, Rigid conduit would be much better.. Perhaps, if possible you might be able to find some shielded cable of sufficient guage to run the PV in cable. Normally one would bond the shield, or conduit to the common point ground, and nowhere else.

Attenuating VHF interference can be simpler than lower frequency interference, as filters are often more effective at higher frequencies. This is especially true of choke type filters, such as ferrite cores. But the chokes should be very close to the source of the interference.

Regarding heat and solder joint problems, yes, anything IS possible. However, to me, it seems much more likely that this is the more common situation of a switching device (and the MX-60 is a VERY LARGE switcher) creating unwanted signals in a receiver which responds to very small signals.

RE: why are the comm sites noted in the original thread so variable ? Well each of them is juite probably very different. Especially when it comes to the exact layout, configuration, wire routing, tower location, antenna gain/height/directivity, lead dress and so on.

As usual YMMV. My off-grid site was constructed to support HF communications. I am NO expert. And, each situation varies markedly in large and small ways which can be very important. Good Luck, let us know how you are doing. Sometimes making one or two small experiments, such as with ferrites, can reveal a lot, without much investment, are essentially non-invasive, and quite reversible. Vic
4/20/08: 18 Shell SQ 175-106 Vmpp, Stacked 5548 SW+, 1350 AH Surrette 4KS25's, MX-60, Kubota SQ-3250 25 KVA Polyphase Diesel genset. Thanks OutBack for this Forum + the great Support and Service.

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Joined: Thu Nov 06, 2008 4:30 pm
My RE system: We have a solar charging system aboard our boat that is controlled by an Outback MX60 and has 4 Kyocera 130 watt panels run as two pairs in series at 44 volts. This charges six 2 volt 55T25 batteries as a single "house" 12 volt bank.

Re: VHF interference

Post by solar sapphire » Tue Nov 18, 2008 2:47 pm

Thanks Vic: I will work at the suggestions and I am seeking additional ideas. I will keep you posted on solutions/results of attempts but we need some SUN here in the NW. I will try the ferrite cores but need to get larger clip on ones for this.
The VHF antennae are are well above the PV array (one on tall mast and second on shorter pole at least 10 and 15 feet higher) and the hand-held VHF needs to be within 10 feet (approx) for the interference to be significant.
Retrofitting shielding over the full length of the PV feeds is a problem in this installation although I may be able to shield most of it with foil on a temporary basis to determine if this will help.
At this point I am still seeking ideas before I proceed. Thanks

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