Dealing with RFI and CMC - HAM Radio - TheSmokinApe
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- čas přidán 21. 07. 2024
- Dealing with RFI and CMC - HAM Radio - TheSmokinApe
In Lid Tips videos we discuss topics of interest to Ham or Amateur Radio Operators. In this episode, we discuss my Ham Shack and how I was able to overcome some issues with CMC / RFI.
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I was diggin’ in the crates to find out more on CMC, found this and got learnt. Thanks for another good one.
lol, ole school. Thanks for checking it out!
Hi there, Ape, brilliant run-down!
It needs to be remembered as well, sometimes RFI may not even come from your own QTH.
Earlier on this year one of my neighbours had some solar panels installed and the installation company really cheaped out on the solar charge controller, this pretty much blanked out most of the HF spectrum and VHF/UHF was almost unusable.
We managed to get it all sorted out and you have to be really tactful when things like this happen and not just rush into apportioning blame on people that may not even be aware that this is going on.
Good point and glad you got it sorted out. I've hear all kids of nightmares from problems with street lights!
I don’t understand HAM radio very much but somehow you kept my interest until the end of this video!! Great video keep it up!!
Awesome, glad you liked it 👍
Thanks Ape will have to give the a try with my setup once I get familiar with the 7300
Best of luck with it Mike 👍
Thank you for breaking this all down so even i understood
Glad it was helpful Cliff, thanks for watching 👍
Good one @thesmokingape thanks
Thanks, glad you liked it 👍
Plain English and practical. Thanks!
Glad you liked it, thank you for watching!
Too dang funny...I started watching this video and smokin ape knows why....and he holds up a miller lite as I just sat down with one!
The best beer on Earth 🍻
You had one choke there made from powdered iron, not ferrite (red core). Usually they don't provide nearly as much reactance, choking action.
It’s debated quite a bit and I tend to agree with you, I’ll likely replace it with a t140-31 or 43 👍
Great video Ape. I’m a new subscriber. In your video you mentioned that you use a choke on both ends of your coax (one at the antenna feed point and one at the antenna tuner in the shack), but at the end of the video you did not show the choke at the antenna tuner. Are you using the same Chameleon choke at the tuner that you used at the antenna feed point? Also, do you use any lightning protection in line with your coax? Thanks in advance for your reply.
Thanks for the sub! The choke at the tuner is a t240-31 toroid with about 11-12 wraps of coax, if I recall correctly. This spring I'm installing a ground rod next to where I run antennas that will have lightning protection.
Hi, just checking out your Channel after a name check by Leah. Thank you for this video it has helped me a lot. Just to be clear did you say a 1:1 Balun is actually a choke? If so, that makes complete sense to me, cheers de 2E0TWD.
Yeah, it’s the same thing. Glad you liked the video 👍
Newer rigs are more susceptible to cmc than older rigs. Radios, tuners and amps. A ham now days must go to lengths to cmc proof their station from the start or there will be a bad experience with the hobby. I know of way too many instances were the ham attributed the problem to a new rig where in reality the issue was longstanding but not noticed until the new expensive rig was installed and QSO was attempted. Toroidal cores are essential to success in isolating cmc. The eight turns of coax on a four inch form does nothing at 160, 80 and 40m and should be avoided.
All of your suggestions should be done as a starting point in any well designed shack.
Thanks for the great video & 73'...
de K4WRF
Awesome post Watt, thank you!
A isolated ground/clean power can help with grounding issues/ground noise. (Typically) An isolated ground wire is MC cable with a bare AL ground wire and a green w/ yellow strip insulated CU ground wire. The bare AL grounds/bonds the IG receptacle's frame and metal work box, while the insolated CU ground only connects to the IG receptacle's grounding prong. The insolated CU ground wire is installed onto an isolated ground bar/plate inside the panel, not bonded to the panel's main grounding/bonding bar/plate or bonded to enclosure. The isolated ground bar/plate is then wired to building's main grounding system (footer ground, ground robs, etc) with a #6 green insolated CU wire. Isolated ground/clean power is used for medical equipment, computer servers/equipment, 911 call centers, and cash registers. In a pinch for residential wiring methods, I have used 14/3 or 12/3 romex. I used the red wire (taped green) as the isolated ground. The wire is not shields, so bleed over can still occur but it is better than nothing. Also if you have a older house, the grounding/bonding system is probably poor or non-existent, which can cause massive noise. Driving (2) grounds rods (spaced the length of rods or no less than 6ft together) and running a uncut bare #6 from one ground bar to the next (using ground rod acorns to connect wire to rods) then into the panel, where you can install a grounding/bonding lug to the panel's enclose to terminate the #6. Then if you have metal sewer and water lines in the basement/crawl space, run a #4 copper from the panel to where the sewer line enters the home and bond it. Do the same with the main water line, may have to jump bond both sides of the water meter (if insulated bushing were used on the water main) and bond the cold and hot water lines together with #4 above the water heater. If any of the metal sewer or water pipe has been cut out and PVP/CPV/PEX pipe has been installed, just use #4 copper wire and bond the pipe back together. Proper grounding and bonding can really make a difference.
This is a really good post, thanks for sharing!
@@TheSmokinApe I don't understand the post. Could you or Bacon83 explain it.
Using a conventional power supply instead of a switching power supply can reduce RFI a lot, especially on HF frequencies. Good station grounding also makes a huge difference.
Agreed on both points, thanks Ivan!
I’m surprised there was no mention of differential mode currents, their foibles and cures. EMI suppression, both conducted and radiated for DM needs to be addressed just as well as it is for CM. This is especially true when trying to mitigate noise from power supplies and other external but connected devices.
Tami, I try to keep these videos focused to the main topic. There were a number of rabbit holes I could have gone down but chose not to for the sake of keeping the video short, I did originally have a slide on CM vs DM but ultimately choose to pull it out during editing. Thanks for bringing the topic up.
RF ground planes can equalize all static charges and take them to earth ground/ ground plane is an rf buss.
Yeah good point. If your radio connects it’s chassis ground to the bus you still run the risk of RFI entering the radio along the path to the bus. I want to eliminate the RFI at the source if possible. Thanks for the comment and for watching 👍
@@TheSmokinApe Grounding and bonding pub. as reference 73
Very informative vid!!
Would using too many ferrite beads lower power output going out to the antenna?
It would have to be allot
@@TheSmokinApe Ah ok Thank you!
I really need to focus on this. It's gotten really bad this spring for some reason. Time to start choking things for sure
Good luck, RFI can be a constant battle
@@TheSmokinApe Fat Stack of Roids came in today. Let the choking begin!
Would you put the choke on the antenna side or the shack side of the ground rod clamp bracket???
Hey Alvin, I would put it at the antenna if I only had one, if I had two I’d do both 👍
How is the ratio of the un to un determined? One is nominally 50ohm and the other end (antenna) is a value that means we use either a 9:1 or a 49:1; these being the most common that I see in print and on the web. Is that feed point impedance determined by the wire length? I don't know the math of it, but would like to. 73 (Looking for elmerly advice)
Hey Alvin, sorry man, I don’t know the maths 😕
I have a 2022 gmc limited audition truck how should I ground and bond it for a 981 yaesu with a mfj outback antenna
Sorry Louis, I’m not your guy. I really have limited experience with HF vehicle installations.
Im a really new HAM....just got my Tech in June 2020. Have my Extra as of August. With that being said, I have really tried to set my shack up as “cleanly” as possible. With my limited experience, here is what I have done.
Antenna connection points extremely close to shack
Purchased LMR 400 Coax
Each Coax coming from an antenna has an individual lightning arrester and is directly grounded
Grounding is via two 8’ ground rods bonded together, as well as the mast being grounded
Copper plate inside shack with 1” braided ground directly connected to 8’ ground rods
HF rig, Power supply, and EQ individually grounded to copper plate with 1/2” braided
Have also converted everything possible to 12v DC as opposed to AC (includes lighting, fan, HT charges etc
Have separated any AC cables (cpu, monitors etc) from any DC powered lines and antenna coax.
How effective is all of this? Seems okay....but with so little experience Im not sure exactly. I feel like I have tried to be conscientious to keep everything clean and organized
Should like a nice set up, and grounding does help with noise. What antennas are you using? I do want to mention that CMC wants to go to ground too, that's why I use things like chokes to stop it... for example it can come in on the antenna, traverse your tuner / radio and right to the ground, all the while causing havoc. How is your noise floor?
TheSmokinApe .....right now using a Chameleon Emcomm III in an inverted L configuration. Looking to set up a solid 20 and 40 meter dipole by spring. The endfed goes vertical up the mast to about 22’, then horizontal.
@@jay-rus4437 I’d add a choke are the feedpoint for the End Fed and make sure that there is a 1:1 on those dipoles 👍
I have DirecTV connected to my LED flat screen TV. I have noticed that on certain channels it will cause RF interference to come over my Baofeng UV-5R on one of the repeater frequencies I monitor. It actually comes through like I'm receiving a transmission from the repeater. HELP!!! Would a chock on the cable from the DVR to the TV help? Thanks for an interesting video.
I’d choke the TV and cable box power supplies first. 👍
@@TheSmokinApe Thanks for the help. I'll try it and let you know how it works out.
Come on 1.930 in the evening toad harbor net. We have at least 10 guys running 7300 on ladder with a loop. Or dipoles
I'll try to check it out, thanks!
Not ~30 in and a miller lite is already on screen
Right 🍻
That feedline choke looks like it really would be hard to get past if you didn't belong. RF-wise that is...
Right, thanks for checking it out Alvin 👍
What about using ferrite beads instead of toroid @@TheSmokinApe
Hi,, do you have a link for the $40 feedline choke? W6CRT, temecula , Ca
chameleonantenna.com/shop-here/ols/products/cha-rfi-choke
chameleonantenna.com/shop-here/ols/products/cha-rfi-choke
I don't understand a choke on the ground! Or did I misunderstand you. My understanding is that we want to ground any RF from the radios and equipment. I don't think I want RF on the case of my radio equipment.
Yeah, don't choke any chasis ground. I do choke the incoming power from the PSU with is grounded. Does that make sense?
Get rid of all that coax 1st switch to home made ladder line get a old Denton super tuner or a balanced tuner not mfjUNK. Yes I agree the 7300 is more susceptible to noise. KC3ONO
🏅🏅🏅🏅🏅🏅
🍻👍
A topic all you 7300 owners know about 😉😳🤔 good grounding. lots of palamar ferrite chokes and ground /ground poise/transformer
KC3ONO
Haha, thanks for watching Kevin 👍
When discussing antennas and transmission lines, we can look at the analysis of these by converting the antenna into a circuit component. The antenna can be described as R+jX. You can get these values from antenna analysis programs or hook up a nanoVNA directly to an antenna and get values there.
Common mode currents (CMC) come from non resonant antennas. When the Xc doesn't match the XL of the antenna, you will have a load (the antenna) either voltage leading the current if it's inductive or the current leading the voltage if the antenna looks capacitive. This offset will create a current that will be offset within the transmission line. Differential currents are where your currents add up to zero at any particular point in time at any particular point on the transmission line.
Can we make a 40m Dipole antenna where the elements are coax cables and the center conductor and the shield are tied together? Of course. We can picture that working well. Why? The center conductor and the shield have 100% common mode currents flowing in them. Voila. Common mode currents radiate very well. Thank you.
I know I'll have someone saying, "There's no way to get rid of all of them there common mode currents," and they're right. But we can make them small with resonance.
Thanks for the insight BD, much appreciated 👍
An antenna imbalance causes cmc for example if one leg of a resonant antenna is shorter than the other ,antenna current needs to be equal in each leg ,non resonant antenna is usually only one leg of an antenna so outside of braid of coax will serve as the other side of the antenna, an impedance mismatch at the feedpoint doesn't cause cmc but can be effected by the cmc
@@paulm0hpd319 how do you propose to minimize the Common Mode Rejection Ratio (CMRR)?
@@BusDriverRFI provide the antenna with balance, add the appropriate groundplane/counterpoise ,add a choke,keep away from other objects etc
So, in other words, choke everything.........
Yep 👍