Understanding Harmonics & How They Pertain To Antennas

Why Are Some Bands Resonant & Others Not? How To Mitigate RFI With Solar, And What Do You Need To Get Started In POTA & SOTA?
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[@robmccray6360]

Make a checklist for portable. You'll thank yourself, and as you mentioned. Do a practice run at a local park or the back yard to make sure you know what you're gonna need.

[@paulsengupta971]

I think you missed a bit on the harmonic description. The original question was asking about third harmonics and other odd harmonics and why an 80m antenna wouldn't work on 40m. The missing part of the explanation is that of impedance. The original question will relate to a centre fed dipole. I'll put in an explanation here: On a half wave wire, the impedance on the fundamental varies along the length, from a few thousand ohms at the end, to somewhere between 50 and 100 ohms in the centre, depending on height above ground. If you draw a half sine wave on a half wave wire, you get the current/impedance distribution along the wire. On the second harmonic, you get a full wave on the half wave wire. For this, draw a full sine wave along the wire. It starts off with low current/high impedance, goes up to the current maximum then goes to a low current/high impedance point at the centre of the wire before dipping below the line echoing the first half. Thus, while the wire is resonant at the second harmonic (and other even harmonics), it doesn't match 50 or 75 ohm coax in the centre. On the third harmonic, it goes back to there being a high current/low impedance point in the centre, so can again be fed with 50 or 75 ohm coax.

[@floydteter4323]

Thanks for responding to my question. And, just as importantly, kudos to you for rocking Pink Floyd!!!

[@jameyevans29]

💯. Looks like an image from the pompei concert

[@KO4AFL]

on the home solar. I have a micro inverter system from enphase and love it. My neighbors have a string inverter system and it was causing me RF issues at first. Bonus on the micro inverter system is if one panel gets shaded you only loose that panel not the full string or percentage of the string.

[@floydteter4323]

the micro inverters they’re using for my system are from enphase. So that’s really good to hear. Thank you!

[@KI7JOM]

I've got a two panel setup with a Victron Energy Smart Solar 75/15. It is very RF quiet.

[@robertmeyer4744]

For home solar I have Victron MPPT controllers and not bad on RFI . I do have Ferrite on everything. even under the panels at the MC4 leads. The RFI can come from MPPT and transmit RFI out the panel like a antenna. The outher big RFI maker is the inverter . With out knowing what kind of solar system. grid tie or battery / inverter . Check into RFI quit systems. Have to look them up do research. 73

[@pcramil]

Bring all your CRAP: Cables, Radio, Antenna, and Power. When I'm at home in the Carolinas, I bring water and snackies to go POTA. Depending on the season and whether you're gonna activate outside or from the car, I'd consider a lightweight jacket in colder months, and a fishing hoodie for the hotter months. I keep a small folding chair in the trunk all the time now, because I've run into other activators a few times already and we might turn it into a 2 or 3 op activation. Like you said, a couple baofengs to get 2m/70cm P2P with your new friends. If you really wanna push it, a dummy load so you can work your new friends all the way through all the bands for N1CC. Other permanent general keep-in-car stuff are a first aid kit, spare pen and paper, multitool, big flashlight (small one in my radio kit), bug spray, sunblock, towel, and hand sanitizer.

[@N8ESP]

Definitely shake down your POTA/SOTA/Portable stuff before venturing off into the wild. I prefer to do all my testing in the front yard. In spite of living in the same neighborhood for 20+ years, there are still a few neighbors who still hold out some hope that I'm somewhat normal. Nothing like a bright yellow 25' Rybakov antenna on a 40' telescoping mast to convince them of the folly of their ways. Definitely a good call on the first aid kit and H2O. Both are easy to overlook, but the absence thereof can put a quick end to an outing.

[@mike-M0MSN]

Solex inverters are RF quite 😊

[@ac0m-glennthompson432]

Always excellent advise from Mike!! Can never go wrong listening to him!

[@DarkShadowCustoms]

Doing a few test runs at home is great if possible. I always have a tendency to over pack no matter what I am packing for. I don't completely empty out my bag all the time and stuff that never gets used tends to stay in the bag.

[@BradSnyder1]

Great advice and information as always Mike!

[@N2YTA]

You need a first aid kit. Recently I pinched the tip of one finger and I couldn’t believe how much it bled. I didn’t have a first aid kit, I got blood all over everything. I bet the crime scene investigators are still at that picnic table!

[@kennethblackwell1137]

Great MBM....neat answers....

[@adcraziness1501]

@12:00 I want to think they intended to write REEBOW Gear backpack not "Reebok" they look like decent enough packs.

[@derbemobile]

Thanks for the videos. I need my roof re-shingled from a storm. I want to install a stealth antenna on the roof and I live in an HOA. Is there anything I should do before they put the shingles on the roof? Wondering if anything would give me a better chance of making contacts. Mostly interested in digital modes. Currently a Tech and working on General.

[@1shARyn3]

Prime first aid items: Paper towels and electrical tape --- makes excellent bandaids

[@rclark999]

Loves your videos, Mike!

[@Jody_VE5SAR]

Copied from live chat: "​​I've got 36 Enphase IQ7 microinverters on my roof... and my noise floor doesn't change one bit if they're running flat out or are completely isolated."

[@floydteter4323]

Great news, as my installer informed me we’ll be using enphase micro inverters.

[@ChrisRobinsonKF6NFW]

Just because there are harmonics doesn't mean the EFHW is a Multiband antenna. it isn't. Just because the VSWR is resonant does not make it a good antenna either. More amateurs need to model the patterns of each band of there EFHW or EFRW in any environment and they will start to see that it becomes extremely unpredictable once you leave the fundamental band. The dipole should have a nice smooth round pattern to it when modeled, and the EFHW does when modeled on the fundamental frequency ONLY. On the second harmonic, you will see the pattern split into what looks more like 2 lobes, and the 3rd harmonic will cause 4 lobes, and each harmonic will cause the multiplication of lobes in the radiation pattern. These lobes are mostly predictable if modeled properly, but if you just throw your antenna up in the air like most do, nope, you dont stand a chance. It will be hit and miss, you dont know where your signals are going, from one setup to the next, and its not fair to your experience overall because nothing is consistent about your antenna. It isnt like example only: an EFHW vertical on a tripod that you setup the same way every time at each park and control the radials or groundplane environment for proper tuning, and use only on the band its properly tuned for.( I am comparing the typical EFHW 40-10mtr wire strung out vs. something like a 17/25ft whip on a tripod with radials, or groundplane ) Otherwise, the EFHW and the typical dipole we all think of have the same radiation pattern. If you force your antenna to do what its not designed to do, it may do it, but it will not necessarily do it properly. You will force the balun to match loads potentially "multiple magnitudes" greater than can be matched properly , This is causing the heating effects and why you see great inefficiencies. You will start seeing skewed patterns. I do use EFHW and EFRW as MONO band antennas as a permeant antenna, or in limited situations as multi-band with a tuner, as temporary. Many confuse me for railing against the EFHW and I am not, I just want more to become educated about what the antenna actually is, and it is not a magic wire, it is just a simple END FED DIPOLE. A dipole, nothing special about it. Folks confuse it for a magic wand because its fed at the end and can be waved around on the end of their hand held radios. Its kinda funny really. The truth is, its a dipole, it just has a much higher impedance to feed it on the end. In regards to the POTA/SOTA supplies, I never go alone, as a safety reason. My wife and I own an emergency prep company and are consultants as well. We advise others to also not do some things on your own in some areas for safety reasons, not just from other persons, but from trip and fall hazards, or from your own health risks. We also carry many variety of First Aid, and EDC to cater to the environment we will be in, and the wife is also a ham, so we keep a variety of radios.

[@paulsengupta971]

What you're actually saying with the radiation patterns, is that when you get away from the fundamental, the antenna becomes more omnidirectional rather than being bi-direction - it becomes quad-directional, etc, and especially if you mount it as an inverted-V, it will have great properties on the harmonic bands... :-)

[@ChrisRobinsonKF6NFW]

@@paulsengupta971 no not at all. Those lobes do not go out in directions typically of N-E-W-S, they typically launch upwards, and outwards in sudo-random patterns, meaning that as an example nothing is radiated at 6,12,25, 50, degree elevation points. which then means you could be skipping a signal right over the folks you do want to talk to, that your antenna becomes a NVIS at other angles or useless. These arent points on a compass. Unless you are like my ex-wife and thinks N is pointing straight up and S is pointing straight down and E or W is any other direction in the horizontal plane?? Please model your antenna, dont just assume you understand how these patterns look. Think of a bicycle wheel, and the spokes from the center of the hub. Each spoke pointing the direction out as as the angle of radiation. Well if you remove some of those spokes, you will have dead spots. Those will be where your Nulls are. Nothing in, nothing out.

[@carson3210]

Victron makes the best charge controllers...

[@1shARyn3]

Try the 21st Harmonic of 7MHz

[@george_KC1TQF]

Wouldn't the panels on the roof act as a faraday cage to a point and block the antenna in the attic?

[@hamradiotube]

Sadly no. Plus the charge controller/inverter is generally located inside the house/RV so it wouldn't matter anyway.

[@floydteter4323]

I had the installer designer place the solar panels on the attached garage roof, a little south and a touch lower than the attic over the house. So I should be good on this point.

[@benwilliams8596]

well solar on the roof is going to block the antenna in the attic

[@floydteter4323]

Fair point. I had the installer designer place the solar panels on the attached garage roof, a little south and a touch lower than the attic over the house. So I should be good on this point. Thanks for raising this.

[@hazer72]

I don't think Satan is a fan of mail bag monday 😈

[@hazer72]

never mind, glitch in the matrix 🙀

[@hamradiotube]

They're called Zoomies

[@soulstudioshamradio]

And buy a real tourniquet..bad time to find out that cheapo failed

[@BMCTackle]

Great explanation, best I’ve seen on Harmonics. Louis WW7GBA