The Ionosphere, Shortwave Radio, and Propagation

Philip Erickson
MIT Haystack Observatory
Dr. Philip J. Erickson, W1PJE, is an assistant director and head of the Atmospheric and Geospace Sciences group at Haystack Observatory, operated by Massachusetts Institute of Technology (MIT). Since the late 1950s, MIT Haystack, located in Westford, MA, has used radio science to conduct frontier research into the properties of the near-Earth space environment, including the ionosphere, neutral atmosphere, overlying plasmasphere, and the magnetosphere that surrounds our planet. Dr. Erickson is a licensed Extra class amateur and a member of ARRL, RSGB, the Nashoba Valley Amateur Radio Club (NVARC), and the HamSCI initiative. He holds B.S. and Ph.D. degrees in electrical engineering and space plasma physics from Cornell University and is a member of both the American Geophysical Union and the International Radio Science Union. Dr. Erickson is the lead principal investigator of a National Science Foundation sponsored UHF megawatt class ionospheric radar at MIT Haystack, and has authored or co-authored 75+ refereed articles in the areas of ionospheric and magnetospheric phenomena and radio physics. Dr. Erickson started his radio career with a random wire and a Hallicrafters SX-110 receiver, and enjoys 6 meter and HF propagation, QRP, EME, RF design, and digital weak signal modes.
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[@appliedphysicist]

Loving the candid discussion of video and funding issues in the intro

[@l.d.9903]

I feel so fortunate to be able to watch this lecture! Thank u!

[@privateness.network]

Solar cycles are badass, never imagined the Sun's magnetic poles were flipping every 22 years, I knew of Sun's "seasons" but that blew me . Very nice

[@johnwest7993]

I think the multi-wire T top-hat was to add sufficient bandwidth so the operator could operate at not just 1.5 MHz, but also below. The 1.5 MHz is probably just an indication of the 'maximum' frequency of the station. There was no real legal limitation on the frequencies available to amateur radio experimenters until the Communications Act of 1934.

[@MrCSRT8]

My understanding is that the (non-radiating btw) horizontal T-hat wires serve to force more current into the too-short-for-resonance vertical radiator in applications where it would be impractical to have a full quarter-wave vertical due to the very long wavelength. This makes the short vertical radiate "brighter" than it would otherwise.

[@rfengr00]

Great lecture!

[@tixilx]

‘So we can’t record it in arbitrary resolution” 🤪🤪🤨

[@jisa98]

Great lecture, I am interested in shortwave radio and propagation of HF radio waves. This helps understand the science behind the fascinating world of world radio.

[@nukelewman]

Fascinating lecture!

[@justsam0511]

I will like to have permission to share some of the knowledge I gained from here with my colleagues this weekend at national guard drill. I will be giving special thanks to Dr. Erikson and MIT .

[@usuthu65]

Hi Sam - this is way late (just saw your comment), but these are available here on YT precisely so the information can be shared. Drop a comment here on how you ended up using the material. Thanks for the interest.

[@space-time-somdeep]

Fascinating lecture

[@jimwillis176]

The best explanation of propagation on the web!

[@jarrodanderson2124]

What is it that gives the sun its 11 year cycle?

[@rodericksibelius8472]

I continue to LEARN = There are so many things I DON'T KNOW... Thanks for this LECTURE. Microwave Training Institute, a school now 'defunct', owned by ALAN SCOTT, I learned all this STUFF in 1985 in Mountain View, California in 9 MONTHS: taught by working Physicists and Engineers in the SILICON Valley: Klystrons, Magnetrons, TWT's, YIG resonators, use of spectrum analyzers, vector network analyzers, microwave transistor circuits, low noise amplifier design lecture/microwave amplifiers 4-18 GHZ, practical use of the SMITH CHART, normalizing impedance, Admittance/Impedance, VSWR, Reflection coefficient and laboratory work. SHUNT and SERIES LC MATCHING and RADAR BASICS = We graduated to become COMPETENT Microwave Electronics Technicians readily to be employed by the industry.... kTB, Boltzmann constant... etc... etc...

[@SeaMonkey137]

There are some interesting things going on right now in geology with regards to studies of the lower mantle/liquid core modeling and their effects on changes in the magnetic field. So this lecture makes me think there may be some exciting times ahead as we struggle to understand better space weather's interaction with the Earth and the implications that could have on the future climate change debate.

[@mikeh39]

Index of near earth atmosphere is very close to unity. In the presence of plasma (equal distribution of positive and negative charge) the refractive index will drop below 1, depending on the frequency of the electromagnetic wave. This is the optics of metals as described in Born & Wolf. The radio wave is reflecting from what it perceives as a metallic layer. One slide in the presentation correctly identifies this as total internal reflection as occurs in an optical fiber, but I don't believe it is correct to characterize this as refraction -- at least not from the perspective of ray tracing and classical optics.

[@MegaVikas1984]

I like it. do anyone let me know what kind of effects we see during 846 kHz medium wave propagation through 35 meter antenna. How our signal respond to bad weather like storms and heavy rain and lightening.

[@anonviewerciv]

The medium changes the message. (5:30,1:10:30) 51:00 Ionosphere.

[@johnnywilliams2641]

I don't think the Soviet union was too happy with that ship broadcasting the Voice of America.

[@Este730]

Do you think ufos are recharging energy from the atmosphere

[@angus4949]

Moralim bozuluyor şunları gördükçe.

[@mikemcdonald5147]

Frank W3LPL knows thats the correction on Marconi because he was there LOL :)

[@lalchandra4590]

Why 4 people dislike this?

[@RESISTAGE]

I bet 1 of them was my wife.

[@johnwest7993]

I'm one of the 12 people who is watching!

[@robseal3073]

only 142 likes and 2 thumbs down?! but mnm sold a million albums?! geesh!! haha

[@peterfriesen4885]

I-on-no-sphere

[@tonydesaire9326]

Geospace vs ionosphere? That's my biggest pet peeve with academia, always picking a new name for something that already has a perfectly good name.

[@fredriko.zachrisson9711]

100% agree.

[@usuthu65]

@@fredriko.zachrisson9711 Thanks for your interest. Geospace != ionosphere. The ionosphere refers to the charged portion of the upper atmosphere. Geospace refers to the larger set of processes occurring in near-Earth space, such as those farther out in the magnetosphere (portion of space where Earth's background magnetic field is a dominant force; plasma densities are very low compared to the ionosphere). So the names are not describing the same region, and are appropriate.

[@akinbulifeyisara4770]

I need a friend who is vast in ionospheric physics who can help me become better.... I'm from Nigeria

[@bluecarriage5876]

Hello)

[@hallieboy]

Great lecture, but those soy boys in the beginning😝

[@papa8293]

Would the guy that keeps interupting the speaker, please shut up.

[@aricanto1764]

The whole cold war was just to cover up ionosphere research lol

[@fredriko.zachrisson9711]

Is that Jim Jefferies?

[@RadioAntics]

Great lecture!