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Complete Idiots Guide to RF Propagation – Amateur Radio Foundation

Complete Idiots Guide to RF Propagation – Amateur Radio Foundation


WARNING – COMPUTER GENERATED SUBTITLES haha very good day well
listen I’m digging into the foundation now but this is the kind of 2018 spec
there’s not much difference between this and the 2019 exams if anyone you’re
taking this but check back because at the end of this video I may well put a
little strap up here somewhere if I’ve done an update to this all do be that
size what side does the card come out I think
it’s over here anyway so propagation all right where do we start normally at the
beginning mr. mckormick thank you very much
all right they just want blights to tell you and then I’m gonna show you the fun
okay so not more than 10 minutes it here we go um well first of all it says in
the book here that radio waves spread out like a torch you put a torch up
unless it’s a laser beam which is a very fine you know straight line at all she
goes out and it spreads out it gets weaker and weaker doesn’t it so you know
you want to shine a torch in your backyard and you you in your back garden
you can see the tree really easy unless is a very powerful torch you can’t see
the woods a mile away can you because it’s spreading out and getting weak and
weaker you see so and then particles in the air you know bla bla bla
you know all that it’s just the same so radio waves spread out that’s what
that’s what that’s saying oh yes
see here I didn’t read this bit it says and just as the torch has moved further
away the light is more spread out and appears weaker if moves sufficiently far
away it is not visible at all I should do that in a sort of a 1950s grain
shouldn’t I be good and also says that radio waves can penetrate buildings but
at the very height and concrete things like that but that the higher in
frequency you go so that walkie-talkie frequencies will have much tougher job
getting through solid concrete than the low frequencies on what we call the
shortwave all the HF bands okay chef bans a little bit more immune you
know it’s much more sort of low fear long-wavelength you’ll go through
concrete UHF we’ll have a hell of a time so I’m obliged to tell you that as well it says here honestly I don’t know rice
this stuff whatever really but you know there is
one small advantage for the higher frequencies if the wavelength is smaller
than a window the window appears is big enough a big enough hole for it to get
through well luckily my windows are 80 meters wide anyway let’s just talk about
the Sutton Coldfield radio transmitter about 20 miles from here
so that’s on a bit of high ground and I live over here Sutton Coldfield radio
transmitter has at 800 foot tower transmitting 1 million watts of all TV
digital channels these days and I’m down here and I could receive that very
easily because it’s effectively line-of-sight okay however if I am a
droid snow Deneau as an artist is you as snow covered to thing and I’m down here
with my I’ll draw a little walkie talkie with a on it that and there’s my friend
with a little walkie-talkie in his aerial I’m gonna have a hell of a proper
talking to him because the radio signal will be absorbed if you like mountains
getting away no way out of it however there’s two ways we could get signal to
him there’s something called the ionosphere so if that’s the curvature of
the earth the ionosphere is between 70 and 470 and 400 kilometers where metric
here guys multiply by 6 and you get the miles by
the way 67 – 42 17 42 miles 6 12 24 and 240 miles we’ve got the ionosphere and
what happens in the ionosphere is that the Sun and the radiation of the Sun
heats up all little my molecules and I are knives is them I don’t even know
what that means but apparently it does makes the
ionosphere and these jiggle about and we end up
with this sort of conductive gas if you like so when we transmit on our little
at a vertical antenna DD and we transmit those off the head torch there’s every
word on it some of it happens to go there some of the go there where else as
well it will refract and it will come back
down the maximum hop you can get for that apparently is four thousand
kilometers six four twenty four twenty four two thousand four hundred miles
he’s that biggest hop if a mountain is here then we’ll go right over mountain
back down outside so that’s one way out the problem incidentally we have
something called a maximum usable frequency maximum usable frequency is a
frequency they measure with these weird widget ePro be things I honest blobs I
come up with the name and what they do is a test this is they being scientists
universities NASA you know they test by sending radio signals straight up some
of it depending on the frequency will come straight back down again not at all
somebody comes right down the frequency that stops at which it could be anywhere
between sort of one and probably ten eleven twelve megahertz depends um is
know where it just won’t get any further is known as a maximum usable frequency
but that’s when you’re using an antenna called n vis near-vertical
be a vertical instance skywave propagation so you send your signal
straight up and you just get down the other side of the mountain and I’ll be
using envis you see and so the point is our maximum usable frequency is is for
this however we can still use the frequencies above it above the maximum
use of frequency because coming at an oblique angle like this just check on
recording in night never wasn’t thank God at oblique angle we can use
higher and higher frequencies you see because it’s kind of doing less work it
reflects a little bit easier so now work right up to 30 Meg small H capital small
Z or Zed for our spritz and beyond actually there’s other ways the
propagation can work as well incidentally you can get cold and hot
air and in the summer and you can get ducting and tropospheric where our VHF
signal goes up trundles along and then comes down somewhere else and actually I
was on a hundred foot tower many moons ago for whittles field day first field
day I went to actually and I said I was what you call CQ contest and I went on
there and this guy from Romania came back on two meters and our little mini
pileup must have found his friends and this mini pilot was a Romanian every
thought was amazing but I actually thought what I did I’m 40 meters all the
time what’s the big deal girls that realize it was on two beaters it was on
a high very high frequency VHF so who knows hey wait a minute me just check
range 4000 we’ve done that frequency affects the range yeah the only thing I
haven’t done is the time of day so when there’s a lot of ionospheric ghibli
Pokkiri going on in other words the sun’s up the ionosphere is doing its
thing the molecules are jiggery-pokery around then our our propagation be very
good for the higher frequencies and then at night when when this it stops
jiggling about so much their lower frequencies coming
so it actually depends on the time of day and propagations you subject and it
will take you years to really get a grip of it and really understand it some
people just go you know I’m just gonna work on 30 meters or 20 meter band for a
couple years to really understand it I was a 40 meter freak as it happens
that’s yeah really gonna words for 40 weirdly enough
and I got really to understand it fascinating man but all the bands are
you see it just depends how well you know them I I could get a VK you know
what one day at seven in other words Australia from the UK you
know quite often because I don’t know what I’m doing and I know exactly what
time of day it’s gonna happen you know now I’ve done that I’ve got a bit of a
Easter Egg for you little bit of fun here that this so this is and if you
like I’ll try and I’m going to put this link to the bottom of the restrictions
so this is just the horizon so I thought this would be quite handy to understand
for VHF and uhf but I was amazed by the way if you believe in the Flat Earth
dial away now this is not so it’s not gonna help you so this has bottom left
here H zero which is our height so let’s say we stand on a tower and it’s 75 feet
high we could do this in meters as well and then our target distance we got a
friend of ours on another tower and he’s 20 miles away all right I can calculate
this and it’ll tell me the distance to the horizon is 10 miles and the target
will be hidden by 58 feet ‘we don’t have to be a lot taller actually to clear not
only the horizon but this Ben as well but now I’ve had VHF contacts you see it
like say 120 and I’ve had like 120 miles on VHF you know just general chitchat
hundred watts can you hear me yes I can but calculate that my hidden target
would have been 8,000 feet beyond ya service I’m thinking it was
line-of-sight it couldn’t have been my signal must be ducting must be following
and that’s why I some nights I could hear these slightly longer stations very
easily and other nights I could hardly hear them at all something to do with
propagation I just coughed in and cut that out so you didn’t have to
observe it have lovely day enjoy your weekend great videos coming up if you’ve
enjoyed this by the way hit the subscribe button give me a like why not
if you haven’t liked the film give me a like anyway just for the hell of it have
a lovely weekend over its back holiday weekend here in the UK you know that
means we get three days off so you get a couple more films happy by the end of
the weekend all of us thanks for tuning in my name is Callum good luck

37 comments on “Complete Idiots Guide to RF Propagation – Amateur Radio Foundation

  1. Our club tutor better watch out your videos are getting close to replacing him. Not really, but they do supplement very well. Thanks for a great resource for the guys who cant get to a tutor or club. 73

  2. Great stuff I've passed the foundation series onto our lads at the club for additional learning Cal :-), top job fella!!

  3. Good show om! But you build this as propagation for dummies and then you started talking about the curvature of the Earth. All the dummies think the Earth is flat! I wonder if you got their panties all twisted!

  4. I've experienced meteor scatter sporadic E but Ionospheric jiggling … that must be what we used to call "bitofalifton" 😀 nice one Callum … off to play on 30m now 😀

  5. As this is an educational video, I thought I’d clarify that converting km to miles is approximately km x 0.6 not 6 although you come up with the right answers in the video by subconsciously dividing the answer by 10. 😋

  6. Callam do you still work on two meters or seventy centameters ? Why I am asking is because I would like to get in touch with you on the bridge 3100 talk group . KN4KBH is my call sign. 73s .

  7. Loved it….tittered all the way along 😁…..Looking forward to the next little treat 👍🏻👍🏻 Mark ( m0mco)

  8. This was great information! In the middle of the night sometimes I hear far off stations on VHF some a pretty good distance. haha

  9. Hmmm…Years from now, when we are all dead and gone, and the man from Sotheby's holds up these drawings, he will pronounce that : "These date from his Landscape-period, and are exceedingly rare"….

    Cuddles!

    Paddy

  10. If the max distance a signal can travel bouncing off the ioinosphere is 4000 km, how do people get from one continent to another? Or long path? Not trying to poke holes in the video, I really wanna know. Thanks Callum!

    EDIT: I did some looking around. Multiple hops! I didn't know that was a thing. Thanks Callum!

  11. Like like like …… and yes Callum propagation is a big subject, as for flat earth that’s even funnier, better not mention HAARP,.. to us it’s nothing more then a big amateur radio , to the conspiracy guys that’s a whole different ball game lol.

  12. Being new to amateur radio I've found the learning curve to be quite steep even though I have a technical background. Your videos are invaluable to my learning as they are informative and fun to watch at the same time. Thanks and keep them coming as long as you enjoy creating them. KN4MNA

  13. I get a huge thrill when tropo ducting occurs. I live in Iowa and back in 2015 I was making contacts all the way up to the Canadian border and all the way down to the Kansas/Oklahoma border. All of my contacts that day were on FM with an omni NMO mount on my car.

    Needless to say, the weather radios were completely useless since they use 162.4 to 162.55 frequency range. All pushing 1500 watts and all I could hear was a garbled mess. Even being about 20 miles away from one.

  14. Haha love this. When I was first learning about radio theory and EM propagation in the atmosphere, it seemed like all of the rules of thumb (maybe just "all the rules" period) had an asterisk after them.
    "So VHF and higher is line of sight?"
    "Yes…well, kind of. It depends."
    "And HF is the one to use for longer range contacts?"
    "Yes…well, it depends."

  15. I've just watched this … I might take this exam thing it looks interesting 😀 … when do you do Valve theory 😀

    Well done Cal, nice to see someone is putting back into the hobby.

    Nick
    G8SYE
    (ex BRS40625)

  16. Callum you got the earth incorrect its flat with holes in the poles for the ET and friends space ships ect

    Behave mate

    Hi hi lol
    Graham

  17. This should come from what you have learnt NOT from a book. Would have been easier to say what book it is.

  18. I used to be on one island, where the TV transmitter was 10 km (cca. 6 mi) away on the another side of the bay, so it was perfect line of sight, with no obstacles. The signal was breaking anyway, I was using small room rabbit ears, and neighbour told me that he had even worse signal than me, with roof yagi. At home I have tried many locations (no location was further than 24 km (15 mi) from the transmitter), antennas, and receivers, but digital TV sucks. How it happens to you to get the great signal? On analog we saw even 60 km (40 mi) away transmitter with small rabbit ears clearly. It is just not easy to get signal to me.

  19. What you want is a HAARP array. Heat up the ionosphere, AND upset the flat earthers. But don't forget to wear a tinfoil hat while you're operating it. Works best if you can find someone else to pay the electricity bill. Dipole propeller on the top of your skull is strictly optional.

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