Understanding VHF Propagation
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- เผยแพร่เมื่อ 6 ก.ค. 2024
- This video provides a technical introduction to both common and uncommon propagation modes at VHF.
Timeline:
00:00 Introduction
00:12 Presentation overview
00:44 About VHF
01:49 VHF versus HF
03:07 Why study VHF propagation?
04:12 About “line of sight”
05:02 Common VHF propagation modes
05:41 About refraction
06:28 Refractive index (N)
07:32 Tropospheric refraction and the radio horizon
08:34 About reflections
09:47 Extending range using reflections
10:31 Reflections and multipath
11:36 About diffraction
12:25 About scattering
13:19 About uncommon VHF propagation modes
14:34 Uncommon VHF propagation modes
14:51 About temperature inversions
15:33 About tropospheric ducting
16:19 Ducts and frequency
16:59 Ducting and weather
17:39 Two types of tropospheric ducts
17:54 Surface ducts
18:34 Elevated ducts
19:06 Propagation along ducts
19:32 Sporadic E
19:41 Ionospheric propagation (skywave)
20:26 Ionospheric propagation (skywave) - E layer
20:41 About Sporadic E (Es)
21:54 Mapping Es
22:28 Causes of Es and predicting Es
23:28 Es or tropospheric ducting?
24:05 Meteor burst
24:13 About meteor burst
24:57 Meteor size / velocity and ionization
25:43 Types of meteors
26:04 Shower meteors
26:54 Sporadic meteors and time of year
27:24 Sporadic meteors and time of day
28:22 Applications of meteor burst
29:34 Meteor burst: distances and frequencies
30:46 EME
30:44 The moon as a reflector
31:52 Advantages of EME
32:49 EME challenges
33:20 EME path loss
34:00 EME antennas
34:37 EME and noise
35:34 Position of the moon
36:50 Motion of the moon
38:02 Surface of the moon
39:06 EME and the ionosphere
40:02 Summary of uncommon VHF propagation modes
41:51 The (future) role of uncommon VHF propagation modes
43:07 Summary - วิทยาศาสตร์และเทคโนโลยี
These videos are really helping me for my radio amateur license exam! Thx!!
Thanks and good luck! 73 DE KO4LZ
That is a True 5 stars ratin video ! Absolutely perfect !
Thank you!
Wow, very comprehensive overview! Thank you.
Thank you!
Another fantastic video! You had me watching the whole way though. Listening to the Soviets off the moon ... thats insane!
So this is how the Sputnik satellite was used to measure some properties of the ionosphere
Wow, 250dB path loss for EME is wild! If the noise floor is at -170dBm, a I suppose a 1kW=60dBm transmitter and a 10dBi tx antenna + 10dBi rx antenna would barely make the link budget pencil out, right at the edge of what's possible. Cool! What kind of process gain is typical in modern protocols?
EME has (for now ...) more or less moved entirely into the amateur realm, so the "modern" digital protocol is mostly JT65, which has 10-15 dB of processing gain over CW.
I would like this, but there are already 73 likes!
Please don't let that stop you :) Thanks for the comment!
EME. Wow. Could this be the source of space music?! I jest of course but makes you think what we as humans have thrown out into space. All those broadcasts in not just VHF but all frequencies emitted since the beginning of radio. It would be weird if one day in the future, where we have even more sensitive equipment than now, to pick up spark gap radio signals from say the RMS Titanic or Moon landing "data", that bounced off of celestial bodies. Talk about time travelling. Its not out of the realm of possibility to stumble across "time capsules". We have questionable asteroids that have turned out to be space junk such as the S-IVB stage of Apollo 12. The LEM of Apollo 10 a.k.a. Snoopy is still out there somewhere as well.
I suppose instead of "aircraft scatter" one could also have a "spacecraft / space junk scatter" mode :)
360p Team !! :D
Video is available up to full HD (1080p) :)