116 lines
6.4 KiB
Markdown
116 lines
6.4 KiB
Markdown
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draft: true
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---
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# You're telling me a Ham Fisted this Metaphor?
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----
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# Amateur Extra
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# Rules and Shit (E1)
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- **PRB-1** is an FCC document that basically says that localities can't fuck with ham radio equipment (within reason)
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- your HOA can't legally do anything about your massive fucking Antenna but they're damn well gonna try
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## TV (E2B)
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- Cable TV uses the same frequency range as the Amateur 70cm band, so you can fit Fast-Scan TV into the same channels
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- what the fuck does this mean (**E2B08**)
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- Transmitting on Channel 2 (VHF TV) is illegal for amateurs
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- **Upper Sideband (USB)** modulation with a sound card is only used for SSTV
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- **NTSC** runs at 525i, 483 of which are visible, the rest is for vsync and other meta stuff
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- so basically 480i with extra metadata
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## Modes and Procedures (E2D)
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- MSK144 is designed for Meteor Scatter
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- Contact can be made on VHF up to 1300mi using Meteor Scatter
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- APRS (Automatic Packet Reporting System) sends packet data, ie locations/text/weather
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- WSPR (Weak Signal Propagation Reporter) is for testing propagation
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- Hellschreiber is for some sort of Fax Machine?
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## Propagation (E3)
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- **Trans-equatorial propagation** can be afternoon or evening
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- Afternoon
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- 4000-5000 miles
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- limited to 60MHz
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- High signal strength, but moderate distortion due to multipath bs
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- Evening
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- Peaks at 7PM-11PM
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- Up to 220MHz, sometimes even 432MHz
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- quenched(tf does that mean?) by moderate to severe geomagnetic disturbances
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- depends on high solar activity
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- **Sporadic-E Propagation**
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- ~~is what happenes to my endocrine system when I'm on a family trip~~
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- is when signals sometimes bounces off the E layer, which gives you less range
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- usually the bouncing happens higher (in the F layer), which gives you more range
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Happens around solstices, especially summer
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## Measuring Stuff (E4A,B)
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- **Frequency Counters** depend on the accuracy of the **Time Base**
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- aka a **Reference Frequency**
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- **Standing Wave Ratio**
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- checks for impedance mismatch
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- measures ratio of peak to trough in a standing wave(?)
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- how do you get a standing wave here?
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- can be measured by an **Antenna Analyzer**, **Directional Wattmeter**, or **Vector Network Analyzer**
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# Receiving Stuff (E4,C,D,E)
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- **Intermodulation** happens when you have two signals with different frequencies passing through a "nonlinear system" (what?), which I guess causes constructive? destructive? interference
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- everything is at least a little nonlinear (again what the *fuck* does that mean)
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- seems like the base frequencies and all their harmonics join in on the interference, I think it's like some sort of clusterfuck of a beat frequency?
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- 
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- okay so plugging $f\left(k,x\right)=\sin\left(2.7\cdot kx\right)+\sin\left(2.75\cdot kx\right), f\left(1,x\right)+f\left(2,x\right)+f\left(3,x\right)+f\left(4,x\right)+f\left(5,x\right)+f\left(6,x\right)+f\left(7,x\right)$ into desmos looks nothing like this graph so
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## Circuit City (E5,6,7)
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- Microwave freqs need short connections to reduce phase shift
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- what?
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- Emitter Follower/Common Collector Amplifier
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- has the RX and TX signals in phase
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- Has a gain close to 1 (doesn't amplify voltage, but boosts current?)
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- ....I'm not actually sure how this works and I'm too sleep to look it up
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- **Op-amp**
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- Voltage amplifier
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- in theory, infinite input impedance, 0 output impedance
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- **Parasitic Inductance** is a thing that fucks with Capacitors
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- physically bigger capacitors have more of this, tends to cause issues for RF
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- Two types of Semiconductors
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- N-Type is negative since it has extra electrons
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- P-Type is positive since it doesn't have enough electrons
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## Digital Signals (E8)
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- **Audio Freq Shift Keying (AFSK)** sends beep boops into a transmitter which sends them as AM/FM/SSB/what have you
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- if the beep boops are too loud going into the transmitter, shit goes wrong with the Carrier Frequency (Overmodulation)
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- This does AoE damage to the band and pisses off everyone whose signal you just interfered with
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- tl;dr It's like talking in a room, if you're too loud you'll piss off everyone in the room next to it (okay the metaphor is dogshit but)
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- you also need to turn off Automatic Level Control/reduce gain to prevent distortion
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- 8-Bit ADC can quantize signal down to 8 bits
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- I honestly don't know what you expected
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## Antennas (E9)
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- Two $\frac14\lambda$ vertical antennas can be used for directionality
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- $\frac12\lambda$ apart in phase yields a figure-8 radiation pattern broadsidei to the axis
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- if they're out of phase, it's the same pattern along the axis
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- $\frac14\lambda$ apart in phase $90\degree$ out of phase is a cardioid
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- 160m and 80m Antennas need directivity due to atmospheric noise
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- At low HF frequencies, ligthning and other stuff generates RF interference that travels far (due to ionosphere refraction)
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- tl;dr Antenna gain isn't gonna do shit to fix the SNR wrt atmospheric noise
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- An **Isotropic Antenna** is the spherical cow of the radio world
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- **Yagi Antennas**
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- 
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- can use a Beta/Hairpin matching system to change the impedance
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- involves using a loop (sometimes shaped like a hairpin) across the terminals of the antenna, which makes the coil act as an inductor
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- This improves antenna performance by reducing reflections of RF energy back down the TX line
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- **Pennant Antenna** is a single-turn terminated loop?
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- tf does this look like
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- Creates a cardioid radiation pattern
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- **Folded Dipole Antenna**
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- $\frac12\lambda$ with a wire in parallel connecting both ends
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- how is this different than a pennant
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- it's literally just a $1\lambda$ wire folded in half
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- I can't find a copyright free pic but just imagine the schematic looks goofy
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- **Gamma Matching** is when a you (impedance?) match a coax cable to an antenna by connecting the shielding to the center of the antenna and putting the coax conductor some fraction of the wavelength away
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- if your impedance is less than 50ohms,this should do the trick?
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- I'm gonna be honest I barely understand what impedance is, forget impedance matching
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- anyway Yagi Antennas rarely have 50ohm impedance so like gamma matching is good for those
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--------
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# Technician
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- nvm I passed this by grinding [hamstudy](https://hamstudy.org)
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- nearly passed the General one too at the same time so uh
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- callsign format
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- standard 2x3
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- `K\w\d\w\w\w`
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- vanity 1x3
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- `K\d\*\*\*`
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