howto:hambasics:sections:practice
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howto:hambasics:sections:practice [2020/10/24 16:11] – va7fi | howto:hambasics:sections:practice [2020/12/30 09:08] (current) – va7fi | ||
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Now back to the receiver. | Now back to the receiver. | ||
+ | |||
+ | |||
+ | ==== Filters ==== | ||
+ | Sometimes a specific noise or interference is mixed in the signal and we'd like to reduce or eliminate it. One way is to use filters. | ||
+ | * A filter that lets high frequencies through but blocks low frequencies is called a //high pass// filter. | ||
+ | * A filter that lets low frequencies through but blocks high frequencies is called a //low pass// filter. | ||
+ | * Combining a high pass and low pass filter we get a //band pass// filter, which lets audio between two frequencies. | ||
+ | * An SSB voice signal can use a 2.4 kHz filter where as | ||
+ | * A CW signal can use a much narrower 250 Hz filter. | ||
+ | * The " | ||
{{ notch1a.png }} | {{ notch1a.png }} | ||
- | {{ notch2.png }} {{ notch3.png }} | + | This picture has three main parts. From top to bottom: |
+ | - The frequency is 7.100 MHz on LSB. | ||
+ | - The scope shows this frequency relative to the entire band (7.000 Mhz to 7.300 Mhz) | ||
+ | - At the bottom is the audio spectrum of what we hear (with a 2.4 kHz band pass filter). | ||
+ | You'll notice that there' | ||
+ | <WRAP centeralign> | ||
+ | {{notch2.png? | ||
+ | </ | ||
- | ===== Stability ===== | ||
+ | |||
+ | ===== Stability ===== | ||
+ | This is the ability of a receiver to stay on the right frequency and not //drift//. | ||
====== Transmitters ====== | ====== Transmitters ====== | ||
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- | ======= Questions | + | ====== Questions ====== |
* B-003-010-001 -> B-003-011-001 | * B-003-010-001 -> B-003-011-001 | ||
- | [[stationassembly |{{/ | + | [[stationassembly |{{/ |
howto/hambasics/sections/practice.txt · Last modified: 2020/12/30 09:08 by va7fi