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- Why do hams often conclude messages with 73?
The usage of "73" for such a purpose comes from the Phillips Code, originally devised in the era of telegraphs to speed up transmission of common messages by mapping them to numbers "73" mapped to "best regards" or "my compliments" and was intended as a general valediction for transmitted messages It is still used for that purpose today in morse code transmissions and often makes its way
- What is the impedance of an end-fed half-wave antenna?
Model the 1 2 wave center fed antenna using the wire size, altitude, and all location attributes to determine the center fed impedance divide 600 by the 73 ohms or whatever you calculate the center fed impedance to be then multiply the answer by 600 --- you're home Example: 600 73 = 8 22 × 600 = 4900 600 73 = 8 22 × 600 = 4900 ohms This is the original and correct quarter wave transform
- Coaxial Folded Dipole Antenna Matching Impedance
The site above depicts a regular dipole, with a simple matching system First, a bit about dipole impedance The impedance of a dipole is 73 Ohms at resonance, but away from the resonant frequency the impedance is different At frequencies lower than resonance, i e when the antenna is too short, it is capacitive, and its resistance is lower The Smith Chart is the usual way of plotting this
- Understanding how antenna mismatch can damage a transmitter
Antenna impedance is largely due to radiation resistance: a center fed half wavelength dipole has a radiation resistance of about 73 ohms Resistance due to heat loss is negligible, and I believe reactance negligible as well Let's say we have an oscillator consisting of a 1 MHz voltage source (30V RMS) in series with a 75 ohm resistor
- How to estimate a dipole feedpoint impedance? - Amateur Radio Stack . . .
An ideal dipole, at resonance, will have an impedance around 73 ohms A folded dipole, around 280 ohms How can I calculate the impedances when not at resonance? Let's assume I have a span of 15M
- How does one read a ferrite datasheet? - Amateur Radio Stack Exchange
For example, Fair-Rite's 73 material: What's a μ′s μ s and a μ′′s μ s ″? What do these numbers represent, and how can I use them in amateur radio? Do they allow me to predict inductance or losses of inductors made on cores of this material? What is the relevant math?
- Core mix preferences for a balun (or unun) vs a choke
The MnZn ferrite cores (Mix 31, 73, 75) have high permeabilities above 800 µ, have fairly low volume resistivity and moderate saturation flux density They offer high ‘Q’ factors for the 1 KHz to 1 MHz frequency range
- Whats the difference between saying “CQ” or “QRZ” in a contest?
The best thing to do is to listen for a while, and notice which stations are being responded to Sometime operators will prematurely respond with their callsign, without waiting to hear if the other station has finished broadcasting It's about %80 timing and %20 luck! And, as always, good luck and 73!
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