When: Saturday, April 13, 8am – noon.
Admission: $5.00
Location:
North High School Cafeteria
1400 25th Street
Columbus, IN 47201
From a presentation on decibels by Gary Davis, KD9SB: what they mean and how to compute them.
Practice Circuit with Morse Key, AM Radio, and Power Source
Note: the FCC allows low-power, unlicensed transmission (effective service range < 200 ft without interference) in the AM and FM bands. See: Part 15 Devices. Check your local jurisdiction before transmitting.
Antenna coax must be momentarily shorted before each use, or damage may occur to the MFJ269 Antenna Analyzer.
Simple impedance check: use an accurate SWR meter and divide Zo, 50 ohms, by the SWR. Do not use this method unless Xs reactance is very close to 0 ohms, if antenna Z is greater than Zo, or if SWR is very high. Antenna load should be resistive only. For more information about formulas used in the calculations below, see: Radio Electronics Formulas
Run each test several times. Tests can be inaccurate due to nearby metal structures or elements, as well as other conditions, including strength of the mag
mount, earth ground, etc.
| Resonance Freq. (MHz) | Rs (ohms) | Xs (ohms) | SWR | Zo / SWR (ohms) | Z measured (ohms) | Z calculated (ohms) |
|---|---|---|---|---|---|---|
| 14.380 | 27 | 9 | 1.9 | 26 | 26 | 28.46 |
| Resonance Freq. (MHz) | Rs (ohms) | Xs (ohms) | SWR | Zo / SWR (ohms) | Z measured (ohms) | Z calculated (ohms) |
|---|---|---|---|---|---|---|
| 14.148 | 41 | 20 | 1.6 | 31.25 | 45 | 45.617 |
Note: High Xs reactance leads to poor impedance estimation via the simple impedance check.
| Resonance Freq. (MHz) | Rs (ohms) | Xs (ohms) | SWR | Zo / SWR (ohms) | Z measured (ohms) | Z calculated (ohms) |
|---|---|---|---|---|---|---|
| 146.73 | 45 | 3 | 1.1 | 45.45 | 45 | 45 |
| Resonance Freq. (MHz) | Rs (ohms) | Xs (ohms) | SWR | Zo / SWR (ohms) | Z measured (ohms) | Z calculated (ohms) |
|---|---|---|---|---|---|---|
| 146.45 | 41 | 8 | 1.2 | 41.66 | 40 | 41.77 |
| Resonance Freq. (MHz) | Rs (ohms) | Xs (ohms) | SWR | Zo / SWR (ohms) | Z measured (ohms) | Z calculated (ohms) |
|---|---|---|---|---|---|---|
| 103.97 | 52 | 1 | 1 | 50 | 50 | 52 |
Prepared by Gary Davis, KD9SB, 07-11-18