Contents
How do you calculate local oscillator frequency?
Calculation of the Image-Frequency
- 108,5 MHz = foscillator + fIF foscillator = 108,5 MHz – f. IF
- 87,0 MHz = foscillator – fIF foscillator = 87,0 MHz + f. IF
What does Vfo mean in ham radio?
variable frequency oscillator
A variable frequency oscillator (VFO) in electronics is an oscillator whose frequency can be tuned (i.e., varied) over some range. It is a necessary component in any tunable radio transmitter or receiver that works by the superheterodyne principle, and controls the frequency to which the apparatus is tuned.
How is image frequency rejection?
The image rejection ratio, or image frequency rejection ratio, is the ratio of the intermediate-frequency (IF) signal level produced by the desired input frequency to that produced by the image frequency. The image rejection ratio is usually expressed in dB. In a good design, ratios of >60 dB are achieveable.
What are the 2 meter simplex frequencies?
2 Meters (144-148 MHz)
| 144.00-144.05 | EME (CW) |
|---|---|
| 146.40-146.58 | Simplex |
| 146.52 | National Simplex Calling Frequency |
| 146.61-146.97 | Repeater outputs |
| 147.00-147.39 | Repeater outputs |
What does mode mean on radio?
A mode is a way of changing electromagnetic waves, modulating them so that transmission of information is possible. Modulating signals can be either analog, for example, sound or digital, for example, simple binary on-off.
What is the frequency of a VFO circuit?
The circuit, with the values shown, operates between 4.570 and 4.646 MHz. To change the values for the frequency you want, multiply the values by the ratio of your desired frequency to 4.570 MHz.
Which is the best NPO for a VFO circuit?
C9 and C10 should be the best NPOs that can be obtained. They are critical for good stability. Any drift in these caps has a huge effect on VFO frequency. Again, different values can be used, as long as the total capacitance is the same. C16 is one section of the original main tuning capacitor of the HQ-140-X.
How does C4 shorten range of VFO circuit?
The formulas for calculating the proper values are on page 21 in the November 1981 of QST. Working without the formulas, C4 in series with C6 will effectively lower C6’s value and shorten its range. The parallel capacitor C5 will also shorten the range of C6, and lower the low end frequency of the VFO.
Which is the best transistor for a VFO?
The FET, a transistor low-noise design, and the NE602 used as a VFO. I have built and used them all except the transistor low-noise design. My favorite is the NE602, which I use in almost all my equipment where I need a 10 to 14MHz VFO. I have the FET at 10MHz in two receivers and it works great.