1. What is the J Pole Antenna Frequency Formula?

The J Pole antenna is a popular omnidirectional vertical antenna for amateur radio. The formula calculates the resonant frequency based on the antenna's physical length.

2. How Does the Calculator Work?

The calculator uses the J Pole antenna formula:

Where:

• \( f \) — Resonant frequency in MHz
• \( L \) — Length of the antenna in feet

Explanation: The formula accounts for the relationship between the physical length of the antenna and its resonant frequency.

3. Importance of Antenna Length Calculation

Details: Accurate length calculation is crucial for proper antenna tuning and optimal signal transmission/reception at the desired frequency.

4. Using the Calculator

Tips: Enter the antenna length in feet. The value must be valid (length > 0).

5. Frequently Asked Questions (FAQ)

Q1: Why 234 in the formula?
A: The number 234 is derived from the speed of light and the antenna's electrical length, accounting for the end effect.

Q2: What are common J Pole lengths?
A: For 2m band (144-148 MHz), length is typically around 1.6 feet. For 70cm band (420-450 MHz), about 0.5 feet.

Q3: Does this account for velocity factor?
A: The formula already includes typical velocity factor for copper pipe J Pole antennas.

Q4: How accurate is this calculation?
A: It provides a good starting point, but final tuning should be done with an SWR meter.

Q5: Can I use meters instead of feet?
A: Yes, but you'll need to convert the formula (use 71.3 instead of 234 for meters).