Interlock is preventing transmission -- but it shouldn't block this

Here's the key concept: your signal is not just a single frequency — it has width.

When you set your VFO to 14.347 MHz and transmit SSB with a 3100 Hz (3.1 kHz) bandwidth, your signal doesn't just occupy that one spot. It spreads out around it.

On USB (Upper Sideband, which is standard on 20m), your signal occupies frequencies above the dial frequency. So with a 3100 Hz bandwidth:

• Lower edge of your signal: 14.347 MHz (the dial frequency)
• Upper edge of your signal: 14.347 MHz + 3.1 kHz = 14.350.1 MHz

The 20m band edge is 14.350.000 MHz.

Your signal's upper edge lands at 14.350.100 MHz — 100 Hz outside the band.

A simple way to think about it:

Imagine your signal is a 3.1 km wide truck. You parked the front bumper at the 14.347 marker, but the truck is so wide that the back bumper sticks 100 meters past the 14.350 boundary into the next property.

You're over the line — even though your dial says you're fine.

The practical fix:

On 20m USB, keep your VFO at 14.347 MHz or lower and make sure your bandwidth doesn't push the upper edge past 14.350. Many operators use a guideline like this:

Dial frequency + transmit bandwidth ≤ band edge

So with 3100 Hz bandwidth: 14,350,000 − 3,100 = 14,346,900 Hz (14.346.9 MHz) is the highest safe dial setting.

Some operators simply reduce their TX bandwidth near band edges, or just stay a safe 3–4 kHz below the edge to be sure.