This is a fascinating and unusual problem. Here's a breakdown of potential causes and troubleshooting steps

Understanding the Problem
Interference

The key suspect is electromagnetic interference (EMI) generated when you switch on the fluorescent lights. Fluorescent lights, especially older ones or those with failing ballasts, are notorious for producing a broad spectrum of EMI.

Over-the-Air Signal

Distant over-the-air (OTA) signals are weaker and more susceptible to interference than cable or streaming.

Frequency Specific

The fact that it only affects one channel suggests the interference is particularly strong at the frequency that channel uses.

Different Circuits - NOT Always a Guarantee

While the circuits are separate in your breaker box, wiring can still run in close proximity within walls, potentially allowing interference to couple from one circuit to another. Also, both circuits might share a common ground somewhere.

New Observation, Changes?: As you mentioned you likely didn't notice before, it's likely not a longstanding situation. Have you changed anything recently? Changed the location of the antenna, new appliances etc.

Possible Causes1. Fluorescent Light EMI



Ballast Issues

The ballast (the electronic component that regulates the current in the fluorescent tube) could be failing. Failing ballasts often produce excessive EMI. Old magnetic ballasts are worse than newer electronic ballasts.

Unshielded Fixture

The fluorescent fixture itself might not be well shielded, allowing EMI to radiate freely.2.

Antenna and Coaxial Cable Issues



Poor Shielding

The coaxial cable connecting your antenna to the TV might not be adequately shielded. EMI can be picked up by the cable and injected into the TV's tuner.

Loose Connections

Loose or corroded connections in the coaxial cable can make it more susceptible to interference.

Antenna Placement

The antenna might be picking up the EMI directly. Its position relative to the fluorescent lights could be critical.

Antenna Gain

High-gain antennas amplify both the desired signal and any interference.3.

TV Tuner Weakness



Age

Older TVs might have less robust tuners and be more susceptible to interference.

Factory Defect

Although less likely, a manufacturing defect in the TV's tuner could make it more sensitive to EMI at specific frequencies.4.

Grounding Issues



Improper Grounding

If your electrical system has grounding problems, it can create loops that amplify EMI.

Shared Ground

Even though on different circuits, a shared ground point could provide a path for EMI to travel.5.

Other Nearby Devices

While you're focusing on the fluorescent lights, other devices on the same or nearby circuits (especially those with motors or switching power supplies) could be contributing to the problem.

Troubleshooting Steps1. Isolate the Fluorescent Lights



Test with Incandescent/LED

Temporarily replace the fluorescent bulbs with incandescent or LED bulbs in the same fixtures. LED bulbs are generally very quiet from an EMI perspective. If the problem disappears, the fluorescent lights are definitely the culprit.

Bypass Ballast (If Possible and Safe)

If you're comfortable working with electrical wiring and know what you're doing, you might be able to temporarily bypass the ballast (research how to do this safely!). This would eliminate the ballast as a source of EMI. Warning: This can be dangerous if not done correctly. If you're not sure, don't do it!2.

Antenna and Coaxial Cable Check



Check Connections

Make sure all coaxial cable connections are tight and clean. Use a contact cleaner on corroded connections.

Shielding

Inspect the coaxial cable for damage. If the shielding is compromised, replace the cable with a high-quality, well-shielded cable (RG6 is a good choice).

Antenna Repositioning

Try moving the antenna. Even a small change in position can make a difference. Rotate the antenna, or move it further away from the fluorescent lights.

Try Different Antenna

If possible, try a different antenna, especially one with better shielding.

Ground the Antenna

Ensure the antenna mast is properly grounded, as this can help to bleed off any induced EMI.3.

Test Other Devices

Turn off other electrical devices in the vicinity to see if they are contributing to the interference.4.

Check Grounding



Outlet Tester

Use an outlet tester to check for proper grounding in the outlets used by the TV and the fluorescent lights.

Consult Electrician

If you suspect grounding problems, it's best to consult a qualified electrician.5.

TV Test



Different TV

If you have another TV, try it in the same location with the same antenna. If the problem persists, it's likely not the TV itself.

Rescan Channels

Rescan the channels on your TV. Sometimes the TV needs to re-calibrate the signal after changes.6.

EMI Filter



Line Filter

Try plugging the TV into a power line filter or surge protector with EMI/RFI filtering.

Ferrite Chokes

Clip-on ferrite chokes (also called ferrite beads) can be added to the coaxial cable near the TV and near the antenna to help block EMI.7.

Fluorescent Light Replacement



Replace with LEDs

If the fluorescent lights are old or have failing ballasts, the easiest and most reliable solution might be to replace them with LED fixtures. LEDs are much more energy-efficient and produce far less EMI.

Replace Ballast

If the fixtures are newer, try replacing the ballast.8.

Electrical Inspection



Electrician

If you've tried all the above steps and the problem persists, consider having a qualified electrician inspect your electrical system for grounding issues or other problems that could be contributing to EMI.

Important Safety Notes Electrical Work

If you're not comfortable working with electrical wiring, don't. Hire a qualified electrician.

Power Off

Always disconnect power before working on electrical circuits or fixtures.

Safety First

Be extremely careful when working with electricity.

Why This is More Likely Now DTV Transition

The digital television (DTV) transition shifted some TV channels to different frequencies. It's possible the channel that's now affected is using a frequency that's more susceptible to EMI in your environment.

Aging Components

As components age (especially ballasts), they tend to generate more EMI.*

Changes in Broadcast Power: Although less likely, the broadcast power of the affected channel might have been reduced, making it more susceptible to interference.Let me know if you have any more information or try any of these steps. I can provide more specific advice based on your results. Good luck! Flag for review