HDTV Receiving Interference

The Works wrote:

Bill.Winegard wrote:
Did you measure the voltage at the head of the Batwing? If you have 13.5V on the roof with the fans running I would suspect that the power supply is wired to a dirty 12V circuit or the power supply itself needs to be replaced. If you have a way of connecting to a different circuit (or run something directly from a 12V battery/power source you could determine which is at issue.

I measured 13.5 at the antenna right on the coax cable. Some have suggested placing a capacitor from the +12vdc line to ground, do you think this is feasible and what size of cap would be required. I'm thinking about replacing the oem 12vdc power supply with a 120vac to 12vdc converter and running the antenna off the substituted power supply.

Bill..I'm back with the same pixelization issue I've been having since replacing my OEM TV antenna. When I turn on the bathroom fan the TV's, (2) start pixelating to the point where the TV's are unwatchable. I ran a 14 awg wire directly from the RV battery to the wall plate, disconnected the oem +12vdc power source and connected the battery to the antenna +12vdc connection, the results were the same. I substituted the +12 vdc power source with a 120vac to 12vdc converter and again the results were the same. Both the RV battery and ac converter supplied +13.41 volts to the antenna. When the fan is turned on the voltage drops to +13.39 a difference of two hundredths of a volt, I don't think this lower voltage is effecting the operation of the antenna. I reconnected the RV oem +12 source and re-measured the voltage with both the fan on and off and basically I had the same readings with the same voltage drop. I'm starting to think the antenna might be bad? Your thoughts are appreciated.

Pull the wall plate out and disconnect any cable that is used for going to other televisions. Tighten the ones that are left and test again. If the issue improves reconnect and tighten again. A loose ground connection can cause havoc. If no joy and you feel like experimenting you can run a fresh power and ground lead. However find a different power source if possible.

This isn't a dirty power supply problem. It's likely that the motors are generating RFI that the antenna is picking up. You need to either add ferrite clamps or .01uf caps as close to the motor as possible. The leads coming from the motor is acting as an antenna and must be shunted.

Bill.Winegard wrote:
Did you measure the voltage at the head of the Batwing? If you have 13.5V on the roof with the fans running I would suspect that the power supply is wired to a dirty 12V circuit or the power supply itself needs to be replaced. If you have a way of connecting to a different circuit (or run something directly from a 12V battery/power source you could determine which is at issue.

I measured 13.5 at the antenna right on the coax cable. Some have suggested placing a capacitor from the +12vdc line to ground, do you think this is feasible and what size of cap would be required. I'm thinking about replacing the oem 12vdc power supply with a 120vac to 12vdc converter and running the antenna off the substituted power supply.

the key problem is you are using the oem install line
you need to install the correct 'filtered' sensar power supply

For noise isolation in DC circuits in cars, two approaches are used.

1. Ground the AC component from the offending motor or generator brushes through a capacitor. RF goes right through, DC is blocked from grounding. If the RF noise isn't grounded, your 12V DC wiring serves as an antenna to broadcast it.

2. Block the RF AC from coming into the power supply of the electronic device using a choke. The power supply for the TV probably takes care of this, but the noise is likely coming into your antenna feed along with the 12V DC powering the signal booster. I don't know why the switch for this power lacks the choke, maybe a cost thing.

I suspect the noise is coming from the brushes of the fan motors... Placing a ferrite bead on the 12VDC line right at the fan motor may help... I think What is happening is the brushes are modulating the primary DC line with RFI type noise.

Sometimes just placing a capacitor to ground from the 12VDC line right at the fan motor might help...

I was going to point my thoughts to a newly installed LED LIGHT. You don't by any chance also have a newly installed LED light coming on at the same time the fan comes on.

The regulated type LED lights are known to produce RFI signals that blanks the HDTV sets as well... Just another thought...

Roy Ken

Did you measure the voltage at the head of the Batwing? If you have 13.5V on the roof with the fans running I would suspect that the power supply is wired to a dirty 12V circuit or the power supply itself needs to be replaced. If you have a way of connecting to a different circuit (or run something directly from a 12V battery/power source you could determine which is at issue.