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Weekend Electrical Puzzle

We have the still functional OEM video system in our coach, consisting of crank-up arms with replacement Jack antenna head and the original Winegard video distribution box with antenna power switch in bedroom.  It all works fine and most of time we get excellent reception of the OTA stations on our flat screen TV.  However, we have recently noticed a curious "quirk" in our video reception.  I'm wondering if any of the resident electrical gurus might be able to explain...

Here's the setup:  antenna up, antenna power switch in bedroom "ON", "Antenna" selected with switch on cabinet behind driver's seat.  Turn the TV on, run search for local channels, select a channel to view.  Here's the strange part - in some cases we get the normal, excellent digital video picture on all channels.  In other cases, the picture on all channels is broken up and pixilated.

Here's the puzzle:  We have discovered that the video display is being affected by the lighting combination we are using in the coach.  When the picture is "good", if I turn on one, or both, of the two center fluorescent ceiling lights (the ones controlled by the switches above the entry door), the picture goes "bad".  Then, with the picture "bad', if I also turn on one of the under cabinet fluorescent lights, the picture returns to "good".  It is only the living room/kitchen lights that have this effect - the bathroom/bedroom lights do nothing to the picture.  It took us a while to figure out what combination of lights had what effect on the TV- but now we know!

My question is, why does the fluorescent lighting affect the TV reception?
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Weekend Electrical Puzzle

Reply #1 –
IMO, the only thing common between the lights and the antenna boost is the 12 volt power supply.
Check the voltage at the antenna boost with lights "on" and "off".
No or low voltage to antenna boost will cause pixilation.
Run temporary wires from battery to antenna boost, then turn lights on and off.
Interruption of power to antenna boost could be caused by a bad ground, or bad +12, or blown fuse.
Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: Weekend Electrical Puzzle

Reply #2 –
Quote from: Chuck & Jeannie –

we have recently noticed a curious "quirk" in our video reception.  I'm wondering if any of the resident electrical gurus might be able to explain...

Here's the setup:  antenna up, antenna power switch in bedroom "ON", "Antenna" selected with switch on cabinet behind driver's seat.  Turn the TV on, run search for local channels, select a channel to view.  Here's the strange part - in some cases we get the normal, excellent digital video picture on all channels.  In other cases, the picture on all channels is broken up and pixilated.

My question is, why does the fluorescent lighting affect the TV reception?

It sounds like electrical noise on the power or return.  Besides the suggestions from Wyatt, check the quality of the coax connectors on ALL cables involved.  For years we had intermittent signal quality (sometimes great, sometimes bad, sometimes starting great then gradually degrading over time) on our bedroom TV in the coach.  A couple of years ago it became unusable.  Digging into it further, Steve found poorly done connectors on several cables.  Ultimately he cut off and replaced most of the A/V coax connectors in the coach.  We haven't had a problem since.
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Weekend Electrical Puzzle

Reply #3 –
Thanks Guys, for some good things to check.  I will get the old Fluke out when I have a chance and run some tests.

At least we can get excellent OTA reception - but only if you know the secret light switch combination.  8)
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Weekend Electrical Puzzle

Reply #4 –
It could be the one fixture is feeding ac back into the dc causing the problem. We had several Country Coaches that had the power to the Dometic comfort control and the ceiling flourescents hooked together, The ac's would not work with the lights on so had to separate the power feeds.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Weekend Electrical Puzzle

Reply #5 –
Quote from: red tractor –
It could be the one fixture is feeding ac back into the dc causing the problem.
Good idea, but I don't think would apply here, because both the antenna power and the fluorescent light power is 12 volt.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Weekend Electrical Puzzle

Reply #6 –
If they are on the same circuit that could be the cause. I also had a friend with a Monaco that had a problem with the comfort control and we found it was a bad ballast in one of his florescent lights,
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Weekend Electrical Puzzle

Reply #7 –
I would guess you are getting radio frequency interference (RFI) from the ballast being very near the TV cable in the roof structure. You might change to LED lights instead and eliminate the transformer in the fixtures.

Strange things such as you report seem to happen in many of the older Newmar coaches where the transformers in florescent roof fixtures will interfere with the Dometic 4 button thermostats signals.

Jim
Jim Frerichs
2002 U320 42'

Re: Weekend Electrical Puzzle

Reply #8 –
Quote from: Jim Frerichs –
You might change to LED lights instead and eliminate the transformer in the fixtures.
Thanks, Jim.  Changing the interior lights to LED is already on our future projects list.  Will probably get to it after this trip...or when I get a round tuit.  Where's Bill (Chaplin) when I need him?
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Weekend Electrical Puzzle

Reply #9 –
Reading this topic reminded me that we had a crazy situation back in June when we were staying at the KOA in Winthrop, WA. We were using our OTA RCA antenna perched in the front window for the local stations. I walked to the swivel chair, behind the front passenger seat and the signal improved, if I sat down it pixilated, stand up ,good picture. I did not have any lighting on at the time.
 I had the coax from the RCA antenna plugged directly into the back of our LED Samsung smart TV. Could not figure that one out!
Geoff & Pat Haygarth
1994 U240 SBI GV 36ft Cat 3116, Allison 6 speed
 Build #4448
2015 Jeep Wrangler Sport

Re: Weekend Electrical Puzzle

Reply #10 –
magnetic personality...tee hee

Probably signal cancellation caused by out of phase signal reflection from your body - try moving the portable antenna to improve the station reception. Most portable antennas (bowtie or rabbit ears, etc.) have very little, if any, gain.

Jim
Jim Frerichs
2002 U320 42'

Re: Weekend Electrical Puzzle

Reply #11 –
I know Pat was attracted to me 44 years ago, I guess magnetic fields never disappear!
Geoff & Pat Haygarth
1994 U240 SBI GV 36ft Cat 3116, Allison 6 speed
 Build #4448
2015 Jeep Wrangler Sport

Re: Weekend Electrical Puzzle

Reply #12 –
Yes, but the 12 volt florescent ceiling fixtures use a transformer to boost 12 volts to power the florescent tube. Hence, the magnetic field to cause nearby interference.

Jim
Jim Frerichs
2002 U320 42'