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Old 03-02-2017, 05:20 PM
Electronic M's Avatar
Electronic M Electronic M is offline
M is for Memory
 
Join Date: Jan 2011
Location: Pewaukee/Delafield Wi
Posts: 14,762
BT mods over the air can produce about as good quality as commercial NTSC broadcast did....There are some pit falls to avoid in order to achieve maximum quality. Ground loop hum is a big one. My mods are powered off an isolation transformer so I don't have to worry about the ground level in all the different gear in my A/V sources racks not playing nice with the grounding in the BT cord and PS.
A good TX antenna is essential (an average RX antenna is useful). Shango66 has a good video youtube video on making a TX antenna that I can find for you later if you want. Good TX antenna placement is important (that is trial and error). In setting up the TX an 80's or newer portable TV set can be very useful in checking signal strength, quality and range.
Setting the video and audio levels for no over modulation is important...Start at zero, crank till the over mod lights come on then back off till they stay near constantly out.
Buying a modulator in good shape (or having it repaired) is important. Many have bad lytic caps and such bad power supply hum that you can ground the input terminal to the chassis and the over modulation lights will still come on.
Also be mindful that large pieces of metal or other highly RF reflective objects in your home (other than the TV) may cause multipath reception issues.
If you do all that right and use an empty channel to send all should be good with an hour or two of experimenting with the initial set up.

BT mods can be fun to play with and set up if you, do it right, and know enough about troubleshooting.

All BT modulators I've seen have RF output level control. Also, I've got AM60(strongest RF), BAVM(middle), AM40(weak) and all are capable of sending at least 100' wirelessly with a decent TX antenna.
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