Smallest most compact RF modulator?

[Trekintosh]

Thanks to lnx64, Looks like I've found my modulator for this project. Finally got the matching transformer I was missing to hook up my normal modulator to the TV and I found that there was a *lot* of crawling snow in the signal. Underneath the interference it looked fine, but the interference was really problematic, made viewing a pain. I live in a very EMI noisy home. There's an AC and fan that are running 24/7(the fan is plugged into the same socket as the TV/modulator are), there's wifi running all the time, and there's neighbors' wifi running too. How best can I isolate the TV and modulator to clean up the signal? Will just snapping a few ferrite chokes around the coax and power cables be enough?

[kf4rca]

I built a video only modulator once. It used only half a dozen components. It was a clone of the modulator in the Heathkit IG5240 bar/dot generator. It uses an FET and a channel 3 crystal, which might be hard to find these days. I got my crystal at a hamfest. The guy had a whole bin of them.

[Findm-Keepm]

Originally Posted by Trekintosh

Thanks to lnx64, Looks like I've found my modulator for this project. Finally got the matching transformer I was missing to hook up my normal modulator to the TV and I found that there was a *lot* of crawling snow in the signal. Underneath the interference it looked fine, but the interference was really problematic, made viewing a pain. I live in a very EMI noisy home. There's an AC and fan that are running 24/7(the fan is plugged into the same socket as the TV/modulator are), there's wifi running all the time, and there's neighbors' wifi running too. How best can I isolate the TV and modulator to clean up the signal? Will just snapping a few ferrite chokes around the coax and power cables be enough?

Ferrites might work, but it's best to run whatever displays the interference on an EMI filter. The common mode chokes in most sets ain't enough. Ferrites don't work on TV coax well, if at all. A coaxial line isolator (See a good CATV supplier, or check eBay..) might work - but only with RF interference - they were used with Satellite systems back in the 90s/2000s

Best options:

1) Get yourself an AC line conditioner ($$$$) I use a Sola, but mostly for line regulation (132V at my outlets.....yes, too high, right off the tranny outside.) It filters out everything but >400msec surges. Pricey items - got mine surplus for pennies.

2) Build your own EMI filter ($) Use an IEC EMI input filter, and a wall outlet output. I made one back in 2002ish for a Navy need. Be sure to carry the ground to a common point.
IEC filter:
https://www.google.com/search?q=emi+...w=1280&bih=834

3) Buy a TDK or Murata (may be sold under KEC as well) EMI Filter - used ($), new ($$). We used the TDKs on computers - the dot matrix machines we had (22" platen) would generate all sorts of noise on one phase of the line. The TDKs are only rated for 6 or 8 amps, plenty for a TV. The Muratas are larger and harder to find anymore. Schaffner may make some standalones like the TDKs.

The X10 Home control system also offered one - it used to be available at RadioShack, good for 5A, and $20 or so. Check eBay.

Other tips - use quality coax from Belden/Alpha or Channel Master. Most of the discount store stuff is cheapo 40% coverage - you want >90% coverage, which is braid AND shield foil.

Try plugging the TV into an outlet that is off a different leg than the other items. Tough to figure out if you don't have the means to trace the circuit from the panel to the outlet.

[Trekintosh]

Originally Posted by Findm-Keepm

Ferrites might work, but it's best to run whatever displays the interference on an EMI filter. The common mode chokes in most sets ain't enough. Ferrites don't work on TV coax well, if at all. A coaxial line isolator (See a good CATV supplier, or check eBay..) might work - but only with RF interference - they were used with Satellite systems back in the 90s/2000s

Best options:

1) Get yourself an AC line conditioner ($$$$) I use a Sola, but mostly for line regulation (132V at my outlets.....yes, too high, right off the tranny outside.) It filters out everything but >400msec surges. Pricey items - got mine surplus for pennies.

2) Build your own EMI filter ($) Use an IEC EMI input filter, and a wall outlet output. I made one back in 2002ish for a Navy need. Be sure to carry the ground to a common point.
IEC filter:
https://www.google.com/search?q=emi+...w=1280&bih=834

3) Buy a TDK or Murata (may be sold under KEC as well) EMI Filter - used ($), new ($$). We used the TDKs on computers - the dot matrix machines we had (22" platen) would generate all sorts of noise on one phase of the line. The TDKs are only rated for 6 or 8 amps, plenty for a TV. The Muratas are larger and harder to find anymore. Schaffner may make some standalones like the TDKs.

The X10 Home control system also offered one - it used to be available at RadioShack, good for 5A, and $20 or so. Check eBay.

Other tips - use quality coax from Belden/Alpha or Channel Master. Most of the discount store stuff is cheapo 40% coverage - you want >90% coverage, which is braid AND shield foil.

Try plugging the TV into an outlet that is off a different leg than the other items. Tough to figure out if you don't have the means to trace the circuit from the panel to the outlet.

Seems like we have a winner here.

Unfortunately, the entire home is on one circuit, except the air conditioner which is on a circuit with the other aircons in the building. It's super hard to find a place where I wouldn't have interference. Might get a choke too, just to see what happens.