RF Modulator for vintage TVs.

[maxhifi]

I decided to put my CTC38 back into the living room this weekend, after 4 years in storage. Wow, is it nice to have back.. the picture tube in this one tests as NOS, and with fresh 6GH8As man does it make a nice picture!

I have a couple different RF modulators. One seems to over saturate the video, while the other has a better picture but puts buzz into the audio.

Any thoughts on what is the best modulator I can get my hands on? I want it operating at peak quality. Is a blonder tongue the way to go? If so, which model?

On another topic, I've heard of people using agile modulators to broadcast video around the house. Is this still a valid idea? What sort of antenna is used? I would really like to be able to watch the news on my little 12" New Vista B&W in my home office, but don't want to pay for a third cable box, or run any coax.

[Electronic M]

IMO Blonder Tongue modulators are the way to go for best picture/sound quality...which model to go with depends on your needs. For transmission the AM60 family is best, IIRC the BAVM family if second best power output wise, and the AM40 comes in 3rd. The BAVM family is fixed channel (not agile) so make sure there is no DTV carrier on or adjacent to the channel you buy. The AM agile modulators 3 digit post fix indicates the max frequency it can output (some can only do VHF, some VHF+CATV others everything including UHF).

You can adjust sound and video modulation level on all models I've mentioned to eliminate buzz and have picture look best.

Shango66 on YouTube has a good video on making your own dipole antenna out of lamp cord and an F connector. I followed that recalculating the math for the channels I use and it has worked well.
All BT modulators seem to have the strongest output on channel 7...The AM60 can send signal in a block radius with the output potentiometer cranked, the BAVM about half that, and the AM40 about 200-400'.

Blonder Tongue modulators often have bad lytics, and some times need you to play with grounding (try normal, ungrounded, and ungrounded powered through a line isolation transformer). Antenna placement is important and metal and living things in your walls/house can effect reception.

[maxhifi]

Thank you for this, I was having trouble making sense of the huge variety of modulators on eBay. So something like the AM60-550, will essentially do up to CATV channel 81.

[maxhifi]

Clicked buy it now on an AM60-550B... gonna set it to CH7 when it shows up... shango066 has an antenna video? I'll have to search, I've been subscribed to his channel since he used to be here on VK, but I don't remember that one.

[freakaftr8]

It was my set that inspired you huh lol.. On the topic of RF modulators, surprisingly the built in modulator in the Xfinity box I have seems to work flawlessly on my older sets.. If warranty would permit me, I'd open it up and see what its using for the coax output.

Never had much luck with RF mod units, but I have one here at work I'm bringing home tonight to see what it does. I'll post results and make.

[maxhifi]

Originally Posted by freakaftr8

It was my set that inspired you huh lol..

Daughter moved into room in basement which was storing the CTC38, it either had to go, or had to go back into service.

Your CTC39 certainly did get me thinking about it though. Mine has a replacement RCA CRT which seems to have been installed right before the owner stopped using the set - on account of this, the picture is just fantastic - a big difference from the worn out tubes I usually find in old sets.

It does have some kind of intermittent issue where the picture loses lock for a second, but then it comes back. It seems to happen before the set reaches full operating temperature - it stabilizes after it has been on for over half an hour. I'm living with it for now, there's likely a bad solder or something in there.

[Electronic M]

It is linked under video tutorial in Phill's write up. https://www.antiqueradio.org/HomeTVTransmitter.htm

[freakaftr8]

Feast all your eyes on this sweet lil treat! Brand name, "RF MODULATOR "! Probably short out as soon as I plug it in... but I'll let you know how it works tonight.

[maxhifi]

Originally Posted by freakaftr8

Feast all your eyes on this sweet lil treat! Brand name, "RF MODULATOR "! Probably short out as soon as I plug it in... but I'll let you know how it works tonight.

I've got a few of those. Some work better than others, but I strongly suspect the blonder tongue will be a huge improvement. On some of my old TVs, the audio is over modulated into distortion, and the video tends to saturate. I'd like to be able to dial in the perfect levels.

[freakaftr8]

I agree. Let us know how it works when you get it. Sounds like a good one.

I'm going to open this one up and see if it has adjustments for gain saturation, if not I may try to reconfigure it. Heck it was free from DirecTV years ago. Nothing to lose

[freakaftr8]

And it appears so. Most likely some form of AGC.

[maxhifi]

Originally Posted by freakaftr8

And it appears so. Most likely some form of AGC.

Hmm what am I looking at?

[freakaftr8]

Under the modulator shield there is a peaking coil. Not sure if this is just fine tuning of the ch 3 or 4 set or some form of gain control. Who knows.

[maxhifi]

Originally Posted by freakaftr8

Under the modulator shield there is a peaking coil. Not sure if this is just fine tuning of the ch 3 or 4 set or some form of gain control. Who knows.

Ah, that little can looks like it's for fine tuning, but I can be wrong! There must be a bunch of surface mount parts on the other side of that pcb

[freakaftr8]

I believe there is, I put it back together bit I'll look later.