Not gonna be great, coax and rca’s are the worst possible source for a tv, and throwing an rf modulator in the mix is compounding the degradation. Its a 20” tv, so it shouldnt necessarily be all that grainy, but nowhere near hd quality.

What inputs does you 20” tv have?

tv has hdmi and rca. its a convenience issue. the coax is already run to the kitchen tv from the service panel area in the basement. i ran a 2nd coax from the living room tv(tuner) back to the SP area as it is thru unfinished ceiling and than send the signal thru the coax to the kitchen. there is no easy way to get a rca cable or hdmi to the kitchen as the basement ceiling is finished below it. and i dont want to buy a 30' hdmi cable.

i want to use 1 dtv tuner to feed 2 tv's. dont want to buy/rent a 3rd tuner box as i dont like paying xtra each month for kitchen tv. thats why i dumped comcast when my bill hit $200

If you have high speed internet and wi-fi in the house possible switch to directv now and get hi-def to all the sets and be able to watch seperate programs on each set.

^^ What he said. Or, get that long HDMI cable and figure a way to route it.

All good suggestions here, the RF modulator is not going to give you a very nice picture, as you've discovered. Depending on how far the TV is away from the receiver, HDMI may pick up noise along the way. A better option for longer runs would be am HDMI over single Ethernet transmitter/receiver pair. As an Audio Video custom integrator, I do a lot of these. There are good ones and better ones, and they of course cost accordingly. Another option, which I try to avoid is HDMI over wireless (not your WiFi). This has been known to work well within 30 feet or so, and as long as no major obstructions ( to the wireless signal)

So, you have options, they might be a bit more costly than what you want to get into, but youdo have options.

There also is HDMI over RG6. Depending on the quality of the coax cable, this might work: https://www.amazon.com/single-Extender-Sender-Receiver-connection/dp/B00HWIWEMU Or it could fail spectacularly. Preexisting coax wiring is often in really horrible shape, and sending complicated high-datarate signals over it doesn't always work reliably.

I assume your coax has F-connectors on each end. If so, you could get an F-to-RCA adapter and use it as a video cable (assuming your TV has a video input). Better than a modulator, although not as good as the HDMI or other more modern solutions mentioned above. It sounds as if the TV in question is a high definition TV and you won't get that resolution using my solution. I'm not sure if sound will come over this cable but it's worth a try.