schmudde

Well... I haven't used any of the cheap composite mod boards on the bay, but I know that the mod boards I have used and especially the ones from Bryan's UAV board, have worked on all flat panels I've used with it. 
 
While there are always differences and certainly a YMMV kind of deal with these mods, for the most part there isn't too much science required to make them work. Nearly all of these consoles originally output a composite signal to begin with that is then ran through, amp'd and combined with the audio to create the RF signal from the RF modulator. So most of these mods just tap off that video composite signal and amp it to a level that a TV will see and lock in on to display.

Do you want my honest opinion? You would probably be better off getting an old CRT TV. Digital is good for modern technology but is a royal pain in the rear when trying to get older technology to work with it.
 
Often time you can find CRTs on curb sides free for the taking. Goodwill and most other second hand stores can't accept CRT TVs anymore and just let them stay outside waiting for the trash company to come and take them away. Also check eBay and Craigslist, local yard sales, things of that nature. If you want to play Atari then might as well do it the way it was intended to be played. Getting a CRT TV is a sure fire way to get an Atari p!aging. There is no guarantee that your Atari, even with signal modifying equipment being used, will work with your new TV.
 
I guess it boils down to opinion. But would you rather spend, for example, $50 on a converter of some sort or use a portion of the $50 or none at all getting an older TV that will work with your Atari and any other older game or computer you might want to get someday? Just another option to think about.

Fixed link: https://www.amazon.com/NOVPEAK-Warranty-Converter-Composite-Blue-Ray/dp/B01N0HGKD2?SubscriptionId=AKIAILSHYYTFIVPWUY6Q
 
But no, CrossBow pretty effectively summed up your options, of which modding is probably actually the option which will be cheapest and leave you with the best quality image at the end of it:
 

I'm going to throw in my two cents worth here.  
 
Most modern TV's now have the coax connector for digital-only signals.  Meaning that you can make use of digital TV antennas without any other electronics necessary.  However, in doing so it will never be able to pick up an analog signal again.  But, there might be a trick you can do to get your Atari to work on that TV...that is if it has composite inputs (yellow, red, white).  Find a cheap VCR.  It can be mono or hi-fi doesn't matter.  Connect the 2600 to the VCR and change the VCR channel to the channel your 2600 is set for (2 or 3 in most cases).  Use RCA cables to connect the VCR's video and audio out signals to your TV's composite inputs.  Video will be yellow and if you have only one audio out on the VCR then either the red or white input on the TV should become a mono channel meaning even if only one port is used sound will output to both speakers.  
 
If you don't have a VCR they can be picked up rather cheap depending on your location.  I'm not sure where you are from, and mean no disrespect or anything, I just don't know how much a VCR costs in other parts of the world.  Get a good used one for this...and it doesn't necessarily have to play tapes.  As long as it turns on and can receive and send video and audio signals you can use it as a de-modulator.  Almost all VCRs from the 1980s and up have this built in.  
 
On a side note:  I have a ViewTV digital TV box that does quite a bit (I can play movies from the Internet Archives on this thing from a USB stick!).  I wanted to see if it would also pick up a signal from an Atari console since the ViewTV can record as well.  I was going to try to use it as a game capture device.  But, alas, it wouldn't detect it because it has no way of detecting analog signals.  
 
With that being said you might be better off trying to find a converter that will change your Atari's signal from analog to digital much like those boxes that changed analog antenna signals into digital ones when it was being forced to remove analog TV signals completely.  One of those might actually work if those are still around.  

I will try and sum this up best I can.
 
What you have is an RF signal from the 2600 that needs to be de-modulated in order to work on a composite input on your TV. De-modulators are more expensive. If you are sure your new Samsung isn't able to tune in to the signal from the 2600. Then your options are:
 
- Purchase a De-modulator that takes RF and splits it back out to separate Video and Left/Right audio like this: 
https://www.amazon.com/Analog-NTSC-Tuner-Demodulator-Output/dp/B01KC03BQ2/ref=sr_1_3?s=electronics&ie=UTF8&qid=1521055119&sr=1-3&keywords=rf+demodulator
 
- Or get your 2600 A/V modded
- Use a different TV altogether
 
I know...not the best solutions but that is where you are at. Now, having said that, have you tried to use your Samsung's auto scan function on the channels? Here is what I do with a new TV to be sure it will see the old Consoles. I put a game into the Atari and turn it on. I then go to the channel section of my TV and have it auto scan for channels from the Antenna side. Doing this, the TV should see and lock in on the 2600 video out signal. But if it doesn't or this isn't an option, then you are looking at the suggestions I gave above. But again, for the price of a de-modulator, you might as well get your 2600 AV modded at that point.

what's the model # of the new TV ?
 
I am guessing in the Menu there may be different kinds of "air" signal selections

I have a new Samsung flatscreen to replace my old Samsung flatscreen. My darth vader 2600 worked on the old one but isn't showing a picture on the new screen.
 
The new Samsung has a CBF Signal input rather than the ole RF NTSC. I bought a Samsung BN39-01154P CBF Signal to RF cable. It's not working. Do you think I can just go in composite using one of the Philips RF Moduator Video Converters?
 
There is something I'm not understand about how signals are modulated/de-modulated in these televisions. Any basics would be appreciated.
 
/Schmudde