Questions about recording NBTV on Cassette Tapes

[Gunier J. Kintgen]

(Sorry if this is out of place; I just joined & none of the topics seemed like the right fit for this post)
So, I hope to start something called a "Tape-Pal 3-Way", here's the documentation:
https://munk.org/typecast/2024/07/22/ho ... als-3-way/
These guys are just sending audio on tape. I Want Video. I know it's not gonna look the best, but I was wondering: What's the best resolution video you can cram on a standard audio cassette tape? 60 lines, maybe even 120? Color is not really all that important, I've seen people record color NBTV signals onto cassettes with really high-quality recorders it still ended up looking terrible. My tape deck won't arrive until the 17th, but I'll be using a Yamaha K-220 to record the video. Would Dolby Noise Reduction help me get a better picture, or would it hurt my results? How do I get the best video off a cassette tape? Thanks for the help!

-Gunier J. Kintgen, Your Pal.

[KeithE4Phx]

(Sorry if this is out of place; I just joined & none of the topics seemed like the right fit for this post)
So, I hope to start something called a "Tape-Pal 3-Way", here's the documentation:
https://munk.org/typecast/2024/07/22/ho ... als-3-way/
These guys are just sending audio on tape. I Want Video. I know it's not gonna look the best, but I was wondering: What's the best resolution video you can cram on a standard audio cassette tape? 60 lines, maybe even 120? Color is not really all that important, I've seen people record color NBTV signals onto cassettes with really high-quality recorders it still ended up looking terrible. My tape deck won't arrive until the 17th, but I'll be using a Yamaha K-220 to record the video. Would Dolby Noise Reduction help me get a better picture, or would it hurt my results? How do I get the best video off a cassette tape? Thanks for the help!

-Gunier J. Kintgen, Your Pal.

Hi, Gunier. I'm also a first-time poster, but long-time reader.

The formula for video bandwidth is BW = (L * P * F) / 2, where BW is the bandwidth in Hz, L is lines per frame, P is pixels per line, and F is the frame rate. It's half because two pixels are equal to one cycle. Vertical or horizontal scanning doesn't matter in this context. Sync pulses (if any) are included as part of the line and pixel count.

For example, 32 lines, 48 pixels per line, at 12.5 frames per second (I believe this is the current NBTV standard) calculates to a video bandwidth of 9600 Hz. This is easily done on just about any decent cassette deck. Some decks will handle high frequencies to 15 kHz or a bit more, but most will be good only to 10 or 12 kHz, depending on the quality of the machine and even more depending on the quality of the tape itself.

Given how bad audio cassettes used to sound on a cheap player with a bad motor, I would suggest buying one with the most stable motor you can get. Wow and flutter are probably even worse for low-resolution video than they are for audio.

Good luck!

Keith, W7XTV

[Klaas Robers]

Dear Gunther,

This is a difficult path to follow. Tape recorders store low frequencies deeper in the tape than higher frequencies. This distorts the wave form of the video severe, such that the pictures may be hardly recognizable. That is if you record the video wave form as if it were audio. Your ears don't hear it, so for audio it is Ok.

Then you may store the video as an audio subcarrier frequency modulated with the video signal. This is what video tape recorders do too. So you need a specalized video modulator for recording and a demodulator for play back. That includes that you make an incompatible system, only compatible with yourself.

In the past quite some members wrote about it in the NBTV newsletter. Try to find it back and you can learn a lot from that publications.

The only way out was the use of Compact disc. It has not the strange distortion of (audio) tape recording. That is how we made the NBTV-CD's of the club.

Good luck!!