Klaas Robers wrote:You might realize that television signals are transmitted and received through glass. It is in the glass delay line in PAL and SECAM colour televisions. Althouhg it is not the total signal, it is the colour subcarrier signal, and the delay is 64 us, one TV line. It works on 4,4 MHz and the bandwidth is still about 1 or 2 MHz. You can surely modulate an NBTV video signal onto a 4,4 MHz carrier, send that through the glass delay line and receive it at the other transducer.
As the bandwidth of the quartz transducers is rather limited, you cannot send a baseband video signal through the line, only something centered around the resonance frequency of the crystal.
In the very very beginning of PAL-TV Telefunken used a stretched delay line. One crystal transducer at one end, the other at the other end. The problem was: how to tune the proper delay time? thus a folded line was made, half the length, where the signal reflected against the far end. Both transducers were situated side by side at the same beginning end. By grinding the far end, while measuring the delay time, the tuning was much easier.
Later the super-folded lines were made, where the accoustic wave reflected against side walls and the end wall. By grinding one wall the tuning is performed. Harry, you opened such a line.
MMMM interesting Klaas .
I was about to reply to your last post on the delay lines ...noticed you had posted here
When i was reading up on sound waves sold objects it seems are better than liquid in transmitting sound waves gases the worst ....i suppose the old can with a string and a can at the other end is a way of transmitting voice bandwidth same idea with transducers speakers mic you would think would work as well for say NBTV ..
I will keep that idea in Mind Klass about the delay lines i found a few in my junk box ,all look similar with connections on the edge of them and reflection bumps on the flat glass one side.
The tub i used for these liquid tests would be a delay line too as you mentioned at the end of your message ....length longer or bouncing off more walls more delay .