Glass ultrasonic delay lines - pictures - Page 1
Forum section: electronics / projects

author: mister_rf
author_rank: Contributor
timestamp: January 17, 2023, 12:53:02 pm
content: DL50 - analog delay line (by almost exactly one line period of 64 μs), used in ITT Schaub-Lorenz PAL color televisions sets. 1970s.Glass ultrasonic delay line - ultrasonic transducerGlass ultrasonic delay line showing path of sound waves

author: AndyC_772
author_rank: Super Contributor
timestamp: January 17, 2023, 01:01:28 pm
content: That's cool. Any idea what the input and output signals actually looked like? Is it used to buffer analogue picture data, or just a simpler signal like a sync pulse?I work with ultrasonics a lot, and it's certainly nowhere near the case that the signal coming out of an ultrasonic receiver is "just" a smaller version of the one that went in - it's subject to all kinds of resonance and interference effects, depending on the nature of the transducers themselves and the path joining them.I see a glass substrate and think "great - relatively low attenuation, but sound will scatter in all directions and keep bouncing around inside that block for ages because there's no damping".

author: mister_rf
author_rank: Contributor
timestamp: January 17, 2023, 01:18:40 pm
content: Such devices originally has been used to delay low amplitude analog colour U & V signals, 64 μs, and the bandwidth is around 1.3 MHz.

author: mister_rf
author_rank: Contributor
timestamp: January 17, 2023, 01:29:00 pm
content: DL60 - analog delay line (64 μs), used in ITT Schaub-Lorenz PAL color televisions sets. 1970s.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 17, 2023, 01:36:25 pm
content: Quote from: AndyC_772 on January 17, 2023, 01:01:28 pmThey were analog delay lines, the input video signal was delivered 64us later. Though I didn't know the substrate was glass. Always thought of them as ceramic, no idea why.Inside a PAL Delay Lineanachrocomputerhttps://youtu.be/bsk4WWtRx6MTwo consecutive lines were needed to restore the color information (chrominance signal) in the PAL (Phase Alternating Line) TV standard. Back then everything was analog, there were no memories and no ADC/DAC fast enough to memorize 64us of video signal. PAL was one of the analog TV standards used in Europe (and some other places), the other widespread color TV standards were SECAM (close to PAL) and NTSC (some are saying NTSC stands for Never Twice the Same Color).LATER EDIT:------------------Above info was retrieved from foggy analog memories stored decades ago, might be way off.

author: BrianHG
author_rank: Super Contributor
timestamp: January 17, 2023, 01:59:58 pm
content: The reflections and surface taps within the glass filter means only the color and it's sub-carrier were present at the output of the delay line.I played with NTSC versions, and with a small half-subcarrier-phased delay on the main video added to the source video made a separated Luma signal without any color in it which was used as a Y-C video for your TV's color decoder.The delay line's internal reflections in the glass filter performed a color comb filter effect removing color fringes around fine vertical lines in the picture and also allowed through higher bandwidth video so long as you used the delay lines chroma output as the reference to negatively subtract that info from the source video instead of an old fashioned 3.58MHz notch or LP filter made with inductors and caps.

author: MK14
author_rank: Super Contributor
timestamp: January 17, 2023, 02:12:44 pm
content: Quote from: AndyC_772 on January 17, 2023, 01:01:28 pmMy recollect, for UK PAL TVs. Is that it is to keep a copy of the last display line (a bit less than 625 lines at 25 Hz full frames, so half that at 50 Hz, interlaced (half, i.e. all odd or all even lines, only) fields/frames), so that if the transmission suddenly gets messed up (e.g. brief interference etc), rather than showing a line of solid black or white, which would tend to be noticed by the viewer.It shows the last valid line, it received, one line ago. Which tends to be much less noticeable, by viewers.

author: BrianHG
author_rank: Super Contributor
timestamp: January 17, 2023, 02:18:54 pm
content: Quote from: MK14 on January 17, 2023, 02:12:44 pmAgain, it can only delay and let through the color sub-carrier 1 line later and the higher quality ones had even 3 lines taps all summed together at the output. These glass delay lines cannot delay the low frequency / DC required for the luminance portion of the picture. This degree of improvement was done much later digitally with digital comb filters. The had a 3 or 4 line delay, and used a mathematical to adaptively comb across the 3-4 lines to separate the YC without any color fringes or crawling dots. The Sony XBR2and their studio HI-8 decs and last S-VHS had these adaptive comb filters.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 17, 2023, 02:20:43 pm
content: Quote from: RoGeorge on January 17, 2023, 01:36:25 pmThat is not entirely correct.The transmitted PAL signal did contain both U and V on every active line and could* be decoded without a delay line using essentially the same method as an NTSC decoder. The advantage of PAL over NTSC, that phase errors resulted in changed saturation instead of changed hue, could only be achieved using a decoder containing a delay line. (*But vey few, if any, TVs were marketed that did not have the delay line decoder.)SECAM receivers required a delay line because that system had only one of the two coolur difference signals (frequency modulated on a carrier) per line.

author: MK14
author_rank: Super Contributor
timestamp: January 17, 2023, 02:26:54 pm
content: Quote from: BrianHG on January 17, 2023, 02:18:54 pmHere you go. From 1969/70 ...https://patents.google.com/patent/US3586762It explains about it, apparently.QuoteBut I'm NOT 100% sure. It would take a long time, to dig out the fuller information.Quote

author: Tom45
author_rank: Frequent Contributor
timestamp: January 17, 2023, 02:29:13 pm
content: A computer designed and built at my University back in the 60s used glass delay lines for the main memory. I worked there and this computer was right next to my desk. It was there when I started and I only tried using it a few times out of curiosity. Otherwise it sat unused.I don't remember much about it now, but that it was fiddly and unreliable. There was a memory calibration procedure that had to be run before trying to use the computer and that calibration had a somewhat limited life time before things would drift and the memory would start giving errors. With hindsight, it needed some kind of clock recovery encoding. I don't know whether it didn't have that, or perhaps it did but it was poorly implemented.

author: BrianHG
author_rank: Super Contributor
timestamp: January 17, 2023, 02:32:50 pm
content: Quote from: MK14 on January 17, 2023, 02:26:54 pmYes, that's how to get a supreme Y-C separated signal, but the patent doesn't tell you that the 'luma delay' element is the figures are the current glass delay lines we are looking at here.They do have glass delay lines and state like I said above, that using the previous line mixed the current line by the 'glass element' still separates the Y-C effectively.Look at the figures. The 'luma delay element' and 'glass element' are 2 different things altogether and used and mixed in separate ways.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 17, 2023, 02:34:12 pm
content: Quote from: MK14 on January 17, 2023, 02:12:44 pmYour recollection is totally incorrect.1. Only the chrominance signal went through the delay line.2. The delay line was part of an enhanced method to separate the U and V signals. The V signal was inverted on alternate transmitted lines. U+V, U-V, U+V, U-V and so on. By summing successive lines the V part largely cancels, By subtracting successive the U part largely cancels. However the main reason for the inversion is that phase errors which in NTSC causes hue errors can be converted to saturation errors (which are much less noticeable) when using the delay line decoder. Seehttps://www.csse.canterbury.ac.nz/greg.ewing/c64_pal_decoder/PAL/PAL-Video-Encoding.htmlfor explanation.

author: MK14
author_rank: Super Contributor
timestamp: January 17, 2023, 02:38:55 pm
content: Quote from: BrianHG on January 17, 2023, 02:32:50 pmThere is even at least one ANCIENT thread on here, discussing it.https://www.eevblog.com/forum/blog/eevblog-381-how-do-ultrasonic-delay-lines-work/Example from it:Quote from: TVguy on November 09, 2012, 10:06:07 amOther posts in that thread, also seem to be agreeing with my original explanation.

author: BrianHG
author_rank: Super Contributor
timestamp: January 17, 2023, 02:49:12 pm
content: Quote from: MK14 on January 17, 2023, 02:38:55 pmAgain, look at your patent:https://patents.google.com/patent/US3586762Look at image 2, sheet 2, luminent delay line 102 and 200.Now go to image 3, sheet 3, you will see the 'Glass delay lines' 302 & 308 with Trim Delay line 312. That delay line 312 is 1/2 color phase, for NTSC, only ~150ns. Made with usually 2-3 inductors with cap and resistor. Look as the summer, they are only summing the U&V with the glass delay line output.It is as I described way back in my first post. Only the chroma can make it through the 'glass delay line'.Take a look at 'high-pass filter 306' on image 3 sheet 3. The patent only pushes signals above 3MHz through the glass delay line 308.Tell me why they would do that if the glass delay line can handle all frequencies?Whatever you read in the old eevblog link, it was wrong or you misinterpreted it.There do exist different glass 'delay filters' for VCR playback. Those are different in shape, very low in height with multiple glass elements wired in series inside them (usually a flat long plastic box). This is not the glass delay line we are seeing here is this thread as it is a tall rectangle. This filter is for separating Y-C, color and luma. The 'playback' line filter type used in VCRs weren't available for quite some time.

author: mister_rf
author_rank: Contributor
timestamp: January 17, 2023, 03:02:41 pm
content: Let’s continue with new pics, this time: SDL145- Glass ultrasonic delay line.Manufactured by GTE Sylvania, 1980s.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 17, 2023, 03:03:42 pm
content: Mike put some signals into an analog delay line.Delay line memorymikeselectricstuffhttps://youtu.be/-qerYLM-eEg

author: BrianHG
author_rank: Super Contributor
timestamp: January 17, 2023, 03:07:48 pm
content: Quote from: RoGeorge on January 17, 2023, 03:03:42 pmA creative way to use the delay element. You notice he had to oscillate the '1' data. Pure low frequency digital did not go through.

author: mister_rf
author_rank: Contributor
timestamp: January 17, 2023, 03:11:32 pm
content: RFT Secura CV20 - TGL25182 – Made in German Democratic Republic, 1980s.Glass ultrasonic delay line used in "Cromatic" - PAL-SECAM TV sets manufactured by I.I.S. Electronica Bucureşti, Romania, 1980s.

author: MK14
author_rank: Super Contributor
timestamp: January 17, 2023, 03:14:10 pm
content: Quote from: BrianHG on January 17, 2023, 02:49:12 pmI didn't realize the delay lines, were different, between older colour TVs and more modern VCRs. I also didn't realize, that the luminescence dropout 'delay lines', were much more, or exclusively VCR rather than for TVs.So, this thread is about ones which remove the following effect (as regards PAL TVs, which might not even apply to the ones, the OP, is posting about), it seems:https://en.wikipedia.org/wiki/Hanover_bars

author: BrianHG
author_rank: Super Contributor
timestamp: January 17, 2023, 03:14:22 pm
content: Here are the VCR picture filter delay lines:Inside them, they have numerous glass elements wired in series.

author: BrianHG
author_rank: Super Contributor
timestamp: January 17, 2023, 03:18:15 pm
content: Quote from: MK14 on January 17, 2023, 03:14:10 pmVCRs may have both types. The ones in this thread to decode the incoming video to produce a higher quality recording. (VHS records the luma and chroma on separate carriers on the tape.) And the type I attached in my above thread to help improve video playback noise and dropouts.

author: mister_rf
author_rank: Contributor
timestamp: January 17, 2023, 03:26:07 pm
content: I’ve found these components on various vintage TV sets boards, and I had to take pics before some PCB going to the recycling center. Sorry, but to many items have been kept for so long, and there was a need for cleaning to make room for more important items.VL14 - Glass ultrasonic delay line.Manufactured by Telefunken, 1970s.

author: Gyro
author_rank: Super Contributor
timestamp: January 17, 2023, 04:33:44 pm
content: Quote from: MK14 on January 17, 2023, 02:38:55 pmI was just going to reply that I had an even earlier (single bounce?) one but I see it (the Mk1) is well covered in the other thread. That one feels like a large lump of bottle glass, partly down to the ribbing I guess!

author: coromonadalix
author_rank: Super Contributor
timestamp: January 17, 2023, 05:31:40 pm
content: we need to start a mechanical audio delay line too loll

author: jonovid
author_rank: Super Contributor
timestamp: January 17, 2023, 05:33:24 pm
content: impressive macro photography, spotted one dry joint.have some units my self from 1980s video cassette recorder printed circuit board.s I would struggle repurpose old video analog delay lines.looking at the transducers on the edge of the glass and the all-important driver circuits on the printed circuit board .may with much experimentation, holds posabilitys for DIY unisonics,locating cracks in glass , singing ceramic capacitors,intercepting insect communications maybe? ants entomology.

author: mister_rf
author_rank: Contributor
timestamp: January 17, 2023, 08:08:08 pm
content: Quote from: coromonadalix on January 17, 2023, 05:31:40 pmI have some mechanical filter pics (signal processing filters at radio frequencies), are you interested ?

author: mawyatt
author_rank: Super Contributor
timestamp: January 17, 2023, 08:20:13 pm
content: Interesting devices, thanks to all for posting images.Question: Since these are apparently regular "glass", how is the electrical signal converted to mechanical and then back? Are what look like thin slivers with gold metallization where the wires attach, actually thin piezo electric elements which mechanically couple to the glass?Best,

author: RoGeorge
author_rank: Super Contributor
timestamp: January 17, 2023, 08:28:16 pm
content: Quote from: mister_rf on January 17, 2023, 08:08:08 pmI would be interested for sure, please don't hesitate to post. Make a new category, or keep them all together here, your call. At such great pics I would gladly look even if it were just the close-up photo of an empty sheet of paper.

author: MK14
author_rank: Super Contributor
timestamp: January 17, 2023, 08:51:32 pm
content: Quote from: mawyatt on January 17, 2023, 08:20:13 pmI don't know if this helps, but it seems to give some details.https://en.wikipedia.org/wiki/Surface_acoustic_wave

author: BrianHG
author_rank: Super Contributor
timestamp: January 18, 2023, 01:09:54 am
content: These TV IF saw filters:Were available in 45MHz for North America (I think 38.9 for Europe) and had a 5/6MHz bandwidth where once you went outside the frequency range, the feed through dropped like a brick.Internally, they have 2 inputs for the transducer, and 2 for the output transducer. (center pin is a shield GND) I think they got their brick-wall filter response in a similar to mixing of signals across a glass medium as both a filter and internal summing signal reflection delay like the TV color 1H delay line filters seen here where the output is a mix of reflection of the input plus a 1H delayed version combing out the color sub-carrier to an extreme degree.Seriously, when you properly load the input and output of the glass delay-line filters with an inductor and resistor, feed it not an occasional color signal burst from a function generator, but feed it an actual video picture where all the croma aligns up horizontally in frequency and vertically as in video line by line where the vertical chroma also has repeats because of video low resolution, what comes out of the glass filter is a perfectly separated chroma signal without any hint of any side-band interference from any other luma picture content. No lumps, no spikes, just smooth pure 3.579545MHz modulations.Anyone blindly feeding these delay lines a color pulse train from a function generator is missing their function all together and what you see on the output is a shriveled response of the reality if you instead fed it a real TV video signal where the output is actually ends up being a full amplitude separation of the chroma input signal.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 18, 2023, 03:31:15 pm
content: Took a brief look at the analog color TV standards. What a marvelous piece of engineering, wow!The first one was NTSC, the American standard. They had to keep backwards compatibility with the existing black&white TV receivers, and with the already allocated spectrum, and with the existing channel bandwidth, yet somehow add in there the color information. They come up with a very clever design. Many details were to consider, most of them neglected here, with the focus on the 64us delay line (a delay line that NTSC receiver doesn't need, or have, there might be other smaller delays in NTSC receivers, but not the 64us one - or at least that's my understanding).The color information was to be sent as (analog) AM quadrature modulation with a 3.579545 MHz carrier for NTSC (4.43361875 MHz +/-1Hz for PAL).In the complex plane representation, the amplitude of the (U+V) vector corresponds to saturation, and the phase of the (U+V) vector corresponds to color. In practice, because of propagation conditions, there was a problem with unwanted phase shifts in the (U+V) vector, where anything bigger than 5° was perceived by the eye as a wrong color (such the rant about NTSC as Never Twice Same Color).At a very brief description, R, G, B were the video signals for each color. They were summed together (a weighted sum which coefficients will be neglect in all the following formulas, to keep it simple). That was the Y luminance signal (or luma? don't know the correct English term), same as the video signal in black and white TV.Y = R + G + BMost of the info was in the Y signal. The color info was encoded in two other analog signals, U and V, as a difference between Blue and luma, and between Red and luma (again with some weighted factors omitted here for simplification)U = B - YV = R - YIn practice, the differences were small, and the bandwidth (<1.5MHz) was smaller than the bandwidth of the Y signal. U and V analog signals were used to quadrature modulate a chroma carrier, at 4.43361875 MHz +/-1Hz for PAL. In the end, the spectrum of a color TV broadcast was something like this:Spectrum of a System I television channel with PAL. Source:https://en.wikipedia.org/wiki/PALThe receiver was receiving 3 analog signals, Y, U and V. From these, the R, G, B can be deduced by simple adding and/or inverting of analog signals.PAL TV standard came after NTSC, and one of its goals was to reduce the color errors. Thus, the quadrature modulation was slightly different than in the NTSC. The new trick in PAL was that odd and even TV lines, were sending once the V signal, then the -V signal, a 180° phase shift (inverting the signal) was added, only to the V signal, at each second TV line.Thus, by knowing both the previous line and the current line chroma signals, and assuming 2 consecutive lines will have about the same color info and about the same error phase shift, one can deduce the correct phase (phase = color) by simply mirroring the color vector Ec relative to U axis then averaging it with the vector from the previous line.Such, the need to delay the chroma info with one line (64us). Because of this trick of mirroring and compare the color vector between consecutive lines, in practice the color was still OK to watch in PAL for phase shift errors as big as 18°, vs only 5° in NTSC.As opposed as I thought at the beginning, my understanding now is that the 64us delay line in PAL was not used to delay the entire luma+chrome (from 50Hz to 6.5MHz), but to delay only the 4.43MHz AM quadrature modulated (the chroma signal shown in red in the spectrum pic).

author: BrianHG
author_rank: Super Contributor
timestamp: January 18, 2023, 03:41:00 pm
content: Quote from: RoGeorge on January 18, 2023, 03:31:15 pmIt's not just the delay. The corrected phase summing from line to line is also done in the delay line as reflections within the glass to produce a single sanitized output.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 18, 2023, 05:11:45 pm
content: Quote from: BrianHG on January 18, 2023, 03:41:00 pmThat's what I was trying to understand and what made me do a brief lookup at the PAL standard. Though, that doesn't fit with other pieces of info I vaguely remember. I might remember them wrong, for example a switch pictured in some block diagrams of PAL receivers, for odd/even lines. I'll have to search for some PAL receivers schematics.If the delay line of 64us was also summing two consecutive lines, than why the switch? Also, the quoted remark you made is for PAL or for NTSC? I'm tempted to believe you are talking about NTSC.My understanding so far is that the NTSC standard is different from PAL. NTSC does not alternates the sign for V signal so it doesn't need a 64us delay line, and does not care about the previous horizontal line at all.While asking these, searched more about NTSC, and this guy here says NTSC does alternates the entire chroma signal, not only the V component as in PALQuoteSource:https://www.extron.com/article/ntscdb3At this point it seems both NTSC and PAL are inverting something about color between consecutive lines, just that NTSC inverts all chroma, while PAL inverts only V.You are saying about NTSC, something like in this figure 2 and 4 from the above link, right?

author: BrianHG
author_rank: Super Contributor
timestamp: January 18, 2023, 06:30:47 pm
content: Damn, I cant find a good photo example and I lost my old samples from my Amiga days.Take a look at this test pattern: (Usually it is worse than this example)See the thin vertical lines on the right, the chroma noise within. If I used an NTSC glass delay line to extrapolate the 3.579545 MHz chroma signal for my TV's Y/C to RGB circuit, those vertical lines would be pure white without the color fringes. If it were meant to be a chroma signal instead of vertical white lines, it would have a different phase from the previous line, so a phase inverted addition with a line delayed version would cancel out the erroneous perceived chroma in the source picture. Without the glass delay line, a simple 3.58Mhz band pass filter is used, but any luma picture elements will create those color fringes modulating back and forth between 2 opposite colors. (IE, you need 2 vertical lines with a similar enough color to make it through the glass delay line, everything else with similar frequency, but the wrong phase 1 previous line to the current line reveals 0 coming out of those NTSC delay line filters.)Today, more modern full 3-4 digital line delays which can compensate color fringing by analyzing a line before and after to verify if what you are looking at is a vertically thick color, or a thin vertical line which happens to be just at the 3.57Mhz. The full digital delay also means we can subtract out the comb separated color from a matched delay full video source making a super sharp dot-crawl free luma portion of the picture. Even higher quality dot-crawl and color separation come with 3D comb filters which use 6 fields / 3 frames to interpret the picture.

author: BrianHG
author_rank: Super Contributor
timestamp: January 18, 2023, 06:49:55 pm
content: I guess what I am saying that if you have a picture with a set of vertical lines which happen to match 3.579545MHz, since an authentic chroma signal would invert phase from one line to the next, and vertical white lines wont, a glass delay line properly engineered could negate out the vertical lines only allowing through true color subcarrier information.The example NTSC 2 H-line delay separator could not be done in the 70s & 80s erra without digital memory, but the glass delay line was a good solution. Or, it could be done very expensively.

author: strawberry
author_rank: Super Contributor
timestamp: January 18, 2023, 06:58:47 pm
content: sold them on ebayhad some solid epoxy potted crystal block ~40x50x15 mm delay lines from old tube color TVin picture white block between two coilsold good times, probably

author: mister_rf
author_rank: Contributor
timestamp: January 18, 2023, 07:09:21 pm
content: Should I also try to find my notebooks from my television courses?No PDF at that time, only hard copy.By the way, I was planning to take macro shots of a bunch of SAW filters, just to compare different implementations. At the moment only this old pic of SAW filter I’ve took is here:

author: RoGeorge
author_rank: Super Contributor
timestamp: January 18, 2023, 07:10:24 pm
content: Quote from: BrianHG on January 18, 2023, 06:30:47 pmI believe you, just that some pieces of info I find online about NTSC doesn't fit together. Is it possible that the NTSC standard has had changes over the years? Asking because I've browsed this bookhttps://worldradiohistory.com/Archive-Courses/RCA-Color-TV-1966/RCA-Color-Television-Home-Study-Course-1966.pdfand couldn't find any line to line crominance-related inversions, like PAL has. Or maybe those 1..3*64us delay lines are used in a different manner than the 64us delay line from PAL.There is one inversion mentioned at page 42 of 396, and that is an inversion of the 3.58MHz carrier alone, and it is between consecutive frames, and not between consecutive lines:QuoteI'll let it be for now, maybe the mystery will reveal itself later.

author: MK14
author_rank: Super Contributor
timestamp: January 18, 2023, 07:13:47 pm
content: Quote from: mister_rf on January 18, 2023, 07:09:21 pmThanks for the very impressive photographs.Wow, amazingly complicated, neat and intricate design pattern(s) to it. More like one of the masks for an IC, rather than just a passive component.It must have taken a reasonable or large amount of work, and maybe lots of prototypes, to create that, in the first place.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 18, 2023, 07:19:24 pm
content: Quote from: RoGeorge on January 18, 2023, 05:11:45 pmThe only "inversion" in NTSC is that the precise relationship between the TV line frequency and the colour subcarrier means that the phase of the latter differs by 180 degrees from line to line. (Subcarrier is 227.5 times line rate.)In the frequency domain: Because the luminance signal tends to be the same from one line to the next, the luminance spectrum has most of its energy centred on multiples of the TV line frequency and there are "gaps". The half cycle shift of the colour subcarrier puts most of its energy into those gaps.On the screen. The half cycle means that the amplitude of the modulated chroma is inverted between any point on a line and the point vertically below on the next line. So on a monochrome TV if the chroma signal adds to the luminance and makes the displayed brightness higher than it should be on one line, on the next line at that point the chroma will subtract from the luminance and make the brightness lower than it should be. To some degree the viewer's eye averages that out and reduces the visibility of the high frequency colour subcarrier pattern.

author: BrianHG
author_rank: Super Contributor
timestamp: January 18, 2023, 07:21:43 pm
content: Quote from: RoGeorge on January 18, 2023, 07:10:24 pmThat's called 3D comb filtering. The top notch NTSC color decoders.Note that 90% of NTSC color TVs did not have glass filters, just a RLC 3.58Mhz band pass and band trap for the luma.What the glass delay lines comb filters and later-on the digital multi-line adaptive comb filters was access to picture details in the 3.58mhz zone and above to the 4mhz available on over air broadcasts, the max 6mhz for those lucky enough to have analog C-Band access to direct studio broadcasts (damn best picture for those with the right equipment), or laser-discs.The term 'comb' filter came about because with the delay line, you could see the vertical lines without the color fringes which were due to the 180degree phase inversion from line to line present in a true chroma filled source. You are figuratively and literally pulling a hair comb vertically through the picture straightening out those color fringes.

author: Noopy
author_rank: Super Contributor
timestamp: January 19, 2023, 04:00:58 am
content: Quote from: mister_rf on January 18, 2023, 07:09:21 pmI have a SAW filter here too (not online yet).It seems like there is quite some knowledge integrated in these structures.

author: iMo
author_rank: Super Contributor
timestamp: January 19, 2023, 06:04:43 am
content: Never studied the SAW design, but while looking at the picture the left side is the driver creating the waves, and in the middle it looks like sinc() function, output tapped at sinc() maximum, probably tuned for some frequency.. And a lot of other know-how around it, indeed.. Cool!

author: BrianHG
author_rank: Super Contributor
timestamp: January 19, 2023, 11:40:07 am
content: Quote from: mister_rf on January 18, 2023, 07:09:21 pmI just got to know, considering when such band pass filters became available, when these filters were designed, how much of that trace layout was mathematically derived VS trial and error.I've seen the North American TV 45MHz SAW filters and they magically open a 4.5MHz, 5MHz, 5.5MHz window (depending on model), a complete 'flat' response inside that window, with a cliff-edge drop in db right at the edge of the allocated bandwidth slot. 60.5Mhz, 5.5Mhz BW saw filter's also exist to directly tune into Channel 3 for some CATV converters which have 2 tuner sections needed for Volume control and decoder/descrambler loop connection.I've also seen a special a 65Mhz, 50KHz bandwidth SAW for CATV descramblers designed to look into the 4.5Mhz audio sub-carrier directly of channel 3 without tuning into the picture. This is where the scrambler added an additional AM modulation as codes and synchronization.

author: BrianHG
author_rank: Super Contributor
timestamp: April 02, 2024, 09:50:11 pm
content: Video of modern multi-band microwave saw filters developed because of the iPhone:https://www.eevblog.com/forum/rf-microwave/how-the-iphone-changed-the-rf-filters-saw-to-baw-to-fbar-to-smr/

author: RJSV
author_rank: Super Contributor
timestamp: April 02, 2024, 11:15:02 pm
content: Yes; 64 usec. (microseconds) is the very familiar single scan time, physically moving the electron beam direction as typical video 'sweep'., also, I believe, expressed in frequency as 16 khz sweep rate.The use of CRT in countries on 50 hz power, called for a sweep time of 80 usec. as there were timing issues. Not sure if older TV sets needed to lock on, using reliable power grid timing, or if there are interference or 'beat-frequency' issues when not completely sync'ed with AC ripple components in the system. (??)I do remember, in the Z-80 coded computer terminal, that the actual monitor ran at some tiny tiny fraction LESS than exact 60.0 hz; Something more like 59.8 hz or something.Hazy memories, from the wild 70's, huh