ok. Just personally I don't like sending anything over 1MHz through RCA connectors if I can help it, even though it does work in a domestic environment.
Not that it represents an optimum connector use, but the origin of the lowly RCA cable was as an interconnect between modules in consumer devices like TV tuners and IF strips at 41-46 MHz...and man were those cheap connectors; little more than a steel shell with a phenolic plate supporting the center pin, all soldered up.
Cheers!
Howie
Yup, the hand tuned coupling window with a piece of soldered metal and IIRC 1N62 germanium diode mixer fed into the rest of the works with very sparse RCA connectors. The noise figure on those early UHF tuners was pretty marginal.
Back to some history. The first evidence of an RCA connector I could find was from the 1940's? in an early TV for connecting between the tuner and the IF. It was repurposed for audio in the late '40s or early '50s in some at the time obscure audio products. Its other widespread use starting in the late 1960's was for video composite baseband. All the video was optimized for 75 Ohms but the RCA connector worked well enough and 4 BNC's on the back of a consumer TV was never going to be cost effective. There was a brief period where a DIN connector was repurposed for "S-Video" but that vanished with HDTV. Since early digital audio was carfully mashed into NTSC video to use NTSC video recording it was not much of an effort to use the 75 Ohm cables with RCA connectors for digital audio. Pro stuff used BNC's for reliability but consumer stuff used RCA's like the early Sony recorder and early CD players (the Sony CDP-101 id not have a standard SPDIF output but later units did) and DAC's (e.g. Cambridge audio) did have RCA's.
You cannot make an RCA connector into a correct 75 Ohm or 50 Ohm connector because the ratio of the OD of the center pin and the ID of the shell work out to 30 Ohms. Below 10 MHz is not a real issue however you can see the ghost reflection in a sharp video transition when the termination is particularly bad on an analog display (Remember those? Are you old enough?). The WBT uses a series inductance on the shell to sort of fix it to 75 Ohms and it works but compromises the EMI/EMC performance. I would like to properly test a set but not willing to spend that much to find out.
FWIW a 75 Ohm BNC is not real either. A real 75 Ohm connector (e.g. 75 Ohm N) will have a smaller center pin and is not intermateable with a 50 Ohm connector. Again this is only an issue at 1 GHz and above usually. In the 1980's a compromise mod of the 50 Ohm BNC (change and remove dielectric) got good enough for 75 Ohms. FWIW the ground dimensions of an N connector are the same as a BNC connector and the 50 Ohm version will intermate in a pinch. Mating a 50 Ohm male N connector and 75 Ohm female N connector will destroy the female connector.
You cannot make an RCA connector into a correct 75 Ohm or 50 Ohm connector because the ratio of the OD of the center pin and the ID of the shell work out to 30 Ohms. Below 10 MHz is not a real issue however you can see the ghost reflection in a sharp video transition when the termination is particularly bad on an analog display (Remember those? Are you old enough?). The WBT uses a series inductance on the shell to sort of fix it to 75 Ohms and it works but compromises the EMI/EMC performance. I would like to properly test a set but not willing to spend that much to find out.
FWIW a 75 Ohm BNC is not real either. A real 75 Ohm connector (e.g. 75 Ohm N) will have a smaller center pin and is not intermateable with a 50 Ohm connector. Again this is only an issue at 1 GHz and above usually. In the 1980's a compromise mod of the 50 Ohm BNC (change and remove dielectric) got good enough for 75 Ohms. FWIW the ground dimensions of an N connector are the same as a BNC connector and the 50 Ohm version will intermate in a pinch. Mating a 50 Ohm male N connector and 75 Ohm female N connector will destroy the female connector.
In fact, WTB changed the geometry of both the connector and the socket.
nextgen™ RCA connectors consist of connectors and sockets and are future-proof. Thanks to the 75-ohm line impedance, they are also finally able to carry digital signals with a bandwidth of up to 1GHz. Analogue signal transfer also benefits considerably from the enormous bandwidth.
Products
It always impresses me how cost optimised domestic TVs became very quickly. Just enough bits to work and not one penny more spent.
I also remember first time I saw a calibrated studio monitor at the BBC and realised how much gets lost from studio to house. IIRC the tube alone was 10x the cost of a complete domestic CRT TV
I just need to look at their drawings and talk with their engineer and director.
Yes, by the way, you obviously removed me from your blacklist, you are very generous.
Yes, by the way, you obviously removed me from your blacklist, you are very generous.
And then how can it be compatible with a standard connector? Adding inductance is a nice trick. I explored it many years ago. However that opens a door for EMI.
This is elementary compatible. You simply plug the nextgen ™ connector into the outlet of any manufacturer and listen to music through the audio cable, as you always did before. Nextgen ™ sockets will have less loss.
You seem to have missed my point. The basic dimensions of an RCA connector - OD of the center and ID of the ground contact work out to around 30 Ohms. if the wavelengths are long its not critical but for fast edges it is.
The chassis connector termination is not coaxial on the inside being just two large tabs. I have not found a picture of the inside of the RCA but there is nothing on correct strip length or crimp/clamp connection like any qualifed BNC.
If they weren't so expensive I would get some and put them to the test- VNA and TDR. It would be a good excuse to dust those off again.
The chassis connector termination is not coaxial on the inside being just two large tabs. I have not found a picture of the inside of the RCA but there is nothing on correct strip length or crimp/clamp connection like any qualifed BNC.
If they weren't so expensive I would get some and put them to the test- VNA and TDR. It would be a good excuse to dust those off again.
Where does the source of your information come from say that 30 ohms or 50 ohms is an obstacle to high frequencies? The cable for such a connector, for full matching, will also require 30 ohms or 50 ohms. As in sockets, it should also be 30 ohms or 50 ohms. But, as you wrote earlier, RCA was not standardized by wave resistance at all and can be of any internal size, depending on the manufacturer's company. Now some companies are normalizing it to a value of 75 ohms, since such a cable is very popular. This is bad?
High Speed Digital Design: A Handbook of Black Magic Howard Johnson, Martin Graham
High Speed Digital Design: A Handbook of Black Magic Howard Johnson, Martin Graham
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The impedance is given by the mechanical dimensions and the dielectricum which is
is concentrated at just one thin place. That alone makes it sure that you cannot
get a constant Z along the line but you have at least 4 impedance steps.
The RCA was munzed together with just one goal: low cost.
Sorry, you cannot polish a turd, even if you plate it with gold.
Instead of pontificating here you would better learn the basics.
Yeah, read it if you can.
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30 ohms is not a obstacle in itself but I don't know of any 30 Ohm cable source. both 50 Ohm and 75 Ohm cables are standardized. 93 Ohms as well. but you can't just switch in the middle of a system without some type of matching or accepting losses and reflections. The physical dimensions and dielectric determine the impedance. The dimensions of an RCA are essentially fixed and I don't know of any negative dielectrics so the best you can do is 30 Ohms. Claiming its somehow 75 Ohms with out details is marketingspeak. A spec for return loss (swr) vs. frequency or better yet a return loss plot would help a lot.
Here is how Canare specifies their 75 Ohm RCA:
● Standard 75 ohm construction Crimp Pin & Sleeve.
● DC to 200MHz >26dB Return Loss (<1.1 VSWR) .
Canare Corp.: RCA Connectors: RCA Crimp Connectors( RCAP-C Series)
And they only claim 200 MHz.
Here is how Canare specifies their 75 Ohm RCA:
● Standard 75 ohm construction Crimp Pin & Sleeve.
● DC to 200MHz >26dB Return Loss (<1.1 VSWR) .
Canare Corp.: RCA Connectors: RCA Crimp Connectors( RCAP-C Series)
And they only claim 200 MHz.
You accurately measured the dimensions of the RCA WBT connector
NextGen ™? So do not rush yourself. WBT is not the only company that guarantees 75 ohms in its connectors.
Characteristic impedance Z = 75 Ohm up to 1GHz
https://www.wbt.de/fileadmin/media/data/0110_Ag_engl.pdf
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They indicate the transition resistance Rü <0.1 mOhm for this frequency.
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