Test Equipment Anonymous (TEA) : Discussion and Group Therapy Thread

[synx508]

New arrival, Panasonic VP-8191A. Works, looks to be in good physical shape and will do a signal to spec.
Thought it would do stereo modulation, but no. That was just me in delirious acquisitions mode.

Now researching stereo MPX modulation generators. NJM 2035 plus quite few extra components will do this. Nice little project that. For later in summer.

I'd strongly recommend something more modern than a NJM 2035, if you're planning to use the generator for receiver alignment rather than just "hey, look, a stereo beacon!", although it's one of the better old school single IC solutions. The best option in terms of fidelity (RF and audio/MPX) to price is currently direct to RF using SDR or a decent 192kHz or better computer audio interface with something like StereoTool, but if you want a fun project you could be like me and build the relevant parts of an Inovonics Model 718 using very cheap parts and get a lovely clean signal. I use a slightly cheapened version of this where I replaced the pilot and 38kHz carrier generation logic with a single Tiny84A microcontroller clocked from an easily obtained 7.6MHz crystal. Oversampling and fast centre sampling of the switching waveforms takes all the crud from the cheap switches out of the multiplex passband so you can clean up with a low pass filter so far from the passband that any phase manglement is minimal. Stuff like filtering the audio before coding is critical and the filter needs to have overshoot compensation by some means and prior to this, clipping and limiting, to keep the FM deviation correct. Barring software/DSP, the inovonics approach from the late 1990s is probably the closest I've seen to perfection using very cheap parts.There are no optional steps if you want to test with reasonably expectations of the results meaning anything. There *were* some excellent bench stereo generators (R+S or Radiometer of Denmark if you can't afford that), but they were never inexpensive, the affordable ones cut corners that make the results quite disappointing. You might spot one of those R+S multi-purpose RF boxes that can be spectrum analysers, vector signal generators or bluetooth test sets etc, with the right modules to do FM stereo. Very rare option, though, I've never seen one in person.
There's an excellent formerly Silicon Labs DSP chip that's available on breakout boards, it generates a wonderfully clean multiplex signal with all the processing to keep it technically correct, unfortunately it modulates this onto an RF carrier using their low IF technology in reverse so there's an image response about 350kHz away, it's more than 30dB down but that's still way too much for hifi alignment. I don't think there's a way of getting baseband out of it, sadly.
Multiplex stereo is an amazing hack, really, noisy and prone to all kinds of audio crimes but it works well enough and most of the responsibility for getting to work at all is at the coding end, which is part of why it's so amazing and relatively tricky to do well.

[Robert]

My two Anritsu 15NNF-50-3.0C Phase stable cables arrived today. Initial checks say they are all good

15NNF503C_74510.jpg

15NNF503C_74508.jpg

No change with moving cable.
Can't complain at less than £10 each

[mansaxel]

(I will carefully avoid mentioning what is inside the record player itself as input connectors to the RIAA stage )

Welcome to SDI at 1080p50:

I thought I might hear from you.

Heh.

I left broadcast just as SDI was coming in. Interesting to hear that fibre is the present solution.

Why compensate for delay in a GPS antenna cable? Delay down a cable tends to be of the order of 2/3c, so it's a little slow, but nothing like the time required to receive a signal from a geostationary satellite. Or is that compensation for the delay being slightly different at different frequencies?

Because position and time are affected interdependently, and a length of antenna cable will mess up the timing calculation, leading to loss of precision.

When you leave SDI, MADI and AES3 for SMPTE 2110 and AES67, the wordclock and blackburst signals are replaced with Precision Time Protocol, IEEE-1588 v2. The transport formats put video and audio into RTP streams over multicast, and then use a timestamp in the package to tell when the signal was digitized. That timestamp is derived from PTP, which is required to hold a precision of max 1µs deviation from the grand master clock, on every node in the system. Given this two separate A/D converters with AES67 output, connected to two different networks, can be locked well enough to form a stable stereo pair, should you decide to use them for L and R microphones.

When you know not only how fast 48kHz (or 50Hz, in the picture case) is, but also the absolute sampling times of signals you can do some impressive break up and reassembly of associated signals.

I remember going on a course once where VNAs and associated cables were being used and being given stern warnings about using the correct torque on the connectors.

0,6 Nm is the usual value for SMA connectors.

[25 CPS]

I had a Sparkelec DP-666 radio out last night close to midnight while I was in an easy chair in the living room. The radio only had the stock whip antenna on it but I was able to pull in CHU on 3330 and 7850 KHz. It was noisy but discernible on both frequencies. Like any radio, the DP-666 was pretty seriously limited by the basic telescopic whip antenna on it. I couldn't get anything on CHU's third frequency of 14.67 MHz.

CHU remained on air past midnight so they didn't shut down at the end of the day on the 21st and continued a bit into June 22. I checked again at 10:40 this morning and CHU was gone. I found out later they went off the air after the first pip after 10:10 AM local time.

That closes out an era here. I'm not even sure this is saving the government any meaningful money just like shutting down weather radio, and both were closed down with no public consultation or input. The drop dead dates were unilaterally announced and once they arrived, the transmitters were shut down and that was it. There are petitions out there to have both reinstated but I don't think they're going to change anything.

They've even put an archival notice on the website https://nrc.canada.ca/en/certifications ... dcasts-chu where they've listed a bunch of possible replacements. Interestingly, WWV isn't one of the suggestions though. I guess the elbows are up only to the point of actually running a time station of our own.

[Zenith]

Sad. A lot of radio services are disappearing. In the UK BBC transmissions on 198 kHz will be ending on 27th June. This has been threatened for a year or two. Apart from broadcasting, it was used for other things such as controlling special tariff electricity meters and as a time standard. The frequency was governed by a rubidium source.

Not so long ago there were a lot of stations on Medium Wave (Broadcast Band). Now there are just a couple and a lot of digital noise.

[tautech]

Temporary loss of some stations here in AKL NZ also on the AM bands while they replace old masts.
One mast will be lost but both are down currently, fuck knows why they took them both down at the same time....probably to only have a single crane establishment cost....cheapskates !

While not far from us, only some 10km or so, it was close enuf to clearly see the flashing mast navigation lights at night but no more until a single replacement mast is up and running.
https://www.rnz.co.nz/Henderson

[EC8010]

It's all about money. Follow the money. Operating even a single transmitter is expensive. Once upon a time, it was BBC credo that if there was a choice between a cost being borne by the broadcaster or the listener/viewer, then it should be borne by the broadcaster because that reduced total cost. Thus, we used full AM (expensive on power) because it could be demodulated by a crystal. The Beeb has been under attack for decades but much of the attack has been unseen by the public. "Producer Choice" was introduced around 1991 as a means of creating an internal market at the BBC that (it was claimed) would increase efficiency. What it actually did was to waste resources by letting accountants take control. I remember a number of our rooms being locked and becoming unavailable to save our section paying rent on them. This, mark you, in a totally BBC-owned building. This sort of bizarre self-harm was lobbied for my outside interests who had much to gain financially from the BBC's emasculation.

We now have a BBC governed by people who do not have its interests at heart and who seek to operate it according to commercial mores. Money is at the forefront of their minds, not public service. Thus, the switch from programme delivery by broadcasting to over the Internet. How can it possibly be cheaper overall to distribute programmes individually to the listener/viewer than to broadcast them? But the Internet service providers have much to gain from such a model.

[tggzzz]

Splitting anything across multiple organisations encourages finger pointing and wasteful legal activities.

The BBC is definitely under financial pressure now.
Some would say it has been for 40 years.

[AVGresponding]

Splitting anything across multiple organisations encourages finger pointing and wasteful legal activities.

The BBC is definitely under financial pressure now.
Some would say it has been for 40 years.

Oh absolutely; Thatcher started the squeeze, Major continued it, Bliar didn't really do much to roll it back, and Scameron, Dregg, and Scumborne absolutely fucked the ever-living shit out of them.

[Zenith]

It's all about money. Follow the money. Operating even a single transmitter is expensive. Once upon a time, it was BBC credo that if there was a choice between a cost being borne by the broadcaster or the listener/viewer, then it should be borne by the broadcaster because that reduced total cost. Thus, we used full AM (expensive on power) because it could be demodulated by a crystal. The Beeb has been under attack for decades but much of the attack has been unseen by the public. "Producer Choice" was introduced around 1991 as a means of creating an internal market at the BBC that (it was claimed) would increase efficiency. What it actually did was to waste resources by letting accountants take control. I remember a number of our rooms being locked and becoming unavailable to save our section paying rent on them. This, mark you, in a totally BBC-owned building. This sort of bizarre self-harm was lobbied for my outside interests who had much to gain financially from the BBC's emasculation.

Following the money is always a good idea, but there are other forces at work, and the world changes. For instance, there aren't as many shortwave broadcast stations as there were. I wonder how many people were still listening to Radio 4 longwave. I see it as much the same as landline telephones disappearing or changing to cable. I've no idea what they did about Economy 7 meters.

I was curious about the frantic attempts to push DAB radio, with talk of closing down FM VHF, a few years back. Mercifully it seems to have come to not much. My car radio does DAB. I rarely listen to it.

[EC8010]

DAB used to stand for Dead And Buried, then various people wanted to shut down VHF. The government wanted to shut VHF down because they remembered the UHF mobile phone bonanza. (Yes, I know 88MHz to 108MHz isn't quite the same, but government types aren't technical.) Broadcasters didn't like the electricity and maintenance bills associated with VHF. I listened to R3 on a DAB radio at work, but when I brought it home and listened, the quieter environment revealed how shoddy it was. Didn't often burble, but it was always muddy.

I have discovered I need some more test equipment; my Agilent E3648A linear power supply isn't quiet enough. Looking at its output, there's < 1mV of muck, but when you look at an FFT of it, there's all sorts of clock line hash there as well as ripple harmonics. And it has popcorn noise. Looks like I'll have to make a 0 to 15V 1A supply from scratch. I have an ADR1399, and I can wind a low C_PS mains transformer, so the addition of a couple of decade switches and bits and bobs should do the trick. I've even got a 0.7H 1A choke, so CLC smoothing can be used before the regulator. Probably a two-box job with the transformer, rectifier, and reservoir in one box and the rest in another. Moving coil ammeter is a given. Output on a BNC.

[MED6753]

I had a Sparkelec DP-666 radio out last night close to midnight while I was in an easy chair in the living room. The radio only had the stock whip antenna on it but I was able to pull in CHU on 3330 and 7850 KHz. It was noisy but discernible on both frequencies. Like any radio, the DP-666 was pretty seriously limited by the basic telescopic whip antenna on it. I couldn't get anything on CHU's third frequency of 14.67 MHz.

CHU remained on air past midnight so they didn't shut down at the end of the day on the 21st and continued a bit into June 22. I checked again at 10:40 this morning and CHU was gone. I found out later they went off the air after the first pip after 10:10 AM local time.

That closes out an era here. I'm not even sure this is saving the government any meaningful money just like shutting down weather radio, and both were closed down with no public consultation or input. The drop dead dates were unilaterally announced and once they arrived, the transmitters were shut down and that was it. There are petitions out there to have both reinstated but I don't think they're going to change anything.

They've even put an archival notice on the website https://nrc.canada.ca/en/certifications ... dcasts-chu where they've listed a bunch of possible replacements. Interestingly, WWV isn't one of the suggestions though. I guess the elbows are up only to the point of actually running a time station of our own.

CHU was typically received better here than WWV. It's sad to see it go silent.

[Zenith]

I came across this Youtube video on CHU. It's 8 minute 44 seconds long. I didn't realise it was such a long established station.

https://www.youtube.com/watch?v=dZwGnob6ZdE