Author Topic: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!  (Read 14945 times)

0 Members and 1 Guest are viewing this topic.

Offline bsdphk

  • Regular Contributor
  • *
  • Posts: 198
  • Country: dk
Re: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!
« Reply #50 on: November 03, 2019, 11:31:18 am »
I gather from the debate that nobody here truly appreciate how much of an engineering marvel "carrier-frequency telephony" was back in analog days.

Here are some info to try to put it in proper perspective:

The "L5" system, which for all practical purposes was the final and ultimate in carrier-frequency transmission before everything went digital, modulated 10,800 telephone channels, each 4kHz wide, onto a single coax-cable, and transmited the signal in "toll grade" quality, which includes 44dB S/N ratio, from one side of USA to the other, or rather: up to 4000 US miles.

This required a repeater every single mile, literally 4000 repeaters one after the other, each amplifying the signal 25dB to compensate the loss of one mile of telco-grade coax.  Well, "approx 25dB" because the attenuation depends on the temperature...

And yes, that means the total amplification from coast to coast was 100,000 (a hundred thousand) dB at the top frequency near 60 MHz.

Now, imagine if those 4000 amplifiers due to some accident of design or manufacturing all had 0.01dB dip or bulge at the same frequency ?

Or imagine if the coax had a little nick every N meters, due to a piece of debris on a pulley wheel in the factory ?

Ohh, and since the total frequency range is 1.5 to 60 MHz, better watch those I2 and I3 distortion products.

And did I mention that the repeaters live in a damp hole in the ground or boltet to the top of a tall wooden pole, out in the middle of nowhere ?

*Now* you can start to appreciate why HP, W&G and others built instrumentation to those insane specs, in particular with the ability to measure dB to part of thousands.

The HP3336 and HP3586 for example were built as a matched pair, directly focused on the L4 Carrier systems "only" 3600 telephone channels.  They were some of the first microcontroller controlled instruments ever, which made it possible to measure all 3600 channels in a matter of minutes.

For more information on L5 see: https://archive.org/details/bstj53-10-1901  (And the entire rest of the BSTJ december 1974 issue on archive.org)
 
The following users thanked this post: SeanB, PA0PBZ, Fungus, GeorgeOfTheJungle, SilverSolder, BrianHG, alm, schmitt trigger

Offline vk6zgo

  • Super Contributor
  • ***
  • Posts: 7547
  • Country: au
Re: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!
« Reply #51 on: November 03, 2019, 03:33:12 pm »
I gather from the debate that nobody here truly appreciate how much of an engineering marvel "carrier-frequency telephony" was back in analog days.

Here are some info to try to put it in proper perspective:

The "L5" system, which for all practical purposes was the final and ultimate in carrier-frequency transmission before everything went digital, modulated 10,800 telephone channels, each 4kHz wide, onto a single coax-cable, and transmited the signal in "toll grade" quality, which includes 44dB S/N ratio, from one side of USA to the other, or rather: up to 4000 US miles.

This required a repeater every single mile, literally 4000 repeaters one after the other, each amplifying the signal 25dB to compensate the loss of one mile of telco-grade coax.  Well, "approx 25dB" because the attenuation depends on the temperature...

And yes, that means the total amplification from coast to coast was 100,000 (a hundred thousand) dB at the top frequency near 60 MHz.

Now, imagine if those 4000 amplifiers due to some accident of design or manufacturing all had 0.01dB dip or bulge at the same frequency ?

Or imagine if the coax had a little nick every N meters, due to a piece of debris on a pulley wheel in the factory ?

Ohh, and since the total frequency range is 1.5 to 60 MHz, better watch those I2 and I3 distortion products.

And did I mention that the repeaters live in a damp hole in the ground or boltet to the top of a tall wooden pole, out in the middle of nowhere ?

*Now* you can start to appreciate why HP, W&G and others built instrumentation to those insane specs, in particular with the ability to measure dB to part of thousands.

The HP3336 and HP3586 for example were built as a matched pair, directly focused on the L4 Carrier systems "only" 3600 telephone channels.  They were some of the first microcontroller controlled instruments ever, which made it possible to measure all 3600 channels in a matter of minutes.

For more information on L5 see: https://archive.org/details/bstj53-10-1901  (And the entire rest of the BSTJ december 1974 issue on archive.org)

The difficulties involved are why PMG/ Telecom Australia shifted largely to terrestrial microwave systems.

Those were the days, though---when the "coax" from Perth to Geraldton was laid, they used Cat D9 dozers with a ripper on the back, with the cable direct laid in the trench formed.

All went well with the sandy coastal soil & sandstone, but everything slowed to a crawl when they hit some really hard rock which seemed to go on forever.
The wear of the ripper blades was horrific, too, so much so, that Cat sent an Engineer over from the USA , with the instruction " Don't come back till you find out how to fix it!"

He dutifully studied the problem, sent all the data back to his home base, who came up with special ripper blades which did the job!

I bet you wouldn't see that sort of response these days!


 

Offline bsdphk

  • Regular Contributor
  • *
  • Posts: 198
  • Country: dk
Re: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!
« Reply #52 on: November 03, 2019, 05:25:08 pm »
Well, it's not like microwave didnt come with its own baggage...

For that you want to read about the TD3 system in the September 1968 issue of BSTJ :-)

Link to intro article: https://archive.org/stream/bstj47-7-1143

The technical stuff is all the rest of that issue.

But if you want to read about the *truly* crazy project, read about the WT4 system in the December 1977 issue:  A 60mm waveguide all the way across USA.

Again: Link to intro: https://archive.org/details/bstj56-10-1829

Read full issue for the gory details, especially the article about the 20 millisecond waveguide shunting machine...
 

Offline szymon019

  • Contributor
  • Posts: 10
  • Country: pl
  • Passionate Electronics Developer
    • Electronics R&D Laboratory & Prototyping
Re: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!
« Reply #53 on: November 03, 2019, 06:36:58 pm »
Some other photos of internal parts of SNA-2 (Spectrum Vector Network Analysator -2). Attenuators section on glass.
865898-0
865902-1
 
The following users thanked this post: GeorgeOfTheJungle

Offline vk6zgo

  • Super Contributor
  • ***
  • Posts: 7547
  • Country: au
Re: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!
« Reply #54 on: November 04, 2019, 01:57:29 am »
Well, it's not like microwave didnt come with its own baggage...

For that you want to read about the TD3 system in the September 1968 issue of BSTJ :-)

Link to intro article: https://archive.org/stream/bstj47-7-1143

The technical stuff is all the rest of that issue.

But if you want to read about the *truly* crazy project, read about the WT4 system in the December 1977 issue:  A 60mm waveguide all the way across USA.

Again: Link to intro: https://archive.org/details/bstj56-10-1829

Read full issue for the gory details, especially the article about the 20 millisecond waveguide shunting machine...


The East-West microwave system in Oz suffered from the problem of tube technology, but still did a very good job.
The ongoing fantasy among EEs of turning Techs into "module jockeys" also raised its head.
Unfortunately, not everything could be swapped back through the "Central Maintenance Depots", so a fair amount of "on site" repair was still needed.

Another problem was tropospheric ducting.
Re-use of frequencies was restricted to several "hops" ( you may use the same frequencies every two or three hops).
Unfortunately, "ducting" sometimes caused interference between the local "direct" signal from the desired site & the ducted signal from several (or more) previous sites.

This was minimised by changing the direction of transmission between each site & the previous ones, as much as practicable.
Even so, there were still minor problems  from time to time during the Summer.

Australia lent itself well to the extensive use of microwave systems, with much of the country fairly flat, & large population centres being quite  far apart.
 

Offline Ray Gianelli

  • Contributor
  • Posts: 22
  • Country: us
Re: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!
« Reply #55 on: November 06, 2019, 06:13:05 pm »
I've seen several of these laying in corners in various central office's I've been in.
 

Offline schmitt trigger

  • Super Contributor
  • ***
  • Posts: 2199
  • Country: mx
Re: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!
« Reply #56 on: November 07, 2019, 04:27:13 pm »
The calibration stickers show that the last due date calibration was July 17, 2002.

So it has been a while since they were last used.
 

Offline johnh

  • Regular Contributor
  • *
  • Posts: 213
  • Country: au
Re: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!
« Reply #57 on: November 08, 2019, 06:18:08 am »
I wouldn't' say that.

Where I work we often use some equipment that hasn't being calibrated for a long.
 

Offline exor

  • Regular Contributor
  • *
  • Posts: 78
  • Country: fi
Re: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!
« Reply #58 on: December 01, 2019, 01:03:59 pm »
I have SPM-19 and also NFA-1. They have been resting long time waiting for my new lab bench to get ready.

SPM seems to be fine but it looks that the rest hasn’t done any good for the NFA-1. No picture, just small dot on upper left corner. Maybe (hopefully) it is some power supply issue.. Fortunately I have manual and circuit diagrams for it.

Last week I found SG-4 from eBay (PL) for the SPM, should arrive next Tuesday (there is still one available if someone is interested). I hope that beginning of next year I’m able to fix the NFA and pile them all on my new bench :)
 

Offline jt

  • Regular Contributor
  • *
  • Posts: 91
Re: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!
« Reply #59 on: February 24, 2020, 05:04:59 am »
I watched this when I was a bit tipsy... and I ordered one from ebay...  No regrets
 

Offline Pixelvore

  • Newbie
  • Posts: 1
  • Country: ca
Re: EEVblog #1256 - Most Gorgeous Test Gear Teardown Ever!
« Reply #60 on: January 06, 2021, 11:47:41 pm »


(and it took a while to make up all the cables one needs to get these three things to play nice)
Hi. Does anyone know if it is possible to use the SG-4 display unit without the SPM-16/19, ie providing the x and y deflection voltages on the 14pos connector(i think using cable K145) manually and not interfacing with the IEEE-488 bus at all? I am asking because i couldn't get my hands on a manual for the SG-4, but according to the SPM-16/19 manuals it is possible, at least for the SG-2/3, and i only have the SG-4 and none of the other instruments.
Thank you in advance :)

Hi could you please tell me if the cables attached on SG4 are pin to pin on the spm-19? Do you have a pin out table? Thanks i just bought them but there were no cables included. Please help
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf