EEVblog #720 - Mailbag

[scottwolf369]

Hi Dave, I used to work for Qualcomm in the 90s as a field engineer. My job was to install the ground stations for the Globalstar system.

The satellite system was a "bent-pipe" configuration to keep the costs down.  Basically there's very little intelligence in the satellites.
They merely repeat the signal on a different band back down to Earth from the GS phone and from the ground station back to the phone.

There are three ground stations in Australia.   In 1999 I visited all three sites doing upgrades and got to see a great swath of Australia.

Meekatharra WA     26°36'9.40"S   118°31'39.41"E

Dubbo NSW    32°10'37.97"S   148°36'55.91"E

Mt. Isa QLD     20°41'2.48"S    139°30'17.46"E

The communications themselves use CDMA (code division multiple access) , the same as many non-GSM mobile phones in the US.
However, Globalstar uses twice as many codes as terrestrial CDMA, so many more conversations can happen in the satellite footprint than in a typical cellular "cell".

[n45048]

mm/dd/yy

What kind of moron would ever think of such a thing? ;-)

[miguelvp]

I guess we consider the month more important than the day, and of course we like to start our week on Sunday as well

[Stonent]

Don't forget to put heatsinks to those Xeons, like this one that came from a DELL Precision 490

Last year we auctioned off our old 490s to employees, they averaged 50 to 75 a pop.  They got them with 4GB of ram and XP.
I think most had some $100 FirePro cards in them.  Something they picked up the year prior that was marginally faster than the old Quadro cards in there, though not really for everyone.  The ATIs did better in 3D but the 4 year old Nvidia cards kicked their butts when it came to viewing 2D CAD drawings. (as in people who only dealt with 2D CAD drawings complained and wanted the old cards back)

[Stonent]

Anyway, I'm guessing that may be Seppy?

[n45048]

Dave: Welcome to the Supermicro owners club!

I've been an advocate for Supermicro since I bought my first SuperO board back in 1999 and have used them ever since. Throw some decent RAM (Samsung, Hynix etc...), a half-decent video card and an SSD and your machine will absolutely scream along. You'll also love the reliability. You'll get several months of uptime under Windows which is often ruined with updates ;-)

I order my gear through Alfa Computers in Alexandria (alfa.com.au) just in case anyone in Sydney is interested.

[G7PSK]

The scope's have to be turned like cheese in order to mature them correctly.

The Newage AVR controls the field current on the alternator It takes current from one of the stator windings and feeds it to the field winding of of the exciting generator which is on the same shaft as the main rotating field. The main field windings and the stator of the exiting generator are directly connected on the shaft via a bridge rectifier which rotates with the shaft so the AVR does not control the field directly itself. That particular one registers the voltage from one phase only usually phase A there are others that monitor all three phases. The main reason the AVR's blow is a short in the field winding causing it to try and deliver to much current to the exciter in compensation. I have some that were installed in the 1980's that are still running today with the original AVR, another thing that can bring them down is uneven phase loading such as a large spot welder, such loads should be on the same phase as the AVR or a 3 phase AVR should be used. You can often tell if the AVR is failing or the field winding has a short with a scope as either the waveform will have spikes on it or the voltage will be lope sided either higher or lower about the centre line. I have sent them off in the past to get them repaired by specialist company's but found the hard way that it's best to fit an original new part as replacement. 

[Phoenix]

The AVR (automatic voltage regulator) looks similar in operation and construction to those I've dealt with for synchronous generators on trains. Their basic operation is to regulate the generator output voltage by adjusting the excitation field (remember that the backEMF of a sync machine is proportional to the excitation current).

The output specifications are designed for driving the field winding of the synchronous machine. The output resistance of these is actually an important feature as it helps provide stability/dynamic range into an otherwise almost entirely inductive load. It's also important as the regulator can really only drive a positive output voltage and thus can only actively increase the field current. If the regulator needs to reduce the current in the field it can only freewheel and let the resistor passively dissipate the energy.

Droop control is used when you want to parallel generators together, such as in the main electricity grid. The hand trimmer (an external POT) adjusts the attenuation of the input/feedback signal, implicity setting your sync machine regulated output. The stability circuit would form part of the dynamics of the feedback controller and I'd expect there to be some trimmers to set it up.

In order to test these things you can't really just apply an AC voltage in or else the feedback control will ramp one way or the other way and eventually saturate. Or it'll just self protect somewhere. They are a feedback controller (maybe PI, or type 2 or 3 with some other filtering like peak detection). You really need to think about the circuit operation, bias levels etc., a whole test jig (or a real motor).

Here is an example of an generator that would use such a unit:
http://www.globalmarket.com/product-info/hot-sale-23kw-60hz-230v-copy-stamford-generator-with-avr-2780661.html

[rollatorwieltje]

Dave: Welcome to the Supermicro owners club!

I've been an advocate for Supermicro since I bought my first SuperO board back in 1999 and have used them ever since. Throw some decent RAM (Samsung, Hynix etc...), a half-decent video card and an SSD and your machine will absolutely scream along. You'll also love the reliability. You'll get several months of uptime under Windows which is often ruined with updates ;-)

I order my gear through Alfa Computers in Alexandria (alfa.com.au) just in case anyone in Sydney is interested.

Just looked at the uptime of my router 



I think I may need to update the software at some point
Performance wise it's completly the opposite of Dave's board though, Supermicro X7SPA-HF.

[ornea]

I've been an advocate for Supermicro since I bought my first SuperO board back in 1999 and have used them ever since. Throw

The Supermicro's (10 of) we maintain in our server room (total 100+ servers)  seem to be the most problematic of all the servers we have to work with.

[ornea]

RF Solutions - Elite-XT ... trnamsitters ... Ooops

[G7PSK]

Newage is now part of Cummins.
Here is the web page for the AVR's as they are now for the HC range of alternators which from the power range I saw on the sheet Dave had. https://www.cumminsgeneratortechnologies.com/en/products/avk/voltageregulators/

[ornea]

I guess we consider the month more important than the day, and of course we like to start our week on Sunday as well

I agree, and following the importance logic the only conclusion is

yyyymmdd

It also sorts naturally when used for filenames.

[max666]

Ok, so I just watched the ChipWhisperer-Lite kickstarter video, and I think it's a solid campaign and interesting product.
But what's up with this ... ugh:


I have no confidence in the qualification of the Quality Assurance Manager Luna

[Razor512]

If he needs a good E-ATX compatible case, he should check out the Fractal Design Define XL R2

http://www.newegg.com/Product/Product.aspx?Item=N82E16811352029&nm_mc=AFC-C8Junction&cm_mmc=AFC-C8Junction-_-na-_-na-_-na&cm_sp=&AID=10446076&PID=3938566&SID=

Not flashy, but is very quiet (lots of sound dampening), good cable management, and enough space for long video cards (for when he decides to install a few high end videocards for gaming purposes.

He can then move the rear fan, to the side of the case, then install 2 closed loop liquid coolers (1 at the back, and 1 at the top) (the fan at the side will provide some airflow for the VRM's and videocards.

[Someone]

Hi Dave, I used to work for Qualcomm in the 90s as a field engineer. My job was to install the ground stations for the Globalstar system.

The satellite system was a "bent-pipe" configuration to keep the costs down.  Basically there's very little intelligence in the satellites.
They merely repeat the signal on a different band back down to Earth from the GS phone and from the ground station back to the phone.

Does the 112 emergency dialling number works on the satellite handsets? Without activation? Could make a useful emergency handset.

[n45048]

Does the 112 emergency dialling number works on the satellite handsets? Without activation? Could make a useful emergency handset.

It depends.

For example all satellite operators in Australia support dialing 000. I know the emergency number on the Iridium system used to be 767 (SOS). 112 is considered a 'secondary international emergency number' for digital mobile phones only and won't work on fixed line, some VoIP services and satellite phones.

[scottwolf369]

Hi Dave, I used to work for Qualcomm in the 90s as a field engineer. My job was to install the ground stations for the Globalstar system.

The satellite system was a "bent-pipe" configuration to keep the costs down.  Basically there's very little intelligence in the satellites.
They merely repeat the signal on a different band back down to Earth from the GS phone and from the ground station back to the phone.

Does the 112 emergency dialling number works on the satellite handsets? Without activation? Could make a useful emergency handset.

One of the advantages Globalstar has over Iridium, at least as far as the local provider is concerned (in Australia's case, that would be Vodafone), is that they maintain full control over how the system operates and what it is connected to. 

Iridium has smart satellites. When you make a call, the signal is routed from satellite to satellite until it reaches a satellite that can make the link to the ground station, or to another satellite phone user.

Globalstar's bent-pipe satellites will route through a ground station located in the same country you are calling from and is subject to their control. So if Vodafone, either through their choice or due to local laws, made emergency calling available without an actual subscription, then yes.  (So, as Halon said...it depends.)

My job was installing the racks of equipment, testing the satellite RF chain from the transceivers to the 5.5 meter Alcatel dishes, testing the GPS system, updating software and testing the network connection to the GOCC (Globalstar Operations Control Center).  The phone side was a different set of engineers working with the local provider. So honestly I couldn't tell you how the Australian system was set up as far as the emergency calls. 

[bitwelder]

mm/dd/yy

What kind of moron would ever think of such a thing? ;-)

The American date format, created by me it was.
Yoda

[Someone]

Does the 112 emergency dialling number works on the satellite handsets? Without activation? Could make a useful emergency handset.

It depends.

For example all satellite operators in Australia support dialing 000. I know the emergency number on the Iridium system used to be 767 (SOS). 112 is considered a 'secondary international emergency number' for digital mobile phones only and won't work on fixed line, some VoIP services and satellite phones.

Thanks, they're so cheap second hand that its becoming tempting to pick one up as an emergency alternative to HF sets. Trouble is getting a straight answer out of the providers about the ability to make emergency calls without a plan. So the Iridium handsets will handshake with the network and provide 000 access "out of the box"?

[n45048]

Thanks, they're so cheap second hand that its becoming tempting to pick one up as an emergency alternative to HF sets. Trouble is getting a straight answer out of the providers about the ability to make emergency calls without a plan. So the Iridium handsets will handshake with the network and provide 000 access "out of the box"?

I honestly wouldn't bother. With the mobile network coverage provided by the three carriers in Australia, you'll almost always be in coverage if you're near population and dialing 000 will route the call using any network.

If you're the type of person who goes remote on the odd occasion, you would probably rent a sat phone if voice comms was necessary, otherwise I'd just invest in an EPIRB/PLB. In case of an emergency, especially in remote areas, your location will be known within minutes. They would be far more rugged and reliable than a phone anyway and the shelf-life of the batteries are probably 10+ years.

[84GKSIG]

i know i cant use all my oscilloscopes at the same time but i like my oscilloscopes the right way around

great vid dave 

[Tek_TDS220]

When Dave changed the setting for the mailbag I was one of several commenters who mentioned the upside-down scope.  Ever since then, it's the first thing I look for when the mailbag video appears.  Part of it is simply that I admire the scopes.  This time I noticed it was right-side up, and I wondered when it was fixed.  When the mysterious assistant appeared I just about fell out of my chair.  Good one!

[Someone]

Thanks, they're so cheap second hand that its becoming tempting to pick one up as an emergency alternative to HF sets. Trouble is getting a straight answer out of the providers about the ability to make emergency calls without a plan. So the Iridium handsets will handshake with the network and provide 000 access "out of the box"?

I honestly wouldn't bother. With the mobile network coverage provided by the three carriers in Australia, you'll almost always be in coverage if you're near population and dialing 000 will route the call using any network.

If you're the type of person who goes remote on the odd occasion, you would probably rent a sat phone if voice comms was necessary, otherwise I'd just invest in an EPIRB/PLB. In case of an emergency, especially in remote areas, your location will be known within minutes. They would be far more rugged and reliable than a phone anyway and the shelf-life of the batteries are probably 10+ years.

Dont worry I wouldn't go anywhere interesting without a GPS equipped PLB, having toured the co-ordination centre back in the EPRIB days its a very serious response to all activations and now with the GPS equipped PLB units their targeted time to first contact is down from around 8 hours to around 1. But its those non-life threatening emergencies that it would be useful to have an option for, and also being able to communicate the requirements in case of either.

We've pushed the limits of mobile coverage in Australia and I'm regularly in locations that have zero coverage or used to get CDMA and now get nothing.

One final tip for anyone in a life threatening emergency while outside of cities in Australia, ask for the local Police station (you'll need to know the nearest towns name) and get them to co-ordinate the entire operation, they have many more options and resources than going through the emergency dispatchers.

[n45048]

We've pushed the limits of mobile coverage in Australia and I'm regularly in locations that have zero coverage or used to get CDMA and now get nothing.

Really? That seems unusual. Although if you're with anyone but Telstra, then I can believe it. Optus struggles even in the middle of Canberra.

It also does largely depend on your handset. For example, my other half's iPhone struggles at the fringe of reception whereas my handset (which is Android based) will hang on until it's basically non-existent, data is slow, but it still works. My old Motorola Defy and Razr handsets were also particularly good; Telstra rated them "blue tick" for use in rural areas. On a kind-of related note:

One final tip for anyone in a life threatening emergency while outside of cities in Australia, ask for the local Police station (you'll need to know the nearest towns name) and get them to co-ordinate the entire operation, they have many more options and resources than going through the emergency dispatchers.

In Australia, Police will automatically get notified in Search & Rescue operations. They are the primary response agency and will coordinate SARs.