They spun out Agilent for that role into its own company, so it wasn't a sell off to someone else. I can't speak to the quality of the equipment, but I know they're one of the big shops for that market.
That is a good point, but I'm not sure how well it would work over standard fractional wavelength radials on larger systems. The Marconi drawing has lighting and static charge protection from the grounded side of the voltage transformer that's being fed from the transmitter. It could be very useful for space conscious form factors, and I don't know anyone that wants a radial and whip system for a cell phone.
From Marconi's drawing, it looks more like use of a coil as either a resonant stub or shorted stub being directly fed to a phasing coil that is being fed from a voltage balun from the tank oscillator. It's a little different than traditional ones since it's wound into a coil, though.
Since shorted stub filters are inductive in nature, they typically broaden the bandwidth of the capacitive mono-pole element. Those are pretty interesting microwave tricks, but winding a stub into a coil may reduce material and size requirements where space is at a premium. It's probably a sacrifice on bandwidth of the system with the tradeoff that the stub would probably contain the RF to the center of the inductor. Maybe there's something more I'm missing here.
Well, beyond the theory, it kinda looks like a curly-que J-pole to me
Exactly. That's a multiband antenna system. Change bands, change the tap point. The point they're missing is grounding of the "asymmetric" half of the antenna, and that's to keep a static charge from building in the antenna that'll zap through your electronics (or you) for safety reasons. The center tapped grounded coil feedpoint matching is also less noisy than an inline tuning coil.
Unfortunately, that's not entirely true with cable modems. Connecting to the DOCSIS network grants your ISP admin rights over the device. That's a big reason why you should separate the functionality of your primary gateway route from your DOCSIS demarcation device.
I've always run my own hardwsare for years for a reason: it gives me a buffer beyond which I know the ISP no longer has control of my home network. 2x OpenWRT routers, a managed switch in the middle, and a lightweight embedded PC running the essential network services (dhcp, dns, ntp, etc), and the IT management overhead is fairly low.
Makes sense to me. PostgreSQL is essentially the open source successor to Ingres (even down to being forked from the original Ingres codebase). In fact, PostgreSQL's name even means Post-ingres.
The issue is that a strong transmission in the same band as a receiver can desense the receiver. This can also be done with a cavity duplexer if you need input and output in the same band on adjacent frequencies, but you pay for it with geometric space (since cavity duplexer dimensions are a fraction of the wavelength in free space multiplied by the materials velocity factor). This can be problematic on HF and VHF bands, but UHF and microwave can get away with duplexers the size of a brick. Unfortunately, that's still too much for mobile phones since it's too big to fit in someone's pocket.
Indeed, I have many times run a linux router by doing nothing but installing quagga, Net-SNMP, ipt_netflow, and I've got a lower end equivalent to some of the highest end commercial networking equipment.
Both OSPF and BGP provide the tools you need for policy based routing to various degrees, and quagga gives you that. The rest is just icing on the cake.
Ah, script tags... I agree with you completely. Programming languages merely describe a format electronic data format that can be read in by a computer program or piece of hardware affecting the state of the system in some way. They do not necessarily need to contain procedural instructions, and the definition of turing complete simply determines whether that particularly language is description enough to implement general purpose algorithms. Also, a lot of computer security issues come up from these non-TC programming languages being fed into a system and running instructions anyway.
As a theoretical example, someone's web server delivers a malicious image file that crashes the client image codec library and fools it into running code contains elsewhere in the malicious file. Doesn't matter whether that image was designed to contain procedural instructions or not if someone can fool the parser to run those instructions anyway.
They are not turing complete programming languages, but they are domain specific programming languages. This is the same as making the argument that SQL is not a programming language since you only use it to define/insert/update/delete data in a database and cannot write general purpose programs without another tool that does provide a turing complete function set. ASN.1 and SMI are formats to describe messages and message data types to be used by another higher level protocol like SNMP, LDAP, X.509, etc.
I agree with PP and GP, but there's more to it than just that. Software is like an organ of your computer; your computer typically won't do much worthwhile if there's not a whole bunch of the things working together to make complete systems. Almost every one of the higher level languages are implemented in C at some point in the software stack. Some might argue that certain JVM languages like Scala and Groovy and Clojure are written in pure java, but guess what? The JVM is written in C. Almost every piece of software out in the wild is either written in C or depends on critical components written in C all the way down to the operating system. If you're running embedded, you might not have an OS, but you probably should be using C on microcontrollers and embedded systems unless there's a real good reason not to.
Need is relative. I need to have my network up and functional even when a crapping appliance elsewhere trips the circuit breaker, and I need to keep the inductive load noise of the appliance motors out of my data lines. It's also nice to be able to power any systems that I want to mount there that have more horsepower than a modem, router, switch, and VoiP box. Yes, need is relative, but I suppose you don't need a foundation if you're happy walking around on dirt floors.
I agree that installing a proper data infrastructure in a home is key for proper nerding out, and you have a lot of options to go over.
If you want to go for broke, put a 2" wall mount telecom rack somewhere near ground level (basements and storage closets are perfect for this) to keep noise in the system to a minimum. Go with cat5e or better for data, cat3 or better (cat5 or better works, but is usually more expensive per ft.) for telephone lines, and RG6 or RG59 (RG6 is lower loss, but more expensive and harder to work with, but you're laying down permanent lines) if you want a cable connection. Have a dedicated 20A breaker circuit run to power the installation and a rack level UPS and you're set to run in power outage and brownout situations.
There is a strong interest in 'cutting the cord' with cable, so you may be able to save on the coax and just not bother. The telephone lines can still be used with a voip box to give you access to the telcos with regular equipment, or you can use something more exotic like 802.11 or some enterprise level VoiP equipment. I'm sure you can keep going further and further along until you've punched all the tickets on your nerd card that you want to.
This is just typical politics in the aerospace industry. It's so critical to national defense infrastructures that it tends to develop more cruft on its surface than others despite dealing with such incredibly interesting high tech. Also, US congressional budgets have been starving the budgets for the projects dealing with basic scientific research and study, which is a shame.
I would prefer to see NASA bet on all three horses so you have better odds of one of winning the race!
The current generations of the politically active general public seems to distrust and hate scientists and engineers, and they'd rather all that wonderful "free" government money be spent on turkeys in every pot and cars in every garage or some pet social program instead of sending big tin cans to outer space to prance around and look for little green men. It's a shame to see the US fail to invest in its own technological success, but I have some faith that the readers of this site don't always share that particularly mundane outlook.
There's a lot about safety in the regulations, and you're misrepresenting what those regulations are by only highlighting a circumstance in which the operator hurts themselves. You are breaking the law if your station installation doesn't meet the necessary safety regulations, isn't grounded properly, isn't of a sufficient level of engineering quality, but particularly if you exceed maximum power output and RF exposure limits (especially to recipients unaware of the exposure). Enforcement of that is a different matter... Still, the safety and welfare of human beings trumps little things like interferences, and anyone in a life threatening situation (with or without a license) is allowed to use a radio on any frequency or any communication tool at their disposal to ask for help.
The human body is resonant from 30-300 mhz, and the human head is resonant on VHF freqs (2 meter VHF is the most common amateur band for local FM communication, by the way). Say I have a 100W 2 meter transceiver fed into a 20 db yagi-uda directional antenna which I point towards my local repeater, but it's not high up because I cheaped out on a decent mast installation, and that sucker isn't grounded worth a flip. I could potentially be transmitting 1000W (100W at 20 db is 1000W) into an unsuspecting neighbor's house, and the regulations for individuals aware of the exposure is much higher than those for individuals unaware of their exposure (since those unaware wouldn't recognize the signs of dangerous exposure). You're going to feel a little tingling heat sensation if you have that antenna pointed at you, it will definitely burn you good if you touch it (you'll get this funky ashy grey burn, too), and that is a reasonable setup to encounter for even the most cash strapped ham out there.
Ok, now lets move over to unlicensed services. AM and sideband mode citizens band, 5 watts. Tons of folks operating illegal linear amps on those, and there's regs on amp manufacturers to prevent their equipment from illegally boosting on 11 meters. Family radio service is limited to 1/2 W output, and the radios are required to have permanently mounted negative gain antennas that almost guarantee coming in under that limit every time. Wifi is limited to 1W peak output on the beefiest of access points, and is still only going to go up to 10W with a 20 db directional. Any ham transmitter that outputs below 200W peak envelope power doesn't require any sort of RF survey for installation, but that value takes into account the gain/loss of the feedline and antenna system in use, too. The mode of operation comes into play since it dictates duty cycle of transmission, and most digital systems are typically a fraction of the duty cycle of FM.
You might be interested to note that it's the Amateur Radio and Relay League, making it the ARRL. I'm not sure what the AARL is, but I think you mixed it up with the other old timers club, the AARP.
Well, I guess you got me. That exam the FCC made me take to get my license had a LOT of questions about safety around electricity and RF, maximum peak envelope powers, and the requirements for a formal site survey when installing transmitting equipment. Yep, nothing at all about safety there.
Slashdot Mirror
They spun out Agilent for that role into its own company, so it wasn't a sell off to someone else. I can't speak to the quality of the equipment, but I know they're one of the big shops for that market.
That is a good point, but I'm not sure how well it would work over standard fractional wavelength radials on larger systems. The Marconi drawing has lighting and static charge protection from the grounded side of the voltage transformer that's being fed from the transmitter. It could be very useful for space conscious form factors, and I don't know anyone that wants a radial and whip system for a cell phone.
From Marconi's drawing, it looks more like use of a coil as either a resonant stub or shorted stub being directly fed to a phasing coil that is being fed from a voltage balun from the tank oscillator. It's a little different than traditional ones since it's wound into a coil, though.
Since shorted stub filters are inductive in nature, they typically broaden the bandwidth of the capacitive mono-pole element. Those are pretty interesting microwave tricks, but winding a stub into a coil may reduce material and size requirements where space is at a premium. It's probably a sacrifice on bandwidth of the system with the tradeoff that the stub would probably contain the RF to the center of the inductor. Maybe there's something more I'm missing here.
Well, beyond the theory, it kinda looks like a curly-que J-pole to me
Exactly. That's a multiband antenna system. Change bands, change the tap point. The point they're missing is grounding of the "asymmetric" half of the antenna, and that's to keep a static charge from building in the antenna that'll zap through your electronics (or you) for safety reasons. The center tapped grounded coil feedpoint matching is also less noisy than an inline tuning coil.
Good thing I'm not using bcc as a compiler. Probably not very useful off of PDP-7 or PDP-11 systems, anyway.
Unfortunately, that's not entirely true with cable modems. Connecting to the DOCSIS network grants your ISP admin rights over the device. That's a big reason why you should separate the functionality of your primary gateway route from your DOCSIS demarcation device.
Nope. I did it because I was cheap, and the AMD fusion system on chip board cost a fraction of what it would cost to run big iron grade boards.
I've always run my own hardwsare for years for a reason: it gives me a buffer beyond which I know the ISP no longer has control of my home network. 2x OpenWRT routers, a managed switch in the middle, and a lightweight embedded PC running the essential network services (dhcp, dns, ntp, etc), and the IT management overhead is fairly low.
Makes sense to me. PostgreSQL is essentially the open source successor to Ingres (even down to being forked from the original Ingres codebase). In fact, PostgreSQL's name even means Post-ingres.
The issue is that a strong transmission in the same band as a receiver can desense the receiver. This can also be done with a cavity duplexer if you need input and output in the same band on adjacent frequencies, but you pay for it with geometric space (since cavity duplexer dimensions are a fraction of the wavelength in free space multiplied by the materials velocity factor). This can be problematic on HF and VHF bands, but UHF and microwave can get away with duplexers the size of a brick. Unfortunately, that's still too much for mobile phones since it's too big to fit in someone's pocket.
Indeed, I have many times run a linux router by doing nothing but installing quagga, Net-SNMP, ipt_netflow, and I've got a lower end equivalent to some of the highest end commercial networking equipment.
Both OSPF and BGP provide the tools you need for policy based routing to various degrees, and quagga gives you that. The rest is just icing on the cake.
Nice rig. I had an President 10m for a while until I gifted it to my buddy for passing his tech class. See you 28.400, 73.
Ah, script tags... I agree with you completely. Programming languages merely describe a format electronic data format that can be read in by a computer program or piece of hardware affecting the state of the system in some way. They do not necessarily need to contain procedural instructions, and the definition of turing complete simply determines whether that particularly language is description enough to implement general purpose algorithms. Also, a lot of computer security issues come up from these non-TC programming languages being fed into a system and running instructions anyway.
As a theoretical example, someone's web server delivers a malicious image file that crashes the client image codec library and fools it into running code contains elsewhere in the malicious file. Doesn't matter whether that image was designed to contain procedural instructions or not if someone can fool the parser to run those instructions anyway.
That's PL/SQL, not SQL.
They are not turing complete programming languages, but they are domain specific programming languages. This is the same as making the argument that SQL is not a programming language since you only use it to define/insert/update/delete data in a database and cannot write general purpose programs without another tool that does provide a turing complete function set. ASN.1 and SMI are formats to describe messages and message data types to be used by another higher level protocol like SNMP, LDAP, X.509, etc.
I agree with PP and GP, but there's more to it than just that. Software is like an organ of your computer; your computer typically won't do much worthwhile if there's not a whole bunch of the things working together to make complete systems. Almost every one of the higher level languages are implemented in C at some point in the software stack. Some might argue that certain JVM languages like Scala and Groovy and Clojure are written in pure java, but guess what? The JVM is written in C. Almost every piece of software out in the wild is either written in C or depends on critical components written in C all the way down to the operating system. If you're running embedded, you might not have an OS, but you probably should be using C on microcontrollers and embedded systems unless there's a real good reason not to.
Need is relative. I need to have my network up and functional even when a crapping appliance elsewhere trips the circuit breaker, and I need to keep the inductive load noise of the appliance motors out of my data lines. It's also nice to be able to power any systems that I want to mount there that have more horsepower than a modem, router, switch, and VoiP box. Yes, need is relative, but I suppose you don't need a foundation if you're happy walking around on dirt floors.
You don't want to run cables that might cause you to trip and fall into the toilet.
I agree that installing a proper data infrastructure in a home is key for proper nerding out, and you have a lot of options to go over.
If you want to go for broke, put a 2" wall mount telecom rack somewhere near ground level (basements and storage closets are perfect for this) to keep noise in the system to a minimum. Go with cat5e or better for data, cat3 or better (cat5 or better works, but is usually more expensive per ft.) for telephone lines, and RG6 or RG59 (RG6 is lower loss, but more expensive and harder to work with, but you're laying down permanent lines) if you want a cable connection. Have a dedicated 20A breaker circuit run to power the installation and a rack level UPS and you're set to run in power outage and brownout situations.
There is a strong interest in 'cutting the cord' with cable, so you may be able to save on the coax and just not bother. The telephone lines can still be used with a voip box to give you access to the telcos with regular equipment, or you can use something more exotic like 802.11 or some enterprise level VoiP equipment. I'm sure you can keep going further and further along until you've punched all the tickets on your nerd card that you want to.
I'm honestly surprised that the annexation of Ukraine wasn't enough, but what do I know about global economies? No one here but us chickens.
This is just typical politics in the aerospace industry. It's so critical to national defense infrastructures that it tends to develop more cruft on its surface than others despite dealing with such incredibly interesting high tech. Also, US congressional budgets have been starving the budgets for the projects dealing with basic scientific research and study, which is a shame.
I would prefer to see NASA bet on all three horses so you have better odds of one of winning the race!
The current generations of the politically active general public seems to distrust and hate scientists and engineers, and they'd rather all that wonderful "free" government money be spent on turkeys in every pot and cars in every garage or some pet social program instead of sending big tin cans to outer space to prance around and look for little green men. It's a shame to see the US fail to invest in its own technological success, but I have some faith that the readers of this site don't always share that particularly mundane outlook.
Golden!
No. You have to recite pi to 100 decimal places.
It definitely is, and my prior list was not meant to be comprehensive by any means.
There's a lot about safety in the regulations, and you're misrepresenting what those regulations are by only highlighting a circumstance in which the operator hurts themselves. You are breaking the law if your station installation doesn't meet the necessary safety regulations, isn't grounded properly, isn't of a sufficient level of engineering quality, but particularly if you exceed maximum power output and RF exposure limits (especially to recipients unaware of the exposure). Enforcement of that is a different matter... Still, the safety and welfare of human beings trumps little things like interferences, and anyone in a life threatening situation (with or without a license) is allowed to use a radio on any frequency or any communication tool at their disposal to ask for help.
The human body is resonant from 30-300 mhz, and the human head is resonant on VHF freqs (2 meter VHF is the most common amateur band for local FM communication, by the way). Say I have a 100W 2 meter transceiver fed into a 20 db yagi-uda directional antenna which I point towards my local repeater, but it's not high up because I cheaped out on a decent mast installation, and that sucker isn't grounded worth a flip. I could potentially be transmitting 1000W (100W at 20 db is 1000W) into an unsuspecting neighbor's house, and the regulations for individuals aware of the exposure is much higher than those for individuals unaware of their exposure (since those unaware wouldn't recognize the signs of dangerous exposure). You're going to feel a little tingling heat sensation if you have that antenna pointed at you, it will definitely burn you good if you touch it (you'll get this funky ashy grey burn, too), and that is a reasonable setup to encounter for even the most cash strapped ham out there.
Ok, now lets move over to unlicensed services. AM and sideband mode citizens band, 5 watts. Tons of folks operating illegal linear amps on those, and there's regs on amp manufacturers to prevent their equipment from illegally boosting on 11 meters. Family radio service is limited to 1/2 W output, and the radios are required to have permanently mounted negative gain antennas that almost guarantee coming in under that limit every time. Wifi is limited to 1W peak output on the beefiest of access points, and is still only going to go up to 10W with a 20 db directional. Any ham transmitter that outputs below 200W peak envelope power doesn't require any sort of RF survey for installation, but that value takes into account the gain/loss of the feedline and antenna system in use, too. The mode of operation comes into play since it dictates duty cycle of transmission, and most digital systems are typically a fraction of the duty cycle of FM.
You might be interested to note that it's the Amateur Radio and Relay League, making it the ARRL. I'm not sure what the AARL is, but I think you mixed it up with the other old timers club, the AARP.
Well, I guess you got me. That exam the FCC made me take to get my license had a LOT of questions about safety around electricity and RF, maximum peak envelope powers, and the requirements for a formal site survey when installing transmitting equipment. Yep, nothing at all about safety there.