Home |
Search |
Today's Posts |
#1
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
Wireless is everywhere now, miniaturized to an astounding degree.
Recently, I saw a report on a button size gardening gadget - stick it in the soil, it reports on moisture. Bluetooth earphones, etc. Who's designing these things? In my experience, RF designers are a rare breed, and with the digital market vastly larger, they're even rarer. I'll guess, the IC have been perfected to the no-brainer level. But still, you need need amps, filters, antenna, plus issues of noise and layout, yes/no? That stuff isn't obsoleted. I don't work in this area, but I'm curious, so can anyone elaborate on what's going on, from a system viewpoint? What are the chip functions, options, price, trade-offs? In which situations would you reject them, to roll your own? Is it simple on/off keying, or more sophisticated? Currently, in communications theory, sensor networks are a hot topic, where thousands of sensors are competing for bandwidth, but for mundane consumer apps, I doubt those issues arise. I'm looking to pick the brains of any gurus here - -- Rich |
#2
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
Hmmm, not a big deal I suspect.
Build a general purpose RF block for, say, 2.45GHz BT or 802.11(etc), or whatever. Give it handles to talk with anything (modulations, bit streams, etc.), design and build it on a particular fab process, and like magic, anything incorporating that block will also work. Monolithic inductors can be fabricated with not very good Q at 2.45GHz (I think they usually peak around Q = 10 or 20 around 5GHz), but enough to do "silicon oscillators" and stuff. Voltage regulation (bandgap, or old school buried zener) and temperature compensation are no-brainers, as ICs go. Want a DDS? Just chuck some more IP at it! Then whatever ancillary function (moisture, temperature sensor, etc.) simply plugs into this mess of transistors and functions. Quite crazy, as all that circuitry is squeezing into a few milimeters of silicon, when a few decades ago it was, well of course it was migrating to thick film before monolithic, but before that, it was all machined cavities, hand-soldered RF transistors, and microstrip everywhere. I suppose Bluetooth would've taken up a whole rack, back in the 70s, and that's assuming the computing power to provide whatever spread spectrum, encoding, error detection, etc. functionality is required. Tim -- Deep Friar: a very philosophical monk. Website: http://seventransistorlabs.com "RichD" wrote in message ... Wireless is everywhere now, miniaturized to an astounding degree. Recently, I saw a report on a button size gardening gadget - stick it in the soil, it reports on moisture. Bluetooth earphones, etc. Who's designing these things? In my experience, RF designers are a rare breed, and with the digital market vastly larger, they're even rarer. I'll guess, the IC have been perfected to the no-brainer level. But still, you need need amps, filters, antenna, plus issues of noise and layout, yes/no? That stuff isn't obsoleted. I don't work in this area, but I'm curious, so can anyone elaborate on what's going on, from a system viewpoint? What are the chip functions, options, price, trade-offs? In which situations would you reject them, to roll your own? Is it simple on/off keying, or more sophisticated? Currently, in communications theory, sensor networks are a hot topic, where thousands of sensors are competing for bandwidth, but for mundane consumer apps, I doubt those issues arise. I'm looking to pick the brains of any gurus here - -- Rich |
#3
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On 7/3/2013 8:05 AM, RichD wrote: Wireless is everywhere now, miniaturized to an astounding degree. Recently, I saw a report on a button size gardening gadget - stick it in the soil, it reports on moisture. Bluetooth earphones, etc. Who's designing these things? In my experience, RF designers are a rare breed, and with the digital market vastly larger, they're even rarer. I'll guess, the IC have been perfected to the no-brainer level. But still, you need need amps, filters, antenna, plus issues of noise and layout, yes/no? That stuff isn't obsoleted. I don't work in this area, but I'm curious, so can anyone elaborate on what's going on, from a system viewpoint? What are the chip functions, options, price, trade-offs? In which situations would you reject them, to roll your own? Is it simple on/off keying, or more sophisticated? Currently, in communications theory, sensor networks are a hot topic, where thousands of sensors are competing for bandwidth, but for mundane consumer apps, I doubt those issues arise. I'm looking to pick the brains of any gurus here - -- Rich You are right, but seems like someone has solved the RF problems once for each of the useful bands, then its a piece of cake to interface with sensors and one end and display/alarm at the other. For an example, the tyre pressure monitor systems at 433 MHz. 10 gram package, including battery, you screw on a tyre valve. Monitors tyre pressure and temperature for about 1-2 years of operation. Reports real time, every minute or so, to in-car readout. -- Regards, Adrian Jansen adrianjansen at internode dot on dot net Note reply address is invalid, convert address above to machine form. |
#4
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On Thu, 07 Mar 2013 12:49:27 +1000, the renowned Adrian Jansen
wrote: You are right, but seems like someone has solved the RF problems once for each of the useful bands, then its a piece of cake to interface with sensors and one end and display/alarm at the other. For an example, the tyre pressure monitor systems at 433 MHz. 10 gram package, including battery, you screw on a tyre valve. Monitors tyre pressure and temperature for about 1-2 years of operation. Reports real time, every minute or so, to in-car readout. Frequently fails mechanically, causing loss of tire pressure, allows tire shops to charge for a "rebuild kit" whenever they swap a tire, requires a trip to the dealer (or specialized equipment/knowledge) to replace, even with an OEM replacement part.. other than that, they're just spiffy. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
#5
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
"Spehro Pefhany" wrote in message ... On Thu, 07 Mar 2013 12:49:27 +1000, the renowned Adrian Jansen wrote: For an example, the tyre pressure monitor systems at 433 MHz. 10 gram package, including battery, you screw on a tyre valve. Monitors tyre pressure and temperature for about 1-2 years of operation. Reports real time, every minute or so, to in-car readout. Frequently fails mechanically, causing loss of tire pressure, allows tire shops to charge for a "rebuild kit" whenever they swap a tire, requires a trip to the dealer (or specialized equipment/knowledge) to replace, even with an OEM replacement part.. other than that, they're just spiffy. So pretty much like many of the new gadgets on modern cars, something else to go wrong that costs you money, even if you never wanted it in the first place :-( Trevor. |
#6
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
In sci.electronics.misc Tim Williams wrote:
Hmmm, not a big deal I suspect. Build a general purpose RF block for, say, 2.45GHz BT or 802.11(etc), or whatever. Give it handles to talk with anything (modulations, bit streams, etc.), design and build it on a particular fab process, and like magic, anything incorporating that block will also work. Monolithic inductors can be fabricated with not very good Q at 2.45GHz (I think they usually peak around Q = 10 or 20 around 5GHz), but enough to do "silicon oscillators" and stuff. Voltage regulation (bandgap, or old school buried zener) and temperature compensation are no-brainers, as ICs go. Want a DDS? Just chuck some more IP at it! Then whatever ancillary function (moisture, temperature sensor, etc.) simply plugs into this mess of transistors and functions. Quite crazy, as all that circuitry is squeezing into a few milimeters of silicon, when a few decades ago it was, well of course it was migrating to thick film before monolithic, but before that, it was all machined cavities, hand-soldered RF transistors, and microstrip everywhere. I years ago I was given a box of microwave "plumbing" from what may have been a broadcast engineer. The stuff would have worked with microwaves or hydraulic fluid. The guy who made the stuff seemed to be really good with a jewelers saw, copper pipe, brass discs rods and solder. |
#7
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On a sunny day (Thu, 7 Mar 2013 17:37:13 +1100) it happened "Trevor"
wrote in : "Spehro Pefhany" wrote in message .. . On Thu, 07 Mar 2013 12:49:27 +1000, the renowned Adrian Jansen wrote: For an example, the tyre pressure monitor systems at 433 MHz. 10 gram package, including battery, you screw on a tyre valve. Monitors tyre pressure and temperature for about 1-2 years of operation. Reports real time, every minute or so, to in-car readout. Frequently fails mechanically, causing loss of tire pressure, allows tire shops to charge for a "rebuild kit" whenever they swap a tire, requires a trip to the dealer (or specialized equipment/knowledge) to replace, even with an OEM replacement part.. other than that, they're just spiffy. So pretty much like many of the new gadgets on modern cars, something else to go wrong that costs you money, even if you never wanted it in the first place :-( Trevor. I have this: http://www.ebay.com/itm/Car-Motor-Ti...d0dc493&vxp=mt (ebay item 300866716819 ) Extremely expensive, and does get you hands dirty.. But electrickity free! GREEN |
#8
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
"Spehro Pefhany" wrote in message ... On Thu, 07 Mar 2013 12:49:27 +1000, the renowned Adrian Jansen wrote: You are right, but seems like someone has solved the RF problems once for each of the useful bands, then its a piece of cake to interface with sensors and one end and display/alarm at the other. For an example, the tyre pressure monitor systems at 433 MHz. 10 gram package, including battery, you screw on a tyre valve. Monitors tyre pressure and temperature for about 1-2 years of operation. Reports real time, every minute or so, to in-car readout. Frequently fails mechanically, causing loss of tire pressure, allows tire shops to charge for a "rebuild kit" whenever they swap a tire, requires a trip to the dealer (or specialized equipment/knowledge) to replace, even with an OEM replacement part.. other than that, they're just spiffy. Best regards, Spehro Pefhany -- I read somewhere that Ford is experimenting with their wheel speed sensors to detect a deflating tire. If they can make that work, it would do away with all the pressure sensors and associated hassles. And yes, I didn't ask for that feature, but you have to admit, it is handy and could save a bundle on a replacement tire. Tom |
#9
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On Mar 7, 1:51*am, "Tim Williams" wrote:
Hmmm, not a big deal I suspect. Build a general purpose RF block for, say, 2.45GHz BT or 802.11(etc), or whatever. *Give it handles to talk with anything (modulations, bit streams, etc.), design and build it on a particular fab process, and like magic, anything incorporating that block will also work. *Monolithic inductors can be fabricated with not very good Q at 2.45GHz (I think they usually peak around Q = 10 or 20 around 5GHz), but enough to do "silicon oscillators" and stuff. *Voltage regulation (bandgap, or old school buried zener) and temperature compensation are no-brainers, as ICs go. *Want a DDS? *Just chuck some more IP at it! *Then whatever ancillary function (moisture, temperature sensor, etc.) simply plugs into this mess of transistors and functions. I remember working on making bluetooth in a "single chip" we had a working radio and build an evolution of an existing SOC to stack on top of it in a single package Everything worked great when we tested the first samples, but then the software guys started running their code in ROM then the sensitivity dropped turned out that the ROM being in a different corner of the SOC coupled noise into the radio VCO inductors, but the RAM where the test code was run didn't Quite crazy, as all that circuitry is squeezing into a few milimeters of silicon, when a few decades ago it was, well of course it was migrating to thick film before monolithic, but before that, it was all machined cavities, hand-soldered RF transistors, and microstrip everywhere. *I suppose Bluetooth would've taken up a whole rack, back in the 70s, and that's assuming the computing power to provide whatever spread spectrum, encoding, error detection, etc. functionality is required. Tim I worked on one of the very first bluetooth implementations, it was; a DSP, a flash, an FPGA, an RF chip, a saw filter, a whole bunch of passives it was probably 5*5cm PCB fully packed on both sides -Lasse |
#10
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
|
#11
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On 7/3/2013 1:44 PM, Spehro Pefhany wrote: On Thu, 07 Mar 2013 12:49:27 +1000, the renowned Adrian Jansen wrote: You are right, but seems like someone has solved the RF problems once for each of the useful bands, then its a piece of cake to interface with sensors and one end and display/alarm at the other. For an example, the tyre pressure monitor systems at 433 MHz. 10 gram package, including battery, you screw on a tyre valve. Monitors tyre pressure and temperature for about 1-2 years of operation. Reports real time, every minute or so, to in-car readout. Frequently fails mechanically, causing loss of tire pressure, allows tire shops to charge for a "rebuild kit" whenever they swap a tire, requires a trip to the dealer (or specialized equipment/knowledge) to replace, even with an OEM replacement part.. other than that, they're just spiffy. Best regards, Spehro Pefhany Really I was commenting on the RF stuff. Certainly that seems to work as well as needed. Whether the rest of the design is as good as the RF section is a different kettle of fish. The aftermarket units using sensors like Tyredog seem to have a learning mode to accomodate sensor changes without special tools. Personally I would be happy if the system just warned that a tyre is going down, before it wrecks the tyre. Identifying which tyre is at fault is a secondary, and usually very easy, job. -- Regards, Adrian Jansen adrianjansen at internode dot on dot net Note reply address is invalid, convert address above to machine form. |
#12
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On Wed, 6 Mar 2013 14:05:56 -0800 (PST), RichD
wrote: Who's designing these things? In my experience, RF designers are a rare breed, and with the digital market vastly larger, they're even rarer. Most such gadgets have very little RF inside. Todays BlueGoof, Wi-Fi, all digital AM/FM receivers, SRD radios, and 433/900MHz weather station chips are almost all digital with maybe a MMIC RF amp or receiver pre-amp on the PCB. The design is being done by digital chips designers, not RF engineers. However, one place where the RF engineer is required is when the product has to pass FCC certification. I'll guess, the IC have been perfected to the no-brainer level. But still, you need need amps, filters, antenna, plus issues of noise and layout, yes/no? That stuff isn't obsoleted. Yes and no. Each of the items you mention are somewhat separate from the basic function of the radio and are most often a purchased part from a company that specializes in the device. It is conceivable, that someone with only a minimal knowledge of RF can assemble a sellable and certifiable product using off the COTS modules and components, including the actual radio. I've cleaned up the design on a few such attempts. To be honest, the problems I fixed were oversights due to lack of experience, which will eventually be overcome by the designer. I assume by "noise and layout" you mean digital noise trashing the receiver sensitivity. Yes, that happens, but with clever design, careful layout, and decent grounding, such problems can be minimized. (Notice I didn't include shielding). The trick is that traces (wires) radiate, while components do not. By simply reducing the size of the device or PCB to the point where the radiating traces are sufficiently small that they don't radiate enough to matter, many such "noise" problems solve themselves. In addition, the power levels found on todays radios are much lower than what was common even a few years ago, making noise pickup less of an issue. Clever protocol design also helps. For example, a GPS receiver with a processing gain of 43dB will not have a noise problem until the noise maybe 30dB above the receive signal. Another example is the common 60KHz WWVB receiver, where the 1 baud data rate results in such a narrow bandwidth that the atmospheric noise inside the approximately 3Hz receiver bandwidth is sufficiently low that it can almost be ignored. I don't work in this area, but I'm curious, so can anyone elaborate on what's going on, from a system viewpoint? No. I can't. I might be able to provide some insight into current trends in a specific product area, but not the entire world of RF design. What are the chip functions, options, price, trade-offs? In which situations would you reject them, to roll your own? Same problem as before. Too broad a question. As I mumbled, it is possible to assemble a working product out of COTS (commercial off the shelf) parts and pieces. Some volume production areas have been heavily integrated, with plenty of mostly working chips available. Others are specialty products, which are less well integrated. Today, I would roll my own only when I have the projected volume to justify a custom design, or when I want to protect the IP with a custom chip. Is it simple on/off keying, or more sophisticated? There's quite a bit of OOK (on-off keying) modulated products available. TV remotes, WWVB receivers[1], wireless weather stations, car security dongles, etc. OOK has the advantages of being very low power, cheap, simple, and reliable. Sensitivity and efficiency (bits/baud) are terrible, but for many applications, you don't need the speed. Currently, in communications theory, sensor networks are a hot topic, where thousands of sensors are competing for bandwidth, but for mundane consumer apps, I doubt those issues arise. Sensor mesh networks add a new set of challenges. The search for the ultimate routing protocol for store and forward mesh networks is the holy grail of sensor knotworks. This brings the level of complexity well beyond the RF level and into the realm of queuing theory and statistics. There's also the problem of scaling mesh networks. Too few nodes, and the path could easily dead end. Too many and mutual interference, loops, airtime consumption, and bottlenecking near the backhaul point become issues. Incidentally, one of my favorite tests with mesh networks is to put all the nodes in one room, turn them all on, and try to pass some data. I've seen some that fall over badly where nothing moves. They're not competing for bandwidth, but rather for air time. As long as all the devices are using the same frequency hopping code and RF channel, only one radio in view can be transmitting at the same time. As for "mundane" consumer apps, Wi-Fi mesh networks have all the problems of sensor networks with the added enjoyment of multiple incompatible protocols, overkill tx power, monster antennas, and plenty of possible interference sources. I'm looking to pick the brains of any gurus here - Sure, but try to be more specific. What are you trying to accomplish? [1] Yes, I know that it's not really OOK because the carrier is reduced by 10db at the beginning of each UTC second. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#13
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On Thu, 7 Mar 2013 07:14:39 +0000 (UTC), Cydrome Leader
wrote: In sci.electronics.misc Tim Williams wrote: Hmmm, not a big deal I suspect. Build a general purpose RF block for, say, 2.45GHz BT or 802.11(etc), or whatever. Give it handles to talk with anything (modulations, bit streams, etc.), design and build it on a particular fab process, and like magic, anything incorporating that block will also work. Monolithic inductors can be fabricated with not very good Q at 2.45GHz (I think they usually peak around Q = 10 or 20 around 5GHz), but enough to do "silicon oscillators" and stuff. Voltage regulation (bandgap, or old school buried zener) and temperature compensation are no-brainers, as ICs go. Want a DDS? Just chuck some more IP at it! Then whatever ancillary function (moisture, temperature sensor, etc.) simply plugs into this mess of transistors and functions. Quite crazy, as all that circuitry is squeezing into a few milimeters of silicon, when a few decades ago it was, well of course it was migrating to thick film before monolithic, but before that, it was all machined cavities, hand-soldered RF transistors, and microstrip everywhere. I years ago I was given a box of microwave "plumbing" from what may have been a broadcast engineer. The stuff would have worked with microwaves or hydraulic fluid. The guy who made the stuff seemed to be really good with a jewelers saw, copper pipe, brass discs rods and solder. Not many folks making hard coax runs anymore. Semi-rigid and a few others abound. |
#14
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
In sci.electronics.design MrTallyman wrote:
On Thu, 7 Mar 2013 07:14:39 +0000 (UTC), Cydrome Leader wrote: In sci.electronics.misc Tim Williams wrote: Hmmm, not a big deal I suspect. Build a general purpose RF block for, say, 2.45GHz BT or 802.11(etc), or whatever. Give it handles to talk with anything (modulations, bit streams, etc.), design and build it on a particular fab process, and like magic, anything incorporating that block will also work. Monolithic inductors can be fabricated with not very good Q at 2.45GHz (I think they usually peak around Q = 10 or 20 around 5GHz), but enough to do "silicon oscillators" and stuff. Voltage regulation (bandgap, or old school buried zener) and temperature compensation are no-brainers, as ICs go. Want a DDS? Just chuck some more IP at it! Then whatever ancillary function (moisture, temperature sensor, etc.) simply plugs into this mess of transistors and functions. Quite crazy, as all that circuitry is squeezing into a few milimeters of silicon, when a few decades ago it was, well of course it was migrating to thick film before monolithic, but before that, it was all machined cavities, hand-soldered RF transistors, and microstrip everywhere. I years ago I was given a box of microwave "plumbing" from what may have been a broadcast engineer. The stuff would have worked with microwaves or hydraulic fluid. The guy who made the stuff seemed to be really good with a jewelers saw, copper pipe, brass discs rods and solder. Not many folks making hard coax runs anymore. this stuff was pretty darn old. are there power levels where they stil use wavegides and the like? Semi-rigid and a few others abound. |
#15
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On Sun, 10 Mar 2013 02:43:08 +0000 (UTC), Cydrome Leader
wrote: Not many folks making hard coax runs anymore. this stuff was pretty darn old. are there power levels where they stil use wavegides and the like? In countries still using analog TV, the UHF final amplifier is often implemented with klystron in the 100 kW range. The waveguide is quite large, due to the low frequency. DVB-T digital TV transmitters typically operate with only 1-10 kW, consisting of multiple redundant solid state modules, so there is not much need for waveguides any more. |
#16
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On Sun, 10 Mar 2013 02:43:08 +0000 (UTC), Cydrome Leader
wrote: are there power levels where they stil use wavegides and the like? As much to do with frequency as power level. I've recently completed the design of a Ka band transceiver for satellite (30GHz uplink, 20GHz down). It is a domestic product for delivery of broadband to rural areas. All of the internal RF filtering is done in waveguide, as is the external combining of the transmit and receive signals into a single horn. The transmitter power is just 3W. d |
#17
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
|
#18
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On Sun, 10 Mar 2013 04:21:03 -0400, "Michael A. Terrell"
wrote: wrote: On Sun, 10 Mar 2013 02:43:08 +0000 (UTC), Cydrome Leader wrote: Not many folks making hard coax runs anymore. this stuff was pretty darn old. are there power levels where they stil use wavegides and the like? In countries still using analog TV, the UHF final amplifier is often implemented with klystron in the 100 kW range. The waveguide is quite large, due to the low frequency. DVB-T digital TV transmitters typically operate with only 1-10 kW, consisting of multiple redundant solid state modules, so there is not much need for waveguides any more. How do you get that to the antenna without waveguide? Coax losses are much higher than waveguide, and is less likely to have problems since there is no dielectric to break down. Andrew's Heliax is pretty low loss, and good for VHF and UHF runs. Dielectric amounts to nothing more than a thin spiral spacer - the rest is all air. d |
#19
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
Don Pearce wrote: On Sun, 10 Mar 2013 04:21:03 -0400, "Michael A. Terrell" wrote: wrote: On Sun, 10 Mar 2013 02:43:08 +0000 (UTC), Cydrome Leader wrote: Not many folks making hard coax runs anymore. this stuff was pretty darn old. are there power levels where they stil use wavegides and the like? In countries still using analog TV, the UHF final amplifier is often implemented with klystron in the 100 kW range. The waveguide is quite large, due to the low frequency. DVB-T digital TV transmitters typically operate with only 1-10 kW, consisting of multiple redundant solid state modules, so there is not much need for waveguides any more. How do you get that to the antenna without waveguide? Coax losses are much higher than waveguide, and is less likely to have problems since there is no dielectric to break down. Andrew's Heliax is pretty low loss, and good for VHF and UHF runs. Dielectric amounts to nothing more than a thin spiral spacer - the rest is all air. Heliax for 10 KW? Ever had the filter fail on the compressor and get water in Heliax? I had a stupid SOB for a boss 30 years ago who was too sheap to replace filtes on schedule and ruined a piece of 3" Heliax used at 4 GHz. Waveguide is better at high power, and better than Heliax. I had over 1700 feet of it at one TV transmitter. It carried about 195 KW of RF to the top of the tower. We had to maintain a set pressure of dry nitrogen on the waveguide to keep from compressing the sync pulses. |
#20
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On Sun, 10 Mar 2013 08:15:56 -0400, "Michael A. Terrell"
wrote: Don Pearce wrote: On Sun, 10 Mar 2013 04:21:03 -0400, "Michael A. Terrell" wrote: wrote: On Sun, 10 Mar 2013 02:43:08 +0000 (UTC), Cydrome Leader wrote: Not many folks making hard coax runs anymore. this stuff was pretty darn old. are there power levels where they stil use wavegides and the like? In countries still using analog TV, the UHF final amplifier is often implemented with klystron in the 100 kW range. The waveguide is quite large, due to the low frequency. DVB-T digital TV transmitters typically operate with only 1-10 kW, consisting of multiple redundant solid state modules, so there is not much need for waveguides any more. How do you get that to the antenna without waveguide? Coax losses are much higher than waveguide, and is less likely to have problems since there is no dielectric to break down. Andrew's Heliax is pretty low loss, and good for VHF and UHF runs. Dielectric amounts to nothing more than a thin spiral spacer - the rest is all air. Heliax for 10 KW? Ever had the filter fail on the compressor and get water in Heliax? I had a stupid SOB for a boss 30 years ago who was too sheap to replace filtes on schedule and ruined a piece of 3" Heliax used at 4 GHz. Waveguide is better at high power, and better than Heliax. I had over 1700 feet of it at one TV transmitter. It carried about 195 KW of RF to the top of the tower. We had to maintain a set pressure of dry nitrogen on the waveguide to keep from compressing the sync pulses. No, not at 10kW. At 100W or so it is fine. On a long run I would always opt for waveguide - tower dimensions permitting. d |
#21
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On 03/10/2013 06:30 AM, Don Pearce wrote:
On Sun, 10 Mar 2013 08:15:56 -0400, "Michael A. Terrell" Heliax for 10 KW? Ever had the filter fail on the compressor and get water in Heliax? I had a stupid SOB for a boss 30 years ago who was too sheap to replace filtes on schedule and ruined a piece of 3" Heliax used at 4 GHz. Waveguide is better at high power, and better than Heliax. I had over 1700 feet of it at one TV transmitter. It carried about 195 KW of RF to the top of the tower. We had to maintain a set pressure of dry nitrogen on the waveguide to keep from compressing the sync pulses. No, not at 10kW. At 100W or so it is fine. On a long run I would always opt for waveguide - tower dimensions permitting. d You can't use waveguide for digital TV transmission-something about the joints making unsuitable anomalies. Air dielectric co-ax is what's used. |
#22
Posted to rec.audio.tech
|
|||
|
|||
rf everywhere
On Sun, 10 Mar 2013 06:43:13 -0700, dave
wrote: On 03/10/2013 06:30 AM, Don Pearce wrote: On Sun, 10 Mar 2013 08:15:56 -0400, "Michael A. Terrell" Heliax for 10 KW? Ever had the filter fail on the compressor and get water in Heliax? I had a stupid SOB for a boss 30 years ago who was too sheap to replace filtes on schedule and ruined a piece of 3" Heliax used at 4 GHz. Waveguide is better at high power, and better than Heliax. I had over 1700 feet of it at one TV transmitter. It carried about 195 KW of RF to the top of the tower. We had to maintain a set pressure of dry nitrogen on the waveguide to keep from compressing the sync pulses. No, not at 10kW. At 100W or so it is fine. On a long run I would always opt for waveguide - tower dimensions permitting. d You can't use waveguide for digital TV transmission-something about the joints making unsuitable anomalies. Air dielectric co-ax is what's used. Hmm? Digital TV signals are regularly fed through my designs, which are brimming with waveguide. You may be talking about dispersion, though. Group velocity through a waveguide is frequency-dependent, so with a long enough run, the phase of the modulation gets distorted. You can pre-correct for this though. d |
#23
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
dave wrote: On 03/10/2013 06:30 AM, Don Pearce wrote: On Sun, 10 Mar 2013 08:15:56 -0400, "Michael A. Terrell" Heliax for 10 KW? Ever had the filter fail on the compressor and get water in Heliax? I had a stupid SOB for a boss 30 years ago who was too sheap to replace filtes on schedule and ruined a piece of 3" Heliax used at 4 GHz. Waveguide is better at high power, and better than Heliax. I had over 1700 feet of it at one TV transmitter. It carried about 195 KW of RF to the top of the tower. We had to maintain a set pressure of dry nitrogen on the waveguide to keep from compressing the sync pulses. No, not at 10kW. At 100W or so it is fine. On a long run I would always opt for waveguide - tower dimensions permitting. d You can't use waveguide for digital TV transmission-something about the joints making unsuitable anomalies. Air dielectric co-ax is what's used. Cites? You can't use existing waveguide on a new channel. You have to calculate the location of the nodes and they are related to the channel frequency. I can see usinig coax for the pre-transistion phase, but not after. Have you ever designed a UHF broadcast plant? |
#24
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
Don Pearce wrote: No, not at 10kW. At 100W or so it is fine. On a long run I would always opt for waveguide - tower dimensions permitting. A tower that will support a high power antenna will have have room for waveguide, if the tower isn't overloaded with other antennas. A tower that won't support a high power antenna definately won't have room for waveguide. |
#25
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On 03/10/2013 06:05 PM, Michael A. Terrell wrote:
dave wrote: On 03/10/2013 06:30 AM, Don Pearce wrote: On Sun, 10 Mar 2013 08:15:56 -0400, "Michael A. Terrell" Heliax for 10 KW? Ever had the filter fail on the compressor and get water in Heliax? I had a stupid SOB for a boss 30 years ago who was too sheap to replace filtes on schedule and ruined a piece of 3" Heliax used at 4 GHz. Waveguide is better at high power, and better than Heliax. I had over 1700 feet of it at one TV transmitter. It carried about 195 KW of RF to the top of the tower. We had to maintain a set pressure of dry nitrogen on the waveguide to keep from compressing the sync pulses. No, not at 10kW. At 100W or so it is fine. On a long run I would always opt for waveguide - tower dimensions permitting. d You can't use waveguide for digital TV transmission-something about the joints making unsuitable anomalies. Air dielectric co-ax is what's used. Cites? You can't use existing waveguide on a new channel. You have to calculate the location of the nodes and they are related to the channel frequency. I can see usinig coax for the pre-transistion phase, but not after. Have you ever designed a UHF broadcast plant? Designed and built close to 2 dozen. http://broadcastengineering.com/RF/s...smission-lines |
#27
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
In sci.electronics.misc Michael A. Terrell wrote:
Don Pearce wrote: On Sun, 10 Mar 2013 04:21:03 -0400, "Michael A. Terrell" wrote: wrote: On Sun, 10 Mar 2013 02:43:08 +0000 (UTC), Cydrome Leader wrote: Not many folks making hard coax runs anymore. this stuff was pretty darn old. are there power levels where they stil use wavegides and the like? In countries still using analog TV, the UHF final amplifier is often implemented with klystron in the 100 kW range. The waveguide is quite large, due to the low frequency. DVB-T digital TV transmitters typically operate with only 1-10 kW, consisting of multiple redundant solid state modules, so there is not much need for waveguides any more. How do you get that to the antenna without waveguide? Coax losses are much higher than waveguide, and is less likely to have problems since there is no dielectric to break down. Andrew's Heliax is pretty low loss, and good for VHF and UHF runs. Dielectric amounts to nothing more than a thin spiral spacer - the rest is all air. Heliax for 10 KW? Ever had the filter fail on the compressor and get water in Heliax? I had a stupid SOB for a boss 30 years ago who was too sheap to replace filtes on schedule and ruined a piece of 3" Heliax used at 4 GHz. Waveguide is better at high power, and better than Heliax. I had over 1700 feet of it at one TV transmitter. It carried about 195 KW of RF to the top of the tower. We had to maintain a set pressure of dry nitrogen on the waveguide to keep from compressing the sync pulses. what exciting things happens when you get moisture ingress? how hot can coax or waveguides run at high powers? I've never been by large transmitters, so the concept of anything but a power cord running warm is just strange to me. |
#28
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
T wrote: In article , says... wrote: On Sun, 10 Mar 2013 02:43:08 +0000 (UTC), Cydrome Leader wrote: Not many folks making hard coax runs anymore. this stuff was pretty darn old. are there power levels where they stil use wavegides and the like? In countries still using analog TV, the UHF final amplifier is often implemented with klystron in the 100 kW range. The waveguide is quite large, due to the low frequency. DVB-T digital TV transmitters typically operate with only 1-10 kW, consisting of multiple redundant solid state modules, so there is not much need for waveguides any more. How do you get that to the antenna without waveguide? Coax losses are much higher than waveguide, and is less likely to have problems since there is no dielectric to break down. Hardline! In essence it's a solid shield with a center conductor. That's enough for RF into the 900MHz and 1.2GHz range. There are many types of hardline, and more in use by CATV systems than anything else. I engineered in that field for four years and designed extensions and upgrades. I also designed community loop systems. Specify a brand, type length, frequency and power level. There is a reason they have so damn many trunk amplifiers in a system. I found a link to some 5.5" heilical air dielectric that doesn't look too bad, but the specs stop before a GHz. look at the power handling spec at .5 MHz, and at 894 MHz. It drops from 1890 KW to 43 KW. The insetion loss goes from .0045 dB to .215 dB over that range. http://www.rfsworld.com/dataxpress/D.../?q=HCA550-50J |
#29
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
Cydrome Leader wrote: In sci.electronics.misc Michael A. Terrell wrote: Don Pearce wrote: On Sun, 10 Mar 2013 04:21:03 -0400, "Michael A. Terrell" wrote: wrote: On Sun, 10 Mar 2013 02:43:08 +0000 (UTC), Cydrome Leader wrote: Not many folks making hard coax runs anymore. this stuff was pretty darn old. are there power levels where they stil use wavegides and the like? In countries still using analog TV, the UHF final amplifier is often implemented with klystron in the 100 kW range. The waveguide is quite large, due to the low frequency. DVB-T digital TV transmitters typically operate with only 1-10 kW, consisting of multiple redundant solid state modules, so there is not much need for waveguides any more. How do you get that to the antenna without waveguide? Coax losses are much higher than waveguide, and is less likely to have problems since there is no dielectric to break down. Andrew's Heliax is pretty low loss, and good for VHF and UHF runs. Dielectric amounts to nothing more than a thin spiral spacer - the rest is all air. Heliax for 10 KW? Ever had the filter fail on the compressor and get water in Heliax? I had a stupid SOB for a boss 30 years ago who was too sheap to replace filtes on schedule and ruined a piece of 3" Heliax used at 4 GHz. Waveguide is better at high power, and better than Heliax. I had over 1700 feet of it at one TV transmitter. It carried about 195 KW of RF to the top of the tower. We had to maintain a set pressure of dry nitrogen on the waveguide to keep from compressing the sync pulses. what exciting things happens when you get moisture ingress? Corrosion, which increases the attenuation. If it gets bad enough, the conductor will get a hot spot and burn through leading to spectacular fireworks. The mositure tends to collect in low spots, which are at regular intervals in helical cable. vertical runs will let it run down to the first horizontal section and pool. It also changes the impedance of the air dielectric, which increases attenuation. how hot can coax or waveguides run at high powers? I've never been by large transmitters, so the concept of anything but a power cord running warm is just strange to me. IR losses turn current into heat, the frequency doesn't matter. RF power costs a lot more than power from the utility company, and using a bigger transmitter to turn that RF into heat costs more for the hardware & air conditioning. |
#30
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
In sci.electronics.misc Michael A. Terrell wrote:
T wrote: In article , says... wrote: On Sun, 10 Mar 2013 02:43:08 +0000 (UTC), Cydrome Leader wrote: Not many folks making hard coax runs anymore. this stuff was pretty darn old. are there power levels where they stil use wavegides and the like? In countries still using analog TV, the UHF final amplifier is often implemented with klystron in the 100 kW range. The waveguide is quite large, due to the low frequency. DVB-T digital TV transmitters typically operate with only 1-10 kW, consisting of multiple redundant solid state modules, so there is not much need for waveguides any more. How do you get that to the antenna without waveguide? Coax losses are much higher than waveguide, and is less likely to have problems since there is no dielectric to break down. Hardline! In essence it's a solid shield with a center conductor. That's enough for RF into the 900MHz and 1.2GHz range. There are many types of hardline, and more in use by CATV systems than anything else. I engineered in that field for four years and designed extensions and upgrades. I also designed community loop systems. Specify a brand, type length, frequency and power level. There is a reason they have so damn many trunk amplifiers in a system. I found a link to some 5.5" heilical air dielectric that doesn't look too bad, but the specs stop before a GHz. look at the power handling spec at .5 MHz, and at 894 MHz. It drops from 1890 KW to 43 KW. The insetion loss goes from .0045 dB to .215 dB over that range. http://www.rfsworld.com/dataxpress/D.../?q=HCA550-50J how does one terminate such cables? What sort of wiring goes on inside a giant transmitter or the antenna end of such a monster? |
#31
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
Cydrome Leader wrote: wrote: ? ? I found a link to some 5.5" heilical air dielectric that doesn't look ? too bad, but the specs stop before a GHz. look at the power handling ? spec at .5 MHz, and at 894 MHz. It drops from 1890 KW to 43 KW. The ? insetion loss goes from .0045 dB to .215 dB over that range. ? ? http://www.rfsworld.com/dataxpress/D.../?q=HCA550-50J how does one terminate such cables? What sort of wiring goes on inside a giant transmitter or the antenna end of such a monster? A matching network to get it as close to the characteristic impedance of the cable. The antenna is designed for the same impedance to get the maximum signal into the airwaves. 50 ohms is the nominal impedance for these systems -- Politicians should only get paid if the budget is balanced, and there is enough left over to pay them. |
#32
Posted to sci.electronics.design,sci.electronics.misc,rec.audio.tech
|
|||
|
|||
rf everywhere
On 03/13/2013 12:17 PM, Cydrome Leader wrote:
http://www.rfsworld.com/dataxpress/D.../?q=HCA550-50J how does one terminate such cables? What sort of wiring goes on inside a giant transmitter or the antenna end of such a monster? The transmitter end would have a fancy bandpass filter and the antenna end may or may not have a matching section. In high power RF 50 Ohms is standard for almost everything that needs interconnecting. Get too far away and stuff starts snapping. Zzzt! |