标签: transmitter

At one of the Gadget Smackdown sessions at the EE Live! 2014 conference and exhibition, I introduced a conceptual project that I hope to make reality soon. This project is an open-source radio transmitter for RC hobbyists. This transmitter will be reconfigurable, allowing it to operate over multiple frequency bands using multiple protocols. The plan is to create a modular, open-source, software-defined radio (SDF), but what brought about the need for something like this? Typical hobbyist RC transmitter.   With the advent of WiFi and other chips operating in the 2.4 GHz band, there has been significant development in the miniaturization and integration of RFICs. Due to the integrated nature of these chips, and the many features they offer, the RC industry has moved from the traditional 72 MHz and 75 MHz bands to 2.4 GHz. This transition has been anything but clean. The old frequency bands operated under an (relatively) industry-standard protocol. This was a simple analog frequency-shift keying (FSK) protocol -- effectively pulse-width modulation imposed on an FSK signal. There were only two variations of this protocol, but both were well known and well- documented.   When the industry started its shift to 2.4 GHz, all the vendors used their own proprietary protocols. This means that transmitters and receivers from different vendors are incompatible with one another. This was not the first time the industry had tried this, and it quickly became apparent that the various vendors were up to the same old tricks. As the switch to 2.4 GHz continued, the number of proprietary protocols kept growing; there are now at least 10. The switch also reduced the number of vendors offering hardware in the old transmission bands. For those (like myself) operating RC submarines, this has been very detrimental, since 2.4 GHz signals don't penetrate the water.   What is one to do? This is where my solution comes into play. There have been great advancements in software-defined radios, which can transmit across multiple bands and be reconfigured to support multiple protocols. Lime Microsystems has a new RFIC that can transmit from 50 MHz all the way up to 3.8 GHz. This would allow for coverage of legacy bands as well as the new 2.4 GHz band. Since it is a software-defined radio, one could also configure the device for each proprietary protocol. As manufacturers develop new protocols, once they are reverse engineered, they could be uploaded to the transmitter. Then all the user would need to do is select the desired protocol at startup.   With the RF section conceptualized, the rest of the device would consist of a reconfigurable board that would allow the user to implement 1-20 channels. Each connection could be a simple on-off switch, an analog potentiometer for a standard set of gimbals found in current transmitters, or serial protocol devices. Devices using serial communications might include such things as motion and position sensors, magnetometers, or pressure transducers. Once connected to the inputs of the core, they would be configured either via a desktop application or on the screen of the transmitter itself. With the RF section, interface connections, and screen, this would form the core of a handheld transmitter.   The beauty of this approach to designing a RC handheld transmitter is that it allows users to create and customize their transmitters as required. Custom enclosure designs can be created and shared. If one needs to add another channel, this will be as easy as attaching the user input device to the core and configuring it. This transmitter customization approach will add a new element to the hobby. This element would be consistent with both the Maker/Hacker movements.   Personally, I want to design an enclosure similar to a device found from the TV series Leverage . In the " First Contact Job " in the fifth season, Harrison had a handheld device that he called the Marvin. This had a very unique shape that I think would lend itself to support the features I need for my RC submarines.   The Marvin, Leverage (Season 5, Episode 3, "The First Contact Job").   To pull this RC transmitter concept off, I will need to learn a lot. I have yet to really play with designing any sort of graphical interface on a microcontroller. I do not see this as a major hurdle, but it will require some learning. I will also need to learn a bit about general RF design and the nuances of ultra-high-frequency PCB design. Is this a lot to learn? Well, yes, but I find that having a project is the best way to start learning. If you happen to have any ideas, or if you would like to contribute your efforts to a project like this, please let me know in the comments below.   Adam Carlson is Senior Mechanical Design Engineer at Eagle Technologies .

There is a conceptual project that I hope to make reality soon. I was able to present it at one of the Gadget Smackdown sessions at the EE Live! 2014 conference and exhibition. This project is an open-source radio transmitter for RC hobbyists. This transmitter will be reconfigurable, allowing it to operate over multiple frequency bands using multiple protocols. The plan is to create a modular, open-source, software-defined radio (SDF), but what brought about the need for something like this? Typical hobbyist RC transmitter.   With the advent of WiFi and other chips operating in the 2.4 GHz band, there has been significant development in the miniaturization and integration of RFICs. Due to the integrated nature of these chips, and the many features they offer, the RC industry has moved from the traditional 72 MHz and 75 MHz bands to 2.4 GHz. This transition has been anything but clean. The old frequency bands operated under an (relatively) industry-standard protocol. This was a simple analog frequency-shift keying (FSK) protocol -- effectively pulse-width modulation imposed on an FSK signal. There were only two variations of this protocol, but both were well known and well- documented.   When the industry started its shift to 2.4 GHz, all the vendors used their own proprietary protocols. This means that transmitters and receivers from different vendors are incompatible with one another. This was not the first time the industry had tried this, and it quickly became apparent that the various vendors were up to the same old tricks. As the switch to 2.4 GHz continued, the number of proprietary protocols kept growing; there are now at least 10. The switch also reduced the number of vendors offering hardware in the old transmission bands. For those (like myself) operating RC submarines, this has been very detrimental, since 2.4 GHz signals don't penetrate the water.   What is one to do? This is where my solution comes into play. There have been great advancements in software-defined radios, which can transmit across multiple bands and be reconfigured to support multiple protocols. Lime Microsystems has a new RFIC that can transmit from 50 MHz all the way up to 3.8 GHz. This would allow for coverage of legacy bands as well as the new 2.4 GHz band. Since it is a software-defined radio, one could also configure the device for each proprietary protocol. As manufacturers develop new protocols, once they are reverse engineered, they could be uploaded to the transmitter. Then all the user would need to do is select the desired protocol at startup.   With the RF section conceptualized, the rest of the device would consist of a reconfigurable board that would allow the user to implement 1-20 channels. Each connection could be a simple on-off switch, an analog potentiometer for a standard set of gimbals found in current transmitters, or serial protocol devices. Devices using serial communications might include such things as motion and position sensors, magnetometers, or pressure transducers. Once connected to the inputs of the core, they would be configured either via a desktop application or on the screen of the transmitter itself. With the RF section, interface connections, and screen, this would form the core of a handheld transmitter.   The beauty of this approach to designing a RC handheld transmitter is that it allows users to create and customize their transmitters as required. Custom enclosure designs can be created and shared. If one needs to add another channel, this will be as easy as attaching the user input device to the core and configuring it. This transmitter customization approach will add a new element to the hobby. This element would be consistent with both the Maker/Hacker movements.   Personally, I want to design an enclosure similar to a device found from the TV series Leverage . In the " First Contact Job " in the fifth season, Harrison had a handheld device that he called the Marvin. This had a very unique shape that I think would lend itself to support the features I need for my RC submarines.   The Marvin, Leverage (Season 5, Episode 3, "The First Contact Job").   To pull this RC transmitter concept off, I will need to learn a lot. I have yet to really play with designing any sort of graphical interface on a microcontroller. I do not see this as a major hurdle, but it will require some learning. I will also need to learn a bit about general RF design and the nuances of ultra-high-frequency PCB design. Is this a lot to learn? Well, yes, but I find that having a project is the best way to start learning. If you happen to have any ideas, or if you would like to contribute your efforts to a project like this, please let me know in the comments below.   Adam Carlson is Senior Mechanical Design Engineer at Eagle Technologies .

In the late 70s, there was a TV programme called WKRP in Cincinnati . The station manager was the son of the station owner. He mismanaged the station and could not be fired, because, after all, "What mother would fire her own son?" I worked for such a station as a contract engineer. It was smaller, and the manager was younger and less competent than the guy in charge at WKRP. The station transmitter was located in a riverbed, which provided an excellent ground and no structures within nearly a thousand feet of the tower. The building was made of concrete and contained a Gates BC-1T one-kilowatt transmitter, along with some audio processing and monitoring equipment. The single tower was next to the building, and the matching network was just inside the building. Because of the concern of flooding, there was a large sump pump and a plank forming a tall door jam at the bottom of the only door. Just as long as the power did not fail, the pump could easily remove any water that seeped through the floor or concrete walls. One day, I got a call from the owner's son that the station was off the air. I rushed out to the transmitter. When I arrived, I discovered that what had been an open field only days ago was now a large lake with a tower in the middle. I asked him what happened. "I went out to see if the transmitter was OK, and when I opened the door, the transmitter turned off," he said. He had some waist-high boots for me. I yanked them on, and we went out to the transmitter shack. It was scary walking through two feet of strong river current to the transmitter several hundred feet from the shore. By this time, the water level was below the plank, and we went into the building. The sump pump had removed most of the water. I opened the transmitter and made an assessment. Every transformer was damaged except the modulation transformer, because it was well sealed. The transmitter was dead. Every minute that a station is off the air means lost revenue, and this particular station was so poorly managed that it was losing money even when it was on the air. I had to work quickly. I decided that I needed to replace the main power transformer (which was 220-6,000V), the intermediate power (IPA) transformer (which was 220-1,000V), and the modulation choke. I contacted a friend who lived nearby and asked if he had any transformers lying around. He said he had a few television power transformers. I said I'd take them. He said that there was a big transformer lying around at an FM station some 40 miles away, but it weighed a ton. I was sure that his statement was hyperbole, but I did not want to take any chances. I got every man who worked at the station into my little Toyota, and we went to the distant station. By the time we arrived, it was dark. The distant FM station had a graveyard of old transmitter parts in the basement. I dug through the parts until I found a big transformer. The trip to the distant station was not bad, but after we loaded the transformer into my trunk, the Toyota did not handle too well. When we got back to the station, the river had acquired a layer of ice. We all worked to get the transformer from my car to the transmitter shack and placed it next to the transmitter. Everybody, except me, went home. I watched them cross the semi-frozen river in the darkness, and then they disappeared at the shore of this strange new lake. I stared into the darkness and heard the eerie cracking of the ice as the water receded beneath it. I suddenly realised that I was alone. I was all alone. I felt like the last living cell in a dying corpse. I closed the door to preserve the heat. When I turned around, I saw directly in front of me a dead transmitter. I wondered if it was really possible to take old discarded parts to reanimate a dead transmitter. But I knew that I had until sunrise to find out. I wired the two-television transformer in series to get about 800V centre tapped, more or less. I ran some long wires from where the power transformer was originally mounted to the temporary transformer. The next problem was the modulation choke. The modulator used a push-pull amplifier consisting of two 833A power triodes. The balance prevented saturation of the transformer. Running the RF amplifier plate current through the transformer would have saturated the core and reduced the fidelity, so the designers bypassed the RF plate current through a choke. Since the choke was unusable, I ran the RF plate current through the secondary of the modulation transformer. I decided not to run the transmitter at full power until I could replace the modulation choke. After many hours of work, I stood back and looked at the transmitter. Would it come back to life? Or would it explode? With great trepidation, I reached for the plate switch. I wondered if a giant spark would jump out of the transmitter and zap me. With all the courage that I could muster, I pressed the plate switch. I looked at the meters, and they had proper readings. I screamed, "It's alive! It's aliiive!" I knew that the villagers would have their little pitchforks ready to eat bacon and eggs with their morning news and music as the sun rose over the receding river. I had not disappointed them. Before going home, I brought the damaged power transformer and the modulation choke to a local motor repair shop. Then I ordered a replacement IPA transformer. Finally, I went home and got some sleep. Within a week, the transmitter was completely repaired and back to full power.   This story was submitted by Frank Karkota for Frankenstein's Fix, a design contest hosted by EE Times (US). Frank Karkota started work in broadcasting in the late 1960s as an engineer and subsequently worked as a contract/consultant broadcast engineer. From 1968 to 1970, he worked with a team that maintained a tactical troposcatter system in Vietnam. He later operated a small company, ComPol Inc., that manufactured SCA receivers.

Back in the latter years of the 70s, there was a television programme called WKRP in Cincinnati . The station manager was the son of the station owner. He mismanaged the station and could not be fired, because, after all, "What mother would fire her own son?" I worked for such a station as a contract engineer. It was smaller, and the manager was younger and less competent than the guy in charge at WKRP. The station transmitter was located in a riverbed, which provided an excellent ground and no structures within nearly a thousand feet of the tower. The building was made of concrete and contained a Gates BC-1T one-kilowatt transmitter, along with some audio processing and monitoring equipment. The single tower was next to the building, and the matching network was just inside the building. Because of the concern of flooding, there was a large sump pump and a plank forming a tall door jam at the bottom of the only door. Just as long as the power did not fail, the pump could easily remove any water that seeped through the floor or concrete walls. One day, I got a call from the owner's son that the station was off the air. I rushed out to the transmitter. When I arrived, I discovered that what had been an open field only days ago was now a large lake with a tower in the middle. I asked him what happened. "I went out to see if the transmitter was OK, and when I opened the door, the transmitter turned off," he said. He had some waist-high boots for me. I yanked them on, and we went out to the transmitter shack. It was scary walking through two feet of strong river current to the transmitter several hundred feet from the shore. By this time, the water level was below the plank, and we went into the building. The sump pump had removed most of the water. I opened the transmitter and made an assessment. Every transformer was damaged except the modulation transformer, because it was well sealed. The transmitter was dead. Every minute that a station is off the air means lost revenue, and this particular station was so poorly managed that it was losing money even when it was on the air. I had to work quickly. I decided that I needed to replace the main power transformer (which was 220-6,000V), the intermediate power (IPA) transformer (which was 220-1,000V), and the modulation choke. I contacted a friend who lived nearby and asked if he had any transformers lying around. He said he had a few television power transformers. I said I'd take them. He said that there was a big transformer lying around at an FM station some 40 miles away, but it weighed a ton. I was sure that his statement was hyperbole, but I did not want to take any chances. I got every man who worked at the station into my little Toyota, and we went to the distant station. By the time we arrived, it was dark. The distant FM station had a graveyard of old transmitter parts in the basement. I dug through the parts until I found a big transformer. The trip to the distant station was not bad, but after we loaded the transformer into my trunk, the Toyota did not handle too well. When we got back to the station, the river had acquired a layer of ice. We all worked to get the transformer from my car to the transmitter shack and placed it next to the transmitter. Everybody, except me, went home. I watched them cross the semi-frozen river in the darkness, and then they disappeared at the shore of this strange new lake. I stared into the darkness and heard the eerie cracking of the ice as the water receded beneath it. I suddenly realised that I was alone. I was all alone. I felt like the last living cell in a dying corpse. I closed the door to preserve the heat. When I turned around, I saw directly in front of me a dead transmitter. I wondered if it was really possible to take old discarded parts to reanimate a dead transmitter. But I knew that I had until sunrise to find out. I wired the two-television transformer in series to get about 800V centre tapped, more or less. I ran some long wires from where the power transformer was originally mounted to the temporary transformer. The next problem was the modulation choke. The modulator used a push-pull amplifier consisting of two 833A power triodes. The balance prevented saturation of the transformer. Running the RF amplifier plate current through the transformer would have saturated the core and reduced the fidelity, so the designers bypassed the RF plate current through a choke. Since the choke was unusable, I ran the RF plate current through the secondary of the modulation transformer. I decided not to run the transmitter at full power until I could replace the modulation choke. After many hours of work, I stood back and looked at the transmitter. Would it come back to life? Or would it explode? With great trepidation, I reached for the plate switch. I wondered if a giant spark would jump out of the transmitter and zap me. With all the courage that I could muster, I pressed the plate switch. I looked at the meters, and they had proper readings. I screamed, "It's alive! It's aliiive!" I knew that the villagers would have their little pitchforks ready to eat bacon and eggs with their morning news and music as the sun rose over the receding river. I had not disappointed them. Before going home, I brought the damaged power transformer and the modulation choke to a local motor repair shop. Then I ordered a replacement IPA transformer. Finally, I went home and got some sleep. Within a week, the transmitter was completely repaired and back to full power.   This story was submitted by Frank Karkota for Frankenstein's Fix, a design contest hosted by EE Times (US). Frank Karkota started work in broadcasting in the late 1960s as an engineer and subsequently worked as a contract/consultant broadcast engineer. From 1968 to 1970, he worked with a team that maintained a tactical troposcatter system in Vietnam. He later operated a small company, ComPol Inc., that manufactured SCA receivers.  

Finally. I am now not the only person who is annoyed by the fact that with all of the small, and increasingly smaller, consumer electronics devices in our lives, the only one you can find with any ease when you have misplaced it is your cell phone. Now joining me are David Schneider and Drew. About the only consumer electronics device that I can find after it has been lost is my cell phone: you can use another phone to call it up. When it rings, if you or a friend is nearby, you can find out where it is. But forget about the half dozen or so TV remotes, two or three MP3 players, and any number of electronic devices that have entered our lives, though. No doubt similarly plagued is Drew, an illustrator and artist whose drawings are popular with college students and who makes his efforts available on his Toothpaste for Dinner Website . I came across his most recent effort ( shown below ) in the local student newspaper. (E-thing marketers should take note of the demographics). It shows a saddened device user and has the following caption: " Replace me with a new one. (Why haven't you dropped me or lost me yet?") Why haven't you lost me yet? (Courtesy of Drew at www.toothpastefordinner.com )   More substantive in his contribution to the topic of lost E-things is David Schneider. In his article " Forget-me- not beacons, " in the July IEEE Spectrum Magazine, he describes his lifelong battle with losing things. While owners of iPhones now can purchase a variety of radio beacons they can attach to their clothes or whatever, what if, like Schneider (and me) you do not have an iPhone? ( Panasonic is also offering a similar capability according to the brochure contained in the package with my wireless home phone ). Inspired by a teardown he read on EETimes, he describes the do-it-yourself project he undertook to build a transmitter that he could attach to devices and a similarly compact receiver. It made use of an off-the-shelf Nike+iPod transmitter that he modified and a receiver he built using an Arduino Pro Mini and a Nordic radio receiver. Of course, the three of us are not the only ones who are frustrated by this proliferation of small, easily-losable electronic devices and no way to find them. Do a Google search and you will see dozens of links to products that you can attach to your various items, including E-things, that will signal you in various ways, by some sort of sound, by sending an alert to your phone, cell phone or email address, either immediately, telling you you have misplaced it. The advantage of such devices is that they can be applied to many of the various small personal items that inhabit our lives, electronic or not. And I have tried out many of them. Some work, some don't. But usually, because they are add-ons, they also get lost. And what if you lose something to which a beacon has not been attached? Or lose the beacons, or forget where you put the extra ones until you needed to attach one? For E-things why can't this capability be built in to each consumer device, especially the smaller and more loseable ones. If the manufacturers of all these wondrous devices were serious about making consumers happy, such capabilities would not only be included, but sold as a must-have feature. The ideas are there, in their multitudes in the patents that are applied for. What I notice about the patents, though, is that most are individuals, unaffiliated with any major electronics company, and having run into the problem in their own lives, have come up with a solution and waited for the companies to NOT beat a path to their door. I don't think this problem is going away. It will probably get worse, especially with all the grand plans for a wireless Internet of Things. Right now we are talking about maybe half a dozen such devices at most that each of us depends on to some degree. In the IoT world, in our homes, autos and personal lives we will no doubt be dealing with dozens of such devices. And because they are wireless, easily misplace-able. My first thought about why such capabilities are not built into most electronic devices is economic: it is not in the financial self-interest of the companies to incorporate such a capability. Not only is there the cost of incorporating such a feature, there is the loss in potential sales of a new device when I lose the old one and have buy a new one. Because I know that the smaller the device the more likely I am to misplace it, I usually buy two on my initial purchase. So, why would a company invest in a adding feature that would virtually guarantee to cut its sales in half? ( Truth be told, though, I usually buy three, because most consumer electronics executives' ideas of long term planning is about three months to a year: if the device sales do not immediately go off the charts in that time, it is taken off the market and never seen again. ) More likely it is a problem that is too complex for the industry to solve, even though there are dozens of systems sold to allow major organisations and companies to track goods around the country, around a building, or on an industrial campus using such things as GPS and RFID tags. Beyond the cost and sophistication of such systems, what is appropriate for finding lost E-things in the home may not be appropriate for when we are in the car, or in the office, or out shopping. I guess it is just a problem that is beyond the capabilities of an industry that brought us the microprocessor, the Internet, and the Internet of Things. Too bad. I will just have to face a future of either constantly misplacing the dozens of wireless IoT devices with which I'll be sharing my life, or not buying them at all. The latter seems very appealing right now.