6 ms·

The technology is not there, that's the big joke on top of all the management blunder. There are multiple radios used in the field for different distances and

The technology is not there, that's the big joke on top of all the management blunder. There are multiple radios used in the field for different distances and bandwidths: VLF, LF/MF/HF, V/UHF, SAT, and ultra high frequency SAT. There is very little in common between those radios in terms of total equipment mass, space and cost. The "waveform" is an insignificant part. The significant mass, space and cost is on band-specific power amplifiers (PAs), antennas and front-end filters, and those 3 elements are not interchangeable nor can they be software-defined. What they have done after >15 years is to ignore all the frequency bands except V/UHF, and call the result a success.

remarkEon 11y ago
Remembering back to my training a few years ago on all these radio systems, I'm not really sure there's a replacement for gaining a deep understanding of radio wave theory and actually getting out there and building antennas and systems. In one course, we built all the antennas we needed from things like claymore wire and constructed resistors from hammering a nail into the ends of a battery. IMHO that radio hardware itself really does need to be something that "just works" and isn't weighed down by trying to do too much.
kayfox 11y ago
Harris actually makes two radios that do support a wide range of frequencies: http://rf.harris.com/capabilities/tactical-radios-networking/an-prc-152/ http://rf.harris.com/capabilities/tactical-radios-networking... http://harrisradio.com/products/unity-xg-100p/ http://harrisradio.com/products/unity-xg-100p/ The tech is there. Also, as for front ends and PAs, you can make wideband transciever frontends, the PAs in JTRS appear to be specific to bands, so it does not appear that they are trying to do the impossible. Tho they do appear to be trying to make it compatable with every thing under the sun: https://en.wikipedia.org/wiki/Joint_Tactical_Radio_System#Waveforms https://en.wikipedia.org/wiki/Joint_Tactical_Radio_System#Wa...
- Aloha 11y ago
  You can build a radio system that will do damm near DC-Daylight but that doesn't mean it will perform as well as a radio with a narrower bandpass. Usually its a pretty solid constant, the wider the bandpass of the radio, the lower performance, its sometimes a worthy tradeoff, but often not.
  - bsder 11y ago
    And, of course, battery life is a big problem for SDR. High bandwidth ADC/DAC conversion combined with FPGA is a recipe for battery sucking. A radio with single-purpose chips and multiple antennas is always going to be more power efficient. The other problem is that the military often wants HUGE power outputs. It's non-trivial to get good sensitivity on receive when your radio antenna wants to transmit watts of output power.
    - kayfox 11y ago
      You don't have to use high bandwidth ADCs, in another post Aloha brings up the XTS3000 which uses a ADC/DAC setup that only digitizes about 400KHz of bandwith and it gets along fine as far as power consumption. My main point is that we already do this sort of thing in the radio industry and the RF requirements of the JTRS are not at all far fetched. The issue with the project is the software outside of the actual SDR code. Also, as a little bit of extra trivia, antennas designed for higher transmit power don't have any less performance than equivalent antennas for lower transmit powers. Infact the opposite may be true on HF as you will be more likely to tune (both actively and passively) the antenna you have connected to an HF transceiver than connected to just a receiver.
  - kayfox 11y ago
    You can make radios that do really wide swaths with really good performance. ICOM already makes receivers that go from 50KHz to 6GHz with little performance issues other than those related to antenna interfacing. In another post you mention the Astro and Astro25 radios (XTS3000/XTS5000), if we look at a Spectra as an example, the UHF R2 units do 438-470, thats 33MHz, the XTS3000 has a 66MHz tuning range it can work with (403-470MHz for example) the XTS5000 has a range of some 90MHz (380-470MHz for example)... this is achieved through more finite control of the analog portions of the transceiver circuits and through software defined first IF. So we are already seeing the fruits of SDR in some 20 year old Motorola products. We can go in the opposite direction and look at how older radios like the Syntor had tunable working bands of 12 or less MHz, and theres always the MX300 series, with its crystals and tuning needed after that. As the quality and bandwidth of RF parts gets better year over year we will be seeing more improvements like this. So, in conclusion, I do not see how making one common base transceiver of about 5W output and using separate external power amplifiers per-band is not an achievable goal, considering this is already a product that is currently being manufactured by Harris for both the military and public safety markets.
rayiner 11y ago
The technology was supposed to be there. The grand vision was radios that could operate anywhere in a multi-GHz range, opportunistically use that spectrum, and be reconfigured via FPGA and pluggable wave-forms. JTRS was supposed to be the software platform gluing it all together. The vision was possible.[1] You can have multiple PAs, wide-bandwidth omnidirectional antennas, replicate front-end filters, etc. As part of the XG project, the company I used to work for actually developed a very wide-bandwidth front-end that implemented WiMax in FPGA. The trouble is that analog doesn't scale like digital. The tuner alone was $5,000, and that doesn't decrease every 18 months like digital. [1] In fact, to really take full advantage of opportunistic spectrum usage, it's necessary to have a radio that can operate over a very wide frequency range.
- PhasmaFelis 11y ago
  > The trouble is that analog doesn't scale like digital. The tuner alone was $5,000, and that doesn't decrease every 18 months like digital. I don't know much about radio hardware. What is it that makes this so expensive, and (it sounds like) resistant to economies of scale?
  - jacquesm 11y ago
    Analog hardware that is robust enough for military deployment is crazy expensive because it tends to require parts of very high precision in order to achieve repeatable results. It's one thing to build an analog circuit in the lab that performs a certain function, another to make this as a consumer grade device and a completely different kettle of fish to build it in such a way that the military will accept it as a part of their command-and-control infrastructure. Military comms gear is overdesigned to a degree that is hard to imagine if all you've seen is consumer stuff. By comparison, making a digital circuit with very high reproducibility of features is childs play. Digital, by its very nature is a lot easier to get right because every state-transition is 'hard' whereas with analogue parts variability and noise are much harder to control and will lead to circuitry becoming un-usable (especially over time, in the presence of vibration or over a large temperature and humidity range).
hydrogen18 11y ago
I was talking about the technology for the specific project I worked on. Not in general. The RF hardware had underwent significant development and refinement to the point that it's problems were worked out and the limitations were known. There is of course no magic wand (yet) that gives you a broadband transceiver with good performance over 1 mhz - 100 ghz. The WIN-T program always aimed to deliver a variety of different radios into the hands of the soldier so they'll have some degree of comms in all opertional scenarios. They just don't want to have soldiers dealing with 10 different radios when 3 or 4 will work.

remarkEon 11y ago

Remembering back to my training a few years ago on all these radio systems, I'm not really sure there's a replacement for gaining a deep understanding of radio wave theory and actually getting out there and building antennas and systems. In one course, we built all the antennas we needed from things like claymore wire and constructed resistors from hammering a nail into the ends of a battery. IMHO that radio hardware itself really does need to be something that "just works" and isn't weighed down by trying to do too much.

kayfox 11y ago

Harris actually makes two radios that do support a wide range of frequencies: http://rf.harris.com/capabilities/tactical-radios-networking/an-prc-152/ http://rf.harris.com/capabilities/tactical-radios-networking... http://harrisradio.com/products/unity-xg-100p/ http://harrisradio.com/products/unity-xg-100p/ The tech is there. Also, as for front ends and PAs, you can make wideband transciever frontends, the PAs in JTRS appear to be specific to bands, so it does not appear that they are trying to do the impossible. Tho they do appear to be trying to make it compatable with every thing under the sun: https://en.wikipedia.org/wiki/Joint_Tactical_Radio_System#Waveforms https://en.wikipedia.org/wiki/Joint_Tactical_Radio_System#Wa...

Aloha 11y ago
You can build a radio system that will do damm near DC-Daylight but that doesn't mean it will perform as well as a radio with a narrower bandpass. Usually its a pretty solid constant, the wider the bandpass of the radio, the lower performance, its sometimes a worthy tradeoff, but often not.
- bsder 11y ago
  And, of course, battery life is a big problem for SDR. High bandwidth ADC/DAC conversion combined with FPGA is a recipe for battery sucking. A radio with single-purpose chips and multiple antennas is always going to be more power efficient. The other problem is that the military often wants HUGE power outputs. It's non-trivial to get good sensitivity on receive when your radio antenna wants to transmit watts of output power.
  - kayfox 11y ago
    You don't have to use high bandwidth ADCs, in another post Aloha brings up the XTS3000 which uses a ADC/DAC setup that only digitizes about 400KHz of bandwith and it gets along fine as far as power consumption. My main point is that we already do this sort of thing in the radio industry and the RF requirements of the JTRS are not at all far fetched. The issue with the project is the software outside of the actual SDR code. Also, as a little bit of extra trivia, antennas designed for higher transmit power don't have any less performance than equivalent antennas for lower transmit powers. Infact the opposite may be true on HF as you will be more likely to tune (both actively and passively) the antenna you have connected to an HF transceiver than connected to just a receiver.
- kayfox 11y ago
  You can make radios that do really wide swaths with really good performance. ICOM already makes receivers that go from 50KHz to 6GHz with little performance issues other than those related to antenna interfacing. In another post you mention the Astro and Astro25 radios (XTS3000/XTS5000), if we look at a Spectra as an example, the UHF R2 units do 438-470, thats 33MHz, the XTS3000 has a 66MHz tuning range it can work with (403-470MHz for example) the XTS5000 has a range of some 90MHz (380-470MHz for example)... this is achieved through more finite control of the analog portions of the transceiver circuits and through software defined first IF. So we are already seeing the fruits of SDR in some 20 year old Motorola products. We can go in the opposite direction and look at how older radios like the Syntor had tunable working bands of 12 or less MHz, and theres always the MX300 series, with its crystals and tuning needed after that. As the quality and bandwidth of RF parts gets better year over year we will be seeing more improvements like this. So, in conclusion, I do not see how making one common base transceiver of about 5W output and using separate external power amplifiers per-band is not an achievable goal, considering this is already a product that is currently being manufactured by Harris for both the military and public safety markets.

rayiner 11y ago

The technology was supposed to be there. The grand vision was radios that could operate anywhere in a multi-GHz range, opportunistically use that spectrum, and be reconfigured via FPGA and pluggable wave-forms. JTRS was supposed to be the software platform gluing it all together. The vision was possible.[1] You can have multiple PAs, wide-bandwidth omnidirectional antennas, replicate front-end filters, etc. As part of the XG project, the company I used to work for actually developed a very wide-bandwidth front-end that implemented WiMax in FPGA. The trouble is that analog doesn't scale like digital. The tuner alone was $5,000, and that doesn't decrease every 18 months like digital. [1] In fact, to really take full advantage of opportunistic spectrum usage, it's necessary to have a radio that can operate over a very wide frequency range.

PhasmaFelis 11y ago
> The trouble is that analog doesn't scale like digital. The tuner alone was $5,000, and that doesn't decrease every 18 months like digital. I don't know much about radio hardware. What is it that makes this so expensive, and (it sounds like) resistant to economies of scale?
- jacquesm 11y ago
  Analog hardware that is robust enough for military deployment is crazy expensive because it tends to require parts of very high precision in order to achieve repeatable results. It's one thing to build an analog circuit in the lab that performs a certain function, another to make this as a consumer grade device and a completely different kettle of fish to build it in such a way that the military will accept it as a part of their command-and-control infrastructure. Military comms gear is overdesigned to a degree that is hard to imagine if all you've seen is consumer stuff. By comparison, making a digital circuit with very high reproducibility of features is childs play. Digital, by its very nature is a lot easier to get right because every state-transition is 'hard' whereas with analogue parts variability and noise are much harder to control and will lead to circuitry becoming un-usable (especially over time, in the presence of vibration or over a large temperature and humidity range).

hydrogen18 11y ago

I was talking about the technology for the specific project I worked on. Not in general. The RF hardware had underwent significant development and refinement to the point that it's problems were worked out and the limitations were known. There is of course no magic wand (yet) that gives you a broadband transceiver with good performance over 1 mhz - 100 ghz. The WIN-T program always aimed to deliver a variety of different radios into the hands of the soldier so they'll have some degree of comms in all opertional scenarios. They just don't want to have soldiers dealing with 10 different radios when 3 or 4 will work.