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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://r

by 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.

by kayfox 11y ago

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.