4 ms·

rtlsdr + gqrx + multimon-ng pole around 929.600mhz and you'll eventually find a shitload of phi in most metro areas. you'll probably also find a ton of industr

rtlsdr + gqrx + multimon-ng pole around 929.600mhz and you'll eventually find a shitload of phi in most metro areas. you'll probably also find a ton of industrial traffic, and the occasional weather and sports scores. it's also not far fetched to think it's used as a means to broadcast to/from field operatives. most pager lines offer an smtp gateway, so a bit of "spam" could have a intended recipient anywhere in the region, or possibly country based on network.

phonethrowaway 7y ago
https://en.m.wikipedia.org/wiki/POCSAG https://en.m.wikipedia.org/wiki/POCSAG
DrAwdeOccarim 7y ago
I was just about to buy an SDR rig to play around with, so the timing of your comment is wonderful. I have been looking off and on for a year now and there are just too many choices. I have my tech license, but then I had two kids and haven't been able to go for general yet. I've been bored not getting on HF, which is where I hear all the "action" is. So what SDR would you recommend I get if I also wanted the ability to transmit HF one day?
- jrockway 7y ago
  I don't think it's economic to buy an SDR rig with the intention of maybe transmitting on HF one day. Most HF digital modes are audio-jack based, meaning that you connect any radio, particularly a used one that you can get cheaply on eBay, to your computer via a line-in/line-out connection. You do not need any fancy SDR stuff going on; popular digital modes like FT8 put the entire band in the space of one normal voice conversation. So no special equipment whatsoever is necessary to use digital modes. One time I had my audio misconfigured to use my microphone instead of the line-in, and I had my radio disconnected from the computer to tune the antenna. As I was listening through the radio's built-in speaker, my computer properly decoded a number of FT8 transmissions... through the microphone. You really don't need anything expensive or interesting to do SDR stuff on the HF bands. People that buy the "real" ham SDRs are doing things like contesting, where they really need to see entire bands, or even multiple bands, at once. And they're paying over $10,000 for that. The cheap "hacker" SDRs are largely inadequate for ham work. They are OK, but not great. They don't have proper frontends, so transmit a lot of out-of-band garbage. They don't have niceties like an antenna matching network, or even a power amplifier. I have a KX3 which has a maximum transmit power of 12W. But these hobbyist boards will max out in the mW range. It is adequate for some digital modes, but even then, it's pretty low. I typically run FT8 at 1-3W. So generally, would not recommend these for someone new to the hobby. Buy an RTL-SDR stick for $20. Listen to some stuff. When you get bored, find a proper HF radio in the $300 range and use that. If you then decide you want to spend $10,000 on the hobby, then you can start looking into the SDRs ;)
- jdietrich 7y ago
  Fully-fledged SDR transceivers are available from FlexRadio and Apache Labs and are hugely flexible and capable, but you'll spend $3000+ for the privilege. Apache Labs are the more hacker-friendly option. A much less costly (but still highly flexible) option is to combine a high-performance SDR receiver from Elad or SDRPlay with a conventional transceiver. A T/R switch like the MFJ-1708SDR will protect your SDR receiver when you key up, while CAT control allows both rigs to be operated from the same software.

phonethrowaway 7y ago

https://en.m.wikipedia.org/wiki/POCSAG https://en.m.wikipedia.org/wiki/POCSAG

DrAwdeOccarim 7y ago

I was just about to buy an SDR rig to play around with, so the timing of your comment is wonderful. I have been looking off and on for a year now and there are just too many choices. I have my tech license, but then I had two kids and haven't been able to go for general yet. I've been bored not getting on HF, which is where I hear all the "action" is. So what SDR would you recommend I get if I also wanted the ability to transmit HF one day?

jrockway 7y ago
I don't think it's economic to buy an SDR rig with the intention of maybe transmitting on HF one day. Most HF digital modes are audio-jack based, meaning that you connect any radio, particularly a used one that you can get cheaply on eBay, to your computer via a line-in/line-out connection. You do not need any fancy SDR stuff going on; popular digital modes like FT8 put the entire band in the space of one normal voice conversation. So no special equipment whatsoever is necessary to use digital modes. One time I had my audio misconfigured to use my microphone instead of the line-in, and I had my radio disconnected from the computer to tune the antenna. As I was listening through the radio's built-in speaker, my computer properly decoded a number of FT8 transmissions... through the microphone. You really don't need anything expensive or interesting to do SDR stuff on the HF bands. People that buy the "real" ham SDRs are doing things like contesting, where they really need to see entire bands, or even multiple bands, at once. And they're paying over $10,000 for that. The cheap "hacker" SDRs are largely inadequate for ham work. They are OK, but not great. They don't have proper frontends, so transmit a lot of out-of-band garbage. They don't have niceties like an antenna matching network, or even a power amplifier. I have a KX3 which has a maximum transmit power of 12W. But these hobbyist boards will max out in the mW range. It is adequate for some digital modes, but even then, it's pretty low. I typically run FT8 at 1-3W. So generally, would not recommend these for someone new to the hobby. Buy an RTL-SDR stick for $20. Listen to some stuff. When you get bored, find a proper HF radio in the $300 range and use that. If you then decide you want to spend $10,000 on the hobby, then you can start looking into the SDRs ;)
jdietrich 7y ago
Fully-fledged SDR transceivers are available from FlexRadio and Apache Labs and are hugely flexible and capable, but you'll spend $3000+ for the privilege. Apache Labs are the more hacker-friendly option. A much less costly (but still highly flexible) option is to combine a high-performance SDR receiver from Elad or SDRPlay with a conventional transceiver. A T/R switch like the MFJ-1708SDR will protect your SDR receiver when you key up, while CAT control allows both rigs to be operated from the same software.