Bitcoin and ham radio

[AlPutino]

a packet radio that is specifically listening for signed bitcoin transactions to be sent to the network.

[Riniaiokl]

Not a ham operator but I've looked into it a bit. Problem is it has to little bandwidth for full nodes. It could possibly be used in a SPV manner for linking a specific payment terminal to a radio connected to a full node. But considering the block limit today is 1MB and that will have to be increased I don't think it can be used for the kind of emergency network I'm thinking of.

[Riniaiokl]

Look up the TNC-PI for how packet radio can be realised.

[Tenarlty]

There's some discussion here https://bitcointalk.org/index.php?topic=74924.0

 I don't think anyone has tried this yet. And, he hasn't said this to my knowledge, but I get the impression that MoonShadow may be a HAM so you might ask him.

[WindMaster]

You'd need about 2kbps to download seven 1MB blocks an hour.  That's a lot of bandwidth 24/7/365 on a global HF network.  I think the Bitsat project and the use of UHF and SHF for a lot more relative bandwidth is the best solution for a global wireless network - https://bitcointalk.org/index.php?topic=334701.0

6 blocks/hr * 1048576 * 8 = 50331648 bits/hr

50331648 bits/hr / 3600 seconds = 13981 bps = 13.981 kbps   (with no additional overhead)

For 7 blocks/hr, 16.311 kbps   (with no additional overhead)

These rates exceed conventionally available AX.25 packet radio / TNC throughputs for HF and VHF ham bands (generally 300 baud FSK for HF, and 1200 baud AFSK or 9600 baud AFSK for VHF/UHF).  Either use of higher frequency bands or a custom modulation format that would tend to have a bandwidth exceeding amateur radio rules in most ITU countries on HF, VHF and UHF frequencies would be needed.  At that point you might as well just set up a 900MHz, 2.4GHz or 5GHz 802.11 link.

Yes, anyone can tune in to listen to ham radio, but it's important that we have parts of the radio spectrum to ourselves, otherwise all frequencies from DC to daylight would be licensed for commercial and public safety (much of which isn't listenable without buying horrifically expensive gear, if it isn't completely encrypted for no reason other than to eliminate transparency) use.

$10 to $15 for a Realtek-based DVB-T USB receiver dongle used as an SDR (software defined radio), and you can receive whatever you want from 24 to 1766MHz (in the case of versions of the dongle using an R820T RF front end).
http://sdr.osmocom.org/trac/wiki/rtl-sdr

[TheButterZone]

Woah, I want that but I think we'd all prefer it to be plug-n-play on all operating systems...

[matthewh3]

6 blocks/hr * 1048576 * 8 = 50331648 bits/hr

50331648 bits/hr / 3600 seconds = 13981 bps = 13.981 kbps   (with no additional overhead)

For 7 blocks/hr, 16.311 kbps   (with no additional overhead)

These rates exceed conventionally available AX.25 packet radio / TNC throughputs for HF and VHF ham bands (generally 300 baud FSK for HF, and 1200 baud AFSK or 9600 baud AFSK for VHF/UHF).  Either use of higher frequency bands or a custom modulation format that would tend to have a bandwidth exceeding amateur radio rules in most ITU countries on HF, VHF and UHF frequencies would be needed.  At that point you might as well just set up a 900MHz, 2.4GHz or 5GHz 802.11 link.

Yeah it looks like the full blockchain over HF is a no go'er.  We'd be best supporting the Bitcoins in Space project - https://bitcointalk.org/index.php?topic=334701.0 - Or in setting up a project to build a cheap WiFi mesh-networking router that can hold bitcoind.  As even the public PMR446 UHF band only permits 3.6kbit/s per channel.  Although possibly maybe we could use the unlicensed 900MHz 33cm UHF band for a custom mesh-network with better propagation than the 2.4GHz 802.11n.  There's off the shelf license free 802.11g 900MHz 33cm UHF equipment like this - http://www.alvarion.com/products/product-portfolio/breezeaccess/breezeaccess-900 - and this - http://www.xgtechnology.com/xMax-articles/xmax-system-overview.html - That we could attach a cheap lightweight nettop too to hold bitcoind.

[matthewh3]

There's also the new 802.11ah: WiFi Standard for 900MHz coming out.

EE Times says the spec aims to support a range of options from throughput of 150 Kbits/s with a 1 MHz band to as much as 40 Mbits/s over an 8 MHz band. Distances supported could be about 50 percent longer than those of the streamlined 802.11n - http://www.dailywireless.org/2013/08/30/802-11ah-wifi-standard-for-900mhz

This may work better for WiFi mesh-networks.

[Robert Paulson]

how about a radio that calculates the frequency randomly for every packet by continuously SHA256 hashing an initial seed.
that way if you want to communicate with someone who knows the initial seed you can do it without the authorities knowing which frequencies are being used.

[beaknuke]

ex-G0--F (removed my call sign) here... i was into Ham radio 20 year ago (ouch), I used to be on Packet Radio on 144mhz and also did HF packet (which didn't work very well).  I used to run a repeater 20 miles away which used to pass traffic to somewhere else, it was okay for listing your 'email' as it was back then, took ages to get a message and the packet radio would be stuffed if it did hear another transmission.  If I was at the repeater and turned on the radio you would hear hundreds of packet radios trying to transmit all the time, it was that slow, just a big pile up of radio transmissions and the strongest would be king.  The problem was is the amount of time it took before re-transmission.

Here is a video, about 4 minutes in you can hear the signals.
https://www.youtube.com/watch?v=9dfqPQui4NU

Other technologies like RTTY/PACTOR/AMTOR could allow you to do it over HF, AMTOR had the abilities to locking a connection so you could keep talking and have mistakes corrected. This is PACTOR, I didn't use it myself but you see a file transfer going on https://www.youtube.com/watch?v=RaAKJRfaKiE

[matthewh3]

If Kryptoradio in Finland can do broadcasts in only a 7.5kbps channel.  Then instead of only broadcasting in UHF line of site. The same service could broadcast on SW/LW/MW over digital AM to much larger regions from a single transmitter using Digital Radio Mondiale technology.  A single LW transmitter could potentially give coverage to the whole of Scandinavia. 

Using the Digital Radio Mondiale codec you could broadcast =>7.1kbps over a 5kHz channel on SW/MW/LW.  Although renting SW transmitter broadcast time costs around $25k per month for 24/7/365 broadcasts.  5kHZ though is about half the bandwidth that AM stations use on MW.

Another idea to look at terrestrial broadcasts although this time with full duplex is UHF IEEE 802.11ah meshnetworks.  With a good external antenna you could get very good local range at 900Mhz so it could really work well for mesh-networking.  The first IEEE 802.11ah chips are supposed to come out next year while the protocol should be finalised by 2016.  Plus it's an unlicensed band so no one would need a ham license to set up a low power node.