9 Feb
2021
9 Feb
'21
6:01 a.m.
We already have hundreds of SDRs available via IP. One aggregation is at
http://websdr.org/
Frankly, sending 50MHz bandwidth at say 16 bits over IP is perhaps the worst way to do
it... Just to find that elusive 50Hz CW signal!??
The latest SDRs have a massive A/D for baseband capture, perhaps 250MHz, immediately
processed by multiple FPGAs, then perhaps sent to Gnu Radio on a very fast multicore CPU.
This is no simple trick. But my point is, people smarter than me have figured out it is
better to decimate and process locally, not at the end of an IP connection.
So i am still at a loss for compelling high bandwidth applications.
(Thanks for indulging my detour here. Back to regularly scheduled BGP etc.)
Cliff K6CLS CM87
On February 6, 2021 3:54:12 PM PST, Tony Langdon via 44Net <44net(a)mailman.ampr.org>
wrote:
On 7/2/21 8:32 am, pete M via 44Net wrote:
We dont have high bandwith application?
What about 50 Mb/s ? is that high speed enough?
SDR kike the Hermes-Liet 2.0 can feed the HF spectrum to a software
remotely By IP
stream at up to 50Mb/s
Would it be a nice thing to have multiple SDR transceiver on multiple
bands all
over the world available to ham that run a 44net adress?
Now that would be neat - having access to SDR IFs remotely, though
those
speeds are only going to be available at a regional level if routing
over the Internet. While I have 80+ Mbps available downstream, that
really only applies to relatively local (within VK for me) endpoints.
Once I'm going overseas, usable bandwidth can drop to 10 Mbps or less,
from end to end. But the 2-2.4 MHz bandwidth of RTL-SDR class devices
might be more practical on an international scale, which means a
transport that can scale to suit available bandwidth. Also, for
latency
reasons, we would want optimal routing on our core infrastructure,
which
ties back to the previous discussion.
Nice out of the box thinking there. :)
Would it even be a nice intitative to build an high speed RF linking
system for
that use case?
The biggest challenge with high speed RF is cost and complexity. Not
everyone is able to build UHF/microwave equipment reliably. I have a
number of issues in that area - some intrinsic, some are time related,
and the cost of high speed/wide bandwidth microwave equipment tends to
be rather expensive, given that amateur applications tend to be low
volume, compared to something like mobile phones or wifi.
I can think of many more project like that.
Most people dont think of such project for a simple reason, most of
the mode we use
are narrow by definition, and since the FCC limit the
maximum Bandwith available by bands to a bare minimum and that the USA
ham's must comply to this insane thing, the rest of the world is kind
of being drag to that fact.
Just take the New pascket radio project, Canadian hams could use it
at the maximum
spead it was designed for, US, nope 70cm bandwith limit
will prevent it. Frustrating I must say.
I'm pretty sick to death of being held back by archaic US regulations.
Here, we can also use whatever bandwidth a mode requires, provided we
stay within the band limits (on VHF and up). There may be some
interesting band plan issues on 70cm, but we hams can resolve those.
On
1.2 GHz and up, there's bandwidth to burn, and it would be good to make
use of that. :) Maybe the rest of the world should just get on with it
and encourage US hams to lobby to get their regulations updated to
match
the rest of the world, and in the meantime, the US battles on as best
it
can until they can sort out their regs and join us RF wise.
--
73 de Tony VK3JED/VK3IRL
http://vkradio.com
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