
Open IP over VHF/UHF - zdw
http://www.rowetel.com/?p=7207
======
non-entity
So this might he a little off topic, but I picked up an SDR with some cool
projects in mind. And when I opened SDR programs I quickly realized I had no
idea what I was doing. Much of the terminology seemed foreign, etc. What kind
of background knowledge do I need to get up to speed with this stuff? Would a
few signals/ DSP course suffice to start out?

~~~
unoti
I recommend getting all 3 ham radio licenses: technician, General, and extra
class. In the process you’ll learn all kinds of things and have a lot of the
concepts down. You’ll learn about many different aspects of electronics,
antenna design, RF propagation, and fun ways to use radios along the way. And
you’ll be ready to put it to use right away with your first license.

So if you research learning materials for those licenses you’ll be off to an
awesome start. There’s excellent free and paid books available.

~~~
mmaunder
I have all three (WT1J) and I found them to be thin on digital signaling,
SDRs, and understanding real world signals. I’d suggest getting a cheap SDR
and starting here:
[https://greatscottgadgets.com/sdr/](https://greatscottgadgets.com/sdr/)

You’ll learn how to build a basic fm radio using gnuradio along with other
cool stuff, like a simple explanation of decibels among other things.

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mikece
This is an awesome idea. I’ve questioned why the Amateur TV “channels” in the
430MHz range can’t be re-purposed for digital TV or just 6MHz wide pure data
channels (over which digital TV could be sent). Much of the resistance is from
old HAMs who don’t want anything to change. Hopefully TAPR can get behind
something like this as well as lobbying for updates to encryption where TLS
over IP over amateur radio is happening.

~~~
dbcurtis
DATV is a thing on 430. The problem is equipment. MDARC runs DVB-S, I believe.
For DVB-S, you can re-purpose satellite equipment. KH6ATV is a proponent of
DVB-T (which in theory should be better than DVB-S for terrestrial paths).
There is one company in Taiwan that makes DVB-T transmitters and receivers
that are usable in the ham bands (available in their E-Bay store), and people
have done DVB-T in the ham bands with LimeSDR. BATC has done a lot of work
with DVB also. Sorry to be vague, I haven't been keeping up on my reading...
about 1.5 years ago I was going to try setting up for DVB-T on 430MHz and
1.2GHz, but life got in the way.

In theory, you should be able to run 780p in a 6 MHz wide channel in the 430Hz
band, or even squeeze 480i down to fit a 2MHz wide channel. (The max bandwidth
allowed for amateur video in the USA on 430 is 6MHz, DVB-T does have 8MHz wide
formats used in some countries for broadcast.)

Contact KH6ATV if you are interested in doing some experiments. I recommend
reading his notes first: [https://kh6htv.com/application-
notes/](https://kh6htv.com/application-notes/)

For those that haven't stopped reading already: DVB-C -- optimized for cable.
DVB-S -- optimized for satellite path loss and fading, but not for multi-path.
DVB-T -- optimized for terrestrial paths which may suffer from significant
multi-path propagation. ATSC -- The US standard, which unfortunately was
standardized earlier than the rest and is expensive to generate and has
outrageously poor weak-signal performance, both of which make it a
ridiculously bad choice for amateur radio.

~~~
aidenn0
My understanding is that ATSC has fine weak-signal performance at UHF in rural
areas; it's just extremely sensitive to multipath interference _and_ it
doesn't do well with the terrestrial noise in the high VHF range, so anywhere
with large flat surfaces (like city buildings) is not so great.

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th0ma5
Amateur radio, at least in the US, has a ban on encryption, so while we also
have signal speed limits that may prevent it, secure sockets are forbidden.
I'm not sure how some of the proprietary digital modes get away with it, but I
guess money talks.

~~~
userbinator
Arbitrary restrictions like that just make me want to get around them... and
reminds me of this phrase I heard many years ago (in the era when encryption
laws were _far_ stricter):

"What's the difference between encryption and steganography? You don't know."

~~~
arghwhat
Don't. Follow the rules, and get them changed if you disagree with them.

Amateur radio enjoys the privilege of pretty lax regulation, largely due to
the players not making any trouble. Speaking as a fellow radio amateur, we
don't want our hobby ruined just because someone wants to be a troublemaker.

~~~
teddyh
> _Amateur radio enjoys the privilege of pretty lax regulation_

What. You literally have to have a license issued to you personally (no
anonymity) by the government to even be allowed to do it. And the rules of
what can and can’t be sent are, to my Internet-accustomed mind, excruciatingly
onerous. No encryption? No _foul language_?

~~~
arghwhat
The rules are _extremely_ loose.

1\. You need a personal license to identify you, as an operator of a radio
station. This is similar to how radios on ships and airplanes work - you need
to be able to identify every transmission (even cellphones are uniquely
identifiable). This is not only _part of the entire sport_ (we're trying to
contact and _identify_ each other), but is also used to identify problems.

2\. Just like for airplanes and ships, there are some rules to what you can
transmit, as your transmissions can be heard (and cause troubles) for tens,
hundreds and even thousands of kilometers away.

3\. You have _countless_ frequency allocations available, all over the
spectrum, despite the scarcity.

4\. Unlike everyone else, holding that license permits you to build your own
equipment and transmit with _kilowatts_ with no certification needed. It's
extremely easy to cause _massive_ issues with this, such as interrupting
cellular communication/gps/wifi an a large area, blowing up your neighbors
stereos, and fun things like that.

There's a _reason_ that everything else needs to be tested, certified, and
require dedicated band allocations - we avoid it by showing that we have the
sufficient skills to practice our hobby and not cause trouble.

Unlike _everyone else_ , we can do pretty much whatever we want as long as we
keep it around a kilowatt and talk nice. I consider that to be _extremely_
relaxed rules.

~~~
teddyh
I am reminded of what Chinese people say when they are asked about how they
feel about the oppressive government. They say “What’s the problem? We have
perfect freedom to do whatever we want, as long as we don’t talk about
politics, and who cares about that?”. It’s perfectly normal to them, and they
don’t feel particularly oppressed.

Those rules about absolute identifiability are only “part of the entire sport”
because you have defined it to be that way. What if Internet chat had been
defined the same?

Also, enumerating what you are allowed to do once you are granted a license
does not help the argument that the requirement for a license is oppressive.

> _There 's a reason that everything else needs to be tested, certified, and
> require dedicated band allocations_

Maybe there were reasonable technical reasons in the 1970’s, but now with
modern technology, there should be no problem, or at the very least
significant relaxations of what the regular public is allowed to do.

I repeat: Having to get an individual government license to practice your
hobby is draconian. But, of course, regulations don’t really ever get _less_
restrictive.

~~~
int_19h
It happens to be a hobby that has significant potential externalities, so of
course it's heavily regulated. But OP's point is that the initial barrier to
entry is so high precisely because once you get past it, nobody is looking
over your shoulder, and the limits are lax enough that even very disruptive
activity can still fall within them.

~~~
teddyh
Firstly, I doubt that the externalities are that severe nowadays, and with
modern frequency-hopping technologies, I believe that it could all be fixed by
upgrading existing hardware (even though this would be hard).

Secondly, the _original_ argument was that, and I quote, “ _Amateur radio
enjoys the privilege of pretty lax regulation_ ”. And a requirement to get a
government license, tied to your personal name and identity, gated by a large
fee and difficult exam, is not my idea of “lax regulation”.

~~~
deirdrehbrt
So, there is no large fee at all for getting a Ham Radio license. You can get
your license for $15.00 at most testing sites. And if you've studied, you can
go all the way to Extra class for that one $15.00

As to the difficulty, children at about 5 or 6 have passed the Technician
class test. It takes some studying, but it is really easy. The most difficult
part is in understanding the bands that you're permitted to operate on.

In reality, getting a license is easier than it's ever been. There are no more
requirements for Morse Code - though some still use it. There is no longer a
requirement to go to an FCC field office for testing - your local Ham Radio
club can give you the exam. It used to be that you got your Novice ticket, and
had to upgrade to Technician within a fairly short period of time - now you
begin with the Technician exam.

As for the regulation, there is a real legit reason for this. As Amateurs,
we're permitted to operate on a wide range of frequencies - some of which are
close to those used for Radar, Wi-fi, and many other services. Some of the
frequencies we can use are very long range. The reason for the regulations
that exist are in order to prevent interference to other services, to avoid
breaking international treaties, etc.

The technical knowledge is important because you're permitted to build your
own equipment. It's important, if you do, to know that your equipment is
operating properly, so that you don't disrupt many other services with
transmitters that are spewing noise and harmonics on many unintended
frequencies.

In short, Amateur Radio is FAR LESS regulated than any other service, because
of the technical abilities that we have historically displayed. It's a
worthwhile hobby and lots of fun. I don't know of any other hobby that has its
own satellites in orbit, that has bounced radio signals off of the planet
Venus - and regularly uses the Moon or even ionized meteor trails as a
reflector for radio signals...

Seriously, given what we can do with the hobby, passing a relatively simple
test and paying $15.00 to get your license - and no recurring annual fee ... I
don't consider that restrictive at all.

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drmpeg
How about 30 Mbps with OFDM.

[http://www.w6rz.net/ofdm3.png](http://www.w6rz.net/ofdm3.png)

~~~
superkuh
Looks like you spent about 1000x more $ on SDR, RF bits, and computer hardware
for that setup than the rpi/rtlsdr options explored in the main article.

Still, very cool.

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monkeycantype
Oh this is awesome. In ancient times I set up email over uhf in a remote
village in bougainville (the only link I can find is a paywalled pdf
[https://shop.ata.org.au/shop/renew-
issue-84](https://shop.ata.org.au/shop/renew-issue-84)) We had to pretend to
be a ship the mv sunrise to access a system that ran out of san diego that was
only licensed to provide service to ships in international waters. There was
an internet provider in the solomon islands that did something similar, but
for political reasons they were not allowed to help.

~~~
thatlongthrow1
There is a one page preview here:
[https://www.jstor.org/stable/renetechsustfutu.84.16?seq=1](https://www.jstor.org/stable/renetechsustfutu.84.16?seq=1)

Fascinating stuff.

~~~
monkeycantype
Thanks for finding that, I haven't seen that photo for a long time, I remember
the feeling of exhausted relief that it was finally working.

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holidayacct
Ignore open IP over VHF/UHF if anyone wants a challenge I found out recently
that...

People have been able to eavesdrop on homes by targeting pretty much anything
containing metal coils (including appliances) with advanced HAM radio
equipment since the early 1970s.

