Digital Comms
What a very broad term !

Packet Radio, Amateur Television, CW, AMTOR, PacTOR and PacTOR II, RTTY, SITOR, NAVTEX, Fax, GTOR / Golay, ASCII modes and all of the newer modes can be put into this general category !!!

Some day, I'll get some pictures up here to make it a bit easier to visualise how to put together and use a digital communicatons set-up !
Stay tuned.... =)
So, lets start with first mode:
Packet Radio
Sample sounds, Sample sounds, Sample sounds.
General info.

 

You send information over the air in Packets, probably why the amateur population called it Packet eh ?!
If you've every listened or made contact with packet it's easy to hear why it's called packet. Two stations sending each other little packets of info until the whole message is sent correctly! These messages sound like bursts of binary noise, or if you've ever heard the noises from a fax machine...something similar to that. It's hard to describe properly if you haven't heard it before.
Basically, one station sends a packet of info, the receiving station sends a packet back, either saying "I missed you're last message, send it again" or "got that, next !".
When the transmitting station is finished it sends a final packet to the receiving station to say "righto, I'm done - you ready to transmit?" and once the other station sends an acknowledgement packet saying "yep, QSL!" the receiving station switches and becomes the transmitting station. The same process happens again.
Packet radio is a very cheap mode to use, there are extremeley simple decoders/encoders all over the place, but, depending on where you live as to their availability ! If you live somewhere in a built up area  there should be a shop around somewhere close where you can buy a TNC or HamComm style interface for Packet.
A TNC is a Terminal Node Controller - it's got heaps of features and likely heaps of modes ! Various plugs and sockets for up to two radio's, morse keyers and a lot more. Depends which model you buy of course !
A HamComm style interface is a very simple circuit - in the case of the one I got, it's made of only an RS-232C connection, a 5 PIN Din connector for tx/rx connected to a simple curcuit design for amplifying the sound, all in a small plastic case about the size of a packet of smokes.
If you're like me ( live 2300 K's away from anything remotely looking like a good shop !!) then you're gunna have to order one of these interfaces if you wanna get into the wicked realm of Digital Communications !.
So what do you look for?
Simple and cheap interfaces:
Well, there is a very simple interface, costs about $10 AUD, which comes with a program called HamComm (HamComms's Unoffical Site...since I can't find the official one). Written by W.F. Schroeder in Germany, this program will be perfect for anyone...if you're a Short Wave Listener you can listen in on amateurs and any other transmission sources you can find, and read what comes up on your screen. Some of the stuff I have picked up is unreal !!
HamComm needs a computer to run on and you'll have to buy the cables to connect to the computer and the radio, unfortunately they're not supplied...but then what do you expect for something so cheap ??!! These cables are very common and you can probably buy them from the nearest computer shop ! The person who sells you the HamComm interface should tell you what you need and where to get it. If not, ask them ! :-)
A second hand AEA PK-90 (Packet only TNC) inerface is quite cheap (about $90 AUD or so), but once you get into it, you'll probably wanna use all other common modes like RTTY, AMTOR, PacTOR and that, so looking at a PK-232MBX is a good idea. They cost about between $200 and $400 - depends if you shop around or get lucky.!
MFJ also has Packet only and all mode TNC's although I dunno their model names, if you have a look for a second hand one they should be about the same price for the same amount of modes as the AEA products.
Complex and expensive interfaces:
If you've got a bit of money, then you might wanna look at buying a PK-232 MBX , PK-900 or maybe even splash out big time and get a PK-2232 DSP from AEA, or one of the MFJ products....like the MFJ-1278B, 1270. If I could find a local MFJ supplier in Australia I'd link them here...lemme know if you find one !!
There are other companies that make Packet only TNC's, and all mode TNC's like Kam, PacComm, Universal and some others, but I have not seen these controllers in use so I can't give an opinion. That doesn't mean they're no good....give 'em a go if you want !!
There is probably other stuff out there for Packet, but, I have not come across any...

As a hint, the only AEA web site I found was pretty crap for such a good quality company...and it makes AEA look unprofessional, something they're not ! They only provide American phone numbers to contact, I'll include here if I find any Australian contacts.
Packet Radio call frequencies
11 metres:
27.600 +/- 150 kHz

15 metres:

21.101 LSB +/- a strong station from YB and JI.....
Generally below 21.150 LSB for digital on 15 Metres.
20 metres:
14.060 - 14.110 LSB -  but there is a lot of digital transmission on this area of 14 Megs, so, check it out.
Usually, any of the lower parts of the HF bands are good for digital, although....some are backwards..ie the higher part of the band has the activity :-)
Above HF, I am not sure about digital comms, for the simple reason that I don't live close enough to any other operators who have digital to know about it....will let you know when I do though.
Amateur Television
3 SSTV Sample sounds below
General

Amateur operators use two different types, SSTV or Slow Scan Television and FSTV or Fast Scan Television.
What's the difference between these two other than scan speed ? Bandwidth !!!!
SSTV uses about 3kHz of bandwidth, which makes it a really popular mode for image transmission on HF!
FSTV takes up a few megahertz, so it is only useful above 50 MHz band.
Why? Well, above 6m the bandwidth of the band increases to about 10 to 20 megaherts ! For example, in Australia, the 420  Megahertz / 70cm amateur band covers 420 - 480 Megaherts...plenty of room for a few FSTV channels, but heaps of room for a thousand SSTV channels......

SSTV

Sample sounds, Sample sounds, Sample sounds
SSTV images
General
Never heard SSTV and you wanna get in the on the listening action? probably the best way to describe the sound - listen for a sound similar to that which Rolph Harris makes when he wobbles a piece of metal or cardboard, only about 3 times as fast.!! =)
The most common SSTV mode is Scotty 1 for Australia, Asia and USA and Martin 1 in Europe.
Different modes sound different !
Slow Scan Telivison scans pictures very slowly and for that reason it does not need much bandwidth at all to send an SSTV image. SSTV is not like normal TV, where normal TV is moving pictures, slow scan is still pictures, like one's you'd take from a camera.
If you know a lot about the internet, think of it this way - you don't need a lot of bandwidth to download an ordinary image off the net, on the other hand, to stream movies you need a hell of a good connection, which means bandwidth !!! The same general rule applies to Amateur Television.
When an SSTV station transmits you'll hear a few seconds of what you might call the "Front Porch", this is where the SSTV program sends out a message to the receiving station saying "get ready to sync and start the image, here it comes !" and then starts the image. The Front Porch is the beginning of the picture and it usually contains the transmitting stations details.
At the end of the image there's what might be called a "Back Porch", this the same idea as the front porch but it's telling the receiving station to prepare to receive the end of the image. At the last sample sound you can hear the back porch, it's a very quick sequences of tones, but, it is very clear !
(All forms of Digital communiation have a back and front porch of some style, otherwise no program would know when to start or stop transmission or reception !.)
What do you look for?

Simple and cheap interfaces:
The most common type of interface to use is the sound card on your computer, since most computers these days have them as standard !!
Although my first interface used the Com Port to work, I got JVFax 7.0 (by Eberhard Backeshoff) for free with the HamComm interface and it's a bloody good program for SSTV and Fax !!.
I got JVFax 7.0 from John Tower - VK6IM at his business, Tower Communications, an amateur radio dealer way out in the sticks at Hazelmere, which is a suburb in Perth - Western Australia's capital city.
The HamComm interface is made of only an RS-232C connection, a 5 pin Din connector for tx/rx connected to a simple curcuit design for amplifying the sound, all in a small plastic case about the size of a packet of smokes.
Programs that allows you to transmit and receive SSTV and Fax with your computers soundcard.
JVFax , JVComm.(SSTV and Fax) Windows 95 SSTV or the new version, ChromaPix (SSTV Only)
JVFax / JVComm, Windows 95 SSTV and ChromaPix are Windows 95/98 32 bit programs that utilises your sound cards input and ouput to send and receive SSTV (only JVFax / JVComm works with SSTV and Fax and has the ability to use more than just your sound card as radio interface), they are shareware.
If you want to register your copy of JVComm it
costs $112 AUD ($68 USD), the shareware version will work just as well if you can't afford to buy the registered thing but it has annoying reminders to register and pay for the software with "DEMO" written everywhere on received fax images and with "JVComm Demo" written in the top left of SSTV images. JVComm will work with 4 or 5 other Hardware interfaces (choose from EasyDSP, PTC-II, HariFax IV or Other - meaning you can make or buy a hardware interface that is made to work with JVComm) but the easiest to go with is a soundcard !
You need to make or buy a shielded (to keep out interference, which computer are good at producing lots of !) 3.5mm audio cable with stereo plugs at each end. Plug one end into your audio out or spk jack on your radio, and the other end into the mic/line in jack on your sound card. With some small configuration the software does the rest ! Get stuck with JVComm? the help file is great and there is a Forum on Eberhard's home page where you can get help !
ChromaPix and Windows 95 SSTV work the same way as JVComm although unlike JVComm (with it's DEMO reminders) these programs are time limited...they run for 30 minutes before closing. The other thing - they will ONLY work with a sound card. You can register for either of these two programs also, but for ChromaPIX it costs $198 AUD ($120 USD), more than what it cost to buy Windows 98.!
Complex and expensive interfaces:
The only complex interfaces I know of which have SSTV capabilites are theAEA products PK-232MBX, PK-900, PK-2232/DSP and MFJ products MFJ-1278 and MFJ-1278B/DSP etc. If your careful and you look around you can probably get one of these TNC's fairly cheap second-hand compared with retail prices, but also good working quality. Be careful if you buy second-hand, for obvious reasons. That's not to say you can'y get some good second hand deals but sometimes you don't really know what you're buying.!
If you decided to buy one of these units, you're going to have available a LOT more modes than just SSTV, as I mentioned above in the section on Packet.
If you can afford them and you wanna experiement with extra modes, TNC's like the MFJ-1278B or AEA-PK232MBX are pretty good. They both cover Fax, SSTV, Packet, PacTOR, AMTOR, RTTY, CW and NAVTEX. They'll defnately have some newer TNC's out now, so, maybe contact them for prices and brochures on what products you want ?
The PK-232MBX uses a program called PC-Pakratt which is available for DOS and Windows, it's great !
The MFJ-1278B uses a program called Multicom wich is just as easy to use, although, from personal experience with the SSTV facility of Multicom on the 1278B I would not recommend it for SSTV - the images are received at a poor resolution, probably 400 x 300, compared to JVFax 7.0's resolution of probably 1024x768 ! The 1278B is great for all othe digital modes it offers, just in SSTV it needs some work.
I can't comment on the PK-232MBX's SSTV capability because I haven't seen it used. I've only ever seen the other modes used with it and it worked great. I saw Fax being used to receive Australian AXM and AXI Radio fax broadcasts from the Bureau of Metorology....perfect !! =)

You're choice if you wanna stay with SSTV/Fax or go with something more costly and have nearly every mode under the sun.!

SSTV Frequencies

11 metres:
27.600 +/- 50kHz
15 metres:

21.340 +/- 20 kHz
21.340 USB: Call chennell
21.350 USB is generally considered the end of the SSTV calling and contact frequency.
21.320 USB is generally considered the beggining of the calling and contact frequency
20 metres:
14.230 +/- 20kHz.

14.230.00 USB: Call channell
14.239.00 USB is generally considered the end of the SSTV calling and contact frequency.
14.260.00 USB is generally considered the beggining of the calling and contact frequency


Contacts, calls, and QSO's have sometimes been heard out of this area.
As usual, these frequencies may differ, depending where abouts in the world you are.

If anyone has any other frequencies that are used on HF, please let me know !

Some example SSTV pictures.

FSTV
Sample sounds (none yet)
General
Fast Scan Telivison scans pictures very quickly and for that reason it needs to be able to send enough frames per second to fool the human eye into thinking an image is moving - for this to work, we need a lot of bandwidth for all those frames. FSTV is like normal TV, you can take your video camera outside and film a new creation that you call an antenna - if you want, this footage can be recorded or sent live over the air to whoever is tuned to the same frequency, with the right equipment, and listening.!
If you're gunna ask "Could I make a TV station out of it?", yes, you can, in fact, there is an Amateur Radio Club in Gladesville, Eastern Australia that has it's own amateur radio TV station, which looks just like a commercial TV station if you went inside and had a look. Many amateur operators have really cool FSTV set-ups that are awe-inspiring !!
What do you look for?
A FSTV set-up is not as cheap as SSTV and since I am not experienced with it I can only give an opinion.
At minimum you'll need:
A video camera (camcorders are commonly used)
A TV
A TNC of some sort (?) and maybe even a computer to process images and make banners and stuff.
FSTV Frequencies

Good question ! I have not used it at all, I wouldn't have the slightest idea about call frequencies....sorry !
All I can tell you is that because of the bandwidth that FSTV demands for motion pictures, it is only used above 50 MHz !
Anyone know? please let me know so I can include the information here. Thanks.

CW
Sample sound. Sample sound. Sample Sound
General
CW is the abbreviation for Continous Wave - otherwise known as Morse Code...yup, that's right, the mode that is in the middle of all this controversey !!! Morse Code is a sequence of on and off pulses....dits and dahs....arranged in a pattern to make sentences.!
If you listen to the last sample sound you'll hear a common CW shorthand for end of signal - it's SK followed by a double dot. ie ooo-o- oo
I think CW is the best mode to get through bad conditions ! Unlike all other modes, including voice, CW has the ability to break through really bad conditions, if it's noisy with QRM or QRN or if there's QSB, th ol' code can stil get through where everything else drops it's bundle, and gives up !
CW can be sent by hand and received by ear or alternatively, by computer, although your brain is more effective at this once you get the hang of it ! I know some operators who can reach a constant speed of about 35 Words Per Minute !!!!! At the moment, I can only reach 7 or 8, but, practice makes perfect and I have full intentions of passing 10 word per minute morse receive to get my full license, even if the licenses DO change... =/.
There are a number of ways you can learn CW, get a hold of a study guide, which should be available from a club (local or interstate) or maybe your countries equivalent of Australia's WIA...I don't know, but, they are not hard to find !! Grab yourself some sort of magazine like Radio and Communications (you don't have to buy it....just get the contact details) and read the ads, probably more helpful to find an amateur around, a group of them, or a club. It is much easier to have other people help you than it is to learn by yourself.
If your an Aussie or your in Australia and you wanna learn morse code (or find out how to become an amateur operator), contact the Wireless Institute of Australia and see if they can help you, or if your in VK6, the NCRG (in Carine, Perth) holds exams on behalf of the WIA !!
What to look for
The TNC's already mentioned in the packet and SSTV sections can receivee CW ok, if the signal is good enough, but I reckon NOTHING can beat your brain for receiving CW !!!
If you want to use a TNC, that's fine....but you will get all the other modes with it !

CW Frequencies

11 metres:
27.450 to 27.680 USB
15 metres:

21.000 to 21.150 USB

20 metres:
14.000 to 14.200USB


Usually, the lower edge of any band on HF, although it can be found all over the place .!
VHF and UHF, I am not sure...sorry.
AMTOR Sample sounds. (None yet)
General AMTOR stands for AMateur Teleprint Over Radio. An AMTOR signal has the same types of bleeps and bloops that packet does, but, it's not quiet the same. It's very hard to describe AMTOR.
It is supposed to be one of the less stable ways to communicate in digital. AMTOR has no built in error detections when you're using it, you don't listen for signals from the receiving station that say "got that, ready for the next one" or anything like that...you just send ! , that's why the error rate of AMTOR is not crash hot unless signals are really good.
AMTOR doesn't have acknowledgement reqeusts, it just sends it's information and hopes the other station can hear it.! No "can you hear me" or "you want that message again?" messages are sent, it just sends..the same as what RTTY does !
What to look for Any of the above mentioned TNC's will do the trick.!
AMTOR Frequencies 11 metres:
27.600 +/- 20 kHz
15 metres:
21.000 - 21.150LSB
Generally below 21.150 LSB for digital on 15 Metres.
20 metres:
14.040 - 14.110 LSB -  but there is a lot of digital transmission on this area of 14 Megs, so, check it out.
Usually, any of the lower parts of the HF bands are good for digital, although....some are backwards..ie the higher part of the band has the activity :-)
Above HF, I am not sure about digital comms, for the simple reason that I don't live close enough to any other operators who have digital to know about it....will let you know when I do though.
PacTOR Sample sounds, Sample sounds, Sample sounds.
General PacTOR is a combination of Packet and Teleprint Over Radio. It sounds like crickets chirping.
This hybrid mode is supposed to VERY good for low signal communications ! It sounds like two Packet and AMTOR signals thrown together.! PacTOR uses packets error correction with AMTOR's message sending design to make it a very stable mode to use.
Although PacTOR is most common on 20 metres I have heard it used on other frequencies...hahahaha, even 27 megs !
I think PacTOR is the first mode to be smart enough to tell what skip conditions are doing and send at an appropriate baud rate to compensate and include more or less "did you get that ?" messages to the receiving station depending on the quality of the skip !!! Pretty cool eh !
What to look for Any of the above mentioned TNC's will do the trick.!
PacTOR Frequencies 15 metres:
21.000 - 21.150LSB
Generally below 21.150 LSB for digital on 15 Metres.
20 metres:
14.040 - 14.110 LSB -  but there is a lot of digital transmission on this area of 14 Megs, so, check it out.
Usually, any of the lower parts of the HF bands are good for digital, although....some are backwards..ie the higher part of the band has the activity :-)
Above HF, I am not sure about digital comms, for the simple reason that I don't live close enough to any other operators who have digital to know about it....will let you know when I do though.
PacTOR II Sample sounds.
General PacTOR II is a combination of Packet and Teleprint Over Radio with something extra added, I am not sure what it is. It sounds like crickets chirping with a head cold.
This hybrid mode of a hybrid mode is supposed to VERY good for low signal communications ! It sounds like two Packet and AMTOR signals thrown together.!
I dunno that much about PacTOR II, if the sounds I have been hearing on 20 metres (it sounds like PacTOR but there is a definate difference) are PacTOR then I better save my pennies and get a PacTOR II compliant TNC so I can have a look what it's all about.
I was talking to Ernie - VK6TN who has PacTOR / PacTOR II in his TNC (among the usual modes), he said it cost him nearly $2000 for that TNC, so I'll be saving those pennies for quite a while, even for a second hand unit ! =)
What to look for

I think you have to buy a special PacTOR II capable TNC (?), since none of the TNC's I know of can use this mode.

PacTOR II Frequencies 15 metres:
21.000 - 21.150LSB
Generally below 21.150 LSB for digital on 15 Metres.
20 metres:
14.040 - 14.110 LSB -  but there is a lot of digital transmission on this area of 14 Megs, so, check it out.
Usually, any of the lower parts of the HF bands are good for digital, although....some are backwards..ie the higher part of the band has the activity :-)
Above HF, I am not sure about digital comms, for the simple reason that I don't live close enough to any other operators who have digital to know about it....will let you know when I do though.
RTTY Sample sounds. (None yet)
General Commonly called Ritty, Radio TeleTYpe is similar to AMTOR, it has no error correction but if signals are nice and strong, no worries !!
Ritty sends a front porch, to say, "ok, I'm transmitting" but it does not send acknowledgement requestes, so, what you get is what you get - errors are there to stay ! There is also a back porch to tell the receiving station it's about to end transmission and in effect, swap control. Swapping control doesn't happen like it does with packet, you just hope that the skip hasn't died out and the other station can hear you so they can begin transmitting !
Although with the non-error correctig modes like RTTY and AMTOR you can see when the skip is fading cause received words and sentences become harder and harder to read with QSB. ie When the writing gets to the heirogliphics stage you know the skips gone !! =)
What to look for Any of the above mentioned TNC's will do the trick.!
PacTOR Frequencies 15 metres:
21.000 - 21.150LSB
Generally below 21.150 LSB for digital on 15 Metres.
20 metres:
14.040 - 14.110 LSB -  but there is a lot of digital transmission on this area of 14 Megs, so, check it out.
Usually, any of the lower parts of the HF bands are good for digital, although....some are backwards..ie the higher part of the band has the activity :-)
Above HF, I am not sure about digital comms, for the simple reason that I don't live close enough to any other operators who have digital to know about it....will let you know when I do though.
Fax Sample sounds, Sample sounds, Sample sounds
General Although HF Fax is used by amateurs, I have only heard it a few times being used on 14 MHz..about 14.250 !
HF Fax is similar to SSTV in one way - you can only send still images, like those from a camera.
It does have a front and back porch, and it's principle is similar to SSTV with send and receive, sync pulses and stuff like that.
HF-Fax is not only used by amateurs but, it's used by the Aussie Bureau of Meteorology (BoM) for sending HF Fax transmission so martime operators know what weather conditions are like ! There are a number of HF-Fax stations in Australia on different frequencies and they're all quite clear when the conditions are right !
HF-Fax's sent by the BoM are of various types -
AXM/AXI Schedules (so you know when to listen and on what QRG !!)
Information notices
IPS Recommended
MSL Prog
Australian Region Sigwx
Current Warnings
Sea Surface Isotherms......etc
Click here for the Aussie BoM AXI and AXM HF Radiofax Frequency and Time Schedule
There is also Weather Fax, used on VHF frequencies.
You need a 1.2 metre dish (minimum, depends on your location in relation to the satellite) or a GOOD Phased antenna array to receive VHF Weather fax properly and an azimuth and ele roatator attatched to your antenna so you can track the satellite as it passes,
a good VHF transceiver or receiver and of course an interface to decode the signal.and some high quality LOW LOSS cable to make the job complete.
if you're lucky enough to be in an area where you can receive VHF Weather (Wx) fax, you're in for a surprise. The amount of detail in a Wx Fax is unreal and what you can see is also very surprising at times.
One of the most useful things of VHF Wx Fax is the ability to spot cycones and fires and floods, without having to wait for them on the news, and since you're veiwing in near real time you can have a look at what's going on before anyone else even knows about it.!!
What to look for Any of the above mentioned TNC's will do the trick.!
HF-Fax Frequencies 15 metres:
21.350 LSB +
20 metres:
14.250 - 14.300 USB
Above HF, I am not sure about digital comms, for the simple reason that I don't live close enough to any other operators who have digital to know about it....will let you know when I do though.
VHF Wx Fax Satellites Frequencies Someone can fill me in here?, I am not quite sure and I don't wanna give people the wrong information.
ASCII Sample sounds. (None yet)
General ASCII is the acronym for American Standard Code for Information Interchange.
I do not know that much about RTTY ! I've only ever heard it a few times on HF and then the signal was very week and I could not get a good copy.
If anyone can share information on ASCII, please let me know ! Thanks.
What to look for Any of the above mentioned TNC's will do the trick.!
ASCII Frequencies 15 metres:
21.300 LSB (of what I have been told)
20 metres:
14.010 - 14.150 and 14.250 - 14.300 USB
Above HF, I am not sure about digital comms, for the simple reason that I don't live close enough to any other operators who have digital to know about it....will let you know when I do though.

Well, 'cause I have no experience with SITOR, NAVTEX or GTOR / Golay I can't give you a description of what they do...if anyone has a good description and links to boot, and they would like to send me a copy, please, let me know !!! Tnx.


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