For now this is a place holder
The N4SER digipeater is down but not out.
More to follow:
- how do i use it?
- what’s it l@@k like?
A VERY Brief History:
The rapid expansion of digital communications in amateur radio is all due to the increased computer capabilities and the software that has been developed to process the digital signals. Early on in the years prior to the personal computer RTTY was the only available digital mode (besides CW). RTTY used large mechanical teletype machines to create and decipher Baudot encoded text. Home brew interfaces connected the teletype to amateur rigs. At first these were very complex circuits with discrete components. The interfaces evolved with the electronics into a simple circuit using a 555 chip to encode and 567 chip to decode. A number of manufacturer’s sold interfaces, some quite costly.
The advent of the PC changed everything. In the early 80’s manufacturer’s began to create interfaces called Terminal Node Controllers ( TNC ) that connected the PC to a transceiver. Strange new words entered our vocabulary like AMTOR, Pactor G-TOR. A common mode, called Packet radio quickly became popular as Packet TNCs became readily available at reasonable prices. Amateur Radio U/VHF Packet networks sprung up all over the world, a precursor to the internet.
Somewhere the light bulb went off that every PC contained an analog to digital (A/D) converter; the sound card. The TNC was replaced by a simple, easy to build interface. The signal processing moved from a manufactured black box into the PC and the digital explosion was ignited. Widely used Packet networks quickly disappeared as the internet invaded every home.
PSK-31 was the first real popular non-TNC mode. It was invented by G3PL:X using a decidacted piece of hardware called a DSP (Digital Signal Platform). This was quickly replaced by all software versions utilizing the PC’s soundcard. The first programs used tedious tuning techniques that were more confusing then helpful. In 2000 along came a program called Digipan. It immediately became popular as it was free and very easy to use. Since then there have been numerous other digital modes and too numerous to count software applications to support them.
We’ll try to cover the more popular modes here:
FLDigi: (Free) This is one of the most popular digital mode software applications. it will encode and decode almost every digital mode. is easy to use and can be interfaced with a number of other applications such as N1MM the contesting software and DXLab the free logging program.
MultiPSK (Free) handles more digital modes than any other application, and it is free. Everything from packet to JT-6 can be operated using MultiPSK. The draw back is the user interface is pretty outdated and can be a bit intimidating. But if you want to run some of the less popular modes then this may be the answer.
Rtty, due to its age can be operated in two very different modes fsk and afsk.
fsk (frequency shift keyiing) utilizes a direct connection to a transceiver’s fsk port and various the frequency of the transmitter.afsk (audio frequency shift keying) utilizes your computer’s soundcard to generate the RTTY signal.Both result in identical (well almost) signals in the air and are interchangeable at the xmit and rcver ends.
MTTY (Free): MTTY is both a stand alone application for operating RTTY and it is an RTTY engine used by other applications such as N1MM. It is probably the best soundcard RTTY decoder available. It is very popular hams who are serious about RTTY.
Integrated Logging and Digital Software:
DXLab (Free): WinWarbler is a limited mode digital application that is included in the free logging application suite called DXLab. WinWarbler is not as savy as FlDigi. It can be run as a standalone digital interface or with DXLab. DXLab does support FlDigi through a third party bridge called FlDigi-DXLabs Gateway.
Ham Radio Deluxe (Retail): Digital Master 780 an ‘almost’ all-mode digital software application comes included in the HRD package. HRD is a retail logging application with a fee required to download and for support.
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Due to the nature of PSK it is imperative that you maintain a very clean signal.
Here are examples of a clean PSK signal and one with excessive splatter:
Clean narrow trace
extending out many kHz
What is the difference?
The Good trace is driven properly. The Bad is over-driven, the input level is too high.
Here is how to properly adjust your transmitter to assure a clean trace:
For radios without a power or ALC meter the adjustment becomes a bit more difficult as it is trial and error. Start with a level of 50% and ask the station on the other end how your trace looks.
When starting out or re-adjusting levels it is always a good idea to ask the other station how your signal (trace) looks.
What to do if you see a ‘bad’ signal?
In either case the ham with the wide trace is usually happy to hear about it. No one wants to put out an obviously poor signal.
73 and good trace!
Hi, welcome to Digital Communication, a brief tutorial on digital modes found on the HF bands. This tutorial is spread out over a number of separate articles (or posts and bloggers would say). Please explore them all.
In this article: Background, Equipment and Resources:
Over the past few years there has been a huge upswing in using digital modes on the High Frequency (HF) bands. This is due to the use of a computers sound card to create the digital encoding rather than the need for a dedicated external modem. This reduced the price to enter the HF digital world from $100 and up to practically nothing. (If you home-brew and have a pretty well stocked junk box).
Digital HF modems are still available, such as the TimeWave PK-232, but most have been replaced by software and your computers sound-card.
The sound-card digital era began with a new mode called PSK31 and has been booming ever since. It seems that a new mode or sub-mode is invented almost every month. Each has its advantages and disadvantages. Many are designed for a particular form of communication such as moon bounce. Regardless all are fun and can be enjoyed with a minimal investment.
Even the original digital mode1 RadioTeletype (RTTY) has had a resurgence. When PSK31 started to get popular the demise of RTTY was predicted. Well quite the opposite happened. RTTY moved from modem based into the realm of the sound-card and enjoys greater popularity than it ever did.
Here’s a list of what you need to get started on the HF digital modes:
A simple internet search for digital modes will fill pages of your browser. Here are a few that you may find interesting:
Note 1: Actually CW was the first digital mode after all it is only on or off.
This is part two of the series on Digital communications.
In this article: Background and a brief description of a few commercial interfaces.
In order to operate any of the HF sound-card modes there needs to be some means to connect your radio to your computer. There are three required connections:
Some operators claim they get away with direct wiring between the sound-card’s in/out jacks and the rigs speaker and microphone for #’s 1 and 2 but they are either lucky or do not realize they have a problem. For a successful interface the radio most be isolated from the computer … the grounds must not be directly connected. If they are then there is a very good chance you will create a ground-loop and that will cause feed-back and a dirty signal.
As for #3 above, some sort of logic line that can key the radio so it transmits when the computer thinks it should must be considered.Most I/Os use an optical isolator from a serial or USB port. Some utilize a VOX circuit. Either way you will need a way to key the rig.
Let’s see how we can make the computer and the radio work as one:
By far the easiest approach is to buy a commercially made interface to interconnect your radio and computer. These range in the area of $100 +/- and offer the ease of a quick connection and a nice piece of hardware to display on your bench. BUT wait a minute… I know you read the introduction that this could be done with minimal cost?? Well it can and we will cover a home-brew interface that you can build for just a few dollars. First lets explore the quick and ‘easy’ way.
Manufactured by Tigertronics (www.tigertronics.com) , this is probably the most popular interface, at least in this area of the world. This Interface (I/O) connects directly to a USB port and does not require a sound card. Custom cables are available to connect it to various radios. The unit is small, contains volume controls for both audio signals. To change radios you must change the cable.
Price range is $110 includes one radio cable.
West Mountain RIGblaster line
West Mountain Radio (www.westmountainradio.com) manufactures at least three different digital mode interfaces. They range from the Nomis to the Pro and have a variety of features. The prices range form around $60 to almost $300. Any further discussion would be beyond the scope of this tutorial Visit the West Mountain site. They have a vey nice comparison chart that shows the capability of each of their interfaces.
BUXCOMM (www.buxcomm.com) offers a couple of lower cost interfaces.The one shown hare, the RASCAL Mk III+, is unique in that is does not require a USB or serial I/O on your computer. It utilizes a VOX circuit that senses audio on the computer sound-card output port (speaker). BUXCOMM also sells a more traditional I/O called the RASCAL GLX.
Price range is around $70.
EASY DIGI sound Card Interface.
This unit is as simple as an interface can get. If you were going to make one on your own it would be very similar to this unit. For the price you could not m,make one like this including the USB to Serial adapter. The EASY DIGI is available at times from e-Bay from cliffordwareham. If you are considering a home-brew I/O, which your Elmer highly recommends then this board would be a good place to start. Add a couple of volume controls, an on/off switch and you have a perfectly good I/O.
Note: There are a couple of different interfaces being sold under the name EASY DIGI. Each has slightly different features.. worth looking into.
Price was less than $25
Other Commercial Interfaces
There are other commercial interfaces on the market. This is by no means a complete list nor does it imply any endorsement. Your Elmer owns a very old PK-232 from pre-sound-card days that is collecting dust. All of his other computer to rig I/Os are home-brew
A quick search on the internet should give you quite a list …
This is part three of the series on Digital Communications.
In this article: KK7UQ the Gold standard, Why it is a good design, Changes, Simplified Schematic, Bells and Whistles
The Gold Standard (KK7UQ Interface Model II):
A number of years ago Clinton Hurd (KK7UQ) designed and sold this interface as a kit. It was easy to build and fit very nicely into an Altoids box. Unfortunately the kit is no longer available. Here is a copy of the manual (KK7UQ Interface manual) it includes a complete explanation of the circuit and the interesting radio to interface scheme he uses. Your Elmer has one of these original kits and has created a modified (simplified) version used for portable use.
Why this is a good interface design:
This schematic is the starting point for just about every digital interface. It can be constructed on a small piece of perforated breadboard and have shielded cables connected to the radio and computer.
Radio Connections can be to the speaker jack and microphone jack or preferably to the radios accessory jack. This allows use of the radio’s speaker and microphone and will provide a constant level signal from the radio to the computer. Most modern radios are equipped withe some form of an accessory jack where audio in and out are available.
Bells and Whistles:
For a single radio / computer installation the circuit shown above, hard wired to the radio and computer will make the perfect digital interface. The circuit described in KK7UQ’s manual has a few additions that just may interest you: