Dstar Blog

March 16, 2011

What’s in a Word?  Everything!  An old pseudo-scientific puzzle often thrown out to physics students goes like this:  If a tree falls in the woods, and nobody is around to hear it, does it make a sound?  This question has created more arguments over the years than the “chicken/egg” quandary.  But there is really no reason to argue as it is all in the definition of the word “sound.  If something disturbs the air around us at a rate between 30 and 20 kilo-Hertz, the sensitive mechanism in our our ears will detect that.  We call that “sound” so therefore, no ears, no sound.

A similar question came up at the meeting last night.  In a discussion about the digital modes, the question was asked “is CW digital?”  The presenter opined that indeed it was and intimated that even older forms of communication were digital.  How about smoke signals?  Semaphores?  The midnight ride of Paul Revere; one if by land, two if by sea?  Yep, all digital.  From a well phrased definition of Digital one can go to Wikipedia and find this:  (Digital data) is a data technology that uses discrete (discontinuous) values. By contrast, non-digital (or analog) systems use a continuous range of values to represent information. Although digital representations are discrete, the information represented can be either discrete, such as numbers, letters or icons, or continuous, such as sounds, images, and other measurements of continuous systems.

The confusion comes in, if in fact you are confused, when we picture “digital data” as looking like this:  11001010010100101001010010100101011110010100101010101010.  That’s the stuff that computers look for, and is binary code, possibly describing some discrete data, or maybe not.  The difference between that line of code and a short sentence in CW is that this has been “quantized”, and CW sent so it can be understood by a mortal, has not.  Quantizing is the act of stopping a continuous range of values (analog), measuring it on a known scale, then assigning a number to it.  A typical range might be 128 positive and 128 negative.  If we do this, let’s say 8000 times per second, we can store those values in a binary code and then later use that code to restore the original range of values (decode).

So it’s all in a word:  Is CW digital?  Sure.  Does it sound like dah di dah dit dah dah di dah or does it look like 11010010100110000010101001100101010000?  Quantize it and let your computer do the work

March 12, 2011

Triggered by the disaster in Japan, there has been some discussion about communicating with Japanese hams using Dstar.  A number of people asked about using a particular reflector for this purpose.  One knowledgeable ham says “uh-uh, you can’t do it because Japanese hams don’t have dplus so they can’t use reflectors.”  Well, true enough in one sense; they don’t have dplus but that doesn’t stop them from using reflectors.  Here’s how:  From the heard list, you can easily find a ham in the area you want to communicate with.  The heard list will show you which repeater that ham is using so you simply slash route to it.  Let’s say the Japanese ham wants to talk to K6XYZ who is on K6MDD-C.  He sets his UR to /K6MDD   C and makes his call.  K6XYZ will hear him and so will everyone listening to K6MDD-C.  Not only that, but if K6MDD-C is linked to reflector 014C, which it usually is, everyone on every repeater on 014C will also hear him.  Now K6XYZ can’t just talk….He has to do a one-touch which will put the Japanese op’s callsign into his UR.  Now, K6XYZ is using call-sign routing, the Japanese ham is doing slash routing and everyone else is able to listen.  If anyone else wants to be heard in Japan though, they must also push the one-touch.  The above applies to RF only.  If the Japanese ham is using a dongle* then it’s as if he were here in the US.

* no DVAP operation in Japan

 

March 3,2011

Someone asked the question: “Where is [a certain] repeater located?”  One way to find out is to ask the owner or the admin but that person’s identity is not always apparent.  Another way is to simply look up the repeater on http://aprs.fi .  In the search box put in the callsign including the module, for example w6co-b.  The location may be displayed on the aprs map depending on whether or not the admin entered the information during setup; most did.  If you are familiar with the W6CO site you may notice that the location is close but not exact – this is for obvious security reasons but most repeaters installed in secure locations will display the information exactly.

***

Here is some late breaking news on “DR Mode”,  which has been driving people nuts since Icom released the IC-80 and the IC-880H. To get the whole story search on Dstar Tutorial on this site.

To recap briefly, DR Mode can be a very useful feature if it is employed in a portable or mobile situation where the operator is likely to be using several repeaters. It allows the operator to change only the UR field instead of requiring changing the entire record (memory slot). This greatly simplifies programming the radio but is of lesser value if the radio is used in only one location.

The problem with DR mode however, is it was designed to be used in callsign routing, not in the Dplus environment. Icom’s standard says that if you use CQCQCQ in the UR, you must be operating locally and do not require the gateway. After all, if you wanted to use the gateway wouldn’t you have a valid callsign in the UR? So the firmware logic says “If UR=CQCQCQ then R2=Not Use”. So the thing that had been causing frustration in programming is you would put CQCQCQ in the UR and set both R1 and R2 the way you wanted them only to find that R2 had been erased. The work-around then, was to use something other than CQCQCQ in UR. Something such as DRCQ or DR-CQ and so on. This works just fine except the UR shows up on Dplus Logs and Dongles and DVAPs causing some head scratching for the uninitiated.

So here is the latest scoop from Kay Ishikawa, JI1BQW who was on the Dstar development team.

(I have tested this and it does work although I bet you can’t do it on your first try.)

<begin quote>

Go to DR mode

Select a repeater.

Long press the UR button (select CQCQCQ from your Callsign List) *

Select GRP UR (instead of GRP CQ) by pressing Band button.

Long press UR and select GW instead of NOT USED.

Press DR Button to return to DR Mode.

This works very well and also go out on any gateway connected to that system

You can also check to see if RPT2 is in fact set by pushing and holding CS button on the IC-80, on the 880 you just push the CS button once without holding it.

Rotating the knob on top of the HT the display will show:

CQCQCQ for UR

XX4XXX C for RPT1

XX4XXXG for RPT2

XX4xxx for MyCall

123.456 for Frequency

Push CS again to return to DR Mode. Don’t get confused with CQCQCQ in GRP CQ which does not allow you to set RPT2. *

<end quote>

This last sentence is key. Also, what Kay is not saying is you are unlikely to have CQCQCQ in your callsign list. You need to put it there before you even start.

When you get it working, you will find it works as well as having a Psuedo call such as DRCQ or Voice or whatever, and it will no longer confuse DVAP and Dongle users.

I have heard numerous people inquire about DR mode and what the purpose is. The stock answer is “If you travel to other repeater areas, it lets you change your UR quickly.” The response is usually something like “Well I have all those repeaters programmed into my radio and I don’t have any trouble changing repeaters.” This misses the mark. The best reason is it lets you program all those many repeaters with only a single record (memory slot) per repeater/module. If you don’t use DR mode you need a separate record (memory slot) for each function you might use; eg I,E,U, REF001C thru REF037 for each repeater/module!. That’s a whole lot of programming!

I guess if you don’t ever use a “command” then it doesn’t matter.

How does DR mode compare to non-DR in a radio such as a IC-92 in terms of button pushes?

IC-880H: One push and one dial rotate.

IC-91AD : One push and one dial rotate (using the CQ button) or 3 button pushes and one dial rotate (using the menu button)

73, more later n6xn

n6xn

About n6xn

It all started in 1968 at a small 100 Watt radio station in Napa California. Looks like I finally got my priorities straight: the career is on the back burner and the K3 is getting some air time.
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