GRBAlpha - How to use digipeater or DNxD - 12. To use DNxD

DNxD is the "Delayed Needronix Digipeater".

A normal digipeater responds immediately after you transmit your message to a repeater like as I mentioned in this blog just before. (See "GRBAlpha - How to use digipeater or DNxD - 11. To use digipeater".)

DNxD is different from that. "Delayed" in the name means you can set the delay time that your message will be transmitted after you send it.

It is very easy to use DNxD system. You only add "@xxx " ("@", 3 digits, and a space; "xxx" are 3 digits how many minutes you want to transmit your message after you upload it.) in the beginning part of your message.

When you want to send your message after 90 minutes, prepare your message like as "JI1IZR>CQ:@090 Hello from Japan, my GL is PM95pi". 

GRBAlpha replies "OM9GRB-8>JI1IZR:Your message will be retransmitted in 090 minutes, thank you for using Delayed Needronix Digipeater (DNxD)!" when GRBAlpha catches your message.

After 90 minites, GRBAlpha will transmit a message like as "JI1IZR>CQ,OM9GRB-8:@090 Hello from Japan, my GL is PM95pi". This message will be transmitted 3 times with 1 minute interval.

I recommend you that you include your Grid Square Locator in your DNxD message as a receiver of your message can caluculate how long delay he/she needs to set in his/her DNxD message in the response message for yours.

Please notice that the DNxD keeps only 1 message. If someone has already uploaded a message in DNxD, you will get a response from GRBAlpha like as "OM9GRB-8>CQ:Delayed Needronix Digipeater (DNxD) is busy for next 001min(s). Try later." 
when you transmit your DNxD message.

Even when DNxD is busy, you can use normal digipeater on GRBAlpha.

GRBAlpha - How to use digipeater or DNxD - 11. To use digipeater

When we use a digipeater, we usually set a via station. So you may think you have to set "via OM9GRB" when you use GRBAlpha digipeater. But you need not to set "via" in the case of GRBAlpha.

You only have to transmit your message like as "JI1IZR>CQ:Hello from JAPAN, my GL is PM95pi" in AX.25 format on 437.025MHz (+-doppler) while GRBAlpha is in your visible site. When GRBlpha catches your signal, it responses like as "JI1IZR>CQ,OM9GRB-7:Hello from JAPAN, my GL is PM95pi" at once after you transmission. The response is only one time.

When you want to set a destination station, for example "JA1AAA", prepare your message like as "JI1IZR>JA1AAA:Hello DE JI1IZR". In this case, GRBAlpha responses like as "JI1IZR>JA1AAA,OM9GRB-7:Hello DE JI1IZR".

Please do not try to transmit several times in a short period. Listen for a while after you transmit your message. Someone may catch your message and try to respond to you. If you cannnot get any response from GRBAlpha, I recommend you to check your settings as I mentioned in this blog before.

GRBAlpha - How to use digipeater or DNxD - 10. About sampling rate

When you use a software modem like Direwolf or Soundmodem, you may have difficulty to decode signals. As I mentioned in the Section "06. RF & AF input level", you need the signal level as more than S2. Even when you get this level, you do not have enough result. In this case, try to check your settings about sampling rate.

In case of Windows system, you have to check the system sampling rate at first. Open the control panel of sound on your PC, then check  the detail property of microphone, line-input, line-out, and speaker. You will find the sampling rate there like "16bits, 48000Hz".

The sampling rate should be "48000Hz" at least in case of 9600bps. My Ham friends, JA0CAW and JA5BLZ, pointed me it out.

Additonally, I recommend you to set the sampling rate of Direwolf or Soundmodem as more than 48000Hz.

In case of Soundmodem, set the "TX SampleRate" and the "RX SampleRate" as "48000", or more, in the "Settings" window of "Sound Card" that I mentioned in the Section "07. Settings of soundmodem".

In case of Direwolf, add "ARATE 48000" in the "direwolf.conf" file like as:

#############################################################
#                                                                                                                      #
#                               FIRST AUDIO DEVICE PROPERTIES                          #
#                                        (Channel 0 + 1 if in stereo)                                   #
#                                                                                                                     #
#############################################################
ARATE 48000