Sunday, 22 January 2017

FTM-100D Dual Receive Function

Many amateur radios that have multiple "Bands" such as Band A and Band B have multiple receivers built in. This allows each band to receive a different frequency and share a single transmitter. This makes dual mode operations such as APRS on Band A and half duplex voice operation on Band B quite easy to do. Some, such as the Kenwood TH-D7 have two transmitters allowing them to do full duplex. It appears (I have to admit I'm not fully familiar with the radio yet) that Yaesu built the FTM-100D with only one receiver. At first this seems like a limitation, but modern digital receivers can switch frequency very quickly simulating more than one receiver. In this post I will talk about using this capability to operate APRS and work the repeater at the same time. The procedure could be used to do something simpler as well, such as work one repeater and monitor another.

If you are going to use this procedure to work APRS you should have APRS configured on your radio before you proceed. You can use this post to get started.

The Dual Receive Function utilises the Band Home memory and any other frequency either from memory or using the VFO. So the first step is to program the repeater into the Home memory for the Band you are going to use, I will use Band A but you can use either A or B. Setting the Home memory frequency is covered on page 54 of the manual but the steps are:
  1. Switch to VFO mode and Band A.
  2. Tune in the frequency you want, and set up any other operating settings you want (PL tones, etc).
  3. Press and hold V/M MW for over one second. The Memory Write screen appears.
  4. Rotate the dial to select Home.
  5. Press DISP Setup. The overwrite confirmation screen appears.
  6. Rotate the dial to select OK, and press DISP Setup.
Now you should tune in the APRS channel. If you have programmed it into a memory location for Band A you can enter Memory Mode rotate the dial to select that memory, if not you can enter VFO Mode and enter the frequency manually. Now press the A/B DM button for more than one second. The band display will change from MA if you are using a memory location or just A if you are using the VFO to DA indicating you are in Dual Receive mode. Periodically (every 5 seconds by default) the receiver will quickly switch to the Home frequency to see if there is any activity. Dual Receive mode is covered starting on page 70 of the manual, including how to change the 5 seconds.

One thing to be aware of. When using this for APRS beacons will be transmitted when it is time as determined by the APRS software and the receiver doesn't detect activity regardless of what frequency the unit is actually tuned to. If you get involved in a QSO you may end up transmitting a beacon on the repeater frequency. Not the end of the world, but also maybe something that you don't want to do. An easy way to prevent this is to have the Home frequency stored in a memory location in the other Band (Band B) and have that Band set up to work the repeater. Then by switching to Band B for the QSO the APRS and Dual Receive operations will be suspended until you switch back to Band A.

Another is that if you use APRS Muting from page 59 of the radio APRS manual you won't be able to hear the activity on the home frequency. This is because this is APRS operating band mute and all activity on that Band A or B will be muted. I think we are better off using the voice alert procedure from anyway.

This may seem a little complicated, but I've used this to operate APRS and have had QSOs with a couple of people and it is easy to do once you have practised a bit. So if you want to operate APRS without dedicating the radio to that, or just want to monitor one repeater while you work another give this a try.

This YouTube video may also help although this video shows setting the "APRS" frequency as the Home station, but I don't think that is the base way to do it.


FTM-100D Using APRS

This is the first is a series of posts describing what I have leaned about using the FTM-100D dual band C4FM/FM transceiver from Yaesu with a Fusion repeater. The first thing you need to do is download the APRS manual for the radio from the Yaesu web site.

I found setting up APRS by following the manual was quite simple. The radio defaults and the settings the manual guides you through will get you up and running on APRS quite quickly. In fact by the time you get to page 12 you should be beaconing. You can then go through the balance of the manual to set the radio up just the way you like it.

Here are a number of recommendations I have:
  1. You can use the built in GPS for position, or set the position manually. The GPS works very well, even in my home office surrounded by computers so I recommend using it. If you are in a building where the GPS signal is poor you may have to set it manually.
  2. Our digipeater, like most, is 1200 baud.
  3. Don't use the APRS Mute setting, more on this later in the series. APRS.Org recommends using CTCSS tone of 100.0Hz. This keeps the digital traffic quiet but allows the APRS frequency to be used as an alternate calling frequency when you see someone you want to talk to has wandered into simplex range. This is easily configured on the FTM-100D. Using Setup go into APRS then option 25 VOICE ALERT. Set VOICE ALERT to RX-TSQL and TONE SQL to 100.0 Hz. See page 78 of the APRS manual.
I have found the radio performs APRS beaconing very well. The receiver and demodulator seem to be quite good at picking up weak signals and transmitting on low power allows me to reach digipeaters that are quite farm from my home. It is also very nice to have everything you need to start working simple APRS in one rig without managing several devices and the associated cabling. So go get your FTM-100D on the air beaconing and enjoy.