Winlink Express offers the ability to use all of their radio modes over FM channels, and 50 MHz and 29 MHz FM offers point to point communications that were required. Antennas are small enough on both bands that they can easily be made with any locally sourced wire.
These issues lead to some experimentation in Luzerne County, PA ARES using Winlink Express and FM modes on 2 meters. While 2 meters was used, 6 or 10 meters would have been equally effective. At first attempts were made to establish AX.25 1200 baud packet. Winlink Express allows hardware and software modems to be used. I was able to establish links using a Kantronics 9612, SCS Tracker, and SCS DR-7800. The most difficult issue was discovering the COM port as well as the proper baud rate. The 9612 used a 4-way FTDI chipped Serial to USB adapter. Finding which input (it was #2) was the first challenge, and then setting the comms baud to 9600 on the COM port listed in device manager. This modem worked at both 1200 and 9600 baud as it is a dual port modem. The SCS Tracker is a natural USB connection and used 38400 Baud at the listed COM port and was relatively easy to install. The 7800 used 57400 Baud and was also easy to set up in Winlink Express. Both of these modems are capable of high speed links, but setting the deviation of the radio at these speed as well as the very high signal quality required makes working these speeds difficult.
To send local email in Winlink Express, open up the Packet P2P session and go to the settings option. There is a drop down menu for they type of modem. You can just enter the modem type, add the COM port and Baud rate, and then hit “update.” This should enable the modem without changing any other settings. Type in the target station, even through a digipeater, and the monitored frequency and hit the connect button. This should start the exchange process which will work without further intervention from either user.
The cheaper TNC option is the use a soundcard modem for packet. I use the SoundModem by UZ7HO. In this program you set the radio to AFSK AX.25 1200 Baud and a center frequency of 1700. In the Settings Devices menu, first you select your input and output devices. The settings for an external soundcard device such as a Signalink or built in soundcards in a radio will be the USB codec setting. If you are using the computer’s soundcard, you will probably will keep them at the default. You have to uncheck the AGWPE Server Port and check the KISS Server Port of 8100. Also you should check TX Rotation, Single Channel output, Color Waterfall. The PTT settings depend highly on your controller. Using the Signalink controller, you keep the PTT port to NONE. If you are using a COM port keyed PTT as many Rigblasters do, you need to set the COM Port properly. In the settings Modem, you keep the default modem filters for Channel A, check the ALL filter, and check KISS optimization and non-AX25 filter. Keep the program running, either in a window or minimized. I prefer the window open to monitor the packets and waterfall.
In Winlink Express, open up Packet P2P window and go to the settings. Use the modem drop down menu and select KISS. For COM port you need to set it to TCP which will open up boxes for the IP address and Port. Keep the default IP address of 127.0.0.1 and select port 8100. Switch the TNC mode from NORMAL to ACKMODE. Keep the TNC parameters at the default but check Enable IPoll. Hit update and it should give you the ready command in the main box.
The trouble we had in the Luzerne County experiments was using Packet in general. The signals were strong, but 30-50 watts was required to make links. Due to our location, RF was bouncing off the hillsides like a pinball and there was significant multipath. AX.25 fails completely in the presence of multipath and we had link establishment failures no matter what modems were being used. Also, high power isn’t conducive to field operations. A better solution is required.
The first option we explored was Winmor 1600. This is designed as a HF protocol, but can easily fed into an FM circuit via a soundcard. A 3 KB email was exchanged at 1574 Bytes/minute using the fastest mode. Unfortunately, the overhead packets are sent at much slower speeds. The big advantage in using Winmor is that there is really no set up required, the default settings in the Winmor P2P window worked flawlessly. This makes it very field deployable with little training required. Using this mode on 10M FM in Puerto Rico would have been the way to go. One caution is when using Icom HF/VHF radios, the 2M FM side of the radio uses a dedicated VHF PTT pin, so the cable will need to altered or replaced. This is not an issue with Yaesu. I do not know about other brands.
LCARES makes extensive use of the FLDigi suite of programs. FLARQ offers an email function through FLARQ, but the email program is very primitive and not as intuitive as Winlink Express. The next stage of this experiment is use the high speed modems in FLDigi to move email from Winlink Express. Fortunately you can set up FLDigi to accept KISS inputs, so after adjusting settings, you can set the data packets over FLDigi modems.
In FL Digi go to Configure, Miscellaneous, IO. Uncheck “Lock” then check Enable KISS (NOTE: THIS WILL DISABLE FLARQ as it can only work as a server for ARQ or KISS.) Check TCP/IP, Listen/Bind AX25 Decode, Auto Connect/Retry, and Inhibit 7bit modem. I set the IP address to 127.0.0.1 Addr to 8100 I/O and 8101 O. Next hit save, and restart FLDigi (the port settings will only take effect when you restart FL Digi.) Select the modem you wish to use. Since it’s an FM circuit, you should use modes like 8PSK1000F or 8PSK1200F. The key is that you cannot use 5 or 7-bit modems as it is 8-bit data being moved. Due to the turn around times required for KISS packet exchange, most of the FLDigi modes can’t be used, as their preambles are too long. For best results use 8PSK1000F. I turn off TXID as the header will be sent with every TX and greatly slows the exchange. Have a pre-determined mode and center frequency (1500 is good for the fast modes) monitored on both sides of the link I also turn off AFC and SQL in FL Digi. RXID can be on or off. Leave FLDigi running.
In Winlink Express, open Packet P2P Go to Settings. The settings need to be changed due to the nature of the modems. For TNC settings on 1200 baud the following were used:
Max Packet length 64 (standard 128 bytes takes too long and the Rx station attempts to send the ACK before the packet has been transmitted. This was a major stumbling block for us)
Max Frames: 2 (same issue as above 4 frames only work with AFSK packet)
Slot time 30
Max Retries: 5 (this is up to the user, but for FM, it shouldn’t need to be any more)
You can now establish the link with the FLDigi modems. Just like Winmor, this should fight multipath far better and require much less power. During our testing, when we needed 30 watts for packet, we could reduce power to 5 watts for Winmor link with no loss of speed.
During testing we actually found 8PSK1000F a bit faster than the 1200 baud variety, even with no packet repeats. Throughput for data on 1000F was 2277 Bytes per minute, while 1200F was around 2100 B/Min. I am at a bit of a loss as to why this is, unless the 1200F uses more check bits and therefore fewer data bits per packet. Both of these modes were significantly faster than Winmor 1600.
Testing was done on 2 meter FM simplex at a LOS distance of about 10 miles. Antennas were base models, but not directional and full scale signals were received at 5-10 Watts.
In conclusion, the proof of concept works, and there are several ways to move P2P mail between stations on VHF simplex. The choice of modes will depend on the link scenario and equipment available, as well as the skill of the operators. Cost for the basic setup is minimal, requiring only a radio with antenna and soundcard interface, but it will take some dedication to set up and use the equipment. This system will not replace the excellent multi-point broadcast capabilities of FLDigi (especially in conjunction with FLMsg and FLAMP). This is another tool in the box, but probably will be on a lower shelf.