Split Station

Topic notes for January 21, 2019 (KC7MM, NCS)

1. For a fixed station, the best location for the radios and antennas sometimes is not the best spot from which to operate them.
2. When travelling away from the station, the capabilities of available radios and antennas are generally lower, compared to those of base stations. The lower the frequency, the more this so.

• Divide the station into functional parts, each self-contained and optimally located:
  • Radios and antennas: all the RF components.
  • Controls: all the operator functions.
• Connect them together through some manner of communications link:
  • LAN (WIFI, Ethernet)
  • Mesh
  • Internet
  • ???
• Requires interfaces on each end of the comm link. The general setup:

[Controls] <-> [interface] <-> [comm link] <-> [interface] <-> [Radios]

• Electricity is available from our home solar system, which includes battery backup
• Near the home’s electrical entry, with its ground system.
• There are two openings through the roof that can be used for transmission lines.

• I have another room that is more suited to setting up a comfortable and functional place.
  • It’s more comfortable, and isn’t isolated from the main living area.
  • I has sufficien space for a complete station.

• Ideally, the operating desk would work identically to a single-site station, with all the normal control. That is, it would not be an on-screen computer simulation. I want tactile controls such as tuning dials and CW keys.
• I would like to be able to operate from anywhere in the house, should the need arise. I’m getting old and already have some mobility limitations, which can only get more restrictive as time passes. I want to be able to have my station come to me, if necessary.

The technology to do this sort of thing already exists — witness the remote stations available for use over the Internet. The interesting challenge for me is how to scale that to my needs so that I can both implement it and afford it.

To my mind, SDR makes it a realistic goal — one that can be achieved.

• When the radio is a computer with standard interfaces, it can be treated as just another node on a digital network.
• I expect that all new radios will be SDR within a short time, now that it can be done relatively inexpensively. (Witness SDR QRP rigs available for less that a hundred dollars.) Radio will go the way of audio, printing, photograpy, and so many others.

• Employ proprietary interfaces
• Interfaces are inconsitent between products from the same manufacturer.
• Rely on outdated digital technology (e.g., RS-232) for computer connectivity.
• Windows-based control software predominates, even for SDR — Flex, Icom.

• Much commercial software is written in Microsoft’s .NET languages, which doesn’t compile to Linux binaries, and is difficult or impossible to get to run properly under WINE.
• Proprietary vs. FOSS

• Digital-mode software developed for Linux: fldigi, WSJT.
• There are Linux implementations of useful types of software potentiall useful for split-station operation.
• The popularity of the Raspberry Pi is a powerful force inducing people to use and develop for Linux.
• SDR client software: gqrx, Cubicsdr, rtl-sdr, Osmo-sdr Debian SDR package list

• hamlib library with language bindings (Python and others)
• GNU Radio with language bindings (Wikepedia)

• Preference: use radio, on Ham frequencies if possible.
• On a network, possibly use VNC for remote operation of a station computer.
• Legality question: can control signals be encrypted?

This would be nice, as it would make the entire system Amateur Radio. There are Amateur frequencies on both WIFI allocations of the 3 and 5 GHz bands.

• AREDN
• HSMM-MESH Doesn’t appear to be active

• WIFI
• Ethernet
  • Use rtl_tcp to send data over LAN. Dongle connected to NSLU2. HERE This could be used in a split-station scenario.
  • Using the Raspberry Pi as an RTL-SDR dongle Server
    

• RemoteRig

• Internet
• Cell phone or POTS?