Automated Transverter Band Switching in VHFLOG and KM Rover
Win7 and Win8 Band Switching is supported using a CanaKit UK1104 USB Controller.
Important note: A 12V/1A power source and J1 at position B is required for relay operation.
Frequently asked question:
Why not have an interface between the station and VHFLOG to automatically change bands?
A: Done! Stations may have multiple radios and multiple transverters with or without
transverter switchboxes. Stations may have separate radios for FM or single band
stand-alone radios that don`t get switched.
I decided to provide computer control in the direction that would get the widest usage,
from the computer to the station. The easiest solution is to use a band decoder
connected to the computer, that `switches in` the transverter of choice. When you
change bands in VHFLOG or KM Rover, the decoder`s output will also change. This type
of switching is used by HF operators to automatically switch to the proper antenna
when changing bands. Important note: See #4 below.
Control in the other direction (radios change bands in the logger) is difficult because
of all the station configuration possibilities and the fact that the loggers do not have
CAT radio control.
The decoder I used to test the software was the original Top Ten Devices band decoder.
The new Band Aide decoder should work as well. Steve Kerns, N3FTI designed a VHFLOG LPT
Interface (BCD to relay contacts) that allows 10 bands to be controlled by the logger.
N3FTI is on qsl.net or n3fti at yahoo dot com. Note that the decoder ground is LPT-18.
Once you get the decoder wired into your station, it can be used in the manual mode to
select transverters without using the computer. This type of computer control does not
care what IF radios you have, what the station configuration is or what transverter
switching schemes you implement.
Regardless of the configuration, you need an `auto position` added to your current
setup, so the decoder can take control.
1). If you have a transverter switch box that uses a wafer switch going to ground to
activate each transverter, the output of the band decoder can provide the same ground.
The decoder is wired in parallel with your existing wafer switch.
2). If you have control relays doing the switching from toggle switches, you can wire
the decoder outputs in parallel with the toggle switches.
3). The original TopTen decoder box has 6 positions manually selectable. It would be easy
to replace the wafer switch with a 3 section wafer switch with 3 more positions, so you can
select the other 3 bands not available in the manual mode. For the added 3 positions, just
wire the decoder output lines 7, 10 & 11 directly to the wafer switch, with the common leg
of that wafer connected to ground.
The band decoder connects to the PC`s parallel port with a standard 25-pin printer cable,
and receives BCD band data generated by the logger. The decoder circuitry converts the 4-inputs
to 9-NPN outputs that can sink 500mA to ground. The nine 160-10m positions of the decoder are
equivalent to the VHF/UHF bands from 144-10368 MHz, if your switchbox control circuitry selects
6m as the default band. The logger has encoded outputs on all bands.
4). Important consideration: Keep in mind that when you are talking on a band and you type
a new band in the logger, this will cause your switchbox to change bands. When moving stations
up the bands, it is easy to forget and change bands before we are done talking. This not only
leaves the station `hanging` - but also moves your signal to another frequency where a QSO may
be in progress.
This also causes Hot RF switching that can cause damage to amplifiers, relays and preamps.
A lock-out circuit using a data latch chip and transistor latch enable circuit must be
added to your auto transverter switchbox to prevent the transverter band switching unit
from changing states if one of your transverters is keyed. The lock-out chip is a BCD latch
that stores the BCD input data when a transverter is keyed. If only one IF rig is used, then
only one +V signal (from the IF radio) is required into the latch transistor.
Problems getting the decoder to switch? Use LPT pin 18 for the ground connection. Verify
that it works with 5V at the BCD inputs. The connections and truth table are here.