Background:
When interfacing a FlexRadio with third-party amplifiers or transverters, three essential connections must be made between the radio and the equipment:
1) An RF connection between the radio (exciter) and the amplifier or transverter.
2) A PTT line between the radio and the amplifier or transverter.
3) Some amplifiers and transverters can receive band data from the exciter. Usually, band data can be sent to the amplifier via a CAT, BCD, or Pin-2-Band connection. If this capability does not exist for your amplifier or transverter, utilize manual band switching or rely on the device's automatic band switching or "RF SENSE" feature.)
For this article, it is assumed that items 2 and 3 have already been addressed and are properly configured. And the exciter is a FLEX-6000/8000 using the latest SmartSDR for Windows software.
Connecting PTT output from a FlexRadio:
The FLEX-6000/8000 Series Radios utilize several RCA connectors on their back panels for keying amplifiers and transverters.
PTT: This is PTT IN to the radio for use with a Foot-Switch, Thumb-Switch, or the PTT line from compatible microphones. This connection is not used for a PTT OUT to your external devices.
RCA TX, TX1, TX2, TX3: These RCA connectors send the PTT OUT signal to amplifiers or transverters.
The FLEX-6300 only has one RCA connector, labeled TX.
Other FLEX radios have three RCA connectors labeled TX1, TX2, and TX3. This allows you to connect up to three separate devices; for example an amplifier and two transverters, or two amplifiers and a transverter, etc.
The TX BAND SETTINGS table:
After properly connecting the PTT Lines, it is important to configure SmartSDR to control the PTT lines.
SmartSDR for Windows controls the switching of the RCA TX, TX1, TX2, and TX3 ports independently on a per-band basis. These settings are configured in the TX BAND SETTINGS Table, which is associated with a Transmit Profile.
Open the TX BAND SETTINGS Table from SmartSDR for Windows: Open "Settings > TX Band SETTINGS." It will open the table.
Using a mouse, place a checkmark in the column for the desired RCA Port for each band on which you want that port to send a PTT signal to your amplifier or transverter.
In this picture, the RCA TX1 line is configured to key the connected device on the bands: 160, 80, 40, 20, 17, 15, 12, 10, and 6 Meters. (This would be necessary for most modern amplifiers) 60 and 30 Meters are not selected due to power restrictions on those two bands that preclude using an amplifier in most cases.
For a FLEX-6300: The desired column would be labeled as RCA TX.
Note: The TX2 line is configured to key a transverter only on 2 Meters.
and the TX3 line is configured to key a different transverter only on 432 MHz.
This Band Settings table is part of every Transmit Profile and must be configured for every Transmit Profile used with this amplifier.
To access this table from a Maestro or M-Model Front Panel: open "MENU > TX Band Settings"
From SSDR for Mac: This is available from the "Radio > TX Band Settings" tab
TX DELAY:
To prevent "Hot-Switching" the amplifier, FlexRadio has incorporated a feature called TX DELAY. This introduces a short time delay after PTT is asserted on the radio (the radio is "keyed") before the RF is transmitted from the radio to allow time for your amplifier or transverter's RX/TX relays to finish switching to TX Mode.
Without this feature, many amplifiers can experience "hot switching," which can create "Key Clicks" on CW, or RF Spikes on the make and break of the relay closures or cause the amplifier to fault (shut down). In addition to producing spurious RF transients, "hot switching" may cause damage to your amplifier, transverter, or radio.
To Access the TX DELAY Setting From SSDR for Windows: Open "Settings > Radio Setup> TX"
The picture below shows the TX Delay set to 20 milliseconds. This is usually sufficient to prevent amplifier hot switching. Others may require more or less. For TX delay time information refer to your amplifier's instruction manual.
NOTE: Like the TX BAND SETTINGS table, The TX DELAY setting is part of each Transmit Profile. Always check this setting if using a different Transmit Profile.
To access this from a Maestro or M-Model Front Panel: open "MENU > Transmit."
From SSDR for Mac: This is available from the "Radio > Settings > Transmit" tab.
CW DELAY:
CW Delay is the "Hang Time" that passes when you are finished sending CW before the radio and amplifier drop back into receive mode. (This prevents having the relays constantly clicking between CW characters.)
If the TX DELAY is set to a value greater than zero, you must set your CW DELAY longer than the TX DELAY Setting. For example, if the TX DELAY is set to 20, set the CW DELAY to at least 25 or greater if preferred. This prevents "Hot-Switching" the amplifier or transverter on the "Key-UP" side of the CW transmission.
- From SmartSDR for Windows: The CW DELAY is part of the "Radio Controls" Panel > P/CW Sub-panel.
- From a Maestro or M-Model Front Panel: Open the TX Menu by pressing the "Mic Gain/CW Speed" knob located above the VFO B knob.
- From SSDR for Mac: This is available from the "Radio Controls Panel > CW sub-panel."
The picture below shows the CW DELAY set to 200 milliseconds (this operator prefers "semi-break-in" keying.)