QSK Master FAQ
Q: What is the purpose of the internal keying sense strap?
A: While probably all transceivers have a closure-to-ground for enabling HF amplifiers, this output may only be available as a relay contact closure-to-ground on some radios. For best QSK operation, we recommend driving the QSK MASTER from a solid-state amp-enable output to both eliminate high speed relay operation inside your transceiver, and to eliminate time delays associated with your transceiver’s internal amp-keying relay. Most transceiver brands do include a solid-state closure-to-ground on one of the rear connectors. However, most Kenwood transceivers only have a relay closure-to-ground, or a +12V solid-state enable output. The QSK MASTER can be strapped to interface with the +12V solid-state output of these transceivers.
Q: I have a TenTex Omni VI which does not have an AMP-ENABLE output. It does have TX OUT and TX EN interfaces for loop keying of amplifiers. How do I interface my Omni VI to the QSK MASTER?
A: Older TenTec radios did not have a dedicated AMP-ENABLE output. For these radios, all you need is a simple RCA hard-wired splitter connected to your TenTec as shown below.
Q: What is the purpose of the BIAS CONTROL feature on the QSK MASTER, and should I implement this with my amplifier?
A: Basically the bias control feature in the QSK MASTER permits you to interrupt the amplifier bias when the amplifier is un-keyed – even during spaces between "dits" and "dahs" - so as to reduce power dissipation in the amplifier. So if you don't mind modifying your amplifier, this feature is not too difficult to implement. If you do not implement the amplifier bias control feature of the QSK MASTER, it is always best to switch your amplifier to STANDBY when it is not in use so as to reduce amplifier idling power dissipation.
Whether to implement this feature or not depends on your amplifier. If your amplifier has a high resting plate current and therefore dissipates a lot of heat when un-keyed, then you may want to implement this feature (resting plate current X plate voltage = idling power dissipation). Generally, smaller (600-800 watt output) amplifiers are more tolerant of this, whereas legal-limit plus amplifiers may not be. However, many amplifiers now include a dynamic-bias control feature whereby the amplifier is biased-off when not being driven (Ameritron AL-80B, AL-572, & AL-800 amplifiers for example). So there is no benefit in using the bias control feature of the QSK MASTER with these amplifiers.
Q: Can you give me some specific details on how to actually modify my amplifier for bias switching?
A: This varies some from amplifier-to-amplifier. Typically an amplifier T/R relay has DPDT contacts for RF switching, and another set of contacts for bias switching. Since the amplifier is now continuously keyed when in the OPERATE position, the internal amplifier relay is continuously enabled. If the bias switching in the amplifier is done via a set of SPST contacts on the amp relay, you can just cut the bias wire going to the relay, feed it out of the amp to the QSK MASTER, and then feed it back into the amp to the other end of the cut bias wire. The QSK MASTER interrupts this circuit when the QSK MASTER is not being keyed.
For grounded-grid vacuum tube amplifiers, break the cathode line where the normal bias is keyed by the amplifier relay and insert a 50K ohm 2-watt resistor in series with this cut wire. This 50K resistor should be put in series with any bias zener if one exists in the amplifier. This resistor will totally cut off any current flow in a grounded grid amp. Then short this 50K resistor with the QSK MASTER high speed BIAS relay contacts.
Whether you just interrupt a set of SPST relay contacts or short out a 50K resistor as described above, you can do this cleanly by mounting a 1/8" stereo jack on the back of your amplifier and connecting the two ends of the cut relay bias wire or the two sides of the 50K resistor to the tip and ring connectors on this jack. Then a stereo 1/8" cable can be used to connect from the amp to the QSK MASTER "Bias" connector. If you use a 1/8” shorting jack on your amplifier, then the amplifier will revert to normal non-QSK operation when you unplug the cable going to the QSK MASTER. Or you can use a shorting cable in the jack if you prefer.
Q: How can I check out my QSK MASTER to ensure it is working properly?
A: All QSK MASTER signal paths and SWR (evaluated from 1.5-60 MHz), and switching speeds (evaluated at 80WPM) are tested on every unit prior to shipping. Therefore, it is highly unlikely that there is a problem with your QSK MASTER. Problems typically are associated with incorrectly wired or defective external cables. However, since you asked – here are some simple tests to verify QSK MASTER integrity if you are having problems.
1) Verify that center pins of the four UHF connectors are NOT shorted to ground.
2) With the QSK MASTER turned on but not keyed, there should be continuity from "TRANSCEIVER" to "ANTENNA" on the QSK MASTER. There will be NO continuity from "TRANSCEIVER" to "TO AMP", and no continuity from "FROM AMP" to "ANTENNA" on the QSK MASTER.
3) Key the QSK MASTER by plugging an RCA shorting plug into the QSK MASTER "KEY" input (make sure that the QSK MASTER is turned on). The front red LED should glow continuously. Verify continuity from "TRANSCEIVER" to "TO AMP", and continuity from "FROM AMP" to "ANTENNA".
Q: Why would I add additional turn-off delay to the QSK MASTER (internal strapping option)?
A: Most transceivers do not disable the amplifier (via the AMP-ENABLE control line) until the transceiver RF output has decayed to zero. However, a few transceivers (notably the IC-7000 and IC-706-series and the TenTec OmniV and OmniVII) actually disable the amplifier before the RF has completely decayed to zero. This is not an issue when these transceivers drive a non-QSK amplifier, as the release time of non-QSK relays is quite long – maybe 15-20ms – so there is plenty of time for the RF to fully decay. However, for QSK operation the QSK MASTER can switch the amplifier out-of-line before the RF has decayed to zero with these transceivers. Due to the ~5ms release time of the QSK MASTER, the RF waveform has mostly decayed, but there may be some signal left with these particular (and possibly other) transceivers. This typically results in key-clicks as the signal is suddenly interrupted by the relay action. The internal strapping option in the QSK MASTER extends the typical 5ms drop-out time to 10-12ms drop-out time which eliminates this problem on any transceiver with the “amp-disable before RF is gone” timing.
Incidentally, the QSK MASTER is designed so that the amplifier output signal path is not interrupted until after the transceiver input is switched back to the antenna, so there is no possibility of hot-switching the amplifier.
Q: My TenTec OmniVII indicates a high SWR on its internal SWR meter when keying the QSK MASTER, but there is not transceiver turn-down and I’m still getting full RF output from my amplifier. What is going on?
A: This is caused because the OmniVII unkeys the amplifier before the transceiver’s RF waveform has completely decayed to zero. The QSK MASTER is FAST – like a QSK switch must be. With the OmniVII, the QSK MASTER will switch a little before the transceiver’s RF is completely gone. This switching occurs at a low power level as the RF waveform has been decaying for 3-5ms before the QSK MASTER switches. However, there is still enough power left that the transceiver measures a high SWR when the RF output is suddenly interrupted by the QSK MASTER transceiver input relay. The answer is to simply strap JMP1 in the QSK MASTER to slightly increase the turn-off delay.
Q: What type of cable(s) would I need to purchase in order to connect an Ameritron AL-800H with either the Yaesu FT-1000 Field or FT-2000 and the QSK Master?
A: You can use a RCA cable from the standard RCA
amp-keying output of your Yaesu transceivers for keying the QSK MASTER, but this
requires that the internal Yaesu switching relay be energized (there is a LIN
switch on the back of most Yaesu radios that lets you turn this relay on or
off). This is fine for mostly SSB and semi break-in CW use and for occasional
QSK operation. However, for regular QSK operation it is MUCH better to leave
the internal Yaesu relay off and use the solid-state switching output from the
transceiver. This solid-state switching output is available from the Band Data
connector on all Yaesu transceivers. Array Solutions makes the FT1K cable that
interfaces with the FT-1000/2000 Band Data connector and the QSK MASTER keying
So - you should use the Array Solutions FT1K cable (or
build your own) to plug between your transceiver and the QSK MASTER, and an RCA
shorting plug that plugs into the keying input of the amplifier. You also need
coax jumpers that go from your transceiver to the QSK MASTER, from the QSK
MASTER to the amplifier, and the amplifier output back to the QSK MASTER. Your
antenna system/antenna tuner/etc connects to the ANTENNA port on the QSK
MASTER. Finally, all internal default strapping inside the QSK MASTER is fine
for this transceiver/amplifier combination. So you just need to connect up the
cables and go.
Q: Will the QSK Master work with my Kenwood TS-850 (and that generation of rig) and my older SB-200?
A: The QSK MASTER works with any transceiver/amplifier combination. All the switching is actually done by the QSK MASTER. You enable the SB200 continuously (continuous key on the amp enable input line), and then the amp is switched in and out of line by the high-speed vacuum relay and signal relay in the QSK MASTER. Look at the block diagram on this website and in the QSK MASTER manual.
The TS-850 has two ways of keying (both available on the TS-850 REMOTE connector). There is a pair of relay contacts (pins 4 & 2 which you're probably using now with your SB-200), and there is also a +12V output on transmit (pin 7-to-ground). Since the QSK MASTER has an internal strap to select either way of keying, we recommend that you use the +12V keying output. This will drive the QSK MASTER with a solid-state output which is very fast, and you don't have to enable the internal amp-keying relay in your TS-850 (linear amp switch on the TS-850),
As discussed earlier in these FAQs, there is also a pair of high-speed relay contacts available on the QSK MASTER should you want to switch your amplifier's bias on and off along with the keying (the BIAS jack on the QSK MASTER). This is normally not used in smaller amps like the SB-200 as the resting power dissipation isn't that high. Just flip the amplifier’s OPERATE/STANDBY switch to STANDBY during lo g periods of time when you are not using the amplifier. However, some folks like to make this mod to their amplifiers to really reduce power dissipation all the time (eliminates resting plate current between dits and dahs).
Q: I have been using the QSK Master for a month or so now and like it very much. It works great with my AL80B and Omni VII. I have noticed lately that when using SSB I sometimes get a momentary spike on my AL80B forward and reflected power meter. Any idea what may be going on?
A: This is also an indication of low-level hot-switching due to the OmniVII turning off the amplifier before the RF has decayed to zero. This problem with the OmniVII occurs consistently on CW. It can also occur occasionally with SSB, especially if you are using compression (which could keep low level noise available after the QSK MASTER unkeys). Strap-in the QSK MASTER extra turn-off delay and this will fix the problem.