Updated list below. It’s not finished but for my own purposes I’ve gone as far as I need to go with this. If anybody wants to make changes, expand the list, or fill in the gaps feel free to do so.
- Nick.
QSK List: Version #3
The list below groups radios by T/R switching technology. In this context I define ‘T/R switching’ to include ALL circuit switching that occurs at the transmit>receive and receive>transmit transitions ‑ not just the antenna changeover switch. Thus it includes any T/R switching for control of peripherals such as amplifiers. I acknowledge that noise from such switching is just one aspect of QSK operation but that's all this list is about.
Group 1: Unconditionally Silent QSK
Group 1 radios don’t use any electro-mechanical components for any T/R switching functions. In that respect their T/R switching will always be silent because they contain nothing that could make a noise.
Elecraft K2, K3, KX2, KX3 & K4
(“Nothing gets out of the Elecraft lab until it has silent T/R switching (PIN diodes, not relays) and fast, clean QSK” - Elecraft K4/FAQ/How does the K4’s CW performance compare to that of other direct-sampling SDRs?)
RGO ONE (Confirmed by W9AC in this thread).
Ten-Tec (?) (exact models TBD)
Group 2: Conditionally Silent QSK
T/R switching of Group 2 radios might not be silent under all circumstances. But there is at least one operating condition where they can be. This group could (for example) include radios whose only T/R relay is used for controlling an external amplifier, but only if all such relays can be disabled, either via hardware link or configuration menu. Radios in this group are fundamentally different to those in Group 1, but that doesn’t necessarily make them ‘inferior’ to those in Group 1. A Group 2 radio with the option to use either a transistor or a relay to control an amplifier is arguably “better” (i.e. more flexible) than a Group 1 radio that has no relay option. But the Group 2 radio might be considered inferior (from the QSK noise viewpoint) if that relay cannot be disabled.
[Hypothetical group - no radios yet identified].
Group 3: Very Quiet QSK
Group 3 radios have at least one T/R relay that cannot be disabled. Radios only belong to Group 3 if all such relays are very quiet ‑ such that they would not normally be heard without deliberately listening to them.
IC-7610 (Confirmed by W9AC in this thread).
IC-7851 (?)
TS-890S (confirmation needed)
TS-990S (?)
Group 4: Clearly Audible QSK
Group 4 radios have at least one T/R relay that cannot be disabled. Radios only belong to Group 4 if at least one such relay is always clearly audible without special effort.
FTDX10 (Thread ‘Based on the price of radios ftdx10 is a game changer?’ at groups.io claims ‘CW performance is great, the only down side is the relay noise, it is very audible during QSK without headphones’).
FTDX101 (Thread ‘FTDX101MP QSK OPERATION’ at groups.io refers to ‘clank clank’).
FTDX101 (Thread ‘FTDX101 vs TS890’ at QRZ.com claims ‘Yaesu uses relays that clatter’).
FTDX1200 (?)
FTDX3000 (?)
FTDX5000 (?)
FTDX9000 (?)
FT-450D (Review #9529 at eham.net claims ‘the relay is too noisy for QSK’).
FT-818 (?)
FT-991A (?)
IC-705 (Article ‘Comparing the Lab599 Discovery TX-500 and the Icom IC-705’ at qrper.com claims that ‘both the TX-500 and IC-705 use relays, not pin diode switching, so you can hear relays clicking inside the radio’).
IC-7300 (Video at YouTube shows how to quieten the relay with putty).
IC-7300 (Thread ‘at QRZ.com refers to ‘the relay clacking LOUDLY when using CW Full Break-in).
TS-590S(G) (Thread ‘TS-590SG QSK on CW’ at groups.io suggests some difference of opinion).
Group 5: Full QSK Not Supported
Group 5 radios don’t provide full QSK ‑ i.e. full break-in CW.
Lab599 TX-500 (Article ‘Comparing the Lab599 Discovery TX-500 and the Icom IC-705’ at qrper.com claims that ‘TX-500 doesn’t have full break-in QSK like the IC-705. The TX-500 has at minimum a 100ms recovery time after keying a character).