The first interface is one that I am using to key my Drake L-4B. This
would apply to any of the older amplifiers. Positive keying only, not for
the SB-200 or FL-2100B. The problem that I was having was the relay in
the TS-850S would key the relay in the L-4B. This was too slow, the
RF from the TS-850S was already outputting. This caused a high swr
on the rig. In amplifier circles this is known as Hot Switching and
can cause damage to the rig finals. So what I did was to by-pass
the relay in the TS-850S. Using the 12 volts on transmit output(
pin 7 on the remote connector on the back of the TS-850S) to key a High
voltage/High current transistor. (See figure 1.) I mounted
the transistor and resistors in a small aluminum box. I put RCA sockets
on each end. Transistors that can be used is MPS-A42 or 2N6515, Resistors
are 1K 1/4 Watt.
figure 1.
The box is a standard BUD box and measures 1.5 X 2.0 X 2.5. A smaller box
could also be used. The connectors are RCA phono jacks. As can be seen in the photo above, very few components are required.
The pin connections shown on the schematic will work for both the Kenwood
TS-850S and the TS-570D. The amp connection will depend on your make/model. The
transistor can be either a 2N6515, or an MPS-A42. I have built two of these now,
and have used both types of transistors with success. The resistors are 1K and
can be as low as ¼ watt. The resistors I used were from my junkbox, so the
resistors shown are ½ watt. Assembly is very simple. Solder the transistor collector to the center
conductor of one phono jack, and the emitter to the ground lug. Solder one
resistor to the center conductor, and the other resistor to the ground lug of
the phono jack on the opposite end of the box. Bend the base lead of the
transistor, toward the resistors and solder the resistor leads and the base lead
together. The interface with your rig and amp will depend on type. The box described
here was to interface with the Kenwood TS-850S/Drake L-4B, as described by KØBX.
I used it to interface my Kenwood TS-570D with Eric, WØTT’s Alpha. We used it
during the CQ CW contest last November, with good results. The completed unit, with rig interface cable is shown below. All components
were purchased at Gateway Electronics. The cost is very minimal. 73 Jim, NØAJ Joe, KØBX
The following is how N0AJ, Jim constructed this circuit. Pictures are from
Jim. I built two of these and Jim also built two.
One little note on this circuit from Wayne VE3EFJ
I really enjoy your TS850 web page. It is just terrific.
Regarding your amp keying circuit I have one comment for
"improvement". There really should be a diode from collector to
ground to stop the transistor from being spiked by the relay.
Cathode (bar end) on the collector). A 1N4007 should work fine.
Regards -
Wayne VE3EFJ