Jim Instead of using 8T to drive the keying circuit, you should use the fall of 8R - 8R falls before 8T is asserted and stays down longer than 8T is active. It will follow the menu setting for t-r (8R HOLD) and the delay setting. Using 8T could cause hot switching at the amplifier in some cases.
The circuit on the Elecraft website uses 8R, and in fact 8T is not present at J13 for the B level (post SN 3000) RF Boards. 73, Don W3FPR On 7/21/2011 9:47 AM, Jim Wiley wrote: > > Julian - > > > Yes, there is. Check the K2 notes pages on the Elecraft web site, or > build your own, which is what I did. All that is required, if I > remember correctly, is a resistor (anything between 1000 and 2200 Ohms, > 1/4 watt) and a NPN transistor capable of handling the required > amplifier keying current and voltage. A 2N3053 / ECG125 would be one > example. A 2N2222 would be another, but if you are using a vacuum-tube > amplifier, check the key up voltage across the amplifier keying jack, > and size the driver transistor accordingly. This assumes your amplifier > has a positive voltage across the key jack when in standby mode. If it > is negative,. you may need a small driver relay. Most amplifiers, not > all, will not need the relay. > > > Inside the K2, connect the 2200 ohm resistor from the 8T (8 volts on > transmit) line in the K2 to the 2N3053 base, ground the 2N3053 emitter, > and the 2N3053 collector connects to the amplifier key port. There is > (or at least was) a small kit offered that contains the needed parts and > a small PC board. I used a small square of perf-board and hand wired > the thing using the component leads, not printed traces needed. I also > installed a RCA phono jack on the rear panel using one of the unused > extra holes. Of course, you could drill an extra hole if needed, or > just use a pigtail with the RCA jack hanging on the end. I also > installed a .005 uFd / 500 volt disk ceramic cap across the output jack > just in case there were RF issues, but don't know if it was actually > necessary. In any case, it works fine. > > > - Jim, KL7CC > > > > Julian, G4ILO wrote: >> Due to serious illness I am looking at simplifying and downsizing my radio >> equipment and returning to QRP using my old K2. Unfortunately the K2 seems >> to lack a facility that I used on the K3 namely a KEY OUT jack that could be >> used to key an external amplifier on transmit (or in my case the MFJ noise >> cancelling box, to avoid having to use the RF sensing.) >> >> Is there a solution? >> >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
