[Elecraft] K2 with MacOS Classic

[Dan Barker]

The diodes are doing two different things. Wire them up! It works great
here.

In this case, you are using the computer RS-232 to key the rig, so you'll
definitely be building a custom cable - TxD and RxD to the K2, DTR to your
keying circuit (btw, this can fit into the DB9 shell), and NC all the K2
specific lines.

The two diodes on the K2 end are to allow ADET operation (a keyer and a
straightkey/computer simultaneously connected). If the DTR line pulls the
pair of diodes low, both DIT and DAH go low together and the K2 assumes a
straight key. If they go low at different times, the K2 assumes iambic
keying and acts appropriately.

So ops (up at twice the speed I can run) can fool ADET and need to turn it
off. They don't need the diodes but must switch from paddles to SK/Computer
with the menu.

Other ops only ever do it one way or the other - and switch off ADET too.

hth,

Dan / WG4S / K2 #2456

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net]On Behalf Of Bekir Kemal Ataman
Sent: Tuesday, November 22, 2005 1:04 PM
To: elecraft at mailman.qth.net
Subject: RE: [Elecraft] K2 with MacOS Classic


>Yes, and then you get to buy a bunch of parts for your KIO2<g>!
>
>DO NOT CONNECT RS-232 to your KIO2 without opening all unused (by RS-232)
>pins. ONly Sig Ground, TX and RX go from computer to K2. All other lines on
>the KIO2 are not RS-232 and can't tolerate the +- 15V the computer will
>supply.

Do not worry. I am one of those old generation (!) people who do not move a
finger without reading the manual first. >;-)

Now, as for reading manuals, I have got an interesting case for all of you
to comment on.

Multimode's Documentation starts by saying the following for transmitting
(receiving is via the sound output of the rig):

"If you also want to transmit, you'll need to connect the audio output
(speaker) jack of your Mac to your radio's microphone input jack. You may
need to reduce the audio amplitude using a
potentiometer, or attenuating audio cable. Many have sucessfully usd the
RigBlaster, made by
West Mountain Radio (http://www.westmountainradio.com/)."

Then goes onto describe the procedure for PTT and CW:

"For transmitting, you may want to be able to control your radio's PTT
(Push To Talk) line. A
PTT output is generated from the DTR output of the Mac's serial port. A CW
key output is
generated from the Transmit Data output."

The diagram in the Documentation depicts a little circuit on the line from
Mac's serial port to the CW Key control (and a smilar one to the PTT) such
that:

Mac Serial Port --> Diode (1N4148, etc.) --> 2.2k Resistor --> Transistor
(2N2222, etc.) -->PTT

The other leg of the Transistor goes to ground. On a diversion from this
line, there is a diode (1N4001, etc) which then connects to the first leg
of the transistor going to the PTT.

[I hope I haven't described it too badly. The diagram is on p4. of
MultiModeDocs.pdf. I tried to attach it to this message but the list does
not accept attachments.]

The documentation describes the way the circuit works as follows:

"When the serial port output goes positive, it biases the transistor, so
the collector can sink
current. The 1N4148 diode protects the transistor when the serial port
output is negative. The
1N4001 protects the transistor against flyback from a relay that might be
lurking in the radio.
A faster diode would probably offer additional protection.
The connection on the Mac end would go to the DTR output line. If you'd
like to use a similar
circuit for CW key control, then it would go to the TxD+ line (or TxD- if
you need to invert the
logic of the output)."

There is no problem as far as this description is concerned. All sounds
logical.

Looking at things from the K2 side, p. 95 of the manual says that I should
have two diodes (one on each line from the dot and dash connections) on the
cables going to the computer, when I connect it in parallel to a paddle.

And it describes the reason as:

"When you connect the keying device in this way, you can continue to use
the paddle as usual. But if the external keying device is keyed, both the
DOT and DASH lines will be pulled low simultaneously, via the diodes. The
K2 firmware interprets this as direct external keying rather than as DOT
and DASH triggers."

This sounds quite logical, too.

However, when you bring the two descriptions together on a single circuit
an interesting case occurs. Now, I am not exactly a techie type person and
learnt electronics just enough to pass the exam BUT AFAIK having diodes on
both ends (i.e. on the computer side as well as the K2 side), each
protecting their own respective device, there will not be any current
flowing.

Am I wrong? Or should I put the circuit together and test it anyway?

Thanks for your help in advance.

73!
BKA (TA2RX)




----------------------------------
Bekir Kemal Ataman
ArchiMac BBS Sysop & Webmaster <http://www.archimac.org/>


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