rmktips - 01/29/2003 - Chuck Olson, WB9KZY, Jackson Harbor Press<br><br>
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Adding delay to a message or beacon:<br>
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The special character:  di-dah-dah-dah-dit   can be used to add a word
space anywhere within an RMK memory.  This can be useful to add delay
at the end of a beacon - simply send the word space character to add
a word spaced delay, these can be strung together to make the delay
longer.  Note that if you exagerate the wait time between sending
characters, the RMK recording routine will kerchunk in another word
space automatically.  Also, the recording routine will delete the
last word space recorded automatically (only one).  Each word space
takes one byte of the memory.
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Two version 45 workarounds:  <br>
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1) Dah pullup problem (only required when the pot is NOT used):  Connect 
a 10k resistor from the +4.7 volt RMK supply to pin 6 of thekeyer chip 
socket.
<br><br>
2) Memory recording problem:   If you need to record a memory with a 
shorter message, you can be sure to end the message by sending a 7 dah 
character at the end of the message.  Then terminate the recording with 
the mem switch press and release as usual.
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Alternate method of installing pullups:<br><br>
A couple of users have mentioned that they don't require the speed pot input 
and also, that they don't want to have to uncase the RMK to solder the 10k 
pullup resistor on pin 4 of the keyer chip socket.  The way that they added 
the 10k pullup was to solder it directly to the chip, from pin 1 to pin 4.  
The connection was made very high up on the chip leads, right at the body 
of the part so that the pins are still able to be inserted into the socket.
This idea is recommended only to those adventurous souls who are pretty 
handy with a soldering iron. 
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The following tips are from Chuck Carpenter, W5USJ :<BR>
<BR>
I used a couple of ways to make the pullup connection and another one to do
the speed pot.  I made the mods before replacing the original RM keyer
chip.  I could detect no change in operation of the original chip with the
mods in place -- neat.
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On one Rock-Mite, I removed the wire that goes to the shift pushbutton and
cleaned out the hole. I cut one end of the 10 k Ohm pullup to about 1/4
inch and connected the removed wire close to the resistor body.  The short
end of the 10 k was inserted and soldered back in the hole for the wire.
The other end of the 10 k was routed over to the top of D4 extra length
clipped off and tack-soldered in place.  No cuts or jumpers or etc. easy to
do during initial assembly.
<BR><BR>
For my Super Rock-Mite, I have the speed pot mounted on the front panel of
the enclosure just above the paddle jack.  I super-glued some manhattan
pads next to the pot.  I did the same next to the pushbutton.  I mounted
the parts for the speed pot between the pot and the pads.  I did the same
with the 10 k pullup to a pad at the pushbutton.  Also at the speed pot
pads I added a 5.1 V zener through 3.9 k  and made power connections to the
pads.  The 5.1 V from the zener is also connected to the 10 k pullup at the
pushbutton.  Works great!
<BR><BR>
I noted that your instructions show a connection to 4.7 V for the speed
pot.  Some R-Ms will have 4.7, 5.1 and 6 V zeners.  I'd suggest making the
connection only at D4 and do not make a connection to D5.  D5 will be 4.7
or 7.5 V depending on the band and also could affect the shift offset
frequency.
<BR><BR>
I made a change in the pullup-only connection.  Instead of connecting it
directly to the cathode end of D4 I moved it to the same electrical point
on R8.  The picture, <A href="RMK1cc.jpg">RMK1cc</A> , shows this.  If the parts are
installed the way Dave shows in his layout, this works.  Depending on board
layout vintage R8 is as shown in the picture or closer to D4 in the older
versions. Otherwise use the cathode end of D4.  Pin 1 of the keyer chip and
the cathode end of D4 are the same electrical point.  The voltages for D4
are either 4.7 or 5.1 depending on the board version.  At least in the ones
I have, R-M/40 vs R-M/20.
<BR><BR>
Picture: <A href="RMK2cc.jpg">RMK2cc</A> shows my hookup of the speed pot.  I also put the 10k pullup
in the alternate location for this shot.  The speed pot here is backwards
and is an audio taper.  The only 100 k pot I had on hand -- fix it later.
You can see the 5.1 Volt zener and 3.9 k resistor I used here for the speed
pot supply voltage.  The unused, as yet, pot is for audio volume when I
install the audio filter.