On Sun, 4 Jul 1999 16:06:41 -0400 "Jack Trampler" <n2jt@fast.net> writes:
>
>Recently my FT-1000MP took ill and I had to return it to Yaesu. I
>inquired
>on this reflector about keying the Drake T4XC with the keying circuit
>that
>appears in the TR manual. I received many replies (thank you to all)
>and
>there were two routes to choose from.
>
>Since the Drake uses grid block keying, the first option was to change
>the
>transistor to a PNP type capable of handling the keying voltage.
>This
>measured -34.5 volts at the key. The problem with this option is when
>my MP
>comes back I will have to change the transistor again.
>
>The second option was to use the existing circuit to key a relay.
>Pete,
>N4ZR said:
>
>>I believe the C-line uses -60 to -70 volts DC for grid block keying.
>As
>>such the polarity is wrong, and the voltage rating would be exceeded.
> The
>>simplest fix probably is to put a dip relay in the collector, provide
>5
>>volts to operate it, and use the relay contacts to key the C-line.
>
>I decided to go the route of the relay as it will be compatible with
>all
>rigs. I used a Radio Shack 5VDC reed relay (part #275-232) with the
>coil
>connected between the transistor collector and the junction of pin 17
>and
>the 1K ohm resistor that goes the emitter. Pin 17 supplies 5 VDC.
>I
>tested this relay up to 50 WPM and it works very well.
>
>The only question I have now is the relay draws 20ma. Will this
>additional
>current damage the computer or serial port? I would think not, but I
>don't
>have any specs on this. If anyone know for sure, I would appreciate
>hearing
>from you.
Sometimes it's difficult to get an authoritative answer on a
question like this. Anyway, here's one method that Tree
recommended to me last week that will work for sure.
Connect an external voltage source to your relay, +12vdc
or +5vdc, or whatever is required. Connect the other side of
the relay coil to the collector of the transistor in the regular
positive keying circuit.
Dave Hachadorian, K6LL
Yuma, AZ
K6LL@juno.com
___________________________________________________________________
Get the Internet just the way you want it.
Free software, free e-mail, and free Internet access for a month!
Try Juno Web: http://dl.www.juno.com/dynoget/tagj.
--
FAQ on WWW: http://www.contesting.com/trlogfaq.html
Submissions: trlog@contesting.com
Administrative requests: trlog-REQUEST@contesting.com
Problems: owner-trlog@contesting.com
Feature Wishlist: http://web.jzap.com/n6tr/trwish.html
|