I have been using the W5XD/K5DJ multi-keyer and Writelog on CW for
the past year. I am now moving toward hooking it up for SSB and AFSK.
I have read a huge amount of related material in the Writelog web
pages, at K9JY, the Writelog archives, and the lots of stuff that
comes up in Google searches. Most suggestions are very consistent
(e.g., the need for isolation in the audio lines to avoid ground loops).
The SO2R W5XD/K5DJ multi-keyer set up diagram (SO2RMKSUD)
(www.writelog.com/support/wlso2r.pdf) seems simple enough but, but I
found departures from the diagram in my reading. I realize that there
are different kinds of sound cards and different ways to connect a
sound card to a radio. The large number of combinations has me worried.
I have a few specific questions.
1. For the W5XD/K5DJ multi-keyer/Writelog, the station mic is plugged
into the mic-input of the computer's sound card. I have read and
heard that sound cards are designed for inexpensive condenser
microphones and that some kind of preamp is needed because of the
low-level output for a high-quality dynamic mic (I am using Heil
HC-4/HC-5). In ham-related applications the only references to a
preamp that I saw suggested that it was not needed and could cause
RFI problems. What should I do here (I do not think that my sound
card has a preamp)?
2. The SO2RMKSUD has the sound card line out going (through isolation
transformers) to the Mic inputs of the radios (one channel for each
radio). I have read that a voltage divider/impedance matcher is
needed here (although it is not on the SO2RMKSUD). Would it make
sense to have the sound card line out go, instead, to the radio line
in (perhaps avoiding the need for the voltage divider/impedance matcher)?
3. Similarly, should the sound card line in go to the radio's line
out (one radio on each channel), as suggested by the SO2RMKSUD? The
SO2RMKSUD does not suggest isolation transformers in these lines. Why
not? Seems like it would be a good idea to me, just to have the
electrical isolation.
Bill
K0KT
William Q. Meeker
Department of Statistics
304C Snedecor Hall
Iowa State University
Ames, Iowa 50011
Phone: 515-294-5336
Fax: 515-294-4040
Home Fax: 515-232-1323
www.public.iastate.edu/~wqmeeker
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