This is one for Eric to weigh in on, but with proper in/out routing
between transmit and receive, I wonder if it wouldn be possible to come
up with an algorithm to make the KDSP2 work as an rf clipper/filter in
transmit with baseband audio output? Of course, the settling time
between T/R might well be a problem.
Larry N8LP
[EMAIL PROTECTED] wrote:
In a message dated 04/03/05 11:00:07 GMT Standard Time, [EMAIL PROTECTED]
writes:
I have an old Comdel in-mic-line r-f clipper, which uses fewer than 100
discrete parts on a 4X6in board.
---------------------------------------------------
I have one of the Datong D75 RF speech processors since about 1980 (25
years).
The leaflet that came with it shows it as being derived from earlier
products, the RFC and the automatic model the ASP, though not sure when these were
first on the market. By the time the D75 was introduced the circuitry had been
reduced to 7 IC and 2 transistors. Uses the phasing method to generate an
SSB signal at 60kHz then clipped before demodulation back to audio. Draws 9mA
from a small PP3/6F22 internal 9V battery or can be externally powered from
the radio which is what I did with a Yaesu FT707 used at one time.
It worked well though the resultant audio quality was not for local usage at
higher levels of clipping!
What does what inside the box is a mystery as Datong are infamous for not
releasing schematics, a policy carried through to this day I found out when
trying to obtain circuit information of their DF1 FM RF direction finding
system. I have one with a missing head unit and need to get into operation for
tracking local morons on the repeaters. A request to Datong who are now in the
professional RF surveillance field after pulling out from the amateur market for
help and schematic information led to a polite, but firm refusal.
The main station HF transmitter in use at this end the JRC NSD-515 (1982
vintage) uses RF clipping in the IF chain with 2 filters cascaded, one either
side of the TA7302 clipper IC at 8.7MHz. This works very well with resultant
audio quality good enough to leave it in circuit at all times for SSB and just
varying the amount of clipping to suit the occasion. A great pity that the K2
does not use something similar with the KSB2, but with available space at a
premium, would guess that this would be rather difficult to fit in.
Bob, G3VVT
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