[Elecraft] Speech processing

[Larry Phipps]

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



G3VVT at aol.com wrote:

> 
>In a message dated 04/03/05 11:00:07 GMT Standard Time,  davidjw at cinci.rr.com 
>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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