[DSP-10] probems in TX and RX - DSP-10 with KK7

[kd7ts]

Check this info....

http://members.ispwest.com/kd7ts/html/sr105.gif

"SR105" Diode When the DSP program is first started and before the PC 
program is run, the DSP-10 can come up with BOTH transmit and receive 
turned on.

This sets up a loop that oscillates at full power! Very bad. My DSP-10 
shows about +16 or +17 dBm out. The happens because the shift 
registers (U107, U108) come up uninitialized.

The eventual solution will be to program an EPROM that includes the 
setting of the shift registers at DSP startup.

Here is a work-around until you have an EPROM version: Acquire a 
Schottky diode and solder the cathode (bar end) to the junction of 
R132 and Q104-collector. Solder the anode (non-bar) end to the 
junction of R130 & R131 (base of Q103).

It must be a low barrier voltage diode like the Schottky, but it can 
be either a rectifier or small-signal type. I used a SR105 from 
Digi-Key, but I notice that Radio Shack has 1N5817-1N5819 or 
1N5820-1N5822 on special order status.

W7LHL suggested that a 1N34 type of germanium could work also. This 
work-around prevents the 'transmit' from being enabled when 'receive' 
is enabled. (Added 5 Sept 01, based on 27 Jan 00 reflector posting.)

Thanks Courtney for providing a picture I could copy !!

This might help get farther along.

Mike KD7TS