[DSP-10] SR105 Diode

[Richard Ewing]

Per Bob's web page here's the scoop:
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.)


De KO7N  CN84ia

A DSP-10 Enabled Station


At 04:36 PM 7/27/2002 +0000, you wrote:
>I have just about finished populating the DSP-10 board using the TAPR
>kit.
>
>The only part left is through the hole diode SR105  "no designator".
>Where does it go?
>
>Any help appreciated.
>
>Regards,
>- -
>Rajiv Dewan, N2RD
>-----------------------
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