[DSP-10] Problems Loading UHF3x35A.HEX

[Bob Larkin]

Hi Rich,

The regular morning discussion of your DSP-10 between Mike and I 
suggested that there be some element that is used by the PLL and also 
changes between T and R.  There is not much!  The frequency does not 
change. Neither doe the load on the VCO.  The software that programs the 
PLL is the same.  The one possibility that does change is the load on 
the power supply.  Adding the transmit mA might cause a voltage problem 
at the PLL or elsewhere.  See if you can find a DC voltage change on the 
output of a regulator, or at the PLL.

Also, U104 is unlikely, as it is run the same in T and R.  But, anything 
is possible.

Also, is it the same in all modes?  especially, if you go into transmit 
in the CW mode, but do not actually send RF, is it the same?  i.e., does 
PLL loss happen at the T/R change in CW?

73, Bob

On 12/18/2015 07:52 AM, Richard Miller wrote:
> Hello Mike:
> Yes I have checked and the modification was apparently done when I built
> it. R108 does in fact read 472.
> With regard to Lock recovery after the transition, the answer is no.
> Once the lock is lost, it take a complete reload of UHFA394.EXE and a
> reset of the DSP board to recover from this. There are also other
> issues, such as the one I mentioned about the intermittent A/D level.
> When I say intermittent, I don't mean the level is fluctuating, but
> instead is completely absent. I have also seen cases where I would leave
> the system sit for a half hour, when in a faulted state, and it
> miraculously recovers on its own with no intervention from me (i.e.
> poking or prodding the PCB's).
> Last night I rewired everything, I thought maybe I had an intermittent
> in the wiring harnesses. I have rewired everything inside the DSP
> enclosure, and the harness leading from the DSP harness to the DSP-10
> main board. This too has left me with the same faults.
> With regards to frequency changes while in RX, I am able to navigate the
> entire 144 - 148 MHz span in large sections without a PLL lock warning.
> I think it may be time to look at replacing U104, and if that is not the
> issue, then the only thing left is something on the DSPx board.
> 73
> Rich, AJ3G
>
>
>