[NLRS] 857D

[Dr. Gerald N. Johnson]

On Mon, 2009-08-31 at 07:27 -0700, Joe Belany wrote:
> 
> Good morning all,
> 
> I just received a call from Sandra at Down East Microwave to let me know my 10 GHz transverter is on its way home.  Steve found that both mixers were blown as well as the PA having a bad SMA connector.  The connector was replaced for free as they felt it was a bad part according to Sandra.
> 
> I am curious if anyone else is driving their transverter with an 857D.  Scott, N0EDV, and I talked about my IF rig on the phone.  He recalled hearing or reading somewhere that there is a concern with an output spike when the microphone is initially keyed.  Has anyone heard of this or successfully driving their units with an 857?
> 
>  Joe, AI9Z
> Grid: EN46no
> RV-4, Empenage
> Pounding rivets...
> 
> 
Since I'm planning to use one of my 857D with a DEMI transverter, soon.
I need to know that. I have a fast scope, so I can check one on my bench
soon as I get another rig out of the way. Bill (AWU) asked the same
question a week or so ago. Many rigs do have spikes when the power is
turned down. I'd hope that the 857 in transverter mode wouldn't. It
might be a help to ground the battery indicator pin on the power
connector that also reduces power.

There is also a transmit inhibit pin on the CAT/LIN connector. The books
don't say what it takes. From the schematic it looks like it takes a
positive voltage, 3 to 5 volts is my GUESS to inhibit transmission. I
figure that pin should be held high (12 volts may be too much) by a
sequencer until the antenna is hooked to the transverter and the
transverter is in transmit mode. It will be interesting to check what
the levels required to inhibit transmit and how the radio reacts when
that voltage is dropped rapidly, or slowly. There is also a grounding
PTT output on the same connector that can be used to initiate the
sequencer operation.

With all the nice transverter an interface connections, I'd hate to find
the 857 spikes to fry the transverter. Unfortunately switching from
liaison on 2m to transverter IF requires some careful operator changes
in the last menu entry as well as power entries and that may make it
less useful in both modes, but should be kept to one mode. Or why the
817 is so effective an IF, it won't do enough power to hurt the
transverter.

73, Jerry, K0CQ