[Orion] Connecting Orion to Alpha 87A

[Dick Green WC1M]

No, you don't need a Y-cable. The Y-cable is necessary with the Omni V/VI
because there's no alternative to the TX OUT/TX ENA keying loop for keying a
QSK amp. In contrast, the Orion has two plain-old AMP KEY jacks that are
just fine for keying a QSK amp with PIN diode T/R switching like the 87A.
All you have to do is connect a shielded cable with male RCA jacks at both
ends between the Orion's AMP KEY 1 or AMP KEY 2 output and the 87A's RELAY
input jack. You don't have to connect anything to the 87A KEY OUT jack
because the 87A pin diodes switch so fast that a keying loop is not
necessary.

BTW, the instructions on the Alpha site indicate that the Y-cable should be
connected to two jacks on the Omni (TX OUT and TX ENA), and only to RELAY on
the 87A. In other words, the 87A's KEY OUT is not connected. That means the
87A's keying loop is being bypassed completely and the Omni's end of the
keying loop is being fooled into thinking the amp has a keying loop -- when
the Omni grounds TX OUT, the TX ENA jack is also grounded, allowing the
radio to emit RF.

One might naturally wonder why Alpha would recommend a Y-cable, when the 87A
does in fact have a keying loop. In my opinion, it's because the 87A doesn't
implement the keying loop correctly, or at least not in a way that's
compatible with Ten Tec's notion of how the keying loop should work. Since,
the 87A manual strongly discourages use of the keying loop except in
exceptional circumstances, my guess is that it was never coded correctly to
begin with. My own experience bears this out: in attempting to use the 87A
keying loop with the Orion's keying loop, I experienced keying anomalies
that indicated the 87A wasn't handling it's KEY OUT signal correctly. The
anomalies went away as soon as I changed to a simple hookup between the
Orion's AMP KEY output and the 87A's RELAY input. Sometimes, simpler is
better.

73, Dick WC1M

> -----Original Message-----
> From: Jim McDonald [mailto:jim at n7us.net] 
> Sent: Wednesday, September 15, 2004 9:02 AM
> To: orion at contesting.com
> Subject: [Orion] Connecting Orion to Alpha 87A
> 
> 
> I'm just planning ahead, since I haven't bought an Orion yet.
> 
> The Alpha-Power web site 
> (http://www.alpha-amps.com/html/tentec.htm)suggests
> that the Omni V/VI be connected to an Alpha 87A with a 
> specially assembled Y connector.  The 87A has two phone 
> jacks, a KEY OUT and a RELAY.
> 
> Is that appropriate for an Orion?
> 
> Jim N7US
> 
> 
> 
>