[TenTec] Orion ALC and power output indication meter and speech processing

[Zivney, Terry L.]

Earlier Ten-Tec rigs I have owned, such as the Delta, the Corsair II, and the Omni VI+ all
have wattmeters which attempt to show the actual amount of RF output and reflected power
on a Bruene-type circuit.  The Orion does not seem  to indicate the actual level of RF output
on the meter; rather it seems to show the percentage of full power the operator sets - that is,
100 indicates 100% of full power as set by the internal ALC pot, which could be more or
less than 100 watts.  My experience with two Orions is that the factory sets this level to be
100 watts.

The purpose of ALC in the Ten-Tec radios appears to be to hold the peak forward power
at the level selected by the operator regardless of the SWR.  So, while most JA rigs, and
apparently the West Coast "competition" turn back the peak forward power under high
SWR conditions, the Ten-Tec radios historically have maintained the peak power set until
the rig draws overcurrent which then powers the entire radio down.  If you take a look at
the classical Motorola RF power transistor data sheets, they are specified to provide that
power under 30:1 SWRs; there should be no need to reduce forward power in a properly
designed solid state amplifier.  The key is to maintain the peak power at the desired limit
(100 watts forward power in this case); this means the ALC circuit will need to change
the drive level to maintain that desired forward power as the load SWR changes.

This is an issue for the WRTC-2010 competitors as noted on their reflector.  If the antenna
has a high SWR, the forward power may increase over the 100 watt limit while maintaining
100 watts net power (forward minus reflected).  I measured the foward power of both
my two Orions and my remaining Omni VI+ as staying within a needle's width of  the set
forward power while the SWR went from 1:1 to over 10:1 (using monoband antennas
on the "wrong" bands).  Thus, the Ten-Tec radios met the WRTC-2010 spec while other
radios may have to incorporate an external antenna tuner to avoid rules violations.  (See
the WRTC-2010 rules for additional information on this point about why internal tuners
are not useful for this contest.)   

There were some posts a few years back about the speech processing on the Orion
v1 versus v2 and the effictiveness of that processing.  My personal experience has been
that while I definitely needed the external Ten-Tec RF speech processor on the Omni VI
to be contest competitive, the internal firmware speech processing on the Orion (level
6 or 7) has been equally effective in practice for me.  I have not tried my external processor
on the Orion, as it is waaaaay down on the list of things to do here.

Terry Zivney, N4TZ/9,
still trying to figure out the best way to  get an Orion to Russia with love...