RX366

Background
I've owned a Ten-Tec Orion since January 2004.  Virtually since the first day I got it, I listened with both receivers
simultaneously, feeding the left headphone with the main receiver and the right headphone with the subreceiver.  I
really pushed the subreceiver to its limits in two types of activity:

1. Stereo Diversity Reception
As an avid topband dx'er, I embraced the ability to listen with two Beverage antennas simultaneously.  This allowed
me to better hear targeted weak signals or listen for answers to my cq's over a wider azimuthal range of propagation.
I also listened with the tx antenna in one ear and a Beverage antenna in the other ear, especially on the higher bands.
Besides giving me a performance advantage in copying difficult signals, the stereo listening effect was quite enjoyable.
My Web page describing my experience, along with soundclips, can be viewed here. As I documented
there, using the subreceiver in stereo diversity conferred these benefits:

improving signal readability in the presence of noise (QRN), interference (QRM), or fading (QSB) 
creating a sense of stereo depth to received signals and pileups and improving readability
with directional antennas, allows me to listen for callers from a desired direction in a pileup

2. SO2V Contesting
N1MM Logger opened up the ability to fully take advantage of a xcvr equipped with dual receivers in a contesting scenario,
mimicking to some extent the use of a second radio (SO2R).  I worked with N1MM to initially shape the SO2V control and soon 
the Orion became a powerful SO2V contesting tool under the software's control.  My Web pages describing my SO2V ssb experience 
(with soundclips) can be viewed here and for SO2V cw can be viewed here.  



It eventually became apparent, especially on 160M, that the Orion subreceiver was vulnerable to overloading from strong signals 
due to its less robust design.  Typically this was experienced either as difficult in reading a weak signal with an adjacent
strong signal or phantom signals heard due to overloading from very strong signals elsewhere on the band. The subreceiver just
couldn't match the main receiver performance.

RX366 Delivered
Fast forward to the present and Ten-Tec has introduced the RX366 subreceiver upgrade.  It uses an architecture VERY similar to
the Orion main receiver and is based on the receiver in the Ten-Tec Eagle.  It installs easily in place of the original subreceiver and 
accepts up to three roofing filters in its 9Mhz i.f.  Adjustment is provided using the front panel controls to align the oscillators
between the Orion main receiver and RX366 subreceiver.  It's easy to match them within 0.1hz and lock appears to be well maintained 
over time. I have my RX366 equipped with 6Khz, 1.8Khz, and 300hz filters.  My Orion main receiver is equipped with 1.8Khz and 300hz
narrow filters.  Yes, I have an Orion II 300hz filter wired into my Orion 1Khz filter slot and it works well since I generally
use 300hz cw selectivity.  However, I would generally recommend using the Inrad 600hz filter in the Orion 1Khz filter slot.

I've had the opportunity to use the RX366 receiver for quite a while, in all types of operating.  The bottom line is that it is 
essentially equal in performance to the Orion main receiver and is seamlessly integrated.  The only difference I've ever noticed 
is a small number of weak birdies in the RX366 subreceiver, a trivial matter which I only notice because the Orion main receiver 
doesn't have a birdy to be found.  I can highly recommend the RX366 without reservation to any Orion owner seeking superior
subreceiver performance.


Recordings of the RX366 in action:
1. Stereo Diversity Recording with RX366 -CQ160 CW contest - listen with headphones

left channel - main rx, 580ft NW Beverage; right channel - RX366 subrx, 580ft SW Beverage
notice how clean the passband of both receivers is, despite very strong signals nearby on 160 meters during the contest  
300hz bandwidth, sidetone freq 430hz, gain optimized to minimize AGC - recording is about 80 sec. long
(the treble hiss and slight tx clicks are artifacts from the highly compressed contest recording process and not from the receiver) 

2. Stereo Diversity Recording with RX366 subreceiver - 40M LSB - listen with headphones

left channel - main rx, dipole antenna; right channel - RX366 subrx, 580ft Beverage toward Europe

 
Orion SAF - new v3 firmware feature
With version 3 firmware, Ten-Tec provides a new "SAF" selective audio filtering feature.  It's a very useful audio peaking filter 
that is easy to use and can improve readability of weak cw, ssb, and am signals (and perhaps digitial signals as well).
The RX Menu has new options to change the Notch function to SAF.  There is also the option to have tracking SAF filters
invoked on the main and subreceivers.

CW SAF

Optimal use of SAF in cw is intended for improving readability of weak signals.  Thus, SAF is intended for occasional, 
and not general, use.  Optimal SAF width for cw is 10hz or 20hz.  The SAF center frequency should be set initially to 
the sidetone pitch.  First tune in the cw signal and try to match it  to the sidetone pitch - use the Orion SPOT function 
to help.  Now push the NOTCH button to engage the SAF.  With width set to 10hz or 20hz, slowly vary the center frequency 
till the signal is optimally peaked.  It's important to have the RF Gain correctly set to enhance the signal to noise ratio 
with SAF engaged.  The RF Gain is properly set if you engage SAF with no signal present and you hear slight ringing at 
10-20hz width.  Perform this check by just tuning in band noise with no signal in the passband and engaging SAF.  No ringing 
means not enough RF Gain and moderate ringing means too much RF Gain.

Have a listen to SAF in action on HK3TU's early morning 160M CW signal:
Orion SAF audio filter demonstration (10hz width) - 160M CW Stereo Diversity - listen with headphones 

(the SAF is turned on and off to allow listener to hear its effect)

SSB/AM SAF  

SAF  can greatly improve readability of weaker ssb and am signals.  The SAF width should be set to 300hz.  Tune in the signal 
and engage SAF.  Adjust the center frequency for best readability, usually in the range of 300-600hz.