I was also doing some Orion experimenting during the contest on the bottom
of 40 meters.
Between 7.000 and 7.006 there must have been 3 or 4 s9+20 signals. What I
was
trying to do was find a very small hole amoung these signals where I could
use a tight filter and see how well the Orion would perform. What I found
was to me truely amazing. I was using a DSP filter of 170 hertz and the
tentec 219 250 hertz filter. There is a 12 db insertion loss on the 250
filter, so when I engaged the 250 I also turned on the preamp to make up for
the difference. First of all, I was easily able to hear and copy some S3
signals in this zone. The Orion has the ability to knock out the unwanted
signals and produce a clear, quiet, zone in between. Anyway, I could not
find any noticeable difference of adding the 250 filter to the 170 DSP. I
was surprised at this and tried to be very careful to see if I could tell.
But adding the preamp to make up for the insertion loss made the background
noise sound identical to not having the roofing filter. There may be cases
where the roofing filter helps over having the 1 K standard but I haven't
found one yet. Maybe on 160 in the winter there will be an even larger
signal level difference and it will matter. The bigger issue is keys clicks
from the big signal because you can't do anything about that.
I also compared the same signals with my rx340. The rx340 has even steeper
skirts on its DSP filters in this range than the Orion. But the rx340 could
not get these in between zones as quiet and small signals in these zones did
not sound clean and were almost impossible to copy because of what sounded
like a touch of intermod. I think this is an indication of the IP3
intercept not being as good on the rx340 for close in signals.
Carl Moreschi N4PY
Franklinton, NC
----- Original Message -----
From: <k6se@juno.com>
To: <tentec@contesting.com>
Sent: Monday, May 26, 2003 3:11 AM
Subject: [TenTec] Orion in the WPX contest
> I used my Orion in a CW contest (WPX) for the first time to evaluate it
> in that type of environment. Most of the time was spent trying different
> DSP bandwidths, different roofing filter bandwidths, different AGC
> settings, the NR, etc.
>
> Curious to see how the receiver would perform in a crowded band with a
> lot of strong signals, I forced the widest roofing filter (20kHz) to be
> active no matter what the DSP bandwidth was set to. I was surprised that
> stations 500Hz apart were easily separated when using a DSP BW of 300Hz.
> Switching to the 500Hz roofing filter seem to make no difference in that
> respect. At no time did I ever hear any of the chirps and birdies that
> you hear on other radios with poorer IMDDR3, even with the roofing filter
> set to 20kHz. All of my listening was done with the preamp turned on.
>
> One thing that I *did* notice when changing between a wide and narrow
> roofing filter was the audio output level into the headphones. Using the
> wide roofing filter made the noise and signal both increase noticeably
> (although the S/N ratio of the receiver seemed to be the same), requiring
> me to back off on the audio gain control a bit.
>
> Note: For those of you that want to "force" one of the roofing filters,
> the filter selection does not become active until you exit the menu *and*
> rotate the VFO knob.
>
> Of the four AGC selections, FAST and OFF did not seem useable at all
> because those two positions created audio distortion unless I "rode" the
> RF gain control. Curiously, unlike other radios, the S-meter still
> indicates signal strength when the AGC os off. The best positions for
> the AGC on CW are the MED and PROG positions. PROG works quite well on a
> quiet band (like 20/15/10 meters) and MED seems better on noisier bands
> (like 160/80/40 meters). To gain more insight on the Orion's AGC, I
> recommend that you read the treatise about digital AGC by Doug Smith,
> KF6DX. Doug is the chief design engineer of the Orion and his article
> can be obtained at http://www.doug-smith.net/digitalagc.htm.
>
> The NR worked somewhat on the lower (noisier) bands but seemed to have no
> effect at all on the higher (quieter) bands. This was mainly because the
> NR requires that the DSP BW be relatively wide before it begins to shine.
>
> Neither the hardware nor the DSP noise blanker would eliminate the
> "tic-tic" noise from my neighbor's electric fence unless the roofing
> filter was set to 1000Hz or greater. Both NBs would take care of the
> noise by forcing the 1000Hz roofing filter to be active at all DSP
> bandwidths, with the hardware NB appearing to be slightly more effective
> on the electric fence noise.
>
> Serious contesters and DXers who use CW should spend a lot of time trying
> different combinations of the AGC/roofing filter/DSP filter/NR/NB
> selections to determine how they prefer to have those settings while in
> the field of combat. They all seem to interact with each other and there
> is no one optimum setting for all conditions.
>
> Most of the time I operated I used the "search and pounce" method, using
> only one VFO. Many times after working a station I had to tune just
> barely out of the passband to find the next station to call. Separation
> of two strong signals is no problem with the Orion, even when using the
> 20kHz roofing filter.
>
> I left the CW rise/fall time at the factory default of 5mS and all
> stations seemed to have no trouble copying me at 30wpm due to "soft"
> keying. Even the weak, watery Europeans on 20 meters copied me with no
> problem, so I'm satisfied with the Orion's keying.
>
> No big score, enjoyed playing around on all six bands, and learned more
> about the Orion.
>
> 73, de Earl, K6SE
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