[TenTec] ORION BCI

[Steve N4LQ]

I never said the Orion had a "design flaw". That would amount to the crime 
of heresy on this reflector. No, the Orion is just rather typical when it 
comes to being connected to MY loop. Yes it's a full wave loop cut for 
3.550mhz. It has a 4:1 current balun at the feed point and about 80' of RG8 
for feeder. SWR is less than 2:1 on all harmonics 80-10 meters.
Most rigs I have tried, and I've tried a lot of them, experience some BCI 
from WHAS on 840khz. The worst are the older TenTec rigs such as the 
Tritons, Omni C etc. The best is the TS-480 which is totally clean. The 
Orion falls somewhere in the middle.
Putting a tuner in like eliminates the problem. In fact, the tuner doesn't 
even need to be resonated. Just putting it in line seems to eliminate all 
BCI from WHAS. Since I didn't want to fiddle with a tuner when I didn't need 
one, I use the ICE filter on these slackers.
No, it's not a FLAW. It's just a weakness and I wasn't expecting this on a 
$3k+ radio.
Steve Ellington
N4LQ at iglou.com
----- Original Message ----- 
From: "Lee Crocker" <w9oy at yahoo.com>
To: <tentec at contesting.com>
Sent: Saturday, May 28, 2005 11:14 AM
Subject: [TenTec] ORION BCI


> One other reported a similar problem on his loop
> antenna.  The radio station he reported the problem
> with transmits on 840khz.  1/4 wave on 840 is 278ft.
> If his loop is full wave on 3.6 mhz its length is
> about 278ft.  Suspicious to say the least.  In fact I
> think it is a red herring.  On a resonant antenna a
> couple of miles from a 50kw transmitter, I am not
> surprised significant voltage could be present on the
> antenna terminals of the Orion.  Neither am I
> surprised that a 6db pad might be enough to clear the
> problem.  In fact I would predict such a conclusion.
> So what makes the loop so special?  He did not say he
> had trouble on all  antennas, only on his loop which
> he said was a very challanging antenna for BCI.  He
> also noted that the problem went away when he used a
> tuner, which would give attenuation to the 840khz
> signal, the same as a pad.  So my guess what makes the
> loop so special is that is has a resonance on 840khz.
>
>
> This has not been a commonly reported problem with
> this radio on this list.  In fact just the opposite is
> true.  Many operate these radios in full tilt multi
> station and SO2R contesting situations with success.
> If it was a common problem that a couple of stray
> volts on the antenna terminals made the clamp diodes
> go non linear, people would be howling to the hills
> about how bad the Orion is for contesting.  This is
> not the case.  So given that the experiment has been
> done in contests repeatedly and is probably being
> conducted this weekend during the WPX test, it makes
> me wonder why you have the situation and most others
> do not.
>
> So given your RF engineering background you might
> consider seeing if you lost bias on the diodes, just a
> suggestion of course.
>
> Another tact might be to poll the membership of the
> list and see just how common the problem is.  I'm sure
> there are many hams who live within a few miles of a
> broadcaster.  If it is a design flaw you would expect
> the problem to be common since every radio would
> contain the precursor to the problem.  So that's the
> null hypothesis, a design flaw should lead to a
> predominance of BCI problems.  The alternate
> hypothesis would be that the problem is not common and
> therefore not a design flaw.  I have an Orion, I live
> 3 miles from a broadcast station on 880khz, and I have
> no problem like you describe.  So put that bit of data
> in the "not common therefore not a design flaw"
> column.
>
> 73  W9OY
>
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