There is a mod suggesteb by ACOM for both the 1000 and 2000A which will
cures this ARC FAULT problem. I can send details, but it includes 3
pictures so the file is pretty large (about 600 kB). This is NOT an Orion
firmware issue - it's a fundamental problem which may occur even with other
types of transceivers.
Here is what's going on:
" This modification was introduced about one year ago as a result of
co-operation with Piotr SM7YEA. He was experiencing the Arc Fault problem
when trying to connect a TenTec OmniVI+ to his ACOM1000. Thanks to his
careful research we resolved the problem. The schematic of ACOM1000 and
ACOM2000A are similar in that part so we introduced the meant resistor and
removed the capacitor in both models.
The problem is caused by some different systems of TenTec and ACOM keying.
The TXOUT_TXEN concept of TenTec is that the TXOUT controls the RF
transmission by TXEN. When you tie TXEN to the ground, the transceiver
transmits. However, when the TXOUT finishes, the transceiver continues
transmitting a "rounded" trailing edge for still 1 or 2 milliseconds to have
a good CW symbol.
At the same time, the ACOM amplifiers would expect that the RF drive should
disappear before the KEY-IN transmit request disappeared. Once the
transmit-request signal (TXOUT in this case) has finished (KEY-IN is no more
grounded), no more RF drive is expected until a new transmit request. As a
self-guarding function, the amplifier will wait for the RF drive to fully
disappear, by continuously monitoring RF drive presence via a comparator (U9
in ACOM2000A) monitoring the RF drive at the tubes grids. The problem was
caused by the "rounded" trailing edge which was causing this comparator to
generate several pulses while the falling edge of the RF slowly crosses the
comparison level.
The meant resistor introduces a hysteresis and removing the capacitor
eliminates the meant pulses. The modified amplifier works normally with both
TXOUT_TXEN loop connection as well as the single-cable one. "
(Source: ACOM in Bulgaria)
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Barry N1EU
Sent: Saturday, December 04, 2004 4:54 AM
To: tentec@contesting.com; Orion@contesting.com
Subject: [TenTec] RE: [Orion] Firmware upgrade and CW/ACOM2000A issue again
"Sergei Kulyov" <ua3ap@smtp.ru> wrote:
>Does anybody got an issue while in CW keying ACOM2000 after
>upgrade to 1.372? My ACOM immediatly fails to transmitt
>with "ARC fault" alarm althouth I'm using it in QSK mode.
Sergei, my Orion seems to key my Acom 2000A perfectly with v1.372. Sorry to
hear of your troubles.
73,
Barry N1EU
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