Thanks to those that responded. I think I
have some residual RFI problems, but that
was not the cause of the problem listed below.
The main issue was the shield of the mic in
the Heil TT dongle was intermittantly shorting
to the case of the mic connector. The
Orion really, really does not like pin 2 to
be grounded. (In the Heil setup, pin 1 is the
mic lead center conductor and pin 2 is
the shield.) This was the cause of the
oscillation/instability.
I thought I would document for future google
searches.
73,
Tom - N1MM
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of Tom Wagner
Sent: Wednesday, December 15, 2004 5:42 AM
To: tentec@contesting.com
Subject: RE: [TenTec] Orion Mic Woes
More to report. The symptom is easier to
recreate with the mic gain set at 100, however
it happens with mic gains down to 20, and that
is below what the HC-4 element needs to drive the
radio.
I have been able to get the problem started and
remove the mic and have it continue, so it some
sort of oscillation/instability. I have not
yet been able to get the mode started with one
of my inexpensive mics.
My next step will be to put a resistor in series
with the HC-4 and see if the radio likes a
higher impedance better than the one that the
HC-4 presents.
Is there anyone with an Heil mic with an HC-4
element that is able to reproduce this symptom?
Or do I just have a broken radio?
73,
Tom - N1MM
-----Original Message-----
From: Tom Wagner [mailto:tfwagner@snet.net]
Sent: Sunday, December 12, 2004 11:47 AM
To: tentec@contesting.com
Subject: RE: [TenTec] Orion Mic Woe's
I have been battling with what I thought was RFI for
quite a while now. I won't go into all the details.
My setup is an Orion, Ameritron AL1500 & Heil Proset w/
the HC4 element.
I stupidly set the mic gain by ear, rather than by the
red led. With most radios, that's ok. Not with my Orion.
For whatever reason, the Orion will sound fine at high
audio gain levels, then suddenly sound like RF is getting
into the audio. I have been able to repeat this with
two HC4 mics, but not with a couple of cheap ($10-20)
computer mics.
I have lowered the mic gain dramatically, and things
seem much more stable. Time will tell.
Bottom line, if the audio sounds crappy, try turning down
the mic gain first, even if it used to sound fine.
73,
Tom - N1MM
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