One of the issues I've had for years with not only certain earlier models
from Tentec but with other companies as well. This is the use of the
microphone input for other than microphone usage. In many cases, this was
the only way to get a digital or data signal into the transmit audio chain.
The typical result can be overdrive of the 1st audio stage which is before
the gain control circuit. Once this stage is over driven no amount of
reducing the audio gain will correct the issue. The 2nd issue is that the
level required to operate the audio stages correctly requires the external
source to be a very low level which is followed by quite high gain
amplification. The result as Gary points out is RF in the audio.
While the Paragon provides an Audio In connector, it is simply another input
isolated by a 10K resistor and feeding direct to the microphone input. This
is not a true line level input. Correctly there should be some 20 to 30 dB
of attenuation located between the Audio In and the actual audio stages.
I've found this to be of great benefit hence the driving device is required
to produce higher output level, thus the signal on the cable between the
driving device and the input to the radio is greater, thus the S/N ratio is
improved. Otherwise, one is much less likely to experience RF getting into
the audio.
Today's radios that do provide a Line Input are more likely to have a
separate audio path structured at the correct level configuration. They are
much better suited to handle external devices for digital and data
operations.
As to the Paragon, this can be fairly easily accomplished by added two
resistors along with using the original 10K resistor. The two added
resistors are 10K in series and 680 ohms to ground to form a T network.
This will then require the external driving device to deliver much higher
signal to the radio and greatly lessen the likelihood of RF issues.
I have a basic philosophy to all of this: If it is a microphone then
connect it to the microphone input. If it isn't a microphone then best find
some other way to get the required signal into the radio.
73
Bob, K4TAX
----- Original Message -----
From: "GARY HUBER" <glhuber@msn.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Cc: <wd9hdq@arrl.net>
Sent: Saturday, July 07, 2012 1:57 PM
Subject: Re: [TenTec] PK232 and Paragon 585
As I recall, it was easy to get RF in the SSB audio if a device like the
PK232 was left plugged in. You may be able to avoid the problem with audio
isolation transformers (or RIGblaster nomic) and clamp-on ferrite beads.
73 ES DX,
Gary -- AB9M
-----Original Message-----
From: Tim & Darlene Isom
Sent: Saturday, July 07, 2012 1:28 PM
To: Discussion of Ten-Tec Equipment
Subject: [TenTec] PK232 and Paragon 585
Anyone out there using the Audio in, Audio out, and PTT on the paragon's
rear
panel hooked to a PK232?
If so, having any issues during normal SSB operation with the audio in
plug
remaining plugged in?
Can reply to me directly at wd9hdq@arrl.net
Thanks.
Tim, WD9HDQ
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