Full FSK as I understand requires that the VFO frequency be shifted. The
Tigertronics SignaLink USB is an audio interface. Perhaps the Bucscomm
Rascal has a way of doing this or otherwise it is just a AFSK modem like
majority of the rest.
73
Bob, K4TAX
----- Original Message -----
From: <qdot22@gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Thursday, July 10, 2014 4:40 PM
Subject: Re: [TenTec] Omni VI & SignaLink USB
It's interesting that the Tigertronics unit does not support full FSK.
That's why I went with the cheaper Bucscomm Rascal.
Rich, AA6VX
Sent from my iPad
On Jul 10, 2014, at 2:15 PM, "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
wrote:
My reference to input and output impedances and to transformers on the
input and output are from Tigertronics
As provided with the SignaLink USB data sheet.
I quote;
"Radio In/Out Z: 600 Ohm (nom). TX/RX Levels are fully adjustable for
compatibility with Hi-Z and Low-Z radio connections."
From SignaLink USB data sheet I quote:
"Unlike some interfaces on the market, ALL SignaLink models COMPLETELY
isolate your computer from your radio. This eliminates troublesome
ground loops and prevents hum and noise from degrading the signals. The
SignaLink USB provides isolation through the use of audio transformers
and a relay-based PTT keying circuit."
73
Bob, K4TAX
----- Original Message ----- From: "Jim Brown"
<k9yc@audiosystemsgroup.com>
To: <tentec@contesting.com>
Sent: Thursday, July 10, 2014 12:18 PM
Subject: Re: [TenTec] Omni VI & SignaLink USB
On 7/10/2014 6:41 AM, Bob McGraw - K4TAX wrote:
Tigertronics i.e. SignaLink has transformers on the input and output
signals for isolation.
A transformer does NOT provide isolation to differential mode signals.
It only blocks common mode signals. For example, audio voltage on both
windings of a 1:1 transformer are equal, and no impedance is added to
the differential circuit. In a 4:1 transformer, the voltages are
proportional to the turns ratio, and the impedance looking into the
transformer is equal to terminating Z multiplied by the square of the
turns ratio.
Remember that "600 ohms" has not been used in pro audio for at least 40
years. Output stages are low-Z sources, typically 100 ohms for pro
products, 300 ohms or more for consumer stuff, and input stages are high
impedance, typically 10K for pro products, 50K for consumer products.
The impedance of a microphone is defined as 1/5 of it's recommended
minimum load impedance, and a low-Z mic's output Z is typically on the
order of 100 ohms. All commonly used ham mics are low-Z, wired
unbalanced.
As you have described the schematic, with individual 10K in series with
both the mic and line inputs, I agree there should be good isolation.
Perhaps the schematic is not accurate?
73, Jim K9YC
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