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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>
>
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