QST just arrived and it has an article on problems associated with the USB
Signalink.
I love my inexpensive EASY-DIGI and get great results with it.
Best regards - Bry Carling AF4K
> On Jul 10, 2014, at 5:40 PM, qdot22@gmail.com wrote:
>
> 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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