[aprssig] FTM-350 cables

Stephen H. Smith wa8lmf2 at aol.com
Thu Mar 10 18:48:23 EST 2011

On 3/10/2011 3:32 PM, Heikki Hannikainen wrote:
>>> Devices such as the Tigertronics Signalink USB have a built-in USB audio 
>>> device.
>> Especially ironic, considering that the Signalink costs $20 LESS than the 
>> West Mountain device!
> That's more like it! But it seems to have some sort of built-in VOX circuit 
> for PTT which probably requires extra txdelay - no built-in serial for real 
> PTT control. And 3 extra potentiometers which should not be needed - the 
> software controls for the USB audio device's mixer seem to be good enough. 
> And it's a bulky extra box.
>   - Hessu

I consider having physical audio pots on the panel a real advantage:

1)    Many apps don't provide convenient access to the software volume 
controls. Microsoft makes it especially clumsy and inconvenient to get to the 
record mixer, if the app doesn't provide a shortcut.

2)    When confronted with only a sensitive mic input (no line-level input), 
the Windows record mixer winds up set barely between zero and the first step.   
With an external pot as a "pre-attenuator", you can set the input level to 
allow the slider to be 2/3rds to 3/4ths of the way up where the gain control is 
less touchy and the gain distribution/signal-to-noise ratio is optimum.

3)     Hardware pots on both TX and RX allow you to quickly accommodate the 
difference between mic-in on the radio vs mini-din data in on the radio without 
shifting jumpers, or to accommodate line-in vs mic-in on the computer.

I've never tested a Signalink USB for fast-draw keying,  but my homebrew 


VOX-keys in about 3 mS, not a significant TXD even for packet.  However, it 
would degrade fast break-in CW generated with audio tones, such as in MixW.  In 
this mode, you would use the "slow" mode of the Signalink or my homebrew device 
to get "semi-breakin" CW -- i.e. hang for a second or so between characters.



Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      WA8LMF  or 14400    [Think bottom of the 2M band]
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

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