[GreenKeys] Terminal unit (HAL ST-5000) adjustment

[Ethan Blanton]

Jeffrey Angus wrote:
> On 1/8/18 8:24 PM, Ethan Blanton wrote:
> > Several people were concerned about the 2-B IF bandwidth and its
> > affect on alignment, but I assure you that I did not try to align
> > the unit through the 2-B.  :-)  I used known good tones at a
> > controllable amplitude for that!
> On bandwidth.
>
> A simple on/off keying at 60 WPM requires about 320 Hz bandwidth. This
> is to allow the 7th harmonics of the baud rate so that the keyed
> signal looks like a square wave. If you use FSK at 170 Hz, this
> increases the bandwidth requirement to 320 + 170 or 490 Hz. A side
> note to this: The 170 Hz shift was picked so to minimize the amount of
> that 320 Hz sideband power in the other tone's response.
> 
> Part of proper receive tuning of the 2B includes putting the passband
> tuning outside of the ._. markers.

Understood and agreed.  It is my belief that the 2-B 500 Hz pass band
is marginal for RTTY use in general (although improved alignment of my
own 2-B might change this belief), as it is difficult to know
precisely where it is aligned around the signal of interest and its
flatness across the top of its pass band is less than ideal. Certainly
it cannot be placed on the dot, which aligns it around the expected CW
tone range of 800 Hz to 1 kHz.

Thanks,
Ethan

> -- 
> "I am a river to my people."
> Jeff-1.0
> WA6FWI
> www.foxsmercantile.com
> 
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