[GreenKeys] TTY-Connect 160V vs 80V

[gil smith]

Hi Tim:

It is not the transformers that run hot, it is the power-resistor/heatsink 
that gets toasty.  The xfrms are oversized at 43VA, but a smaller xfrm is 
about the same price, and I like to be conservative, especially on a power 
design.  Which is why I don't like a heatsink running at 175 F (160V 
loop).  With an 80V loop, the heatsink is only 125 F, and the lower voltage 
is safer as well.

No, I am not a ham.  Well, maybe after a few beers.  I did pick up an HF 
transceiver, so I can start listening for HoffNet and other rtty stuff.  I 
need to find a 12V supply for it so I can free up the lab supply I have 
been using.  Maybe one day I'll get motivated and get a license so I can 
transmit as well.

thanks,

gil


At 08:00 AM 7/1/2004, you wrote:
>The project is really looking good! I, too, wanted to thank you for all
>your effort on this project!
>
>I don't know how much I will implement - probably at least one HV supply
>and the computer section. I have a Heathkit HD-3030 (actually a Flesher 470
>in disguise!) and it really is meant to be interfaced using RS-232.
>
>I am curious as to why the transformers run so hot especially in the 160
>volt mode? You show the transformers to be 43 VA and I calculate that the
>current at 115 volts should be 370 ma. Only drawing 60 ma should mean that
>the transformer is loafing!!
>
>Tim Swarthout, WA5QEG
>
>P.S. I was wondering - do you have a ham license?

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