[GreenKeys] Filterless TU

[Duncan Brown]

Ken - It is not "limiter-less" - it is "filter-less"

Tom - I found the schematic (right where it was supposed to be - 
amazing!) of the "Filter-less TU" - it looks like the same, or very 
similar, to the one Jack built. Schematic enclosed.

It uses two 12AT7s (one as a limiter and one as the DC amplifier), a 
12BH7 as loop keyer and an OA2 regulator.  Mine does not have a bias or 
speed control.  I don't know where I found the design for this unit. I 
built it in 1969, while I was in the Army.  Possibly  it came from QST - 
will have to look it up.  Mine did not have an audio transformer and was 
built on a very small chassis. the power transformer took up about half 
the chassis.  Due to having an external loop resistor, a short burnt up 
the transformer. (Note to loop supply builders - keep at least part of 
the loop current limiting resister inside the loop supply to protect the 
transformer!)

  I kept it around for about four moves, thinking that I would rebuild 
it, but never did. On the last move, a few months ago, it went to metal 
recycling.

Have fun,

Duncan

On 9/16/2019 12:13, Kenneth Gartland wrote:
> Hi Duncan...
>
> I have been following the Greenkeys traffic in regards
> to the "Limiteless" TU which Tom has been seeking info...
>
> Wud you have a wiring diagram, parts list or some foto(s)
> you cud share?
>
> I built many years ago, the ARRL single tube TU,
> with the 5763 keyer tube,
> used it a few years, with a Lorenz LO15ASR,
> it worked surprisingly well for what it was...
>
> I copied a lot of RTTY traffic back then when there was still
> many sources out there...
>
> Hopefully, you may still have some "Build" info
> on this, I wud be interested to try and make this project,
> and take a little trip to "Yesteryear"...
>
> I probably have enuf parts on-hand to build it...
>
> Tks for any help/info you may have on this...
>
> Cheers!
>
> Ken
>
> VE3-HMQ
> i-Telex 61663
>

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