[GreenKeys] Simple PLL TU

[Harold Hallikainen]

They are listed at
https://w2jc.org/candles/TTY-stuff/Currently_available_Teletype_SUPPLIES_200602.pdf

Harold


On Tue, October 1, 2024 7:25 pm, Ralph Mowery wrote:
> While speaking of the simple TUs is there a source for the 88 millihenry
> coils ?  The ST-5 is very simple and works very well but needs 2 of the
> coils.
>
> Ralph ku4pt
>
>
> -----Original Message-----
> From: greenkeys-bounces at mailman.qth.net
> [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Harold Hallikainen
> via GreenKeys
> Sent: Tuesday, October 01, 2024 4:31 PM
> To: greenkeys at mailman.qth.net
> Subject: Re: [GreenKeys] Simple PLL TU
>
>
>
> On Tue, October 1, 2024 12:53 pm, Ken LoCasale wrote:
>> Gang,
>>
>> I found a simple two IC terminal unit for anyone that might want to try
>> mechanical rtty on a budget. I think I'll layout a board and give it a
>> try. Has anyone else seen it before and given it a try?
>>
>> I put the .pdf here. https://qrpbuilder.com/simple-pll-terminal-unit
>>
>> ken - wa4mnt
>
> I built a demodulator like that (based on the NE565) back then. I don't
> think the 741 limiter gains you anything. It's pretty easy to just
> saturate the NE565 input as a limiter. The datasheet (which includes a
> very similar demodulator https://www.fabian.com.mt/viewer/44073/pdf.pdf )
> says only 10 mV is required for the PLL to lock.
>
> A nicer (obsolete) chip is the XR2211 (
> https://assets.maxlinear.com/web/documents/xr2211av104.pdf ). I designed
> several products around this chip. It includes the PLL of the NE555 along
> with the data slicer (comparator typically wired as a schmitt trigger) and
> a lock detector (mark hold). As shown at figure 11
> https://assets.maxlinear.com/web/documents/xr2211av104.pdf#page=14 , the
> lock detect and FSK demodulator outputs are open collector, so they can
> just be tied together to get mark hold.
>
> Harold
> https://w6iwi.org
>
>
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