Hello Stefan and all,
Use something like a 74HC4046, or maybe an equivalent with a voltage
comparators:
http://www.elektronik-kompendium.de/public/schaerer/vco.htm
btw the xyz4046 could also be used as a demodulator for the FM on
the RX side (PLL to track the modulated input; PLL control voltage =
demodulated output).
Cheers,
Wolf .
Am 09.10.2011 14:13, schrieb Stefan Schäfer:
Hi Wolf,
Thanks for the comments. Do you have a hint for a suitable CMOS
VCO
that is easy to get (Reichelt ;-) ) and good for 137 kHz?
73, Stefan
Am 09.10.2011 13:57, schrieb wolf_dl4yhf:
Hi all,
just my few cents..
if you frequency-modulate the LF (or VLF) signal with a
reasonable
square-wave carrier, there are no problems with linearity. Any
reasonable CMOS VCO will suffice. Similar for the receiver.
Absolutely
no need to 'go digital', when the supplied power is limited.
Cheers,
Wolf .
(who tried something similar with a red 'Luxeon' LED some time
ago, but
the system wasn't reliable lacking affordable narrow-band
optical
filters for the receiver)
Am 09.10.2011 11:30, schrieb Jean-L. RAULT:
I wonder if an analog laser link has enough linearity to carry your LF
signals (bad lienarity ==> noise and intermod effects)
A digital laser link would be better, but would increase the complexity
of the project :o)
Jean-Louis F6AGR
Le 08/10/2011 19:26, Stefan Schäfer a écrit :
> Thanks Dex and Scott,
>
> Enough stuff to study now. The seconds page seems more useful for me.
> Ok about that OT.
>
> 73, Stefan
>
> Am 08.10.2011 21:09, schrieb Scott Tilley:
>> Hi Stefan
>>
>> http://www.k3pgp.org/laser.htm
>>
>> I use his detector and modulator circuits for my system.
>>
>> 73 Scott
>>
>>
>>
>>
>> On 10/8/2011 10:09 AM, Stefan Schäfer wrote:
>>> LF,
>>>
>>> Just thought about trying a LF RX in the forest and feed the signal
>>> via a laser link to the building here. There is a good direct view
>>> to several suitable places, a good 1000m distant from the city. A
>>> simple laser diode, driven at 15 to 20 mA should work fine for some
>>> hours when having a solar panel that charges during the day. You
>>> know these small lamps for the garden with a solar panel, switching
>>> on automatically when it gets dark...
>>> Just seen HA6PC at OE3GHB-grabber but nothing here or at DF6NM (yes
>>> Mal, i know, you've all worked them in the past...).
>>> Pure AM is probably not the best choice, rather FM.
>>> Does someone of you has useful experiance of such a laser system or
>>> even a ready to use circuit or some hints about a compact IC that
>>> does the job?
>>>
>>> No warnings about the danger of laser light please.
>>>
>>> 73, Stefan/DK7FC
>>>
>>> PS: Sri for beeing a bit OT
>>>
>>>
>>
>
>
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