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Re: LF: RE: Analog oscillators

To: [email protected]
Subject: Re: LF: RE: Analog oscillators
From: Stefan Schäfer <[email protected]>
Date: Thu, 05 Jul 2012 22:40:30 +0200
In-reply-to: <trinity-6fad7208-33e0-44fe-9c50-e8e46d343d3a-1341519411105@3capp-webde-bs35.dlan.cinetic.de>
References: <[email protected]> <7E7DFBB4D102A04DB5ADC88D66628A4A0FAB99CC@ICTS-S-MBX5.luna.kuleuven.be> <[email protected]>, <[email protected]> <trinity-6fad7208-33e0-44fe-9c50-e8e46d343d3a-1341519411105@3capp-webde-bs35.dlan.cinetic.de>
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Hello Hans,

I alreda y have a DDS from ELV, since several years. But this one has a sine output and needs a +- input volatge. So i added a DC/DC converter from 12V -> +-12V to the circuit. This DDS consumes 250 mA when running.
Apart from that i want to build and run my own equipment, even if it is a bit less comfortable or has some restrictions e.g a mono-band RX instead of a wideband IQ RX like the Perseus.
Another reason is the need to use 4x the frequency i want to transmit on because the PA has a /4 divider inside. So if i can have a very small oscillator that just covers 472 to 479 kHz (actually running on 4x that QRG) then this effect is compensated.

For the ELV DDS i added a circuit that allows DFCW operation, a logic circuit that acts on the increment/decrement sensor. It works well, although with some limitations.

73 and maybe AWDH this evening.

73, Stefan


Am 05.07.2012 22:16, schrieb Hans-Albrecht Haffa:

Dear Stefan,
building stable oscillators was a topic in the eighties, and it depeded all on getting stable components. Later developing OMs reported, that the oscillator for the qrp-TRX was the most difficult and time consuming part in development. My recomendation: Buy aready built up DDS-oscillator, available at Funkamateur.de  (herre with IQ-sigs) or ELV-Elektronik.  It is stable, shows  little noise on LF/MF. Must just be built into a enclosure.  It is a time saving solution. But: DFCW is not possible, and a keyed frequency divider  must be added; I divide by factor ten with CMOS-ICs.  More details on request.
55, Hans-Albrecht, DK 8 ND


Gesendet: Donnerstag, 05. Juli 2012 um 21:30 Uhr
Von: "Stefan Schäfer" <[email protected]>
An: [email protected]
Betreff: Re: LF: RE: Analog oscillators
Hello Ha-Jo,

Can you pull one of the xtals to cover the whole band?

73, Stefan

Am 05.07.2012 20:57, schrieb [email protected]:
> Dear all,
>
> the only parts I have bought so far for MF (still beeing engaged in
> other developments) are two crystals: 6,5536 MHz and 7,0200 MHz, to be
> mixed with each other. The mixer is another bipolar transistor, and its
> emitter current is being keyed. A final source follower after the
> low-pass filter will deliver the output to 50 ohms.
>
> The same solution I have also used on LF.
>
> 73 Ha-Jo, DJ1ZB
>
>
>



  

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