Re: LF: RE: Analog oscillators

[Stefan Schäfer <Stefan.Schaefer@iup.uni-heidelberg.de>]

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" <Stefan.Schaefer@iup.uni-heidelberg.de>
An: rsgb_lf_group@blacksheep.org
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 hajo.brandt.dj1zb@t-online.de:
> 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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