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From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <KOEAKFKINDBIGKCFCJEDGEBJCAAA.victor13@online.nl>  <7E7DFBB4D102A04DB5ADC88D66628A4A0FAB99CC@ICTS-S-MBX5.luna.kuleuven.be>  <1SmrFA-199XcW0@fwd21.t-online.de>  <4FF5EB68.9040507@iup.uni-heidelberg.de> <1Smsua-1XhIH20@fwd18.t-online.de>
Date: Thu, 5 Jul 2012 23:05:03 +0100
MIME-Version: 1.0
Subject: Re: LF: RE: Analog oscillators
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Hi stefam/Ha-Jo....when I did this I chose a pair of crystal that mixes to 
one end of the band then pulled one upwards and the other downwards 
simultaneously. There still is a slight drift problem but id chosed carefull 
the drift on the two crystals is the same so the difference cancels it out. 
The remaining problem is due to the tempco of the tuning components. I also 
used a diferential variable capacitor for the tuning. Good quality caps are 
just as essenial as with VFOs.

Alan
G3NYK

----- Original Message ----- 
From: <hajo.brandt.dj1zb@t-online.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Thursday, July 05, 2012 9:44 PM
Subject: Re: LF: RE: Analog oscillators


> Dear Stefan,
>
> Yes. xtal 7,02 MHz will run stable, and xtal 6,5536 MHz must be pulled
> down by 12,6  kHz to 6,5410 MHz. A coil in series to the crystal and the
> tuning capacitor will do this, in its simpiest form by using a molded rf
> choke.
>
> Or 7,0200 MHz is adjusted for 7,0256 MHz, then 6,5536 Mhz will deliver a
> difference frequency of 472 kHz. And when 6,5536 MHz is pulled down to
> 5.6466 MHz, the difference will be 479 kHz.
>
> OK?
>
> 73 Ha-Jo, DJ1ZB
>
>
> "Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de> schrieb:
>> 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
>> >
>> >
>> >
>>
>>
>
>