Message-ID: <4FC0EA66.8050207@iup.uni-heidelberg.de>
Date: Sat, 26 May 2012 16:36:22 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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References: <495778BC-4950-48D3-B5E4-4DBCE69D729C@numeo.fr> <4FC00C2E.6070101@iup.uni-heidelberg.de> <4FC09285.2060102@kpnmail.nl>
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Subject: Re: LF: 475 kHz exciter
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Hi Jan,


Am 26.05.2012 10:21, schrieb pa3abk:
> On 26-5-2012 0:48, Stefan Sch=E4fer wrote:
>> I've been thinking about using the 2nd D Flipflop of the 4013 and=20
>> build a divide by 4 circuit. With this exciter one could easily use a=20
>> HF TRX like the IC-706 and drive the exciter by transmitting QRP in=20
>> the 160m band. 1900 kHz will then result in 475 kHz and the frequency=20
>> accuracy should be fine. In Split-mode one could transmit on 160m and=20
>> receive directly on MF. Using 3x 150 Ohm / 2W in parallel and another=20
>> 1 kOhm resistor in series with 2 antiserial Z-diodes should be OK for=20
>> driving the input of the 4013 and getting a perfect SWR for the=20
>> TRX... Maybe this is how i will do it.
> A similar set-up is running for some time here.
> I started with de QTX 100W design with a 2MHz x-tal driven.  (I'm also=20
> one of those lurkers of this group)
> Frustrated by the single channel I realized thet the TS-440 has an=20
> "all band" option.
> Simply replaced the the X-tal with a "dummy"-driven single transitor=20
> in saturation, which fed de CD4024 by 4 divider.
> From the dummy there is an attentuation by 4. Drive from the TS440 is=20
> full CCW, almost zero.
> It produces100W from 400-600kHz.  Off course only non-lineair modes=20
> can be used (CW, Opera, Slowhell ect)
> There is small interface which plugs into the transverteroutlet which=20
> drive the  fast reed antenna relais.

Yes, the relais, this is what i am doing in all my HF PAs as well. I=20
have a RX/TX relais that is bypassing the PA in RX mode. It is switched=20
automatically, detecting a input signal on the right band (using a small=20
band pass filter) and then switching to TX. It is fast enough so that a=20
"dit" in CW at 120 BPM can still be detected. So, it is quasi full-BK=20
mode. A delay time for releasing the relais can be adjusted by a pot.

>
> Also experimented with a  mixer from 2MHz to 500kHz  which works fine,=20
> only it requires some caution in relation to the drive.

A mixer for receiving? How do you receive on MF? I still have no=20
concept. Of course there are many but i have no decision so far. Yes, a=20
simple DC receiver is my favirite as well. The IC-706 is an option but=20
not quite /p (takes 1.5A in RX mode!). My K2 doesn't work there i am=20
afraid. So i will need a converter.

The LPF in my PA actually is a BPF so i will have it in series to the=20
RX. That will be a very good first preselector...

> Otherwise a wide noiseskirt is included. The PA is not lineair and=20
> whole circuit has a certain "treshold".
> NL 600m license is restricted to CW only, we consider Opera when=20
> prefixed with a morse ID a such, the rest which follows is just test=20
> and tune signals :-)
> The divider route is therefore best suitable in my case.
> Jan/pa3abk

OK, Jan, hope to meet you on that new band, hopefully this year.

73, Stefan/DK7FC