Message-ID: <383080D3.4F932B98@co.disp.mindef.nl>
Date: Mon, 15 Nov 1999 22:53:23 +0100
From: "J.M. Valstar" <jm.valstar@co.disp.mindef.nl>
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To: rsgb_lf_group@blacksheep.org
Subject: LF: Re : Ropex Mods
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Hello Group,
May be I can give some suggestions/hints.
Hope you will succeed, gd luck !
And pse let us all know your experiences.
73
Jaap/pa3guc

Mike Dennison wrote:

> > I would be glad to supply detailed instructions on the process to anyone
> > contemplating the re-crystallization (?) of a Ropex.
> > 73
> > Andre' N4ICK
> > ************************
> Andre,
>
> I will be getting a Ropex Tx as a Christmas present for my portable
> work. Please let me have details of the crystal mods.

I modified the prototype of the Ropex (in fact the real First, hi).
Nico/pa2njn operates it .
It was very easy to make that modification. I can't give details of the
mods
in particular, cause the PCB of the produced Ropex differs from the
prototype.
I can imagine, you have to make minor modification(s) to the pcb.

Just order an X-tal ; f.e. for SCW 48 x 137.7 = 6609.6 kHz (The used
x-tal is
a standard cheap x-tal (6.5536 MHz) other freqs have to be ordered, I
think.
You will have to check how to place/connect the 2nd X-tal and thumble
switch
on the print and front panel, I cannot give suggestions for that..
It might be possible to make a third frequency just by switching the
x-tals
parallel to each other ! I don't have experience with that, so it has to
be checked out.

> I have a synthesizer for 136kHz. Can this be used to drive the
> Ropex? Are there snags, like it blows up if there's no drive?

No, for  the Ropex oscillator runs on 273 kHz ( the 4060 acts as a
24-divider).
Don't even try to let it run on 136 or 273 directly; Two defective Fets
are a
great risk! The best way is like I did, also Albert/PA0AWN worked this
way.
I made Vfo mod. for Nico's set. I placed a BNC connector in the front
panel. Next to this connector I placed the thumble switch to select
either the original X-tal,
or the VFO-input.
Nico's Vfo's freq is around the x-tal freq and only replaces the X-tal.
Because a lack of space around the oscillator circuit of Nico's set I
made
this mod very simple. I believe to have used pin nr 11 of the IC (a
4060) for the VFO output (50 Ohm ).
I will check this for sure (Nico has to open his set for that).
The VFO output is 100 mW, but can be less I suppose.
Nico is working a few weeks already with this modification.


When there is no Osc. drive a RC oscillator of the Fet-driver IC will
take
over oscillation to prevent the FETs from breaking down. The output freq
was abt 73
kHz(?!), but I don't think this is wise to use, because the output trafo
has been designed for 136 kHz and this freq. is not stable !

> Ideally, I would like to run two crystals, preferably with VXO
> capability (one for normal CW, one for QRSs) but also have a
> socket for the synth.
> 73
> Mike, G3XDV