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LF: Re : Ropex Mods

To: [email protected]
Subject: LF: Re : Ropex Mods
From: "J.M. Valstar" <[email protected]>
Date: Mon, 15 Nov 1999 22:53:23 +0100
References: <[email protected]>
Reply-to: [email protected]
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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.

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
> ************************

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
in particular, cause the PCB of the produced Ropex differs from the
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
You will have to check how to place/connect the 2nd X-tal and thumble
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
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
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
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
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
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.
Mike, G3XDV

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