[NLRS] Protecting a transverter from an IC-746

[David Palm]

That's a good idea if the 746 is dedicated to transverter IF service.  But
would be a hassle if you want your 100 watts on 2 meters back for normal
operation.

On 9/16/09, Chris Elmquist <chrise at pobox.com> wrote:
>
> I was able to set the MAX power out of the 2m port on my IC-746 with an
> internal pot...  so that when the front panel power control was at max,
> at most 1W was produced by the rig.
>
> If you study the schematic, you will find a pot inside that sets the max
> power to which the front panel pot can go...
>
> My '746 then drives into a DEM 902 transverter at a 1W level.
>
> Chris N0JCF
>
>
> On Wednesday (09/16/2009 at 02:52PM -0500), David Palm wrote:
> >
> >
> > My main rig in the shack is an Icom IC-746.  I'm extremely fond of it--I
> > bought it from a ham who had tried to "fix" it, by replacing the surface
> > mount connector for the control head ribbon.  Well, he fixed it alright,
> > hosed it up good and proper.  I got it at a good price, rebuilt the area
> on
> > the surface mount rework station at work, mounted a new connector, and
> > Voila! I have a working 746!  On account of that rig's respectable 100
> watts
> > and decent receiver on 2 meters, I'm now into VHF stuff.
> >
> > I love the rig, but it's not at all transverter friendly.  There isn't
> any
> > low power output port.  You can turn down the main power to about 5
> watts,
> > but even then it's a manual operation that can easily be forgotten.  Sure
> as
> > heck, if I hook that dude up to an unprotected transverter I'll be
> toasting
> > it in a hurry.
> >
> > It seems to me that all I need is a circuit that will detect that the 746
> is
> > in transmit mode, then look at the current on the IF.  If the current is
> > above, say, 100 mA (200 mW into a 50 ohm load) then it leaves a relay
> open,
> > dumps the RF into a dummy load, and turns on a warning LED.  If the
> current
> > from the IF is below 100 mA then it goes ahead and closes the relay and
> that
> > flows to the transverter.
> >
> > I've looked a bit on the 'net and strangely, haven't come up with a
> circuit
> > for that purpose.  Am I on the right track?  I can design it myself, but
> > does anybody know of an existing design out there?  Anything else I'm
> > missing?
> >
> > Thanks and 73,
> >
> > David  W9HQ
>
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> --
>
> Chris Elmquist
>