[time-nuts] LORAN-C antenna

[Carl Walker]

Bill is correct - 10V should do it; these couplers were fed DC up the
coax with ~10mH of choke from a circuit that could detect whether the
load of the amplifier was present or shorted (essentially "open" and
"short" DC antenna status bits so the unit could complain of errors in
the interconnection if required). That circuit supplied voltage that was
a couple Si drops away from the +V rail in the receiver. As long as the
emitter follower doesn't dissipate too much power, you're probably in a
satisfactory operating range for Vin - take a look across the output
resistor and calculate for your particular voltage.

These were the third generation of LORAN-C receivers I worked on at this
company. Now I do feel old.

Thanks for posting the schematic, Bill - having worked for them for so
many years I didn't feel all that comfortable doing so myself - although
now that you've done so, I can comment on it ;-)

-Carl


On Tue, 2007-11-13 at 04:05 -0800, WB6BNQ wrote:
> Didier,
> 
> This should jog Carl Walker's memory.
> 
> Here is the schematic for the NorthStar M1 LORAN receiver WHIP preamp that has
> filtering.  The M1 is an aircraft unit that I snagged along with the preamp.  It
> is a re-draw of a schematic sent to me by NorthStar.
> 
> Obviously, the whip size on an aircraft is small.  So you should use a whip that
> is not to long (maybe up to 3 feet) or it may overload the preamp.
> 
> Also, the preamp is powered by voltage fed up the coax.  At the moment I do not
> remember what the voltage level is.  Perhaps Carl can add to this ???  If not I
> can dig the thing out and plug it all in to see what the voltage level is on the
> coax.
> 
> I can tell you this, it is not over 12 volts as that is the power to the whole
> unit.  My guess, at the moment, is that it is around +8 volts.
> 
> Well, I dug up the M1 paper work.  I have the user and installation manuals, such
> as they are, and neither of them say anything about anything that is useful.  So
> I will have to take some time tomorrow and power it up to see what the voltage
> is.
> 
> Bill....WB6BNQ
> 
> Didier Juges wrote:
> 
> > Speaking of Loran, I have an old Loran receiver (origin forgotten) and no
> > antenna.
> >
> > Is it possible to build a Loran antenna?
> >
> > I understand Loran uses narrow pulses of 100 kHz, so the antenna must have
> > sufficient bandwidth to let the front edge of the pulse go undistorted. On
> > the other hand, there are lots of spurious signals at these frequencies, so
> > some selectivity is probably necessary. I am not sure what design would be
> > best. I have made ferrite bar antennas for other long-wave reception, but it
> > was narrow band, so I am not sure these designs would work.
> >
> > I live on the Gulf coast of North-West Florida, and therefore I believe I am
> > not too far from a Loran station, so I probably do not need extreme
> > sensitivity.
> >
> > Any suggestion welcome.
> >
> > Thanks in advance,
> >
> > Didier KO4BB
> >
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