[ARC5] Fun with the DU-1

[jmfranke]

Nice to hear from someone else who likes the little compact loops.  I am 
currently using one as part of a DGPS receiver on 289 kHz.  With the tubes 
switched to 12V operation, and you do not need the unidirectional pattern, 
you can pull the sense amplifier tube, V-101, and operate in B mode (figure 
8 pattern) to save power.  Leaving V-101 in allows you to use a long wire in 
mode R to tune your receiver before going to modes B or D.  I have six or 
seven of the sets and trying to find new applications.  Many have had the RF 
connector replaced with a SO-239.  Someday I will make some coax adapters 
using the info on Mike Hanz's web site.

John  WA4WDL

--------------------------------------------------
From: <arc5 at ix.netcom.com>
Sent: Sunday, June 06, 2010 7:08 AM
To: "ARC5" <arc5 at mailman.qth.net>
Subject: [ARC5] Fun with the DU-1

> Got a chance to work on my DU-1 Navy direction finder.
> I'm sure most of you recognize it:
>
> http://home.netcom.com/~arc5/DU1/DU-1.jpg
>
> Cleaned it up, touched-up the cosmetics, lubricated,
> De-Oxit-ed where needed etc. and it fired right up
> into my service monitor.
> This one is jumpered for 12-volts.
> Very impressive engineering.  While it is speced
> for 200 volts B+, this little honey was still pulling
> BCB stations out of the noise and DFing
> just fine with B+ all the way down to 12 volts.
> In fact, I found no advantage at all to running
> the B+ any higher than about 45 volts.
> Higher voltages made no difference
> in sensitivity or in noise floor.
>
> Interesting-  The manual specs the set for 200-1600 KC,
> with an 800 KC test point in the middle of the top band.
> But this set tunes and DFs all the way up to 3.3 MC,
> with 800 KC in band #2.
> While I have not yet gone through the manual and
> inspected the components for changes, I can find no
> evidence of ham-hacking (save one) that would indicate
> someone munging the frequencies.  Since a common
> aviation freq at the time was 3105 KC, I wonder if
> there was ever an official modification order.
>
> The one ham-hack: the power connector.
> Please take a look at this photo:
>
> http://home.netcom.com/~arc5/DU1/DU-1bk.jpg
>
> This set has had J-101 replaced with an octal male.
> Given how many of these 5-pin-with-index plugs were
> stripped out, there should be some in junk boxes around.
> I had one, but sent it to a list member years ago.
> The socket includes a black mounting plate that engages the
> matching plug's securing pin.  If anyone has one, I'm be grateful
> and glad to trade or buy.  Also- (hope springs eternal)
> one of the scarce single-pin output connectors would put
> a smile on my face.
>
> TNX OM ES 73 DE Dave AB5S
>
>
>
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