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Adventures in Electronics and Radio
Elecraft K2 and K3 Transceivers
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Adventure of the HP
11710B
Revision History
Written 18 February 2009
It may not be much of an adventure, but today I imagined
myself as Howard Carter in November 1922 in the Valley of the Kings opening
Tutankhamen's tomb. What brought this about? Last week, I purchased a "new in
the original packing" HP 11710B Down Converter from Tucker Electronics via it's
E-bay operations. It arrived yesterday and today I opened it up. Indeed, it is a
time capsule of nearly 30 years ago.
The Hewlett Packard 11710B Down Converter, in case you
aren't familiar with it, is a mixer and oscillator that converts a signal
generator's output in the range 50-61 MHz down to 0-11 MHz, thereby extending
the signal generator's range. It was used with HP 8640B signal generator amongst
others.
Upon opening the outer box, it was obvious that the 11710B
was purchased by the US Defense Department. In addition to the MIL red
stamp, the packing and nomenclature on the box made clear the identity of
the original purchaser.
Note the serial number; it starts with "2322A" identifying
it as manufactured in 1983 (1960 + 23) week 22 at a plant in the United States
("A"). The stamped July 28, 1988 date appears to be the last time it was
repacked for long term storage. I believe the 11710B was unused in its original
packing from 1983 to July 1988 when it was repackaged for long term
storage.
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Despite the "Fragile" sticker, one corner of the box was damaged. The
identifier 6625-01-063-8267 is the "National Stock Number," another indicator
that the instrument was purchased by a US Government agency.
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Unpacking this outer box (box number two if you consider the box Tucker
used for shipping as box no. one), a large airtight sealed metalized bag
appeared. And, by the way, box no. two was sealed not just with tape, but all
the flaps were glued in place. I had to cut the box apart to open it.
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Out came the shears and I snipped the metalized bag away. I've seen these
storage bags before for small components acquired on the surplus market, but
this was the largest one I've run across.What's
inside the bag? Yet another box. At this point, I wondered if this was a large
size set of matryoshka dolls instead of an HP 11710B, but the HP legend
suggested I was getting close.
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Like box number two, the HP labeled box had the flaps glued as well as taped.
And, the sealed bag was very effective. The tape on the outside box (number two)
was brittle and flaked off from touching it. The HP box's tape looked as fresh
and flexible as the day it was applied in 1988.
Cutting the last box open—being careful, of course, to preserve the HP logo
printing—revealed three large silica gel desiccant bags and dense foam packing
material. The foam looked fresh, despite being 21 years old. |
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After removing the foam, here indeed was a brand new, unused, 11710B Down
Converter.
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The power entrance still has its "Wired for 120V" sticker.
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Also enclosed in the box were two manuals, update sheets and the HP inspection
tag.
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I plugged the power cord in and turned the 11710B on. All seemed normal, but
would it work after 26 years of being wrapped up and unpowered? I had great
faith in HP, and this faith was not misplaced.
First, I set my HP8657A signal generator to 50.500 MHz, at -50 dBm output and
connected it to the 11710B's input, with the output to an Advantest R3463
spectrum analyzer. I set the 11710B mode switch to "Direct" and the 50.5 MHz
test signal appeared on the spectrum analyzer.
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I then flipped the switch to Down Convert and reset the spectrum analyzer to
center at 500 KHz.
Sure enough, there's the signal generator output,
frequency translated from 50.500 MHz to 500 KHz. The level is preserved in the
translation within ±1 dB according to the specification and this is certainly
met in this quick test.
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To illustrate a more useful application for the 11710B, consider generating an
FM signal at 50 KHz, with 5 KHz deviation. (Don't ask why one wishes to do
this.) Most modern signal generators stop at 100 KHz or higher. However, with
the 11710B, it's a matter of setting the signal generator to 50.050 MHz, dialing
in 5 KHz deviation, selecting 1 KHz internal modulation and connecting the
11710B, as seen below.
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How much use I'll actually make of the 11706B I don't know. But it does have
some applications for my active antenna development where I need an accurately
calibrated signal source down to 10 KHz. And, for $125 plus shipping, it was
hard to resist acquiring a brand new piece of HP gear.
And, as the image below, from HP's 1982 catalog,
indicates, the original price of the 11710B was $1500, in 1982 dollars.
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