Marvin,
This is excellent! This is exactly the sort of item that makes life easier
for us. Please post as much information as possible, if you would not mind.
I agree that a lead-acid cell would work best in this application. I would
suggest a 6-volt unit used with a low-dropout 5-volt regulator. I would keep
the charger separate for ease of use. A 6.9 volt supply could float charge
the battery for long periods of time without damage. An LM7805 5-volt
regulator boosted via resistors would work, as would an LM317 with
appropriate resistors. I would use a switched dc jack for the charger input.
These disconnect the battery from the load when the (dc)plug is inserted.
5.5 by 2.5 mm is one of the more common sizes in use.

Scott Lacey
Contract Engineer (EMC, Safety, Product Development)
sco...@world.std.com

(I have transferred my address for the emc-pstc to my personal email address
after leaving Foxboro - my network account is not yet set up at my new
assignment - the usual "low priority" with the I.S. people)

-----Original Message-----
From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf
Of Jim Bacher
Sent: Wednesday, June 07, 2000 7:37 PM
To: Wolak; Marvin; emc-p...@ieee.org
Subject: Fwd:1-10GHz source



Forwarded for Marvin

____________________Reply Separator____________________
Subject:    1-10GHz source
Author: "Wolak; Marvin" <marvin.wo...@marconi.com>
List-Post: emc-pstc@listserv.ieee.org
Date:       6/7/00 2:47 PM

A few weeks ago, there was some interest about references sources above 1
GHz.  A few months ago I got tired of trying to find a source and made one
myself.  After some experimentation with batteries, I came up with a source
which emits from 250 MHz through 10 GHz.  The source emits the harmonics of
250 MHz.  The source is stable to about 0.3 dB over the charge of the
batteries which is from 12 to 22 hours depending on how they were charged.

The field produced by the source, as tested at 3 m, is from approximately 68
dBuV/m to 85 dBuV/m in the range of 1 to 10 GHz.

If anyone would like to see plots or stability graphs, let me know.  If the
response is overwhelming, I'll post it.

Basically, what I came up with is as follows:

The box is a simple aluminum project box, a circuit described below, 8 NiMh
batteries (rechargeable), and a built in charger.

The circuit was put together on a circuit board using a Radio Shack etch
kit.  A 250 MHz oscillator feeds directly into a Herotek 250 MHz comb
generator.  The output of the comb generator is put through a 10 dB
attenuator and then connected to a sma bulkhead connector using a short coax
jumper cable.

The antenna is a sma m-f barrel with a wire attached to the center
conductor.  A case from a ballpoint pen was screwed onto the barrel to
protect the wire.  I tapped out the end of the pen case so the connector
would screw on.

Can't remember the manufacturer of the oscillator.

The comb generator from herotek, (http://www.herotek.com/), has removable
sma connectors on the input and output.  I removed the input sma and
connected it directly to the oscillator output.

All in all, the circuit draws 173 mA.

The power for the above is regulated by a 5V regulator with some simple
power decoupling and diode protection.

The first pass used AA alkaline batteries.  This provided for only about 6
hours of operation.  The second pass was with 6 C rechargeable alkaline
batteries.  This provided for about 14 hours of operation but the source
stability was poor.  The output at some frequencies would increase 2-4 dB
over the life of the charge.  Another drawback was that the batteries had to
be removed to charge.

I've since replaced the alkaline batteries with 8 Panasonic NiMh batteries.
This has solved my stability problem (I can live with 0.3 dB variability).
To charge the batteries a bought a MaHa battery charger, disassembled it,
and mounted its circuitry in my box.  The switchover from the load of the
circuit to the charger is done through the main double pole-double throw
switch.

If I had to do it over, I would start from the power side.  The NiMh
batteries are not the best choice for a few good reasons but that was what I
was stuck with if I was to keep the same box.  Lead acid may be a better
choice, but would require a larger project box, something like the popular
EMCO Royce field source.

I would be interested in feedback.  There is plenty of room for improvement,
and lots of talent on this board.

If you have any questions, or if something is unclear, let me know.

Marvin Wolak

Marconi Communications
Senior EMC Engineer, Product Integrity
Ph: 724-742-7453
Fx: 724-742-7474
EMail: marvin.wo...@marconi.com


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