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NEWINGTON, CT, Jan 19, 2000--Hedy Lamarr, the sultry, sexy screen star
of the 1930s and 1940s who also conceived the frequency-hopping
technique now known as spread spectrum, has died. Lamarr was found
dead in her suburban Orlando, Florida, home Wednesday.
She was believed to be 86. 

Born Hedwig Kiesler in Austria, Lamarr came to the US in 1937 after
being signed by MGM. She debuted on the American screen in 1938,
co-starring with Charles Boyer in Algiers. Among her most successful
films was the 1949 Samson and Delilah, directed by Cecil B. DeMille. 

In her 1992 book Feminine Ingenuity, Lamarr describes how she came up
with the idea of a radio signaling device for radio-controlled torpedoes
that would minimize the danger of detection or jamming by randomly
shifting the frequency. She and composer George Antheil developed the
concept and received a patent for it in 1942. 

The concept never saw fruition during World War II, but when the
patent expired, Sylvania developed the idea for use in satellites.
Spread spectrum also has found applications in wireless telephones, 
military radios, wireless computer links, and Amateur Radio
experimentation. 

Lamarr lived in an Orlando suburb in recent years and shunned publicity. 

A more-detailed version of Lamarr's role in spread spectrum is
described in the IEEE book Spread Spectrum Communications, published in
1983.--thanks to Andri Kesteloot, N4ICK and Bill Ricker, N1VUX

Washington D.C. --The FCC today voted to create a class of radio
stations designed to serve very localized communities or
underrepresented groups within communities by authorizing two
new classes of noncommercial low power FM radio services (LPFM). 

In authorizing the new services - (1) LP 100, with power from
50-100 watts and a service radius of about 3.5 miles; and
(2) LP10, with power from 1-10 watts and a service radius of
about 1 to 2 miles - the Commission said it is adopting
interference protection requirements based on distance separation
between stations to preserve the integrity and technical
excellence of existing FM service and to not impede the
ability of existing radio stations to transition to digital
transmission capabilities. 

More at:
http://www.fcc.gov/Bureaus/Mass_Media/News_Releases/2000/nrmm0001.html

Wonderful news about the LP radio finally being approved.

The ARROW ham radio club is sponsoring a class for licensing as a No-Code
Technician, with an option for Element 1 (5 wpm code). The classes start
on 25 October and pre-registration is required before 22 October. Classes
will be held 7:00-9:00 pm at UM's North Campus. See
http://www.cyberspace.org/~arrow/ for details. 

I am now a certified VE, got the certificate and ID badge in the mail last
night.

  Congrats, Glenda. Welcome to the VE club

  I would like to announce that I am the proud owner of an Icom Q7A,
which is principally used as a scanner, but can be used as a ham HT.
It only puts out 350mw on 2m, and 300mw on 440.
  All in all it's pretty neat. The recieve capability is awesome: 30Mhz to
1300Mhz.

Congrats to both!

That doesn't sound like a lot of power, but if all you're doing is hitting
local repeaters, it should be plenty.

How do you like it after a little bit of a break-in time?

Grex has a new ham.  Staci, known as dewshine and/or sea passed her tech
test yesterday.  Now begins the wait for the ticket to show up.

Excellent!  Tell her congrats and I hope to catch her on 2M or 1.25M sometime.

Congrats to Staci!

I recently worked out the transfer function of an arbitrary Twin-T
RC network. It is probably in a book (or some EE students pile of
solved homework problems) but I found it easier to derive it, though
it wasn't easy to derive. If you'd like to know what it is, let me
know. The Twin-T network has found use in audio oscillators and
"notch" filters.

Not that my electronics knowledge is all inclusive, but I'm better than
most at it.  (At least non-engineers.)  I can't recall hearing of a
Twin-T RC network before.  Sounds like it would be a variant of a Pi
network.

There is a version of a Twin-T RC network employed in an audio oscillator at
http://home.att.net/~theremin1/Circuit_Library/twin_t_oscillator.html

The description of the circuit operation is not very good. The component
values chosen in this circuit are closer to the "notch" Twin-T filter,
which can be used to completely reject a single frequency, but which does
require very close component matching. The more general oscillator version
is much more tolerant of component values. 

While I derived the general transfer function, I only created the Nyquist
diagram for one version and have not explored the general behavior. I may
do that as it is an interesting way of obtaining a "notch" like a L-C
resonant circuit but with only resistances and capacitors. 

There is an even simpler version in the 2001 ARRL Handbook in Fig. 26-19.
I'm sure it is in other editions of the Handbook. 

I couldn't resist so converted my Excel spreadsheet for calculating the
Nyquist diagram for the Twin-T network to one for more general component
values. It can now be used to look at the effect of the component values
for the RCA oscillator or the notch filter, or for configurations between
these. I conclude after "playing" with a for a bit that component values
are not at all critical for oscillator use, but very critical for a notch
filter. 

By the way, the Twin-T part of the circuit I cited above at home.att.net
is exactly a notch filter. If the component values are exact, this gives
zero (0) pass at the notch frequency. It is certainly used in a peculiar
fashion in that oscillator circuit, however. The notch filter is used to
*prevent* the oscillator from going into oscillation at any frequency
other than the notch frequency - the positive feedback to cause
oscillation is provided by a direct connection without reactive elements,
but that is cancelled by the Twin-T network except at the notch frequency.
The use of the Twin-T network in more direct fashion in oscillators is
based on the network providing 180 degrees phase shift in a negative
feedback configuration. 

I finally took a minute to look at that site, with a brief review of
the opening text and a look at the schematic.  This is basically what
I thought it would be, but it's in parallel vice the series I had in
my head.

Seems that it would be highly reliable as a notch, without going into
more active components to do so.

I'm going to be interviewed on Marketplace on NPR next week.
About running a home internet business.

Congrats!  (Did you already do the interview?)

Can  you give us a date and time? 

I already did the interview and they'll let me know, probably on the
Marketplace that's on in two weeks from now.

But I don't even know for sure myself.

When did the interview air?

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