[aprssig] RE: 6m meteor Scatter project (radios&ants)
bruninga at usna.edu
Thu Jan 3 08:54:14 CST 2008
> Ah yes the long wire...
> Or of course you could dig in a ground and
> terminate in a 150-300 ohm resistor at the
> far end..
My design used a load resistor and a trick I read about the
other night. Placing the resistor 1/4 wave from the end far end
gives a virtual ground. At 6 meters, that's just 9 extra feet
of wire and much easier to implement than a ground....
My testing with EZNEC showed that it does exactly what they say
it does. It eliminates the by-directional pattern but leaves
the main lobe in the forward direction unchaged. The real
advantage is that it eliminates any standing waves making it
easy to design a matching network.
> (old military field radio trick in
> the 30-76 MHz PRC-25 and VRC-12 band.
> Works well, I (and many others) taught it
> in the Army, personally used it less than
> 2 years ago in a "distant land". Still works!
> and meant the difference between zero comm and
> 5X5. Simple idea, seldom used, ALWAYS works
> better than a whip, AND works better than a
> 5 element beam at 35 feet. Surprised me too
> when we did a controlled side by side test beam
> with a 1-1 VSWR and the vertical half-rhombic at
Yes, and at 2 meters, it is less than 40 feet long...
> b. . -----
> Original Message -----
> From: "Robert Bruninga" <bruninga at usna.edu>
> To: "'tacos AMRAD'" <tacos at amrad.org>; "'TAPR APRS Mailing
> <aprssig at lists.tapr.org>
> Cc: <bruninga at usna.edu>; "'Michael Chisena'"
<ka2zev at yahoo.com>
> Sent: Wednesday, January 02, 2008 2:09 PM
> Subject: 6m meteor Scatter project (radios&ants)
> > Mike,
> > I have updated my Meteor Scatter web page:
> > http://www.ew.usna.edu/~bruninga/meteors.html
> > To focus entirely on setting up a USA Meteor Scatter Email
> > delivery system for emergency comms. We simply add RX's to
> > APRS Igate, and the rest of the infrastructure exists.
> > The new tidbit I came up with is how to cheaply get GAIN
> > antennas for these receivers. And the answer is simply a
> > foot long wire. . Just 100 feet gives over 12 dBi of gain in
> > fixed direction. Just perfect for 6m MS!
> > So get that pallet of radios. I'll kick in $$$ to make sure
> > can get a whole lot of radios...
> > Bob, WB4APR
> >> -----Original Message-----
> >> From: tacos-bounces+bruninga=nadn.navy.mil at amrad.org
> >> [mailto:tacos-bounces+bruninga=nadn.navy.mil at amrad.org] On
> >> Behalf Of Bob Bruninga
> >> Sent: Saturday, December 29, 2007 3:03 PM
> >> To: Paul Rinaldo; tacos AMRAD
> >> Subject: 6m meteor Scatter project.
> >> The #1 advantage of this current 6m MS proposal is that it
> >> does not attempt 2-way exchange. It takes unique advantage
> >> of these primary issues:
> >> 1) APRS Email Mission is delivery of SINGLE Email packets.
> >> 2) A single successful packet results in real-world value,
> >> sender-to ANY human recepient on the planet
> >> 3) Space-diversity: Receivers at IGates all over the
> >> all linked in real time via the internet. THis improves
> >> reliability by an order of magnitude. Not just one area of
> >> the sky, between point A and B, but ALL areas of the sky
> >> beteeen A and B-thru-ZZ are potential meteor reflectors.
> >> 4) Only one packet to one receiver is needed for 100%
> >> 5) Individual testing is one-handed. All IGate receivers
> >> automomous and listening 24/7. SO any tester only needs to
> >> TRANSMIT his email, and then watch his PC for success.
> >> It is this unique "emergeny outgoing email" mission,
> >> unique-existing APRS infrastrcutre and existing email
> >> that make this new project quite viable and not necessarily
> >> dependent on a critical mass.
> >> Lets get some on the air listening...
> >> Bob, Wb4APR
> >> _______________________________________________
> >> Tacos mailing list
> >> Tacos at amrad.org
> >> http://www.amrad.org/mailman/listinfo/tacos
> > _______________________________________________
> > Tacos mailing list
> > Tacos at amrad.org
> > http://www.amrad.org/mailman/listinfo/tacos
> > --
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> Date: 1/2/2008
> > 11:29 AM
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