New head of CENTCOM announced!

Marine Corps Gen. James Mattis has been chosen as the new head of the U.S. Central Command, Defense Secretary Robert Gates announced Thursday. Mattis replaces Gen. David Petraeus, who was recently tapped by President Barack Obama to head the military campaign in Afghanistan.

How to build a $5,000 dollar UHF SATCOM antenna for under $20 Part 3

DIY: Military UHF SATCOM antenna
PART THREE
By Steve Douglass

By now you might be wondering when I’m going to finally write about the nuts & bolts of building my DIY UHF SATCOM antenna.

I mean – isn’t that why you tuned in?

To recap, I wrote (and you patiently read) about my motivation and my rant about the high cost of new and surplus antennas, not to mention a little about the cool Uniden receiver(s) (Uniden BCD-998T/BCD-396XT) I intend to use(said) antenna with.

So without further delay –

I once reasoned that if I ever came across one of the Dorne & Margolin antennas again – if I could just take some photos and (maybe) some measurements I might be able to reverse-engineer one and possibly build my own version.

Heck, I had (on many occasions) built home-brew UHF Yagi beams and in fact sold quite a few in the past, offering them for sale on my now (long defunct) Intercepts Newsletter – with many of them still in use today.

All it would take (I figured) was some educated-best guess-photogrammetric analysis (with something in the image to indicate scale) and I could probably Yankee-engineer a decent-working-prototype with the final goal selling (either antennas or the plans to build their own) to like-minded UHF MILCOM aficionados like myself.

As fate would have it, at an open house (air show) at Cannon Air Force Base I finally (after quite a few years wait) was able to inspect (up close) and take a few photos of another D&M antenna.

It was part of a military PR –display – connected to a DAMA portable (man-pack) UHF SATCOM transceiver. I again pumped the airman (in charge of the display) for information about the system and took a few close-up photos. I couldn’t help but notice his raised eyebrows at my more-than-passing curiosity and intense interest in his radio rig he but didn’t say anything.

I try to reassure him by saying I was a communications-technology-enthusiast, which (from his reply) he took to mean ham-radio-operator. He tells me (in civilian life) he is a ham.

My reply apparently put him at ease as he proceeded to fill me in on more technical details about the DAMA system, even going so far as to show me how to find the elevation and azimuth of the military satellite his rig was communicating through.

Later (as I examined my photos) I came to the (false) realization that the antenna must be a simple X-beam design. I guessed (incorrectly) they weren’t much more complicated than the Yagi’s I had constructed.

The driven elements looked much like two folded dipoles, attached to a short boom (six feet) situated behind a series of x-shaped directors with a wire-mesh reflector at the back. How hard could that be to replicate?


Using the photos as my guide, I experimented and over the years I built many antennas. Although they all worked (as good UHF MILAIR antennas) I was never able to monitor the UHF satellites with any real success. The most I could ever manage were choppy or weak, static filled brief intercepts. My assumption was I just didn’t have the element measurements figured out right.

Then one day while doing some research on the Internet I stumbled across this: http://www.marlboroughcomms.com/MCL/Product.aspx?proId=65

Marlborough Communications Limited is a British Company that builds military-communication gear under various government contracts, for both her Majesty’s special armed services as well for us Yanks.

Like other companies of this type, seeking lucrative government bid-approval, specifications of all their products are (SOP) posted online in downloadable Adobe Acrobat .pdf form.

However, standing out clearly among the usual obtuse list of equipment specifications, frequency ranges and MilSpec nomenclature was something I had never seen - a simplified three-view drawing of their manpack foldable UHF SATCOM antenna known as the AV2040-2 – complete with metric dimensions.

CLICK TO ENLARGE:



Dimensions! Was this the missing data I needed? I quickly downloaded the .pdf and printed it out.

I then took it to my computer guru, Wilhelm Scream (not his real name) since he is to math what Lance Armstrong is to cycling.

He took a long look at the three-view and the dimensions posted, produced a set of digital calipers and placed them on the drawing.

After a few minutes of caliper(ing) calculating and re-calculating, Scream said, “This drawing is to scale. Within a small degree of error – we could upscale it and use them as blueprints to build your antenna. “

Over the next few minutes, Scream produced the measurements that had eluded me for so long. A slow grin spread across my face when I realized that it was very possible to build a working UHF SATCOM antenna, an esoteric passion to be sure, but one that had been floating around in the back of my consciousness for a very long time.

After several brain- sessions with Scream, we drafted up a laundry list of parts we would need, which included: several sections of various-sized PVC piping, aluminum rods of various length, copper wire, RF connectors, RG-6 coax feed-line and flat aluminum bar-stock for construction of the driven elements.

Most of the tools we would need to cut, drill and shape our parts, Scream already had – which included electric saws, a Dremel and a drill press.

Armed with our list we went to the only place that had everything an Interceptor could need to build a UHF SATCOM antenna system – Home Depot.




It took several trips – but soon we had everything we needed – and incredibly I paid something in the neighborhood of $20.00.

To be continued in PART 4.



READ PART ONE HERE!


READ PART TWO HERE!

You might also like: The Interceptors Club & the Secret of the Black Manta

Accused Russian spies due in court today ...

CNN) -- More information about an alleged Russian spy ring that was operating in the United States is expected to be revealed Wednesday at court hearings in Virginia and Massachusetts, court officials said.

Accused Russian spies Donald Howard Heathfield and Tracey Lee Ann Foley have a newly scheduled hearing in Boston federal court at 11 a.m., according to their attorney, Paul Krupp.
Three other suspects, Michael Zottoli, Patricia Mills and Mikhail Semenko, are scheduled to appear for a preliminary hearing Wednesday morning in an Alexandria, Virginia, federal court, the officials said.

Zottoli and Mills have already admitted that they are Russian citizens and have been living as a couple under false identities in Virginia. Prosecutors said that they made the admissions soon after being arrested and authorities have found evidence to support that information.
The other suspect, Semenko, is accused of aiding the plot by allegedly conducting private wireless computer links to communicate with a Russian government official, court documents said.

In all, 11 suspects were arrested in the alleged spy plot in late June.
Meanwhile, a human rights activist has raised the possibility that a Russian researcher convicted of spying for U.S. intelligence services could be exchanged for one of the spy suspects in the United States.

Ernst Chyorny, a member of the Public Committee in Defense of Scientists in Russia, told CNN on Wednesday that the mother of Igor Sutyagin, the convicted Russian spy, told him about the development.

Earlier on Wednesday, Russian news agencies also reported that Sutyagin may be swapped along with other individuals in exchange for the people suspected of spying for Russia and detained in the United States.

Another Most Wanted Taliban Commander Buys The Farm - awww!

CNN) -- The Pakistani army killed one of the most wanted Taliban commanders on Sunday in the country's tribal region, the military said Tuesday.

He is Ameer Ullah Mehsud, one of the founders of the Tehrik-e-Taliban Pakistan, or TTP.
Mehsud, 45, was from the town of Makeen in South Waziristan, one of the seven districts of Pakistan's lawlessness tribal region bordering Afghanistan.

The military said Mehsud, wanted for a bounty of $234,000, was killed during an exchange of fire with soldiers near Miran Shah in North Waziristan. He was known as Mazloomyar, which means "friend of the oppressed."

Surveillance Blimp to watch over oil

New Orleans, Louisiana (CNN) -- A massive, silver-colored blimp is expected to arrive in the Gulf Coast Tuesday to aid in oil disaster response efforts.
The U.S. Navy airship will be used to detect oil, direct skimming ships and look for wildlife that may be threatened by oil, the Coast Guard said Monday.

The 178-foot-long blimp, known as the MZ-3A, can carry a crew of up to 10. It will fly slowly over the region to track where the oil is flowing and how it is coming ashore.
The Navy says the advantage of the blimp over current helicopter surveillance operations is that it can stay aloft longer, with lower fuel costs, and can survey a wider area.
The Coast Guard has already been pinpointing traveling pools of oil from the sky.

"The aircraft get on top of the oil. They can identify what type of oil it is and they can vector in the skimmer vessels right to the spot," Coast Guard Capt. Brian Kelley said.
But the problem since last Wednesday has been the ability to clean it up before it approaches land.

Rough seas have hampered cleanup efforts and tests by the boat -- called A Whale -- billed as the world's largest skimmer.
Tests of A Whale's ability so far are "inconclusive," meaning the massive converted oil tanker--which is 3.5 football fields long -- has yet to prove its Taiwanese owner's claim that it can skim between 15,000 and 50,000 barrels of oil off the sea in a day.

The Coast Guard said the testing period for the A Whale has been extended through Thursday.
So far, crude oil floating in the sea has not been concentrated enough for A Whale to skim effectively, according to oil company BP, even though it appears the ship has been surrounded by pools of oil just a few miles from the gusher.

"We've got oil coming up from over a mile below the surface. And it doesn't always come up in one spot. It's not always predictable. So, in fact, we need to locate the oil first, and then assign the ship to the areas of heaviest concentration," BP spokesman Hank Garcia said.

Bad weather has hindered cleanup efforts, he said.
"When you've got 6-foot, 8-foot seas, it's not going to lend itself to good capture of the oil."
According to the National Hurricane Center's 8 a.m. ET update Tuesday, two low-pressure weather systems over the Gulf of Mexico are persisting for another morning, but neither has more than a 30 percent chance of evolving into a tropical depression or more severe storm over the next 48 hours.

On Monday, authorities said tar balls linked to the crude gushing from BP's ruptured deepwater well had reached Louisiana's Lake Pontchartrain and hit the beaches near Galveston, Texas.

The Coast Guard reported over the weekend that a shift in weather patterns could send more oil toward sensitive shores in Mississippi and Louisiana, and bad weather over the past few days has significantly hampered cleanup efforts.

Anne Rheams, executive director of the Lake Pontchartrain Basin Foundation, said Monday that the pattern was expected to persist for at least three more days.
The National Hurricane Center said early Tuesday morning that a low-pressure area located near the Louisiana coast was producing a few showers and thunderstorms, but it was not likely to develop into a tropical cyclone in the next 48 hours.

Federal estimates say between 35,000 and 60,000 barrels (about 1.5 million to 2.5 million gallons) of oil have been gushing into the Gulf daily since April 22, when the Deepwater Horizon oil rig sank in the Gulf, two days after it exploded in flames.
The accident left 11 workers dead and uncorked an undersea gusher that BP has been unable to cap for 11 weeks.