15kW HF Linear Amplifier

[W6GQ]

http://cgi.ebay.com/RF-Plas....9497966 (http://cgi.ebay.com/RF-Plasma-Products-3CX10000A7-15kW-HF-Linear-Amplifier_W0QQitemZ290099497966)

[VE7NOT]

Quote[/b] (W6GQ @ April 03 2007,18:08)]http://cgi.ebay.com/RF-Plas....9497966 (http://cgi.ebay.com/RF-Plasma-Products-3CX10000A7-15kW-HF-Linear-Amplifier_W0QQitemZ290099497966)
Good for the 21m band. Start a broadcast station. http://www.qrz.com/iB_html/non-cgi/emoticons/wink.gif

[kd7msc]

Quote[/b] (VE7NOT @ April 03 2007,11:24)]Quote[/b] (W6GQ @ April 03 2007,18:08)]http://cgi.ebay.com/RF-Plas....9497966 (http://cgi.ebay.com/RF-Plasma-Products-3CX10000A7-15kW-HF-Linear-Amplifier_W0QQitemZ290099497966)
Good for the 21m band. Start a broadcast station. #http://www.qrz.com/iB_html/non-cgi/emoticons/wink.gif
No Sim, I wil not go with you to pick this up http://www.qrz.com/iB_html/non-cgi/emoticons/laugh.gif http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

[KC0W]

This amp (needs a lot of transformation work to have it successfully operate on 20 meters) has been on eBay for the past 5 weeks now in some incarnation or other.

It was listed at $5000 when I first saw it a number of weeks ago........Price falls every time the auction ends without anyone purchasing it. Poor suckers are now trying to get $1500 for it. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

The price of a tube for this unit is worth more than most amateurs would be willing to pay, let alone have the know how to successfully change this amp over to 20 meters.

Will now turn this thread over so the fools can make their tired, worn out CB comments about this amp......Just watch.


Tom kcØw

[K9STH]

The first thing is that these 13.560 MHz amplifiers are Class "C" only. They will work on CW or FM but not on any type of AM operation (SSB is an AM mode).

They are pretty common in the semiconductor manufacturing industry. In fact, I have had one of these which was manufactured by Henry which uses an 8877 tube sitting in my shop for some time that is being converted to operation from 20 meters through 10 meters (including 17 meters and 12 meters). Modifying it so that it can be used as a linear basically involves a new high wattage zener diode and changing the pi-network output stage to have tunable adjustments instead of those that are "fixed" for 13.560 MHz.

When completed the unit will be basically the same as any amateur radio linear which uses the 8877 tube. Capable of more than 1500 watts, but so are many linears in use today. It is the responsibility of the operator to run within the legal limits.

Now Collins Radio made a number of linear amplifiers that covered the 2.0 MHz to 30.0 MHz range for the U.S. military that ran up to at least 30,000 watts output! Those units had "autotune" capabilities and could "load" antennas under 10 feet long even on 2.0 MHz!

Glen, K9STH

[AG3Y]

Man, Glen, you sure wouldn't have wanted to get within 300 feet of that 10 foot antenna, though, would you ? http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif That is, 300 feet over your head ! http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

At one of the UHF television stations I worked at, we had an "emergency" antenna, located just above the roof of the transmitter building. To my knowledge, it was never even tested by anyone since the day it had been installed. Who would have wanted a half a million watts ERP radiating at just a few feet above eye level ? http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif It was an impressive looking sucker, however !

73, Jim

[kl7aj]

I can guarantee you that's not a linear amplfier. Plasma generators are designed to put out the most R.F. possible...which means Class C. Might make a good CW transmitter though. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

eric

[ab8ro]

Quote[/b] (kl7aj @ April 02 2007,23:11)]I can guarantee you that's not a linear amplfier. #Plasma generators are designed to put out the most R.F. possible...which means Class C. # Might make a good CW transmitter though. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

eric
Shhh, you don't want Texas Star to get any ideas http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

[W0LPQ]

Glen the 205J's that we had in the Comm facility were 22.5/45Kw. Our heliax was rigid 3" stuff. The run from the radios to the antenna farm ranged from about 200 feet to the first omni to over 500 feet to the billboards and first Log Periodic.

What was neat ... an S-3 Line really worked on the LP's.

Bill, W0LPQ/9

[W5HTW]

We used that 1-7/8 inch semi-rigid coax with the push on connectors and locking rings. Six foot or so lengths on the patch panel. It is so much UNfun to disconnect one (accidentally, by all means) when a TX is up. The locking rings were at the antenna end of the coax patch cable, so you had to have a screwdriver to detach it there. That was to prevent some silly idiot from standing there holding a coax cable in his hands that at the other end was attached to a 5 kw transmitter. But at the TX end it was just a slip ring. Very possible to detach, though a DC circuit would kill the transmitter.

Been seeing that sputtering amp on there for a very long time. Amazed some CBer hasn't lapped it up, thinking he is going to be Big Dog on Freeband. I keep hoping! Slap thet thar old leenyar that ain't leenyar at all, onna thet thar ole channel and lay a whuppin' onna all them thar ole Pups while this hyar Big Dog hikes his leg on them thar ole CBers.

Ah, but it hasn't happened yet. Darn!

Ed

[kl7aj]

Quote[/b] (W0LPQ @ April 04 2007,05:19)]Glen the 205J's that we had in the Comm facility were 22.5/45Kw. #Our heliax was rigid 3" stuff. #The run from the radios to the antenna farm ranged from about 200 feet to the first omni to over 500 feet to the billboards and first Log Periodic.

What was neat ... an S-3 Line really worked on the LP's.

Bill, W0LPQ/9
I got to work on the "Giant Talk" radios here, back in the early 80s. We had two rotatable LPs (80 ft booms, they were pretty flat from 2-25 MHZ!) They had a combination of S-line exciters as well as some proprietary stuff.

Neat era.

eric

[W0LPQ]

Eric I think those were the URG-II series. And yes ... it was a neat era...

Elsewhere I have told about the dial pulse (mid 60's to late 70's) control for everything (modes and such) as well as the ability to dial into Andrews AFB and control their stuff (as they could ours) and do the same for Guam, the Phillipines and Hawaii.

Yep ... neat era that is long gone.

Bill, W0LPQ/9

[K9STH]

The technicians in the antenna group at the Collins Radio headquarters plant that was here in Richardson, Texas, used to check out the LPY antennas using a KWM-2A into at least a 208U10 (10 KW output) and sometimes with a 20 KW output linear. Since they were testing the antennas for the military the FCC allowed them to go basically anywhere in the 2 MHz to 30 MHz range.

One of their "favorite" test frequencies was the Class "D" Citizens' Radio Service channel 19. When the technicians gave a "test" transmission and then "stood by" the frequency would be VERY quiet for about a minute. Then the "what was that" comments would start. Of course a signal with up to 200,000 watts e.r.p. just "might" have that effect.


One day, again at the Richardson Plant, a couple of technicians checking out one of the 20 KW amplifiers with autotune (in the 5 MHz band) were using a 200 foot piece of 6 gauge wire lying across the parking lot for the antenna. They noticed that the wire was arcing and sparking at the end and the wire was actually burning and getting shorter. On a "lark" the technicians decided to use a continuous carrier and see just how long the amplifier would continue to work. After about a half hour of continuous operation the wire finally burned down to about a 6 foot length and the protective circuits in the amplifier shut it down.


Every so often rolls of Heliax would be replaced at the Collins location and the old ones sold at the Collins surplus store. There was a woman operator, Eilene, WA5WDW (now deceased), who happened to be in the surplus store one day and noticed the Heliax for a VERY good price. So, she bought the roll and brought it home.

Now Eilene was divorced and her teenage son also was licensed. She held a Technician Class license and was very active on 6 meters through 70 cm. Eilene was pretty good looking and she was popular with a several of the not-married local amateur radio operators. So, the following Saturday after she purchased the Heliax she held an "antenna party" and invited several local male amateurs to replace all of the feedlines on her antennas with the "new" 7/8 inch Heliax. This was accomplished after several hours of work.

After the work was completed she tried to hit various repeaters in the area. Nothing! Eilene wasn't able to bring up a single repeater. The installations were checked and rechecked using a Bird 43 wattmeter and the SWR / reflected power was as close to perfect as it could be. Finally, one of the guys helping with the installation got into his automobile and was working her on 2 meter simplex. He got about 5 blocks away from her house when her signal dropped completely out.

He returned to Eilene's house and the antenna crew started doing some investigation. Collins Radio used to use Andrew 7/8 inch Heliax that was specially made for their use. The feedline was designed to be used as a dummy load for the high powered amplifiers and had a center conductor made from nichrome wire instead of the usual aluminum with copper flashing. Eilene had bought 1000 feet of this "special" dummy load feedline!

Of course all of the feedlines on her antennas had to be removed and the original coaxial cable refitted. From that day onward Eilene used as phonetics for WA5WDW "world's dumbest woman".

Glen, K9STH

[W5HTW]

Probably most of us who did government point to point comms got to play with a lot of interesting stuff, some of it very new (at the time!) prototypes. Wouldn't trade that experience for anythng! I wish I could go do some more of it, but that was far too long ago.

I also put high power on places I probably should not, but I was out of the country and wanted to experiment. I think the biggest thing I put on the air i other than our goverment or military frequencies was 15 kw.

But while I was in Europe, I recall one fellow who, during the days of AM on the ham bands, had a sked with his father in the US. I don't recall where. It was on 20 meters. He would find a frequency he wanted to use and crank up a 15 kw AM transmitter. No modulation, but on a terminate rhombic aimed at the US. After about 30 seconds, he would kill that and crank up his Heath DX35. He usally had a clear frequency, at least for a while. I, too, had a DX35 in a desk panel, with a BC342 receiver. Behind the panel, away from French PTT (their FCC) I had a BC610. The PTT inspector had to come inspect a station before it could be licensed. So he inspected my 342 and DX35. Gave me a license. I used that radio most of the time, but I had the BC610 as my "security blanket." I don't think I ever had the courage to use it. I was sure the PTT guy was listening to me and my new French license.

A couple of years ago most of us remember the use of military radio being tested on the ham bands. The wild case of Yosemite Sam.

In addition we hear utility stations on the ham bands, and some of them run fairly high power I would guess. One of the ones I can no longer find this year, but enjoyed last year, was the PEMEX CW maritime station on 3700. Made good code practice, though it was in Spanish. I still listen around for it, but haven't heard it in a long while. Maybe when we went phone in that portion of the band, they moved.

The most exciting coax story I recall was when one day a balun (the size of a 30 gallon trash can!) that fed open wire line going to a rhombic, suddenly shorted. The 1-7/8 semi-rigid coax going from the 208U10 up the wall, across the ceiling, and down to the balun, disappeared! There was a flash, a HUGE bang, and then the air was filled with some sort of black dust. I heard it inside the control room, but my coworker was out there in the transmitter room. He said his ears were ringing! It took a week, probably to clean up all the dust from things in there, but nothing was hurt, as far as I know. Except the balun and the coax.

Memories.

[WA9SVD]

Quote[/b] (K9STH @ April 03 2007,20:29)]The first thing is that these 13.560 MHz amplifiers are Class "C" only. They will work on CW or FM but not on any type of AM operation (SSB is an AM mode).
Not entirely accurate, Glen. All you need is a 7500 Watt modulator, and you CAN have "true" full carrier AM with a Class "C" amp!

(How you'd explain the need for all that A/C power to the electric co. is another matter...)

[KA4DPO]

Quote[/b] (W5HTW @ April 05 2007,21:49)]Probably most of us who did government point to point comms got to play with a lot of interesting stuff, some of it very new (at the time!) prototypes. # Wouldn't trade that experience for anythng! #I wish I could go do some more of it, but that was far too long ago. #


The most exciting coax story I recall was when one day a balun (the size of a 30 gallon trash can!) that fed open wire line going to a rhombic, suddenly shorted. #The 1-7/8 semi-rigid coax going from the 208U10 up the wall, across the ceiling, and down to the balun, disappeared! #There was a flash, a HUGE bang, and then the air was filled with some sort of black dust. # I heard it inside the control room, but my coworker was out there in the transmitter room. #He said his ears were ringing! # It took a week, probably to clean up all the dust from things in there, but nothing was hurt, as far as I know. #Except the balun and the coax.

Memories.
When I was in Nigeria in the late 70s I was setting up a sattelite station in Kaduna for the Nigerian government (military). We took a direct hit from lightning and it blew the power panel on the wall to pieces. It also vaporized several feet of wave guide and blew out one of the 125 KW generators. It was like a bomb went off in the TX shelter and I and several Nigerian engineers were in it when it happened. Odly enough, the station grounding system showed no signs of stress at all.

Since I worked for Harris we also had some nice HF gear including a 5 KW amp. That was the most power I ever ran on HF but it sure did net us some pile ups in the states. So we did manage to have some fun in spite of the dangerous political conditions in Nigeria at the time.