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Author Topic: Command Technologies 2500 amp aka Dedicated RF aka AN Wireless  (Read 44361 times)
KB1SEL
Member

Posts: 18




Ignore
« Reply #120 on: November 13, 2012, 06:25:11 PM »


"I'm also thinking about selling it and getting something that I CAN get serviced by the mfg and at the same time be a company that will be in business for a while... like Alpha or even MFJ."

Well Alpha has been sold or transferred in ownership a few times . So i say MFJ might be the longest single owner / Manufacture there is currently producing and i doubt there going away any time soon.

Alpha still repairs their older amplifiers and ones made by eto
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KB1SEL
Member

Posts: 18




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« Reply #121 on: November 13, 2012, 06:26:36 PM »

I have just been told by the latest new owner of the Command brand amplifiers, KK3AN, Dan Simmonds, Dedicated RF aka AN Wireless that:

1) they will not service existing amps
2) no parts for existing amps are available

Does anyone know of a person in OHIO that will service the amp.  Just minor issue, but I'm thinking about putting in the new pulse tubes, and will only buy the tubes from the person doing the work.

However, my amp still puts out 1000+ with about 50w drive, so running as is might be an option.

I'm also thinking about selling it and getting something that I CAN get serviced by the mfg and at the same time be a company that will be in business for a while... like Alpha or even MFJ.

Any thoughts?
WS8RM

Their is no such thing as a amplifier that cant be fixed. If you need help send me a pm.

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KB1SEL
Member

Posts: 18




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« Reply #122 on: November 13, 2012, 07:50:36 PM »

Tom,

I have a 1963 conference paper on an amp that used a variable inductor for tuning, as well as vacuum variables. OK, it was continuous 2 - 27 MHz and 80kW. The coil was made of iridium plated copper tube about 3/4 inch diameter with cooling air forced down it. There were two contacting arms arranged to get rid of the Tesla coil effects at one end and the short circuit turns effects at the other, with special silver loaded carbon brushes to make contact,

There you go. The dual contacting arms shorting the unused turns at mid unused area would solve the problem with broad bandwidth systems using roller inductors. A single shorting bar does not make a good broadbandwidth roller.

MFJ tried to handle this with a trip level that pushes a shorting contact into the 1/2 way point when the roller rolls up below a certain minimum inductance, in effect adding the second shorting bar a long distance from the primary bar, but it is a mechanical nightmare.

Quote
Marconi used vacuum variables and switched taps on a pi-L: the 'bandswitch' used cams of Teflon and pushed contacts hard against the coil. Rather better, I feel: variable inductors seem to have a long term problem at high power.


They sure do. Not only do they have problems with Tesla effect and series resonances sucking out signal on some frequencies, any payback is extremely low. Even a 2:1 change in loaded Q is generally unnoticable, so there is no real sweet spot. There is a wide range of Q where things work about the same.
 
Quote
The most succesful variable inductor schemes seem to have been the ones which wind a conductor from a metal drum to an insulated drum: they seem less affected by dirt and dust. Collins, Marconi and Plessey South Africa and probably others have used that scheme.

I've got some rollers like that here. It is a good scheme, but they never looked like any cost or performance advantage over just adding a few taps to a regular system.

The roller inductors main advantage is getting rid of an expensive switch, but the switch allows a progressive pick up and hold contact that prevents unwanted resonances.

73 Tom

I agree with tom, Roller inductors present more problems then they are worth. I would much rather have a conventional progressively band switch.
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KB1SEL
Member

Posts: 18




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« Reply #123 on: November 13, 2012, 08:08:12 PM »

"Part of being professional, Bill, includes not creating a big fuss on the internet at the expense of others"

But Dan,  that is EXACTLY what you are doing and in a very real sense.   By yours and others vague claims as to the legacy
amps being poorly desiged, poorly built, parts not available, that it would be unethical to repair them, that there
was no FCC record of any of the amps,  etc, etc, etc.  you  impact the pocket books of current owners
by decreasing the value of those amps.

And in the process probably blowing the reputation that had been built by Pat, deserved or not, over the years.

My big fuss as you call it clearly showed that one of those statements was demonstratably false.  That pulls
into question the rest of what has been said and that can be used to advantage in any conversation concerning
the value of a legacy amp.  Its not personal Dan, its just business.

BTW, I never claimed to be professional... a quote from Steve Martin comes to mind by it is best left unsaid.

As I said before, good luck.  And I actually sincerely mean that. 

73 de Bill ND0B

BTW  Gary = Pat.  My bad.

How hard would it be for one to take the newest version of each legacy amplifier and write own all of the components used and  take some pictures. So then one would know what additions or modifications were added in the previous versions of each amplifier.I had a early production 1995 henry 8k ultra I fixed for a pal which had been severely abused. I looked at another hams 8k which was the last one made and took notes on each part which had changed  I even took some pictures. From the plate choke to the 393 coax addition between the output vacuum t/r relay and the output connector.I even added some revisions of my own. It can be seen at amprepairguy.com The first one is always the hardest. Once you figure out what needs to be done all of the others are piece of cake. Henry made a lot of their own parts so to fix one that has had a custom part failure  can become quite costly. They made great amplifiers. Its to bad they got out of the tube amplifier market.



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KB1SEL
Member

Posts: 18




Ignore
« Reply #124 on: November 15, 2012, 05:25:05 PM »

Tom,

I have a 1963 conference paper on an amp that used a variable inductor for tuning, as well as vacuum variables. OK, it was continuous 2 - 27 MHz and 80kW. The coil was made of iridium plated copper tube about 3/4 inch diameter with cooling air forced down it. There were two contacting arms arranged to get rid of the Tesla coil effects at one end and the short circuit turns effects at the other, with special silver loaded carbon brushes to make contact,

There you go. The dual contacting arms shorting the unused turns at mid unused area would solve the problem with broad bandwidth systems using roller inductors. A single shorting bar does not make a good broadbandwidth roller.

MFJ tried to handle this with a trip level that pushes a shorting contact into the 1/2 way point when the roller rolls up below a certain minimum inductance, in effect adding the second shorting bar a long distance from the primary bar, but it is a mechanical nightmare.

Quote
Marconi used vacuum variables and switched taps on a pi-L: the 'bandswitch' used cams of Teflon and pushed contacts hard against the coil. Rather better, I feel: variable inductors seem to have a long term problem at high power.


They sure do. Not only do they have problems with Tesla effect and series resonances sucking out signal on some frequencies, any payback is extremely low. Even a 2:1 change in loaded Q is generally unnoticable, so there is no real sweet spot. There is a wide range of Q where things work about the same.
 
Quote
The most succesful variable inductor schemes seem to have been the ones which wind a conductor from a metal drum to an insulated drum: they seem less affected by dirt and dust. Collins, Marconi and Plessey South Africa and probably others have used that scheme.

I've got some rollers like that here. It is a good scheme, but they never looked like any cost or performance advantage over just adding a few taps to a regular system.

The roller inductors main advantage is getting rid of an expensive switch, but the switch allows a progressive pick up and hold contact that prevents unwanted resonances.

73 Tom

I agree with tom, Roller inductors present more problems then they are worth. I would much rather have a conventional progressively band switch.  Correction I meant a progressively shorting band switch
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ND0B
Member

Posts: 11




Ignore
« Reply #125 on: January 01, 2013, 05:25:51 AM »

Will Dedicated RF be offering discounts on any remaining inventory on the 2012 Model?
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W1MSG
Member

Posts: 98


WWW

Ignore
« Reply #126 on: May 11, 2013, 03:13:46 PM »

The Dedicated RF web site is no more, so my guess is they are again defunct ...
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W5CPT
Member

Posts: 557




Ignore
« Reply #127 on: May 11, 2013, 03:34:36 PM »

The Dedicated RF web site is no more, so my guess is they are again defunct ...

It came up for me.

Clint - W5CPT -
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W9GB
Member

Posts: 2654




Ignore
« Reply #128 on: May 11, 2013, 04:46:32 PM »

DEDICATED RF Web site functions properly, from my ISP and tablet.
http://www.dedicatedrf.com/
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W5JON
Member

Posts: 174




Ignore
« Reply #129 on: May 11, 2013, 06:35:39 PM »

The Dedicated RF web site is no more, so my guess is they are again defunct ...

I would have thought that rather then starting a rumor on here, it would have been easier just to give them a phone call first. Roll Eyes

73,

John
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