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Author Topic: A New 250-W Broadband Linear Amplifier Recommendation?  (Read 4142 times)
WA2ELZ
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Posts: 15




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« on: July 31, 2012, 07:10:38 PM »

A New 250-W Broadband Linear Amplifier appears in the ARRL 2011 handbook and other years.
Any one recommend the ARRL 250 watt 1.8 to 55 MHz PA, found on page 17.35? The 6 meter coverage is an advantage, maybe a 7 on a scale of 10.
 
The PCB design can be found in the … \Supplemental Files\Chapter 17\250 W Solid State Amplifier\Combo.pcb It’s a combination of Amplifier PCB, low pass filters PCB and control PCB. The designer used ExpressPCB and is a free download from http://www.expresspcb.com. The Cost for the combination is about $172 (2 boards) from ExpressPCB and about $110 (2 boards) for the amp only.
 
Alternatively, the PCB can be DIY fabricated using double sided photo pre-sensitized board for under $10.00 (amp only). Unfortunately; ExpressPCB does not have an export function for other mainstream PCB file formats.  The DIY procedure requires a method to translate the Handbook combo file into Gerber or some other mainstream PCB format. I could re-do the amplifier from schematic to PCB layout; but, I do not want to mess around with an untested PCB, can’t let the smoke out Wink
Suggestions welcome.
Robert WA2ELZ
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KB4QAA
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Posts: 2279




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« Reply #1 on: July 31, 2012, 08:52:51 PM »

Print out the PCB layouts from PCBExpress, then scan them into a file and make any fixes/repairs using photoshop or Paint, etc.  From there, use standard technique, print on transparent slide and make photo resist PCB's. 
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WA2ELZ
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Posts: 15




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« Reply #2 on: August 01, 2012, 03:24:23 AM »

Thank you Bill for the suggestion. I was able to print directly to Microsoft XPS Document Writer and avoid the scan step. The laser transparency film should be arriving with in a few days. Hopefully I will get good transparent prints.
There are two companies, ExpressPCB and PCBExpress. It's easy to get them confused. Smiley
Robert WA2ELZ
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VE7IU
Member

Posts: 3




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« Reply #3 on: September 24, 2012, 10:48:34 PM »

Robert,

I noticed your post about the 250 Watt broadband amplifier in the 2011 handbook. I have been reading the article and am considering building this amp. My search of the Internet has only found one other post about it.

I would like to keep in touch with others building or considering this amplifier to share knowledge. If you are interested please send me an email at drbellerive.va7to@gmail.com

73,
Darrell
VA7TO
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M0HCN
Member

Posts: 473




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« Reply #4 on: September 26, 2012, 12:05:20 PM »

I have been contemplating something broadly based on it, probably with a driver integrated onto the board (30dB overall feels like a sane sort of gain level) as part of a much bigger and hairier project.

I still need to do the layout job, probably a lunchtime affair using Altium at the office, should take a week or so to get the layout done, and if I do this I will be publishing Gerbers and ODB+ files.

Regards, Dan.

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VE2BQX
Member

Posts: 1




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« Reply #5 on: October 25, 2012, 12:55:22 PM »

Robert
I too would like to hear of news on this amp and know who has had success in building it.
Have 5W from a Flex 1500 available as drive level.
Wonder what this will output?
Do most feel an additional single or a bank of low pass filters are necessary to reduce any harmonics or are most comfortable in going directly to antenna?
Also I am hazy on how T-R Switching should be done here?
Thanks
Richard
VE2BQX
elanacorp@gmail.com
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VE7IU
Member

Posts: 3




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« Reply #6 on: October 26, 2012, 04:06:54 PM »

I have just created a Yahoo Group to further discuss and share information on this amplifier.

Please join us at
http://groups.yahoo.com/group/250WattAmp

73,
Darrell
VA7TO
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