ARS NB9M

K5EF 2500L Broadband Amp


Events 0 Comments 03/26/2019

2018 Jonesborough, TN

Posted By: Bradley Stone (UncleBrad)
Post Date: 03/26/2019

Built by Nick Tusa, K5EF, this beautiful amplifier exploits the "Mysterious" Batchelor Broadband Coupler, which enabled the first no-tune, broadband amp design used in the 100V.  This potted device was explained by Nick, but was a real mystery in the 1950s to Central Electronics' startled competitors.  Per Nick:

"This is a desktop 2500L that I had designed and intended to manufacture in the mid-1980s.   My company then was Crescent Radio Electronics.  We did custom design and radio system work for the offshore petrochemical/oil industry.  As soon as we displayed this unit at Dayton in 1985, the oil industry tanked, which seriously wounded us.  We lost our funding capacity to build these sets. "

"With 75 watts of drive, we could achieve 1,700 watts output on 20M.  The Eimac 8877 is an excellent high-linearity tube that just wants to make power.  The 10M coupler needed further optimization, but my business partner and I had to put our amplifier project on the shelf since we were forced into survival mode for the next several years.  To offset the revenue loss we moved into the paging business building digital paging transmitters and configuring paging systems.  That morphed into 800MHz mobile telephone service…and sadly we never could get back to building the amplifier project.  Eventually I moved into public safety radio systems."

Nick continued: "I recall driving to Wes’ home in Chicago at the conclusion of the ’85 Dayton show to let him see our version of the 2500L and, man, was he in love!  Our plan was to have him in our booth the next year helping drum home sales and wouldn’t that have made some news!" 

Nick lamented that some folks gave him grief; the 2500L couplers couldn't work, and
"Wes got the same noise when he and Joe first showed the 600L at Dayton…some things never change…."


  

W1LSB Finds an EBay Treasure

This 1964 WRL catalog was addressed to Major General Butch Griswold – K0DWC
Category: Vintage Manufacturers
I was first licensed as a novice in 1958, and the WRL catalog was really dominant in those days, with the Globe King, Globe Champ,  and all of the lesser models gracing its pages.  I had a Globe Chief 90 and often dreamed of owning the bigger iron in those pages.   I have since collected most of the WRL catalogs from 1954 to 1964, and the last one turned out to be an interestin...  READ MORE
- Bradley Stone (UncleBrad),  04/30/2019 
  

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Category: Crazy EBay Prices!
Below are some screen shots of incredible prices demanded by some EBay vendors.  Since posting an auction is free as long as the item is not sold, it costs nothing for the unscrupulous vendor to display their (often unremarkable) wares as if they were priceless artifacts.  Enjoy. ...  READ MORE
- Bradley Stone (UncleBrad),  03/22/2019 
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- Bradley Stone (UncleBrad),  12/21/2018 
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- Robert Nickels (rnickels),  08/09/2018 
  

2018 Cave City Hamfest

Cave City, Kentucky, 3/3/2018
Category: Activities
Barry, AC9NK and I attendended the 2018 Cave City hamfest, which was awesome this year.  The facility was packed, with lots of vendors.  We enjoyed the company of my friend Tom, N4LID for dinner the night before. Tom, who is blind, had not been able to get to the hamfest for many years.  You will find more pictures at the Kentucky Phone Net site.  A big thanks to Rod, N4ZIF, fo...  READ MORE
- Bradley Stone (UncleBrad),  03/04/2018 
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- Bradley Stone (UncleBrad),  02/22/2018 
   The tube-type Linear Master Oscillators (“LMO”) used in the Heathkit SB-Line equipment is a very stable and accurate means of controlling the frequency in the equipment. Unfortunately, as the units age, many LMOs develop a “warble” when tuning. This “warble” usually stops when the frequency control knob is not rotated. However, accurately “zero-beating&rdq...  READ MORE
- Bradley Stone (UncleBrad),  02/08/2018 
  

NB9M Studio C Installed

A creative solution to managing big boxes in limited space.
Category: The Radio Shack
(Shown: 1/7/2018 checkin with the DX-60 Net on 3880, using the DX-60/HG-10B/HO-10 and the RME-6900)Using furniture-grade 5/8" plywood, simple tools and cold garage during Christmas vacation, I constructed Studio C, which occupies the south wall of the shack.  Exploiting a sturdy, existing cabinet with drawers that I've had since I was a kid, I devised a scheme to reliably handle the ...  READ MORE
- Bradley Stone (UncleBrad),  01/07/2018 
  

Remembering Fielden Farrington (1909-1977)

CBS announcer, writer, author and announcer
Category: OTR
Remembering Fielden FarringtonAuthor, announcer and long-time CBS writer Fielden Ward Farrington was born July 4, 1909 in Clinton, Indiana.  He was my great-uncle; the younger brother of my grandmother, Thelma (Farrington) Stone.  Two weeks prior to his birth, his older brother Leo passed away with scarlet fever.  Fielden's father Harry, a talented carpenter, built the hous...  READ MORE
- Bradley Stone (UncleBrad),  12/16/2017 
  

Super Hoosier DynaLoop

Construction and Description of a 160M loop antenna
Category: The Radio Shack
The Super Hoosier DynaLoop consists of four 35ft (average) utility poles buried an average of 5ft, 125ft LMR-400 from R&L Electronics, a 5KW-rated 4-1 balun, rope and marine-grade hardware (mostly from EBay) and a 20ft length of 300ohm ladder line..  The closest pole is nearly 100ft away from the shack.  The poles are 140ft apart.  The antenna is far away from any powe...  READ MORE
- Bradley Stone (UncleBrad),  11/25/2017 

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