Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: AL-811H with two 572B's  (Read 2456 times)
AE5JU
Member

Posts: 244




Ignore
« on: February 19, 2010, 12:24:53 PM »

Can the AL-811H produce full rated power with just two 572B's?  Somewhat reduced power?

If so, would running it like this lead to any problems?

I could see some time in the future when tubes become scarce that this might be necessary.

And I'd like to thank Tom for sharing his experience with and knowledge of these amps.

Paul
AE5JU
Logged
AE5JU
Member

Posts: 244




Ignore
« Reply #1 on: February 20, 2010, 05:39:54 PM »

(Insert Jeopardy Theme here)

 Undecided
Logged
KX5JT
Member

Posts: 217




Ignore
« Reply #2 on: February 21, 2010, 12:05:04 AM »

Are you going to fill the other two holes with 811A tubes?  Then it will produce your 800 watts PEP yes.

Two 572B's will not produce your 800 watts PEP at 1500 volts on the plates.
Logged
AE5JU
Member

Posts: 244




Ignore
« Reply #3 on: February 21, 2010, 02:52:21 PM »

I did have one guy tell me he had run 572B's and 811A's mixed, different brands, etc, and so much for "matched sets".  Hahah...


No, just wondering if it would work with only two 572B's, nothing else, without causing any problems.  I know the amp can be run at reduced output with 1, 2, or 3 811A's, but what about 572B's?
Logged
KH6AQ
Member

Posts: 8008




Ignore
« Reply #4 on: February 21, 2010, 04:49:04 PM »

It will run the same power with two 572B's as with two 811A's.
Logged
KX5JT
Member

Posts: 217




Ignore
« Reply #5 on: February 24, 2010, 10:23:27 PM »

572B's essentially are 811A's with a beefier graphite anode.  This allows them to be ABLE to have more plate voltage placed on them and more plate dissipation.  IF those conditions are raised, you will get more output.  

Simply dropping them into an AL-811H does not give you more power, for they are running the 1500 watts of plate voltage that the amp gives as designed for 811A's.  They will take a bit more punishment perhaps but given the same parameters, they will produce the same as the 811A's.

As far as *matched sets* of tubes.  That is important in PUSH-PULL amplifiers.  The AL-811H runs the tubes in parallel, not push pull so the effect is additive not co-operative.  You do not need matched sets in the AL-811H.  It's a great marketing ploy by the tube vendors however to make you spend a few more bucks.

73, John KX5JT
Logged
KX5JT
Member

Posts: 217




Ignore
« Reply #6 on: February 24, 2010, 10:24:55 PM »

1500 volts, sorry, not watts.  My bad.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!