Be careful, sometimes the heat dissipation may not be the only factor. I can
tell you that an internal arc at legal limit can do a lot of destruction. If
the load takes it and runs away from 50 ohms with rapid heat, it could go
boom. I once thought that I was switching from the south pacific leg of 75
array to the northern Europe antenna but instead went to a 20 meter beam.
(result of 807s) It blew the smoking coax completely out of the pl259 and
smoked one of the three 3-500z tubes running. Just a thought that the
conductors inside may be close enough to arc or burn with a shift in voltage
point and it may be the amp that takes the hit too.
Sam N9FUT
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Randall, Randy
Sent: Tuesday, December 07, 2010 10:25 AM
To: 'Mike & Becca Krzystyniak'; amps@contesting.com
Subject: Re: [Amps] Derating Dry Loads
I have used a 15 watt dry load @ 100 watts for 5 seconds without incident.
It is the model that Radio Shack sold approx. 10 years ago. It was also
sold under the Welz (sp) brand. In the specs it was rated for 100 watts for
10 seconds.
Good Luck,
Randy
Randy E. Randall AB9GO
Network Engineer
UC Health
Randy.Randall@UCHealth.com
Phone 513-585-7146
Fax 513-585-7159
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Mike & Becca Krzystyniak
Sent: Monday, December 06, 2010 9:20 PM
To: amps@contesting.com
Subject: [Amps] Derating Dry Loads
I have Bird 8173 Coaxial load rated at 300 watts continuous.
I'm not that familiar with "dry RF loads" and I was wondering if these
loads can be derated for brief periods of higher power like oil filled loads
can?
I'm thinking of 1500 watts of CW dots for 5-10 seconds? Just curious if
I should even try this, or maybe go buy a few hundred feet of RG-58 to put
in front of it...
Thanks in advance.
Mike K9MK
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