[TowerTalk] Dummy Load Rating

[Danny Pease]

Just imagine the spot heating issues with the cheap loads most hams use!

NG9R


-----Original Message-----
From: Gary Schafer [mailto:garyschafer at largeriver.net] 
Sent: Friday, December 04, 2015 2:58 PM
To: 'Danny Pease'; towertalk at contesting.com
Subject: RE: [TowerTalk] Dummy Load Rating

I have a large oil filled Bird load with several large fans on the bottom.
It is rated for 2500 watts continues with no air and 10 KW continues with
the fans on.

Although the above is 4 times the rating with air, I have in the past
contacted Bird about temporary overloading smaller loads (500 watt) and all
that they would say was there is no rating above what is printed on the
load. The explanation was that going above the rated power could cause hot
spots on the resistor that wouldn't dissipate fast enough.

73
Gary  K4FMX

> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of 
> Danny Pease
> Sent: Friday, December 04, 2015 1:30 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Dummy Load Rating
> 
> John, I have wondered the same thing. I have a 500 watt Bird 
> attenuator that we used regularly to tune up a 1300 watt amplifier 
> with no problem at all. I tested it up to 2 minutes at 1300 watts 
> carrier and never hurt anything, the cooling fins just started to warm 
> up a bit.
> 
> I also have 1 KW Bird attenuator and saw what appeared to be the same 
> exact load with a fan added and it was rated at 2500 watts.
> 
> I suspect using the 500 Bird watt load with a small fan would handle
> 1500
> watts for longer than most hams would ever want to run their amp into 
> it.
> 
> That said, I have seen 500 watt bird loads so warm you could barely 
> hang onto them with just under 500 watts at 950 MHz running into them 
> for hours on end, so they will warm up if you push them long enough.
> 
> NG9R
> 
> 
> Date: Fri, 4 Dec 2015 13:41:35 -0500
> From: "john at kk9a.com" <john at kk9a.com>
> To: towertalk at contesting.com
> Subject: [TowerTalk] Dummy Load Rating
> Message-ID: <bf04437703c89f4b66acf6fdd2789144.squirrel at www11.qth.com>
> Content-Type: text/plain;charset=iso-8859-1
> 
> I have a couple of Bird dummy loads, one is rated at 500 watts and one 
> is
> 1000 watts, continuous duty. I have never seen an intermittent duty 
> rating.
> Does anyone have an idea how much power these can safely handle for a 
> short duration?
> 
> John KK9A
> 
> 
> 
> 
> 
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