In free air, the rating should be about 100 W, and in oil, depending on the
design of the
oil container maybe 800 - 1000 W.
If the oil container is designed so there is a convection flow, the rating can
be increased.
The recent ARRL handbooks have some information in this matter.
73/
Karl-Arne
SM0AOM
----- Original Message -----
From: "Paul Whatton" <paul.whatton@ntlworld.com>
To: "Karl-Arne Markström" <sm0aom@telia.com>
Sent: Thursday, August 18, 2005 1:09 AM
Subject: Re: [Amps] [BULK] - Sierra Electronics 5kW load/meter
> On the subject of dummy loads. I have here a carbon tubular 50R resistor
> on a ceramic former. It is about 1ft long and 2" diameter. For some time
> I have been meaning to make a high power dummy load based around it.
> From the size would anyone be able to estimate how much power it would
> be OK for, both in air and in an oil can?
>
> 73 Paul G4DCV
>
> Karl-Arne Markström wrote:
>
> >The time such a load, when rated for pulsed waveforms, holds up
> >for CW loads in the kW range is in the order of a few seconds,
> >at the most.
> >
> >Many of these loads contain thin-film resistors which are
> >very unforgiving even of momentary overloads due to their very
> >low thermal mass.
> >
> >73/
> >
> >Karl-Arne
> >SM0AOM
> >
> >
> >
> >
> >----- Original Message -----
> >From: "Will Matney" <craxd1@verizon.net>
> >To: <amps@contesting.com>
> >Sent: Wednesday, August 17, 2005 9:10 PM
> >Subject: Re: [Amps] [BULK] - Sierra Electronics 5kW load/meter
> >
> >
> >Karl-Arne,
> >
> >If it were, it would be ok as this would become a neet project to convert
> >over to say a 1-1.5 kW load that was air cooled. Say maybe with a 1 minute
> >max rating or so. Then by changing it to where one could read the power from
> >an antenna connection by switching the load out and antenna line in, it
> >would be a good one. That wouldn't be too hard to modify for that I wouldn't
> >think. I knew when I bought it, that it couldn't hold 5 kW for any time at
> >all, maybe say 1-1.5 kW for any time. My homebrew 5 kW load I have here is a
> >monster that uses 8 large 400 ohm resistors in paralell. At that it's 5 kW
> >rating is only good for around 1 minute or so. Heck, at the price I couldn't
> >beat it for a small project.
> >
> >Best,
> >
> >Will
> >
> >*********** REPLY SEPARATOR ***********
> >
> >On 8/17/05 at 8:23 PM Karl-Arne Markström wrote:
> >
> >
> >
> >>This load looks very similar to units that I came across in the 80's when
> >>working for the Swedish military.
> >>
> >>If it corresponds to this general type, it is a peak reading termination
> >>wattmeter intended for
> >>UHF pulse transmissions, and it is not intended to handle more than about
> >>50 W
> >>or so average power, corresponding to a max duty cycle of 1 %.
> >>
> >>A 5 kW air cooled average load would be a very different creature, with
> >>lots of cooling fins...
> >>
> >>There are no simple ways to convert this unit to a "thru-line" wattmeter,
> >>as it does not contain a directional coupler.
> >>
> >>73/
> >>
> >>Karl-Arne
> >>SM0AOM
> >>
> >>
> >>----- Original Message -----
> >>From: "Steve Katz" <stevek@jmr.com>
> >>To: <craxd1@verizon.net>; <amps@contesting.com>
> >>Sent: Wednesday, August 17, 2005 8:02 PM
> >>Subject: Re: [Amps] [BULK] - Sierra Electronics 5kW load/meter
> >>
> >>
> >>
> >>
> >>>I don't know this specific load, but the fact that the meter range switch
> >>>doesn't have any provision for "reflected" may well indicate that this
> >>>
> >>>
> >>unit
> >>
> >>
> >>>is not measuring power using a directional coupler, but rather as a
> >>>calorimeter, measuring thermal rise in the load. If that's the case,
> >>>
> >>>
> >>there
> >>
> >>
> >>>would be no way at all to make it an "in line" instrument, since the only
> >>>way it would indicate is by dissipating power in the load and measuring
> >>>heat.
> >>>
> >>>I'd recommend dismantling the thing to see where the meter is getting its
> >>>current from...
> >>>
> >>>WB2WIK/6
> >>>
> >>>-----Original Message-----
> >>>From: Will Matney [mailto:craxd1@verizon.net]
> >>>Sent: Wednesday, August 17, 2005 10:36 AM
> >>>To: amps@contesting.com
> >>>Subject: [BULK] - [Amps] Sierra Electronics 5kW load/meter
> >>>
> >>>
> >>>All,
> >>>
> >>>I just won a rackmount, 5kW termination load, with peak reading wattmeter
> >>>off ebay. The load was made by Sierra Electronics, division of Philco.
> >>>
> >>>
> >>The
> >>
> >>
> >>>model is a 400A-Z. I'm now looking for a manual on this and checked at
> >>>
> >>>
> >>Bama
> >>
> >>
> >>>with no luck. Do any have any info on this load/meter, or where one might
> >>>find it? A link to the item is below to see which one it is by the pics.
> >>>
> >>>
> >>I
> >>
> >>
> >>>also need to buy a new converter plug from a N connector to a UHF type
> >>>SO-239 female. The one I have here is in pretty poor shape and need a
> >>>
> >>>
> >>good
> >>
> >>
> >>>cheap place to buy one. Last, I wonder how hard it would be to convert
> >>>
> >>>
> >>this
> >>
> >>
> >>>to a thru line type so it can be switched between load and antenna?
> >>>
> >>>
> >>Thanks
> >>
> >>
> >>>all for any help.
> >>>
> >>>
> >>>
> >>>
> >>http://cgi.ebay.com/Philco-400A-Z-Peak-Power-Wattmeter-Rack-Mount-5000-Watt_
> >>
> >>
> >>>W0QQitemZ7537709171QQcategoryZ1504QQcmdZViewItem
> >>>
> >>>Best,
> >>>
> >>>Will
> >>>
> >>>_______________________________________________
> >>>Amps mailing list
> >>>Amps@contesting.com
> >>>http://lists.contesting.com/mailman/listinfo/amps
> >>>_______________________________________________
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> >>>Amps@contesting.com
> >>>http://lists.contesting.com/mailman/listinfo/amps
> >>>
> >>>
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> >>>
> >>>
> >>2005-08-17
> >>
> >>
> >>>
> >>>
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> >>
> >>
> >
> >
> >
> >_______________________________________________
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> >
> >
> >
> >
>
>
>
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