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
>>>_______________________________________________
>>>Amps mailing list
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>>>http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>>>--
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>>>Checked by AVG Anti-Virus.
>>>Version: 7.0.338 / Virus Database: 267.10.12/75 - Release Date:
>>>
>>>
>>2005-08-17
>>
>>
>>>
>>>
>>--
>>No virus found in this outgoing message.
>>Checked by AVG Anti-Virus.
>>Version: 7.0.338 / Virus Database: 267.10.12/75 - Release Date: 2005-08-17
>>
>>
>
>
>
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>
>
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