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
>>
>> _______________________________________________
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>>
>
>
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