Steve,
I was thinking it more than likely was measuring the RF voltage on the load
instead of a caloriometer. I have a 1.5 kW meter/load here from B&W that does
that. They then just rectify the RF with fast switching diodes, etc and use a
resistor to set the power reading of the meter. This meter though is a peak
reading one so I'd say it uses peak-reading circuits like in other peak meters.
No it couldn't be used for reflected power, or SWR, only to measure forward
power or the power across the load. This meter does use 117 Vac so I'd imagine
it's transformed down for the metering circuitry, and most likely a fan by the
vent in the top. It's untelling what the load is, in that it could be open
resistors, or an oil tank mounted inside somehow. I highly doubt the oil type
as there's not enough room for one I dont think. I'll about bet the 5 kW rating
is only good for about 30 seconds or so at the most. What I thought of doing
was just switch the load out to another external type N connector that could be
connected to an antenna if need be. That wouldn't be a big modification I would
think.
I wanted an adapter from type N to UHF for running lower power in it say to 1
kW. RG-8 or 214 is easier for me to handle. If I wanted to run more, then take
the adapter off and use heliax cable with N connectors.
Look at it this way, I can't be hurting for no more than I have in it : )
Best,
Will
*********** REPLY SEPARATOR ***********
On 8/17/05 at 11:02 AM Steve Katz wrote:
>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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