Steve,
Same here as I don't know either. If it's too weak of a load, it might become a
good weekend project to upgrade the load a little. Without seeing its innards,
one can't say much. I was hoping some was familiar with it, and or have the
manual for it. Sierra used to make some through-line loads for the military,
etc that looked similar to some of the Bird meters. The element went in the top
and the meter on the sloaped face. Of course this dont have a through line
section in it or no fwd or refl. One goes to thinking about all the other
wattmeters and antenna impedances. If the meters are set up on a dead nuts 50
ohm load, which I'd bet most are, a few ohms off is going to throw them off
too. So a new Bird or other out of the box may not be what one thinks. That's
the reason I hollered for years that there's plenty of other meters just as
good as a Bird.
Best,
Will
*********** REPLY SEPARATOR ***********
On 8/17/05 at 12:07 PM Steve Katz wrote:
>Could be measuring RF (rectified) voltage, sure. But if you route the
>sensor to an external load like an antenna, it wouldn't be accurate unless
>your antenna was exactly 50 Ohms, like the dummy load was. If it's
>measuring heat (far more accurate, as a calorimiter -- a heat measuring
>device -- is accurate irrespective of waveform and measures average power
>no
>matter what the waveform is), then you couldn't use the meter for any sort
>of external load, at all.
>
>I wouldn't venture any guesses about its power handling without carefully
>inspecting the load and how it's cooled. Could be a combination of liquid
>and forced air, which is a good combination and I have 5 kW loads that only
>weigh about 50 lbs and will handle that power all day long. The resistor's
>immersed in dielectric oil that circulates through radiating fins that are
>cooled by fans. At 2500W steady-state carrier power, it gets warm but
>never
>too hot to touch, even after an hour. Your item might be something like
>that, or maybe not -- can't tell from the photo, without the covers off.
>
>Good luck!
>
>Steve WB2WIK/6
>
>
>
>-----Original Message-----
>From: Will Matney [mailto:craxd1@verizon.net]
>Sent: Wednesday, August 17, 2005 11:44 AM
>To: amps@contesting.com
>Subject: [BULK] - Re: [Amps] [BULK] - Sierra Electronics 5kW load/meter
>
>
>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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>
>
>
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