Don Wilhelm wrote:
Phil Debbie Salas wrote:
I just received a few Ohmite thick film power resistors for an
attenuator I'm making,
rated 20 watts. They are 15mm x 10mm x 3mm. Obviously they have to be
heat-sunk
(heat-sinked?) if they are going to dissipate that much power.
FYI - Both
I apologize in advance, but the smartest guys I know are here.
I just received a few Ohmite thick film power resistors for an attenuator I'm
making,
rated 20 watts. They are 15mm x 10mm x 3mm. Obviously they have to be heat-sunk
(heat-sinked?) if they are going to dissipate that much power.
Hi Vic ...
My first inclination would be to go to the Ohmite website and look at the
datasheet for the resistors and search for any application notes. One or
both of these sources should address, at least in relative terms, how much
heat is typically removed via conduction through the leads vs.
Another thought, Vic ...
If the approach I suggested earlier results in a large, cumbersome or
expensive packaging job for you, the easiest thing may be to redesign the
attenuator using a larger number of lower wattage resistors. This would
distribute the heat better and could result in a
Here's the Ohmite resistor guide web page:
http://www.ohmite.com/resguide.html
73,
Dave KQ3T
Craig D. Smith wrote:
Hi Vic ...
My first inclination would be to go to the Ohmite website and look at the
datasheet for the resistors and search for any application notes. One or
both of these
How do you do this? There's no hole in the middle...I can just clamp them
between a couple
... lets see ... a 10x15x3mm Ohmite thick film rated at 20 watts ...
with a little web research you get:
http://www.ohmite.com/catalog/pdf/tah.pdf
According to that data sheet, Mounting: Requires the
I just received a few Ohmite thick film power resistors for an attenuator I'm
making,
rated 20 watts. They are 15mm x 10mm x 3mm. Obviously they have to be heat-sunk
(heat-sinked?) if they are going to dissipate that much power.
FYI - Both Ohmite and Caddock make versions of these resistors
Phil,
Is this recent data? Has something changed? I have had plots of the
Caddock 50 ohm 100 watt resistors taken to 250 MHz and the return loss
indicated that they made very good attenuators and dummy loads at that
frequency - assuming they were mounted with zero length leads directly
to a
: Don Wilhelm w3...@embarqmail.com
To: Phil Debbie Salas dpsa...@tx.rr.com
Cc: elecraft@mailman.qth.net
Sent: Friday, May 21, 2010 5:50 PM
Subject: Re: [Elecraft] OT: heat sinking resistors
Phil,
Is this recent data? Has something changed? I have had plots of the
Caddock 50 ohm 100 watt
Phil,
Thanks for that information. Mine are mounted to a heat-sink culled
from a CPU cooler, and the connector is mounted to a piece of aluminum
angle also affixed to the heat sink. This assembly is standalone and
does not connect to any other ground plane. Although the heat sink may
Vic,
I would suggest that you do not clamp each resistor between a couple of
pieces of aluminum, because some types of uncapsulated thick film power
resistors are quite fragile. They may not appear to break if stressed, but
there is the risk of creating a hairline fracture across the resistor
clamping things.
73 Tom
- Original Message -
From: Geoffrey Mackenzie-Kennedy gm4...@btinternet.com
To: Vic Rosenthal v...@rakefet.com
Cc: Elecraft Discussion List elecraft@mailman.qth.net
Sent: Friday, May 21, 2010 8:21 PM
Subject: Re: [Elecraft] OT: heat sinking resistors
Vic,
I
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