[Elecraft] K3 + LP100A + Dummy Load

[ab2tc]

Hi,

I highly recommend the 75W dummy load from Ridge Equipment. I have one
permanently connected in my system. I believe it is a military surplus piece
of equipment with absolutely superior characteristics like an SWR at 500MHz
of 1.05 or less. It has no problem with 100W for a minute or less for sure.

AB2TC - Knut


Phil,

All dummy loads are not created equal.  Connect yours directly (no coax) 
to the LP-100 or an antenna analyzer to determine its characteristics 
with frequency (I assume Larry calibrated your LP-100 to NIST 
standards).  A common ham dummy load is something to tune your amplifier 
into and use for general purposes.  If you are going to do measurements, 
you will need something more like lab quality dummy loads.

Both your dummy load and the 6 feet of RG8X will show a frequency 
dependency since you do not have a precision 50 ohm dummy load.  A 
transmission line that is not terminated in its characteristic impedance 
acts like an impedance transformer, and that transformation ratio is 
frequency dependent.

If you want a dummy load that is flat WRT frequency and suitable for 
instrumentation use, take a look at the Caddock 50 ohm Thick Film 
Resistors - they are available up to 100 watt rating.  You must use them 
on a heat sink, and keep the leads as short as possible, and you will 
have a precision dummy load.  Caution - even with the heat sink, do not 
exceed their power ratings, they will go open circuit in an instant.
I use several of those as instrumentation precision loads.

Other sources of precision dummy loads is Ridge Equipment - 
https://www.ridgeequipment.com/store/dummyloads.html.  They have one 
rated at 75 watts for $12 and one rated at 15 watts for $7.50 - those 
are quite good for instrumentation purposes.

73,
Don W3FPR

<snip
</quote>


--
View this message in context: http://elecraft.365791.n2.nabble.com/K3-LP100A-Dummy-Load-tp7119170p7120191.html
Sent from the Elecraft mailing list archive at Nabble.com.