[Elecraft] K3 + LP100A + Dummy Load

[Larry Phipps]

I have been recommending the dummy loads and power attenuators from 
Ridge Equipment for years. They usually have a good selection, excellent 
quality and great prices. They will also provide a VNA plot for 10 bucks 
more as I recall. Remember that these loads usually have N connectors, 
so you may need an adapter.

73,
Larry N8LP



On 12/23/2011 6:48 AM, elecraft-request at mailman.qth.net wrote:
> Date: Thu, 22 Dec 2011 14:29:14 -0800 (PST)
> From: ab2tc<ab2tc at arrl.net>
> Subject: Re: [Elecraft] K3 + LP100A + Dummy Load
> To:elecraft at mailman.qth.net
> Message-ID:<1324592954992-7120191.post at n2.nabble.com>
> Content-Type: text/plain; charset=us-ascii
>
> 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>