[Amps] Dummy Load Blues

[Jim Thomson]

Date: Fri, 15 Jun 2012 22:20:11 -0400
From: "Carl" <km1h at jeremy.mv.com>
Subject: Re: [Amps] Dummy Load Blues

Some of those BCB DL's can barely make it to 160...such as the ones in the 
Gates BC-1n series.

## A fellow across town collects broadcast stuff.  All his dummy loads used for 
AM  550-1600 khz use... are all the same.  They look like the  heater ele found in
a cloths dryer.  NICHROME !    Its in an open frame thingy.   It comes with a huge 
variable cap + fixed parallel cap padders.     The variable cap is used to tune out the
XL  of the dummy load..leaving just 50 ohms  and zero reactance.   You gotta tune
em for flat swr on a given freq.    AM TX is no big deal... they are stuck on one freq.
and never qsy.    Ur right, they barely make it up to 160m.   They also barely maake it down
to 550 khz too.   padders  have to be added-removed, so the variable cap is in its sweet spot.

I said no thanks..and just built my own..using 4 x 200 ohm globars in parallel.  each type
SP globar is 1 inch diam x  12 inch long. I used 4 x 12 inch long aluminum tubes.. sched
40..and 3 inch diam..and had em heliarc  welded together.  One resistor down inside each al tube.
Then the entire mess goes into  7 gals  of  xfmr oil...with a 7-16 din connector.   its  just a 
heath cantenna  on steroids !    each of the 4 x resistors is rated for 275 w ccs  in air.  Sits
on  a dolly..that rolls around the basement.   I gave up on water cooled loads for now. 
hb salt water loads will also work good. 

Jim  VE7RF