[Elecraft] low output on 12m/10m

Thu Jul 31 09:52:00 2003

Hi

I agree your problem is most likely the wire wound resistors in the =
dummy load. Think of a wire wound resistor as a resister with a coil of =
50 to 100 turns in parallel. The inductance of the coil will present =
different impedances values with different frequencies unlikely to be 50 =
ohms at any frequency of interest.

You can make a nice dummy load with a 5 watt 51 ohm MOS resistor (Mouser =
# 286-51) and a PL-259 plug. MOS resistors are non inductive. Just slip =
the resistor up into the shell and solder the resistor lead to the =
center pin. Then bring the other lead out of the end and fold it over =
and solder to the outside of the shell. this will connect directly to a =
SO-239 or you can get a SO-239 to BNC adapter from Mouser or Radio Shack =
so it will fit the K2. I built up several of these with 25, 50 and 100 =
ohm resistors. The 50 ohm I use as a dummy load and all three are handy =
for checking and calibrating the KAT2, KAT1 and KAT100 tuners for proper =
SWR indication. Even though the resistor is rated at 5 watts it will =
handle up to 10 watts for a minute or two. If you fill the void between =
the resistor and the connector with GE Silicone II silicone rubber then =
the connector acts as a heat sink and the load will handle even more =
power.

If you want something that will handle more power the OHR 100 watt dummy =
load kit works well ($35) http://www.ohr.com/rfl100.htm or the 300 watt =
dummy load kit from TenTec is good also ($29). =
http://tentec.com/Tk1203.htm  I have both of these and use them =
regularly in testing radios.

The OHR can be easily modified to be a 50 ohm 20 db power attenuator. =
When connected to the OHR WM-2 ($90) the meter will read 0-100 watts on =
the 0-1 watt scale. http://www.ohr.com/wattmeter.htm  Very handy for use =
on the KPA100

Don Brown
KD5NDB

No affiliation with any of the above companies. I just use their =
products and have found them to work well.

  ----- Original Message -----=20
  From: Rod N0RC=20
  To: Mike Miller ; [email protected]=20
  Sent: Thursday, July 31, 2003 6:44 AM
  Subject: Re: [Elecraft] low output on 12m/10m

  Mike,

  This could be VERY relevant. The wire wound resistors may have enough
  inductance so as to create an improper terminating impedance for the =
K2.
  The ideal dummy load should be a purely resistive 50 ohm load.

  Before going any further, get access to a decent quality dummy load;
  repeat your tests then move on to trouble shooting.

  GL
  73, Rod N0RC

  ----- Original Message -----=20
  From: "Mike Miller" <[email protected]>
  To: <[email protected]>
  Sent: Thursday, July 31, 2003 5:25 AM
  Subject: [Elecraft] low output on 12m/10m

  > Hi,

  >
  >                         I'm using two 100 ohm 10 W wire-wound
  resistors
  > in parallel as
  >                         my quick and dirty dummy load, if this is
  > relevant...
  >

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