[Test-Equipment] Bird Termaline Question

[Richard Knoppow]

    I will repeat what I wrote earlier. I have measured several dummy 
loads and a few low power terminations. All measure about the same on DC 
as RF. The precision terminations were measured up to 1Ghz but are 
speced to about 9 Ghz (General Radio) or higher (Hewlett-Packard). The 
dummy loads were measured up to about 250Mhz using a General Radio 1650A 
bridge up to about 50 Mhz and both a Boonton 250B RX meter and a General 
Radio 1609 Admittance meter above that. In particular I was curious 
about my Motorola dummy load. Its off at DC measuring about 55 ohms 
while its speced at 50 ohms. Same on DC to around 900 Mhz. I didn't go 
higher. This is built in a similar way to the Bird Termaline with a 
conical housing for the resistor and fins for air cooling. I do not 
think its oil filled. It is meant to be mounted horizontally. Since it 
is non reactive despite being the wrong resistance I can compensate for 
the sort of low accuracy power measurements I make with it and also for 
tuning up low power transmitters.
     I have a paint can dummy load, not a Heathkit but I am drawing a 
blank on the maker's name.  This is literally a paint can with about a 
50 watt non reactive resistor mounted in it. I filled it with mineral 
oil, close enough to the correct synthetic transformer oil since I do 
not use it anywhere near its power limit.  I also have an MFJ Versatuner 
with a dummy load in it. This is a non-reactive carbon resistor which 
appears identical to the one in the paint can load. Both of these are 
off value, about  57 ohms, and, again, measure the same with DC or HF. 
I replaced the resistor in the MFJ once. The new one measured about 51 
ohms when I put it in but went up to about 57 ohms after a time.  The 
transmitter this is used with has a maximum output of around 150 Watts. 
The Motorola load is rated for 150 watts continuous. The MFJ for perhaps 
a couple of minutes. The paint can load for continuous use at well above 
this.
     Evidently, these loads are rather delicate.


On 2/4/2017 9:36 PM, Ron Youvan wrote:
>   On 02/04/2017 09:11 PM, Brian VK2GCE wrote:


-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL