[Amps] 50 Ohm Loads

[jeremy-ca]

What about the other  resistors? Immersed in oil they could handle some 
power. The Heath Cantenna used a 50W element.

As mentioned earlier I was looking at single band applications at 1.8 and 
3.8 MHz, please run your program at those frequencies.

I'll recheck my reading with that 100W unit, it is sealed so I cant see the 
turns. The flat ones are clearly visible.

Carl
KM1H


----- Original Message ----- 
From: "Jim Tonne" <tonne at comcast.net>
To: "jeremy-ca" <km1h at jeremy.mv.com>; "Jim Brown" 
<jim at audiosystemsgroup.com>; <Amps at contesting.com>
Sent: Monday, November 12, 2007 4:32 PM
Subject: Re: [Amps] 50 Ohm Loads


>
> Guys:
>
> If a .01 uF cap was used in series with a load
> to tune it to 1 MHz,  then the load had an inductance
> of 2.533 uH.  The return loss would be 20 dB or
> better over the range of 750 kHz to1320 kHz.  I
> find these numbers believable.  If you use such a
> load in a hamband application I spose it would be quite good over one band 
> but surely not a wideband
> load for general testing.
>
> If you use that 50 ohm resistor with its 880 uH
> inductance you will need to tune it to 1 MHz with a
> capacitor of 28.78 pF.  The 20 dB return loss bandwidth will be plus and 
> minus 3200 HERTZ!
> Don't even THINK about using that resistor in a
> dummy load at ANY frequency!
>
> That resistor must have a huge number of turns on
> it;  couple of hundred or more?
>
> By the way, those VLF transmitters used by the
> Navy have antennas that have huge values of
> capacitance in their equivalent circuit.  So they
> are brought to resonance using similarly-huge
> values of series inductance.  Result:  truly narrow
> bandwidths, just barely adequate for narrow-shift
> teletype.
>
> Oh yes.  If it was "Gates" personnel that tuned the
> dummy load, then the frequency units were probably cycles per second, not 
> Hertz.   :-)
>
> - JimT
>
>
>