[Amps] Non-inductive resistors

[craxd]

Marv,
Why sure I am. I just wish I knew where the old one went. I still think 
it grew legs one day I had several visiting my workshop. After that, I 
couldn't locate it after I went looking. That happened about a year ago 
and just so happened you had a copy!  =)

I'll say this, the old books had a lot more worth while information than 
anything now new in print! About like that amp book just published by 
the ARRL. It was touted by ads to be a great piece of work, until one on 
here ordered it, and seen it was junk.

Will Matney

PS; I can vouch for Marvs stuff. It was shipped lightning fast, in good 
shape, and packed good. I'll sure do business with him again!

Radio WC6W wrote:

>Sooooo, using that book I sent you, I see!  :-)
>
>On Mon, 27 Sep 2004 13:20:28 -0400 craxd <craxd1 at ezwv.com> writes:
>  
>
>>I went back and decided to post some texts quoted out of the Radio 
>>Engineers Handbook. I read on and also found a section termed, "Load 
>>
>>Resistors for Absorbing Radio-frequency Power". I'll start first 
>>with 
>>the uses text for the wound resistors then on to the load portion.
>>
>>"The mica-card, reversed-loop, and figure-eight types of resistors 
>>can 
>>be made to have very low phase angles and are the types used in 
>>radio-frequency attenuators. The mica-card, fish-line, and 
>>woven-tape 
>>types of construction are commonly used in decade resistance boxes 
>>designed to have a low phase angle at radio frequencies, 
>>particularly 
>>for the high-resistance units. The Ayrton-Perry winding is also 
>>suitable 
>>for use at radio frequencies, particularly for resistances up to 
>>several 
>>thousand ohms. The simple bifilar winding is suitable at radio 
>>frequencies only for resistances so low that capacity effects are of 
>>no 
>>importance. The slotted type of construction is used in very high 
>>resistance units where only moderately low phase angle is essential, 
>>as 
>>in the case of voltmeter multipliers".
>>
>>"Load Resistors for Absorbing Radio-frequency Power.-Resistors used 
>>as 
>>radio-frequency loads, i.e., as dummy antennas, present a 
>>particularly 
>>difficult problem, since here one desires a nonreactive unit capable 
>>of 
>>dissipating appreciable wattage. When the power is in the order of 
>>fifty 
>>watts or less, several satisfactory arrangements are available. One 
>>
>>consists of a bifilar resistance element supported on mica and 
>>mounted 
>>in a glass bulb filled with inert gas, preferably hydrogen". Sounds 
>>like 
>>a bomb to me..LOL (WM). "Another arrangement consists of a mica-card 
>>
>>type of unit mounted between two large aluminum castings that are 
>>for 
>>the purpose of conducting away the heat. Both these arrangements give 
>>
>>excellent phase-angle characteristics".
>>
>>"When larger amounts of power are to be handled, various expedients 
>>are 
>>used. In most of these, the reactance is eliminated by tuning, and 
>>the 
>>dissipated power is evaluated by a calorimetric or photometric 
>>method, 
>>or by measuring the equivelant circuit resistance at the frequency 
>>involved. Another possibility is to use a metalized type of resistor 
>>
>>immersed in cooling water (1). In this way, the rating can be 
>>increased 
>>to 50 to 80 times that for air, and is of the order of 100 watts per 
>>
>>square inch of surface. The power being dissipated can be determined 
>>
>>from the rate of flow and temperature rise of the cooling water. By 
>>
>>making the resistor the central conductor of a concentric line 
>>shorted 
>>at the receiving end, the reactance at the input terminals can, by 
>>suitable design proportions, be made zero".
>>
>>(1) See G.H. Brown and J. W. Conklin, Water-cooled Resistors for 
>>Ultrahigh Frequencies, Electronics. Vol. 14, p. 24, April, 1941.
>>
>>"The bifilar  winding has negligible inductance, but the capacity is 
>>
>>relatively large, because the beginning and end of the resistance 
>>are 
>>close together. This capacity effect can be minimized to some extent 
>>by 
>>sub-dividing the total resistance into several bifilar sections, as 
>>
>>shown in Fig. 10h (Bifilar-series)".
>>
>>Will Matney
>>_______________________________________________
>>Amps mailing list
>>Amps at contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>>    
>>
>
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