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Resistor Testing Wirewound for Antennas

Bonnie KQ6XA
 

I tested 10 wirewound resistors in parallel on an HP network analyzer, to see if the inductance was small enough to use for BBTD antennas.

The resistors are 10k ohm at 12 watts each. HEI-Vishay model FVTS10R1E.  


Measured combined inductance of the 10-resistor bundle is 6.7 uH.

The inductance is too much, they are not suitable for the antenna application on HF frequencies above 4 MHz.

An equivalent 6.7uH coil made from #18 AWG wire is shown in the photo next to the bundle of resistors for scale.

-Bonnie KQ6XA 




leslie rasmussen
 

Hi, Bonnie, I have been following this discusion with interest, as I am about to put up what was going to be a random length longwire antenna with a 9:1 balun. I have since changed my mind as I believe I have enough wire to put up one of the loop antennas. I am wondering if thick film resisters will work. Mouser has them in 1kohm/1oow with an inductance of <1o nH?

Thanks, Leslie AF7VY

n2msqrp
 

I would use Caddock non-inductive resistors.


<">http://www.mouser.com/ProductDetail/Caddock/MP2060-100K-1/?qs=sGAEpiMZZMtlubZbdhIBILAbzA1esnyy2x%2fU3bBSnlE%3d>


Please note that they require a heat sink and don't take surges as well as larger resistors.


II would parallel them if you intend to keep the antenna up during thunderstorms.


Mike N2MS

 

On March 4, 2017 at 6:04 AM Bonnie KQ6XA <bonniekq6xa@...> wrote:

I tested 10 wirewound resistors in parallel on an HP network analyzer, to see if the inductance was small enough to use for BBTD antennas.

The resistors are 10k ohm at 12 watts each. HEI-Vishay model FVTS10R1E.  


Measured combined inductance of the 10-resistor bundle is 6.7 uH.

The inductance is too much, they are not suitable for the antenna application on HF frequencies above 4 MHz.

An equivalent 6.7uH coil made from #18 AWG wire is shown in the photo next to the bundle of resistors for scale.

-Bonnie KQ6XA 




Bonnie KQ6XA
 

Thick film resistors are perfect for ham radio antenna applications. 

10 nH is very low, it will be no problem in the 1 MHz to 60 MHz range.

Most small size, high power, resistors require heat sinks.

Also, they may have voltage ratings that should not be exceeded.

Usually, these types of resistor can be put in series to provide higher voltage and power capacity.

When you put them in series, they may need separate heat sinks.

-Bonnie KQ6XA