> Looking at the 'Pure NiCh +100R', at 30MHz it behaves like
> 88nH in
> series with 3.3R and at 100MHz, 71nH in series with 26R -
> 23% lower R at
> 30MHz, 28% lower at 100MHz. The ratio from 30 to 100MHz is
> 7.9x
Every suppressor, even a parallel R and silver L, behaves
similar. They just have slightly different slopes in
impedance.
When we compare a nichrome suppressor to an equally VHF
sized conventional suppressor we see the conventional
suppressor and nichrome mainly diverge at HF and lower, not
at VHF.
> For the AL80 unit, the figures calculate at 111nH in
> series with 2.7R at
> 30MHz, and at 100MHz 102nH in series with 29R, a ratio of
> 10.7 between
> the 30 and 100MHz values - slightly lower absolute values,
> but a higher
> ratio than these particular nichrome versions.
The conventional suppressor slopes faster with increasing
frequency, exactly what we want unless our goal is to
suppres HF.
> For further comparison, here's values I've measured:
>
> Suppressor from a Dentron MLA2500
> 30MHz looks like 145nH in series with 2.7R, 100MHz looks
> like 133nH in
> series with 27R
1: 10 ratio with increasing frequency. More slope to a
higher resistance at VHF than nichrome. This means lower VHF
Q for a given HF loss value.
> TL922
> 30MHz 85nH in series with 1.7R, 100MHz 74nH in series with
> 8.9R
1 : 5.23. Not a good slope ratio
> Henry 2KD5
> 30MHz 104nH in series with 1.3R, 100MHz 102nH in series
> with 15R
1:11.53 good slope ratio
> Compared with any of the others, the TL922 compares poorly
> in the vhf/hf
> resistance ratio.
...but can be corrected or improved if necessary with an
adjustment in values.
In every case making the inductor out of nichrome, with no
other changes, will decrease slope. This means for the same
HF losses in a given design suppressor nichrome would have
MORE VHF Q.
73 Tom
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