On 19 sep, 23:19, john Wiener wrote:
Any comments on effectiveness of snap-on ferrite chokes on transmission
lines...here rg8u ?
There seems to be some dispute about that as well as placement on the line.

Thanks

John
AB8O

PS *I was going to finish putting up my Carolina Windom last Sunday but
Ike hit here in Oh...I still don't have power! *Out of respect for TX I
do not complain.

Hello John,

As others say, it depends on the frequency, actual application and
ferrite type.

M o s t snap-on ferrites use "fast" ferrite material, so they are
effective (read: give highest impedance) at several hundred MHz.
When using at low HF, the effect is limited.

I checked the 2008/2009 WURTH catalog (it is on my table): You can
expect common mode impedance (one turn, inner diameter suited for
8..12mm cable) of about 50…120 Ohms at 10 MHz. At 3.7 MHz impedance
drops to about 25 to 45 Ohms. Putting more of them onto the cable
gives proportionally more impedance.

It depends on the common mode impedance at the intended position
whether they will be effective. As OCF dipoles have high common mode
impedance, you have to use many of them (weight increase?).

When you think you need them at low HF, you might add some ferrite
rings/sleeves with high relative permeability (you probably have more
choice in ferrite materials in ring/sleev shape). The rings do act at
the low HF part, while the clamp on ferrites act on the high HF part.

Best regards,

Wim
PA3DJS
www.tetech.nl
without abc you can use the email address.