[RFI] THANKS! (was: Experience with RF-INQUIRY Hi-Q Chokes?)

[Christian Buenger]

Hi,

Thanks for your valuable comments. I will not try these overpriced products 
:). Instead I will stick with some ferrite-beads on teflon coax. As well I 
will try to improve the already placed "coiled coax" "balun" at the 
feedpoint of the antenna.

To me these claimed 50dB sound too high. Additionally there is not much 
info on the web about these commercial chokes. And if they would keep what 
they claim (to be the killer application if it comes to common mode 
current) then you would read much more stuff about them on the net. At 
least google did not find much about it.

Thanks again!

73
Christian, DL6KAC

At 14:00 02.02.2004, you wrote:
>Tom Rauch wrote, in response to:
>>>just came across an advertisement of a common-mode choke produced by
>>>RF-inquiry of Japan. They claim to provide at least 50 dB of reduction of
>>>common-mode-currents.
>I agree with Tom's earlier post, that the 50dB target is hard to hit 
>without accepting a reduced bandwidth.
>
>Also, "at least 50dB" has to be at the top and bottom edges of the claimed 
>bandwidth, so the mid-band performance would have to be better still.
>
>Hmmm... we seem to be deep into the territory where "the more you claim to 
>have achieved, the more you need to prove it."
>
>
>Tom added:
>>By the way, if the common mode source and load impedances are a fraction of
>>an ohm it is easy to obtain -50dB. If the common mode source and load
>>impedances (which have nothing much to do with line impedance) are 1000
>>ohms, we would be lucky to see 10dB.
>>
>>It depends on how they measured.
>
>The standard method is to measure between a 50-ohm source and load - the 
>input being to the coax shield at one end, and the output from the shield 
>at the opposite end.
>
>The 50-ohm source and load may not represent any particular real-life 
>application, but they do allow fair comparisons between competing products.
>
>
>--
>73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
>                            Editor, 'The VHF/UHF DX Book'
>http://www.ifwtech.co.uk/g3sek
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