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Re: Topband: RF attenuators

To: "Bill Wichers" <billw@waveform.net>, <jim@audiosystemsgroup.com>, <topband@contesting.com>, "Hardy Landskov" <n7rt@cox.net>
Subject: Re: Topband: RF attenuators
From: "ZR" <zr@jeremy.mv.com>
Date: Wed, 24 Aug 2011 15:04:09 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Ive tested dozens of CATV splitters over 25 or so years and they range from 
falling apart as high as 7-8MHZ and many good to 80 but useless at 160.
By good I mean at least a 10dB RL (2:1 VSWR) and 20dB isolation.

For the cost of 3 small ferrite cores, some wire and a resistor its 
certainly simple to build much better ones.

Carl
KM1H


----- Original Message ----- 
From: "Bill Wichers" <billw@waveform.net>
To: <jim@audiosystemsgroup.com>; <topband@contesting.com>; "Hardy Landskov" 
<n7rt@cox.net>
Sent: Wednesday, August 24, 2011 10:46 AM
Subject: Re: Topband: RF attenuators


> It would be easy to check if an attenuator is resistive or capacitive by
> checking if it will pass any DC. If the attenuator is all resistive you
> should be able to measure a low (relatively, i.e. not megohms)
> resistance between the ports and between the center pin and ground.
>
> Regarding the splitters not being useable down low in frequency, I think
> I have one of their 10-1000MHz 2-way splitters at home that I can test
> down around 1 and 2 MHz easily enough and post the results.
>
>  -Bill
>
> [snip]
>> In general, many VHF/UHF attenuators are built with capacitive
> dividers
>> rather than resistive dividers, and are unlikely to be useable at HF
> and
>> below.  Conversely, simple resistive attenuators are quite suitable in
>> the 2 MHz range, provided that they are made with resistors that are
> not
>> inductive, whereas their stray L and C would render them useless at
>> higher frequencies.
>>
>> 73, Jim Brown K9YC
>> _______________________________________________
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
>
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_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK

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