[CQ-Contest] Fw: Re: Bandpass filtering

[vk4ti at yahoo.com]

Hi Mario - 
 ICE made a device that protected Rceiver front ends from overload in contest envirionments 
http://www.iceradioproducts.com/reconly.html#rflimiter  it appears this device could be
 used on the SDR without worrying about filtering - if the SDR is used to populate band maps then if there is some splatter no one other than the PC is listening to the unit..
Seems a lot easier than worrying about bandpass filtering - but I may be over-simplifying things - I use these after my AMPs and filters in an SO2R setup...
Trent VK4TI 


--- On Fri, 31/12/10, S56A
 <s56a at bit.si> wrote:

From: S56A <s56a at bit.si>
Subject: Re: [CQ-Contest] Bandpass filtering
To: "VK4TI" <vk4ti at yahoo.com>
Received:
 Friday, 31 December, 2010, 1:37 PM

I am not sure which ICE BPF you have in mind.  I was thinking of 200 W ones with two parallel tuned circuits at both ends and coupling capacitor about 1/4 value.  Nothing else is inside the individual boxes.  Only 10/15 m attenuation is low - 11 dB.

73 de Mario, M/S56A

----- Original Message ----- From: "VK4TI" <vk4ti at yahoo.com>
To: "S56A" <s56a at bit.si>
Cc: <cq-contest at contesting.com>
Sent: Friday, December 31, 2010 2:07 AM
Subject: Re: [CQ-Contest] Bandpass filtering


> Don't ICE make a receiver overload unbuilt into a lightning detection device?
> 
> Trent
 Sampson
> 0408 497550
> 
> 
> On 31/12/2010, at 10:31 AM, "S56A" <s56a at bit.si> wrote:
> 
>> N4ZR wrote: From what W3LPL has told me, I am pretty confident that I can
>> simply parallel the output of the 6 filters, but can I also parallel the
>> inputs?
>> 
>> I very much doubt that W3LPL told you that!  His BPF are triple tuned
>> circuits with top capacitor coupling.  They exhibit low impedance on the
>> frequencies above bandpass.  10 m filter is coupled to 50 Ohms with 33 pF
>> while 160 m has 719 pF.   That gives 475 (square) power ratio or -27 dB
>> loss.
>> 
>> Only serial tuned circuits can be paralleled at 50 Ohms and even that
>> becomes difficult beyond triplexer.  Check http://www.nuhertz.tv/
>> 
>> You don't need any BPF for QS1R, just band STOP filters to prevent input
>> frying from nearby TX.  ICE filters might be easily converted to band-stop
>> with change of both inputs to serial notch and adding just one more small
>> coil for parallel resonance (de)coupling.
>> 
>> HNY & 73 de Mario, M/S56A from London
>> 
>> 
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