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@bit.si> wrote:
From: S56A <s56a@bit.si>
Subject: Re: [CQ-Contest] Bandpass filtering
To: "VK4TI" <vk4ti@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@yahoo.com>
To: "S56A" <s56a@bit.si>
Cc: <cq-contest@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@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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