PI4CC have a very good single stub system.
https://www.pi4cc.nl/tech-info/stubs/
PI4CC have most likely believed the people claiming the double stub would
be just 6dB better than a double stub.
PI4CC result is somewhat better than any 2 stub arrangement would be.
I have an uneasy gut feeling about the presented filters, how they might
drift over time.
At least connecting&disconnecting the cables may present changes to coils.
73,
Jukka OH6LI
2017-04-28 21:45 GMT+03:00 Jim Brown <k9yc@audiosystemsgroup.com>:
> Thanks Peter.
>
> Bear in mind that bandpass filters between transceiver and power amplifier
> will protect the receiver, and double stubs, optimally located along the
> transmission line, can provide more than 70 dB suppression of the
> amplifier's second harmonic (in addition to the 30-40 dB provided by the
> amplifier's output network).
>
> http://k9yc.com/LocatingStubs.pdf
>
> I'm using stubs like these on the amplifier output in addition to 5B4AGN's
> excellent TXBPF filter sets. See slides 16-20 in http://k9yc.com/7QP.pdf
> for a practical installation.
>
>
> Suitable stubs can be built, tuned, and installed for far less than the
> cost of a high power bandpass filter -- it's the cost of the coax,
> connectors, and adapters (Tees and barrels), and any decent RG8 or RG213
> can handle far more than the 1.5kW output that's legal in much of the world.
>
> 73, Jim K9YC
>
> On Fri,4/28/2017 10:34 AM, Peter wrote:
>
>> Hi fellow hams/contest OP's
>>
>> I just want to let you know that PI4CC is ready to bring there high power
>> bandpass filters pcb's available for the ham community.
>> This is hobby project and you can build a good bandpass filter your self!
>>
>> We don't claim really high power, but its calculated for 1kW key down and
>> we tested them 15 min key down with the output of a Acom1000 without any
>> issue.
>> During a 24 hour contest in SSB and CW its works great and weak signals
>> near a second harmonic (2Kc) could be easy copied.
>> It has better numbers as 4O3A, DG0SA, VA6AM.
>>
>> Have a look at https://www.pi4cc.nl/tech-info/hp-filter/ for more info
>> and details.
>>
>> We are is the stage of make an order for the pcb's, but its difficult to
>> get the correct amount.
>>
>> Peter
>> PC2A
>>
>> Reference :
>> 4O3A http://www.4o3a.com/index.php/products/high-power-filters/series-xl/
>> DG0SA Funk march 2017 page 244
>> VA6AM https://va6am.com/
>>
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>>
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