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Question about QRPLabs band-pass filter #lpf #bpf

makkiato@...
 

Hello,

I have a question regarding the BPF kits:

https://qrp-labs.com/bpfkit.html

I know they are supposed to be used as "receiver" bpf's, but I am curious if I could use them to filter the output of a low power amplifier (around 2/3W).

So my question is:

 

Question: does anyone know what is the max power rating of these BPF ?

I could fine on the website that the LPF kits (https://qrp-labs.com/lpfkit.html) can safely handle 10W.

 

Thanks!

Dave
 

The band pass filters use a primary winding to get signal into and out of the toroids.  There are many more secondary turns than primary, and this increases the impedance from 50 ohms to something much higher.

The coupling capacitors between resonant circuits are probably rated at 50 volts, and never see that when dealing with received signals.  But pumping in transmit power and then raising the signal impedance raises the signal voltage which will likely exceed the coupling capacitor rating to the point of damage.

There are several choices of transmit band pass filters available, and they tend to keep the signal impedance low to avoid the high voltages which come with high impedance circuits.  The W3NQN transmit band pass filter design does increase the internal impedance and needs high voltage capacitors, like 3kV!

Dave


On Jun 13, 2020, at 07:43, makkiato via groups.io <makkiato@...> wrote:



Hello,

I have a question regarding the BPF kits:

https://qrp-labs.com/bpfkit.html

I know they are supposed to be used as "receiver" bpf's, but I am curious if I could use them to filter the output of a low power amplifier (around 2/3W).

So my question is:

 

Question: does anyone know what is the max power rating of these BPF ?

I could fine on the website that the LPF kits (https://qrp-labs.com/lpfkit.html) can safely handle 10W.

 

Thanks!

ajparent1/KB1GMX
 

Dave is right the voltage limits of the caps preclude using them for more than
maybe 1.00W.  It would be suggested to say under 200mW.

If you need badpass for highe rpower there are designes out there,,,
See sepetember 1988 QST for an example.

Allison
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Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting

 

"Badpass"... is that like "Leeloo Dallas, MultiPass" ?

For those weirdo's like me who like cult movies.

I'll shut up now.

Julian N4JO.

On 6/13/2020 1:32 PM, ajparent1/KB1GMX wrote:
Dave is right the voltage limits of the caps preclude using them for more than
maybe 1.00W.  It would be suggested to say under 200mW.

If you need badpass for highe rpower there are designes out there,,,
See sepetember 1988 QST for an example.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting

makkiato@...
 

thanks! 

ajparent1/KB1GMX
 

I need to disable spell wreck as there are several copies running
but not on my system.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting

danielu@upcnet.ro danielu@upcnet.ro
 

I noticed that a BPF filter coupled to the TX output seems to filter very well, that is, it transforms some rectangular signal into a sinusoidal one. That is, it brings out the harmonics 3 and 5 very well. With the naked eye, everything looks good because these components have the highest energy. Above, the components 7, 9, 11 and so on  no longer filter well, they pass much easier than when we use LPF. What I wrote is tested with a 10 and 30 Mhz LPF and BPF qrplabs filters. So I don't just recommend BPF for TX.
Daniel Ungureanu  Y08SAK