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QRP-LABS Low Pass Filter upgrade


Timothy Fidler
 

It is possible to armour up say a 40 w PCB for a LP  filter  like the one from Far Ccts  (Also sold out of India  by Sunil Lakarami) with heavy Cu wire , solder stitched along  existinig traces.  you need to handle the bare wire with gloved hands so it does not get sweat on it so you can then spray it with Polyurethane varnish to protect the critical outer layer where RF will be travelling.  DO NOT flow solder all over the copper. you need bead welds of solder to the PCB trace every now and then. Obviously the CU is being run down the guts of the existing PCB trace.  Where you have vias in a PC B you will have to work out a solution.  Navships on Ebay sells TE insulated Cu wire 1.0 mm dia which can be a shovel out of hard place.  take care not to breath teflon fumes if soldering it.  Navships is also known as John's wire shop.  I don't believe he has any solid core wire greater than 1.0mm. TE insulated wire of any sort is a nice thing to have for this sort of duty. 

Sod's law - such a board will be sized for say type T50 toroids. If you want to move it to a HIGHER PLane you may get mechanical clashes. So a 5 filter PCB may turn into a 3 band PCB. " Ya get that on these big jobs"

regards, TE Fid


ajparent1/KB1GMX
 

Also PCB conductor size and spacing are a factor as well.

For example 100W is 1.4A into 50 ohms so heavier and larger
relays become a factor.

20W is easy 50W takes care, more is significant revision.

Allison
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Hans Summers
 

Hi JP 

For 100W everything would have to be BIGGER. Bigger toroids, higher voltage capacitors, larger PCB traces, bigger connectors. You could use the same component values. Just design a PCB around larger components. If wishing to use relay-switching I think you'd also need to use BIGGER relays! 

73 Hans G0UPL
http://qrp-labs.com

On Tue, Sep 8, 2020 at 7:16 AM J P Watters via groups.io <jpwatters=mac.com@groups.io> wrote:
Hans,

I found in past posts that your LowPass Filters could safely handle 10 Watts.

I have a 1.8mhz-54mhz 100W amplifier that I am searching to add switchable LPF's to it.

Is it possible to update your LPF's to handle 100W? If so can you recommend the components to do so.

..jpw J P Watters
KC9KKO
Morris, IL USA


Viktors Miske KC8CKZ
 

QRP and QRO are 2 different ball fields.
Boards are designed for QRP ops. You want same design, but handle higher voltage / current levels. (Example, larger guage wire, much higher voltage caps, torroids that won't saturate and create a smoke stack, etc). Plenty of free info on the web if ya search.

73, KC8CKZ


J P Watters
 

Hans,

I found in past posts that your LowPass Filters could safely handle 10 Watts.

I have a 1.8mhz-54mhz 100W amplifier that I am searching to add switchable LPF's to it.

Is it possible to update your LPF's to handle 100W? If so can you recommend the components to do so.

..jpw J P Watters
KC9KKO
Morris, IL USA