Radio Builders
Radio Discussion => Technical Corner => Topic started by: ZoZo on June 15, 2024, 09:23:48 pm
-
That's quite similar to the ones we make, but we put screens between the coils. I compared the filters with and without the screens, and the improvement in the higher harmonic products was significant with the screens in place.
The best filters we use (for higher power gear) use coax lines as resonant stubs, tweaked accurately for the frequency in use. The higher power gear always uses pairs of output devices, which has the advantage of tending to null even harmonics. The normally predominant 2f harmonic is several dB lower than the 3f before filtering if the PA is accurately balanced! This has the advantage of reducing the stringency of the filters needed, especially for the lower harmonic products.
With a conventional filter like the one Zozo shows above, it's crucial to have really low impedance earthing and make sure that the PA is accurately impedance-matched to the filter to minimise losses and to minimise heating problems. It's interesting to play with the "sense" of the windings - you can get a couple of extra dB of harmonic suppression by winding the first coil clockwise, the next anticlockwise, and so on. The improvement is marginal but reducing the mutual coupling between coils helps a little.
-
Marcel thank you , for reply .At the moment in hand i only have this type .in early time i used to use some philips quality ceramic , wich no more here where i am . or i have to make my own , but if thoses do the job at the moment that will be good fr such power , i dont need more RF.
Happy new year .
-
Use ceramic tube capacitors of at least 500V.
I used these up to about 200W without any problems.
These did have slightly higher losses than silver-plated(Semco)capacitors or ATC type 100B.
-
Hello guys mery christmas and happy new years 2026.
i am on making etching one to use with a 100w amplifier .i will post pictures later of construction. i used the blue capacitor of 1kv rating , i know they were not good for high rf power , but it can work on 100w erp.
-
Hi,
It's quite difficult to achieve the following with an open construction on the printed circuit board.
I've tried everything but 'floating with shielding between the coils work best.
See attached photos which only consists of 3 coils ans 4 capacitors.
-
Hi here,
Am a new user.
The disadvantage of a double-side printed circuit under the tracks is that you more insertion losses and what is forget here, is that the total capacity also increases.
Of course you should not mount this PCB flat on the metal but a little bit above it.
I have the best experience with "floating" filters with the coils is separate (with shielding).
If you don't do that, the harmonics will (happily) blow over.
Without special (high price) measuring equipment (Vector Network Analyzer) you actually have no idea what you are doing.
Marcel
YES sure. that is reason why orginal not heave coper under coil soldering points! nanoVNA doig this job very vell
-
Hi here,
Am a new user.
The disadvantage of a double-side printed circuit under the tracks is that you more insertion losses and what is forget here, is that the total capacity also increases.
Of course you should not mount this PCB flat on the metal but a little bit above it.
I have the best experience with "floating" filters with the coils is separate (with shielding).
If you don't do that, the harmonics will (happily) blow over.
Without special (high price) measuring equipment (Vector Network Analyzer) you actually have no idea what you are doing.
Marcel
-
Guys could i use , Cu wire copper of 1.5mm , just i want to use if it work at max of 80W , 100W .
Thanks.
At the power levels you’re using the gauge wire you intend to use will probably work, however it’s worth considering the RF skin effect at the intended operating frequency, the large of the diameter wire the more efficient the LPF will be and having a lower insertion lose.
-
Guys could i use , Cu wire copper of 1.5mm , just i want to use if it work at max of 80W , 100W .
Thanks.
in that case you need inductance recalculation, if remeber 98nH in out, midddle 108nH
Thank you rigmo , i will see what i have , when i finish it .It could took some time .
-
Guys could i use , Cu wire copper of 1.5mm , just i want to use if it work at max of 80W , 100W .
Thanks.
in that case you need inductance recalculation, if remeber 98nH in out, midddle 108nH
-
Guys could i use , Cu wire copper of 1.5mm , just i want to use if it work at max of 80W , 100W .
Thanks.
-
Thank you Guys.
-
write all on pcb
-
L1 , L4 8mm ID
L2 , L3 9mm ID
14SWG wire
-
4 (Turns) Windings 8mm (ID) inside diameter
4 (Turns) Windings 9mm (ID) inside diameter
Air coils - 14 SWG - 2mm wire
Space between the windings about 1mm
-
@ZOZO
can you supply the coil diameter handling 100W.
cu diameter and thread diameter
tanks.
I haven't got the data for that with me at present, but will get that posted here asap. But someone may post that sooner for you.
-
@ZOZO
can you supply the coil diameter handling 100W.
cu diameter and thread diameter
tanks.
-
the Dutch RF version, which as I recall has a full grounding plane on the bottom side.
For that reason is not good! mine is created long time before Dotch pcb..
-
Looks good Rigmo, I see it has a few extras for SWR monitoring. The Gerbers I shared are more or less a direct copy from the Dutch RF version, which as I recall has a full grounding plane on the bottom side.
-
It's genuine I can assure you. Please find Gerber attached below.
(Attachment Link)
in my posesion i heave one
also on background no copper !
-
ZoZo thank you mate .
-
It's genuine I can assure you. Please find Gerber attached below.
[attachurl=1]
-
Here's the Bottom view. its just a solid ground plane.
(Attachment Link)
This is not good is not geunine draw
-
ZOZO please can you share a pdf or .lay
thanks .
-
Here's the Bottom view. its just a solid ground plane.
[attach=1]
-
Been busy working the RadioBuilders own version of a 500W FM Broadcast LPF.
Here's a sneak preview of the PCB
(Attachment Link)
More details about this to follow.
Bottom view?
-
Looking really good. Defo want to give that a try when the boards are ready.
-
Been busy working the RadioBuilders own version of a 500W FM Broadcast LPF.
Here's a sneak preview of the PCB
[attach=1]
More details about this to follow.