Low pass filter for RF antenna?

Basically I'm looking for filter for antenna for frequency (150 to 155 MHz). I'd google it and got some result but i don't know how to made such type of inductors.

In image if you see there is a specification 2ov/@6mm what it is??

can I put standard inductor instead of coil type inductor??

what will be the value for pass 150 to 155 MHz freq?

The filter shown in the picture has a first elliptic section followed by a 5th order Chebyshev.
C17 is obtained summing the output cap of the elliptic filter with the input cap og the Chebyshev section (in this case 10+10 pF).
2ov/@6mm should means 2 turns on a diameter of 6mm and, obviously, 3ov/@6mm should means 3 turns on a diameter of 6mm.
The lenght of the coils is not specified, I think because the tuning of the filter has to be made streching or compressing each coil, so we cannot estimate a value, but it's possible to estimate a range using the Wheeler formula.

However from the value of the capacitors the first inductor should be 24 nH, while the others two should be 40 nH resulting in a cutoff frequency around 250 MHz.

albbg said:

The filter shown in the picture has a first elliptic section followed by a 5th order Chebyshev.
C17 is obtained summing the output cap of the elliptic filter with the input cap og the Chebyshev section (in this case 10+10 pF).
2ov/@6mm should means 2 turns on a diameter of 6mm and, obviously, 3ov/@6mm should means 3 turns on a diameter of 6mm.
The lenght of the coils is not specified, I think because the tuning of the filter has to be made streching or compressing each coil, so we cannot estimate a value, but it's possible to estimate a range using the Wheeler formula.

However from the value of the capacitors the first inductor should be 24 nH, while the others two should be 40 nH resulting in a cutoff frequency around 250 MHz.

Click to expand...

Thanks for you kind support

Can I use SMD inductor instead of coil type??

My Transmit frequency is 150MHz and received frequency is 155MHz can you please help me to design low pass filter for this frequency.

The type of inductors you have to use depends from the transmit power. You have to choose components that are able to manage all the RF power flowing during the transmission. There are also additional criteria to choose the inductors (f.i. the Q-factor) that comes from the specs of the filter, in terms of insertion loss and edge sharpness.
To start you can use the same topology of the filter in the picture of you post #1. The first 3rd order elliptic filter has a sharp edge so it can cut very close to the frequency you want to pass, the following 5th order Chebychev filter helps to remove the unwanted signal, but also removes the regrowth of the elliptic filter after the cutoff frequency.

However you can design the filter by yourself using the available free tools on the web. For instance you can have a look to the manufacturer coilcraft:

https://www.coilcraft.com/apps/lc_filter_designer/lc_filter_designer.cfm --> Elliptic filters design

futrthemore you can download RFsim99 that is a free RF simulator also able to synthesize Butterworth and Chebychev filter.

jtronix said:

Can I use SMD inductor instead of coil type??

Click to expand...

Not if you don't want to lose a lot of your power in the Q losses. To make your filter as low-loss as possible, make your inductors with as high a Q as your design can enable.

Can I use SMD inductor instead of coil type?

Click to expand...

You didn't yet talk about power. Wire wound SMD inductors are pretty accurate and have good Q values, but of course limited power handling.