I am looking to make a Low Pass Filter for a 2M project I am working on, It is a design by OZ4HZ and I can source most of the components except the board for which I don’t have the PCB design files. I asked around and someone said to me “Don’t you have a Sotabeams 2M Band Pass Filter”, well yes I do but isn’t a Band Pass Filter for receive only, it’s not an LPF.
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The SOTABEAMS filter is rated at 5W for transmit - so works with handhelds… If this is useful. Paul (Well 2W continuous but 5W with a 30% duty cycle…)
I just assumed it was really for receive, I knew about 5W transmit, but it’s not something I use a lot tbh only at Bardon Hill and even then it doesn’t get rid of the Pager interference. Also, the cost is prohibitive, far cheaper to build
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There is this one, but it is still £30 not including postage https://www.dxworld-e.com/product-page/lpf-filter-vhf-2m-band-600w
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A bandpass filter makes more sense, especially for reception. It also cuts out the lower frequencies that cause blocking.
A low-pass filter is more likely to be used to suppress the harmonics that are emitted.
73 Armin
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Yes, that was how I understood it, I need a LPF because I am using Chinese Micro Transceivers, and need to get the harmonics down to an acceptable level, the actual output level is only going to be between 1 and 4W
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According to the data from OZ4HZ, such a filter can be built quickly… you don’t need a special PCB. It only carries components and provides a good ground connection…
This can be checked quickly with a NanoVNA, for example.
73 Armin
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A Bandpass filter is both a Hi-pass and a low-pass with an overlap in the middle so it PASSes the signals in-BAND
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If you build a filter and it doesn’t fit into the TRX itself… then of course you should also have good sockets and an RF-tight housing. If you have to buy everything… the price difference to a ready made available filter will not be that high… building it yourself is often no worth it in terms of price… but you can learn a lot!
73 Armin
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Received an email this morning and I can’t order the coils because the UK distributor will only sell them in batches of 1500 so it looks like I will be spending about £30 for one from DX world
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