Tuesday, May 13, 2008

About Filters.

Many hams often neglect the importance of filtering in their stations and run the risk of causing terrible TVI and RFI to their neighbors. I am a firm beleiver that proper and well designed filter such as low pass and band pass noty only remove the possibility of TVI and RFI but also go a great way in enhancing one's operating conditions. Indeed band pass filters will also improve specifically the receiving elements for the band the filter was designed for allowing only signals within the pass band to reach the receiver and cutting out unwanted signals above and below the permitted pass band. This not only works on receive, but pass band filters have the same functions on TX signals.

Below are a selection (part) of an extensive arsenal of different types of filters I use on the TX and RX side of my station. Most of these filters I feel are examples of the best available that money can buy.
Above is a very sharp Band Pass Filter made specifically for the 430 MHz band by Kuranishi of Japan. It has been with me for many years and will never leave the shack. The KBP-700 was in my opinion one of the best BPFs ever made for 70cm. The unsightly tarnished appearance is due to oxidaion of the silver plating. Yes the whole inside and outside are silver plated as are all other parts for very high "Q'" factor. Unfortunately I beleive that Kuranishi no longer make this great filter.

Below is the famed Shinwa 1001 Low Pass Filter for 50MHz made in the 1980s, Shinwa is no longer in existence.

The twins below are the ICE BPF and LPF for 50MHz. If you know about ICE and filters then I really do not need to make an introduction, they are some of the best filters currently available. The BPF is the model 412W for 50-54MHz, iCS is 250W with .5dB insertion loss, the LPF is the model 426 and is a 9th degree 50 ohm design, 80dB attenuation above 56MHz and handles 3 KW PEP - N Norm.
Futher below is one of my HF Band Pass Filters made by Dunestar and is the model 300-18, this is a very well made BPF and the machine filter enclosure shows the painstaking attention by the manufacturer made to make it a fine piece of work. Dunestar make some very fine HF BPFs.

Further below are two lesser know HF Band Pass Filters for 7MHz and 14MHz designed and built by BG1CHs, BG1CEP and BG1JA from China. Study the spectrum sweep curves also for the said filters.

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