On 6/9/21 11:03 AM, Herb Sims wrote:
I have looked all over the place for Bandpass filters for both 2m and 70cm antennas to put in front off my LNAs.
Any companies in the US that sells them?????
Hello Herb,
Are you trying to avoid de-sense, or do you need a true band-pass for those bands?
If the former; you can use a diplexer[1], such as the Comet CF-4160K, on each of your VHF and UHF paths. See this link:
https://www.amsat.org/a-simple-desense-filter-for-mode-j-satellites/
I, personally, would terminate the unused port in 50 ohms, especially if you intend to transmit through this device. The high-pass/low-pass filters within the diplexer are designed with this impedance in mind. See [2] for details.
If the latter; you can buy a band-pass filter, but they can be somewhat expensive. As a representative sample:
https://www.antennas-amplifiers.com/2-meter-bandpass-filter-transmitting-100...
This is a cheap, low-power version:
https://www.hobbypcb.com/index.php/products/uhf-vhf-radio/144mhz-band-pass-f...
You could also build both diplexers and band-pass filters yourself, usually for far cheaper, depending on your transmit power. A NanoVNA comes in handy to tune these homebrew creations. However, it all comes down to money vs. time. hihi
[1] Note that many amateurs (and some equipment manufacturers!) confuse the terms "duplexer" and "diplexer". See https://en.wikipedia.org/wiki/Duplexer
[2] https://wb4son.com/wpblog/?p=2828
73,
--- Zach N0ZGO