Steve, An alternative is to do the cancellation with all passive circuitry. You can find some designs on the Web but you'll have to build them yourself. An example (one that I built) is this one from WA1ION: https://www.pa4tim.nl/wp-content/uploads/2011/02/passive_bb_phasing.pdf. The drawback to the passive designs is the insertion loss. The WA1ION design works quite well but I've measured its insertion loss as about 12 dB. That may not be acceptable in many situations, particularly on the higher HF bands.
73, John W1FV -----Original Message----- From: Topband [mailto:[email protected]] On Behalf Of [email protected] Sent: Saturday, March 14, 2020 12:41 PM To: Topband Subject: Topband: Slightly OT - amplifier noise This discussion of Hi Z amplifiers has been quite interesting. Excellent information from W1FV and K7TJR. I have an RX amp question, related but slightly off-topic. I have an MFJ-1025/1026 noise canceler. I like to use it on the higher HF bands to cancel power line QRN. The noise is typically S3-S4, but I want it down to S0 to hear the bottom layer of stations. My sense antenna works fine, and the QRN is canceled. However, the MFJ-1025 amplifier noise is quite significant, often negating the QRN cancellation. The MFJ amplifiers are J310's. Any recommendations for something quieter ? 73, Steve, N2IC _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
