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:topband-bounces+john.kaufmann=verizon.net@contesting.com] On Behalf
Of n2icarrl@gmail.com
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
|