[Elecraft] Zipper Noise and Birdies on 6M -- FIXED!

[Allen R. Brier]

I have a number of birdies on 6 and other bands and they sure are annoying.
What's the best way to eliminate them? I am not using an external pre-amp.

Allen N5XZ

ORIGNAL MESSAGE:
Message: 20
Date: Sun, 03 Jul 2011 15:32:21 -0700
From: Jim Brown <jim at audiosystemsgroup.com>
Subject: [Elecraft] Zipper Noise and Birdies on 6M -- FIXED!
To: Reflector Elecraft <elecraft at mailman.qth.net>
Message-ID: <4E10EDF5.6050007 at audiosystemsgroup.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Ever since I started using my K3 on 6M I've been troubled with zipper 
noise as I tune, as well as birdies generated within the K3 that move 
around as I tune.  Today I found and eliminated the coupling mechanism, 
and the noise and birdies are gone.

My setup uses an external ARR 6M preamp at the RXOUT / RXIN patch point. 
(I use it rather than the Elecraft preamp because I already owned it, 
and it's a very good preamp). I also have a switch that brings in my 
Beverages,  with a Tee jumper between the AUX input (for the SUB RX) and 
the RXIN.  That Tee was the coupling path. On a hunch, I replaced the 
Tee with a Mini-Circuits passive splitter that has about 35dB of 
isolation between outputs, with an insertion loss of 6.6 dB.  It's rated 
for use between 10 MHz and 1 GHz, but it passes my Beverages on 160M 
just fine.

Mini-Circuits is an old line, well respected company based in Brooklyn. 
I've been specifying their splitters for about 30 years for the VHF and 
UHF wireless mic systems I designed for performance facilities and 
churches.  The splitter I used with the K3 is a ZFSC-4-175 that is one 
of several I picked up at a hamfest.  While it's a 75 ohm splitter, it 
works just fine in this application.  It's a 4x1 splitter, and a 2x1 
would work equally well.  For optimum isolation, unused outputs should 
be terminated in 75 ohms, and I did that.

http://www.minicircuits.com/pdfs/ZFSC-4-175.pdf

http://www.minicircuits.com/pdfs/ZFSC-2-1+.pdf

El cheapo CATV splitters MAY also work -- IF they have enough isolation.

73, Jim Brown K9YC