[Elecraft] OT: For Sale - Clifton Labs Active Antenna System plus extras

[Craig Smith]

I have for sale a Clifton Labs Active Antenna system plus extras as will be described below.  This is a receive-only active whip with a very small footprint and visual impact that is ideal for use with a K3 as a secondary vertically polarized antenna for diversity reception.  Specified frequency range is 20 KHz to 30 MHz, but will receive up to 100 MHz with reduced performance.

The system has two main components:  A remotely located whip with a preamplifier at its base (Z1501D), and an in-shack control unit /antenna coupler (Z1203A).  The antenna coupler requires the typical 13.8V nominal DC, but will operate over a wider range.  The coupler unit supplies power to the remote preamplifier over the coax interconnecting cable.  A control cable between the coupler unit and a transceiver can be used to turn off the antenna amplifier when transmitting (automatic muting).  This will easily follow CW keying for QSK.   It interfaces well with the K3 for this purpose.

This product was designed by Jack Smith, K8Z0A, and is an example of the bullet-proof (both electrically and mechanically) products that he provides.  I purchased this system new in 2010 and it has been performing flawlessly in my diversity RX setup.  It has been a terrific addition to my CW contesting station which I am now in the process of decommissioning. The amplifier section is very robust.  3rd order output intercept is +40 dBm.  2nd order output intercept > +73 dBm.  In addition to ham band usage, this antenna is great for SWL and broadcast band listening.

For additional information, complete specifications, application notes, photos, etc. see the excellent Clifton Labs website:  http://cliftonlaboratories.com

The black whip antenna is adjustable from 22 to 112 inches in length so that you can adjust it for the sensitivity you desire.  The whip and amplifier assembly can be mounted to a vertical pipe from 1 to 2 inches in diameter with the supplied U bolts.  Or it can be screwed to a post or fence.  I had mine attached to a perimeter wooden fence mounted about 6 ft above ground and it worked very well.  I painted the external amplifier and mounting bracket with a textured medium gray/brown paint which gives a very stealth appearance if you live in an antenna restricted location such as mine.

The transmitter control cable is terminated in RCA connectors.   The power cable is set up with a PowerPole plug.  All the signal cable connectors are BNC.  The length and type of cable between the two units is very non-critical.  It can be either 50 or 75 ohm.  I used a combination of RG-58 and RG-8X, but even smaller cable such as RG-174 could be used as well as CATV 75 ohm cable.

I added a three position switch and a yellow LED to the antenna coupler unit.  The switch allows for manually turning the antenna on or off as well as using the automatic control for muting from a transmitter.  The yellow LED shows the power state of the antenna amplifier itself, while the standard green LED shows when DC is connected to the unit.  This setup provides some additional operational flexibility compared to the stock arrangement.

I also designed and built some common-mode chokes to use in the coax between the two units.   This addition, while not absolutely required, will allow for enhanced common-mode rejection of strong local signals.  There is one small choke directly at the output of the remote amplifier. I am also supplying two other larger chokes, each packaged in water resistant enclosures with BNC connectors.  Each of these chokes is comprised of 6 turns of coax on two type 31 large beads (Fair-rite PN 2631102002).  This provides very good common-mode rejection from below 500 KHz to over 30 MHz.  Test data are supplied.  I mounted one of these midway in the coax run and the second one just before the coax entered the house.  Each of these chokes has a connection to the coax shield on both sides of the inductor.  These can be used to easily connect any of these points to a ground rod.  This connection can be used to optimize the overall common-mode rejection, but experimentation will be required as a function of your location, system layout and frequency of the common-mode signal you are trying to minimize.  In my case, I had two of these points tied to ground.   Note that the system will work well in most all cases without using any of these chokes!

Your purchase includes the whip, remote antenna amplifier, in-shack antenna coupler/control unit, mounting hardware, all manuals and documentation, schematics, DC power cable, control cable for muting when transmitting, and the three common-mode chokes.  You need only supply the coax interconnecting cable(s).

This system currently sells for $290.  My price is $200.  PayPal only, please.   Shipping via insured ground UPS should be from $15 to $20 depending on your lower 48 QTH.  Provide your zip and I can give you the exact amount.

If interested, please contact me directly via email:    craig at powersmith.net		

73  Craig  AC0DS