[Skimmertalk] New MFJ omni-directional horizontally

Fri May 26 13:10:06 EDT 2017

Bob,

By "buffered vertical", I mean a Hi-Z type preamp.  High input impedance to make it work over a wide range with a simple ground, but only unity gain.  Gain is not needed for my QS1R up to 20 meters.  I am using one of the preamps sold by DX Eng for the YCCC phased array kit.  It’s a nice cheap solution for Hi-Z in and no gain at the lower frequencies.  And, the unity gain is quite precise in case I ever wanted to make it part of an array.

The vertical is ground mounted with a fiberglass sleeve to minimize capacitance to ground as in any Hi-Z type vertical.  I am more or less following the YCCC phased array antenna construction, with one element.  I am using two small 4 ft ground rods and no radials.  Not needed for this type of feed.  My TX antennas are about 200 ft away.  I have no overload problems and do not use any bypass switching; the intent is to have the skimmer active all the time, including transmit.  Otherwise, the utility is somewhat limited during contests.

On the horizontal, I went for low noise and about 20 dB gain (PGA-103 MMIC), which again is a good match for the QS1R at the higher frequencies.  The antenna is about 22 ft high, and I hope to go a bit higher if I can do so without guying.  It is on a tilt over mount with large diameter EMT pipe for easy access.  No problems or TX switching here either.  Very cheap to build and MFJ will even sell you parts if you are so inclined.  I bought some of their sheet metal to save time and used my own fiberglass spreader and balun/preamp, while dropping 20M and adding 6M.

73,
Drew K3PA
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Message: 1
Date: Thu, 25 May 2017 09:36:58 -0700
From: "Bob Wilson, N6TV" <n6tv at arrl.net>
To: SkimmerTalk Reflector <skimmertalk at contesting.com>
Subject: Re: [Skimmertalk] New MFJ omni-directional horizontally
	polarized antenna
Message-ID:
	<CAOmNKGLBhD5Xm3NYCC9EfbyTjzZ+hcVTG9i2nRHb_-tP1BwzFg at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

Interesting results.  How high is your horizontal Omni?  Is the 20 ft vertical ground mounted?  How many radials?  Nearby antennas or towers?
Preamp voltage disconnected automatically when you transmit?

What does "buffered unity gain" mean?  A preamp that varies its gain by frequency?  How much gain did you program for each band?

73,
Bob, N6TV

On May 25, 2017 6:28 AM, "Drew Vonada-Smith" <drew at whisperingwoods.org>
wrote:

Bob,

Good idea about skimmer use.  I am already doing exactly this for my second CW Skimmer, K3PA-2-#.  I have a pretty close homebrew clone to the MFJ item (basically a multiband squalo) for 6/10/12/15 M.  Very easy and cheap to build.

My thought was that my buffered (unity gain) 20 ft. vertical would be better on 160-40 and a horizontal omni would be better on 6-10-12, especially with a preamp (I use a PGA103 based board) to complement the characteristics of my QS1R.  I wasn't sure about 20 and 15.

Early results are that the vertical is much better on 160-20, similar on 15M, and the horizontal omni is better on 12-10-6.  I am now running both skimmers with 15M covered by both.

73,

Drew K3PA

-----Original message-----
  1. New MFJ omni-directional horizontally polarized antenna
      (Bob Wilson, N6TV)

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Message: 1
Date: Tue, 23 May 2017 12:04:13 -0700
From: "Bob Wilson, N6TV" <n6tv at arrl.net>
To: SkimmerTalk Reflector <skimmertalk at contesting.com>
Subject: [Skimmertalk] New MFJ omni-directional horizontally polarized antenna
Message-ID:
<CAOmNKGJg8z8Y3PCkmCCHAzgDDmhA73tHoHdc8FbZ=Sg74tLEBA at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

At Dayton, MFJ displayed a new 20 through 10m horizontally polarized HF antenna.  This could be ideal for skimming the high bands, and also for Faros <http://dxatlas.com/faros/>, if you can get it high enough.  They claim a TV mast is sufficient.

http://www.mfjenterprises.com/Product.php?productid=MFJ-1835

73,
Bob, N6TV

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