K7YO Antenna Page  

K7YO VHF/UHF Antennas
antennas deployed, summer 2007:

Antenna projects:

 Compact 2 element yagi for 50 Mhz

Cushcraft 17B2 yagi

This 17 element yagi on a 31 foot boom (4.5 wavelength) is a good standard to judge other high gain 2 meter antennas, meaning it is about as good as similar length yagis.  It does the job dependably and with impressive gain (but not Cushcraft's gain!).  I am now using  a 17B2  at 56' on my HBX  tower.  This antenna location allows me to work areas blocked at the rooftop such as deep south.

17B2 manual

Homebrew 50 Mhz 4 element yagi
This high gain, broad-banded yagi uses a folded driven element for a good match from 50.0 to 52.5 Mhz.  The pattern is best below 51 Mhz however.  I modeled it at 7.64 dbd with about 16 db F/B ratio at 50.150 Mhz.  A 1/2 wave RG-8 coax balun is coiled behind the driven element.  This antenna has been in use since 1997 with excellent results. Information on modeling and building this antenna: 50 Mhz 4 element yagi AO source

50 Mhz, 4 element yagi and Mt St Helens

Two 8 element yagis in phase, 144 Mhz

I had excellent 144 Mhz results with a pair of vertically stacked Telrex 2M-814 yagis. These 2 wavelength, 8 element yagis have been modified by changing to folded driven elements. They are well balanced with 4:1 half wave coax baluns.  I used two RG-11 75 ohm matching sections cut to odd 1/4 wavelength.  AO/YO antenna modeling indicates the Telrex beams were optimized for maximum gain at 145 Mhz by design. This yagi has a narrow bandwidth with reduced F/B, typical of a maximum gain design.  I had them stacked 11 feet apart for 14 dbd  gain as modeled by AO in freespace.  This is within 1/2 db of the 17B2 model but has a much wider azimuth pattern.  I have now switched to the Cushcraft 17B2 as it is easier to mount high on my tower.

K1FO-33 432 Mhz yagi

The K1FO-33 antenna was given to me by W7SZ.  This 10.5 wavelength yagi has 33 elements and is 24 feet long. It's +/-10 degree pattern (-3db) is razor sharp. The inertial backlash after rotating can be a problem when trying to zero in on a signal.  Sometimes the signals fade in and out as the backlash oscillation damps out!  I now have a Landwehr GasFET preamp mounted on this antenna.


 The FO-33 antenna beams east toward Mt. Adams

 

16 element  222 Mhz yagi

KI7JA made me a very nice yagi for 222 Mhz. It performed well during the January 2005 VHF contest, reaching Canada and Idaho with just 20 watts. This 3.9 wavelength antenna design can be found in some ARRL publications. I modeled it at almost 14 dbd gain, 20 db F/B. It uses a T-match feedpoint.

16 element 222 Mhz Yagi

K7YO HF Antennas

Currently there are no HF antennas deployed.  I have a Tennadyne T7 log periodic, 18-30 Mhz, which I hope to get up on the HBX tower soon.

  • Antenna Modeling and Design

    All my antennas are modeled with K6STI software, AO, YO, or NEC Wires. I started using the earlier MN in the late 80's. Elnec/Eznec as well as other modeling software are also good but use different source file formats.  All listed gain figures were modeled by AO or YO software in free space.

     K7YO antenna modeling & source files

       Antenna Links

  • 144 Mhz antenna modeling comparisons
  • ON4ANT Antenna Page
  • Actual Antenna Gain Measurements
  • W3DHJ CableTV Hardline

  • Linear Loaded 40 meter dipole
  • WA5VJB Cheap Yagi Designs
  • KA0TP 927 Mhz super J-pole
  • W7MY cheap yagi construction
  • 144 array of 16 yagis stacked vertical
  • VU2WAP Antenna Page   
    •   

    Last update: July 24, 2007