This 98.5' (32.349 m) long  portable antenna was designed by VE7BQH for W0PT.  This high gain (19 dbd) antenna is relatively lightweight, inexpensive, and very portable - it can be rolled up for transport.  It also has an unusually high Front/Back ratio, which makes it especially good for receiving weak signals when pointed out over a quiet direction toward the moon (such as out over the ocean), and facilitates an operating/equipment position very close to the rear of the antenna (with a very short feedline). The forward gain of this antenna compares very favorably with arrays of four good 13 element yagis; depending on the type of terrain over which it is mounted (near a beach overlooking salt water is the absolute best!), 2m EME contacts with 10-20 stations should be possible - EVEN WITH ONLY 100 WATTS!  W0PT indicates that he built this antenna for
approximately $30.

This design uses .125" (3.175 mm) diameter aluminum elements, which are to be supported on two parallel non-conducting lines that will not stretch, such as dacron, Phyllistran or polypropylene (will not work if the antenna is to be left out in the sun for an extended period of time); the lengths shown for the antenna elements will only be correct if .125" diameter rods are used.  If you need to aluminum rods of a different diameter for the elements, please contact me or VE7BQH so proper element lengths can be provided.  The antenna is meant to be suspended between two end supports, with the two support lines tightened to remove antenna sag.  The yagi can be made more horizontal by hanging a third line above the antenna and extending several vertical support lines (such as in the middle and between the middle and ends) down from it to hold the antenna up.  However, W0PT reports very satisfactory operation by simply pulling the antenna tight at the two ends (without any further support from above).

W0PT connected his elements to polypropylene support ropes with plastic cable ties, and then the mechanical connections was sealed with "Plastic Rubber" to make sure the element locations would remain fixed. The intended use of this antenna is to provide gain in a specific direction, such as over a fixed tropo path or toward a particular azimuth where the moon is intended to rise or set.  It can be steered somewhat (to adjust for the changing moon declination and corresponding change in azimuth of moonset or moonrise) by moving one end of the yagi (such as moving the end support point between two trees).  In an ideal situation, the transmission line to the Driven Element can be kept very short, with the yagi extending out away from the operating position.

NOTE: Be sure to mount the rope yagi at least 12' above the ground.  Mounting it lower than this will cause excessive ground absorption, and loss of gain.
 
 

*The driven element used by W0PT was constructed as a "T Match" as follows:  Overall length of the 1/2" (12.7 mm) diameter driven element was 37.598" (955 mm); each of the two 3/8" (9.525 mm) diameter T-match sections was 15.197" (386 mm) long; center-to-center spacing between the driven element and T-match rods was 1.575" (40 mm); the driven element was fed with a standard half-wavelength balun 29.528" (750 mm) in length (RG-303 coax was used by W0PT).  It may be necessary to slightly re-adjust the T-match if the antenna is set up in a substantially different place (or different amount of sag, height, etc.) than where initially tuned.

Below is a photo of the 51 element 2m rope yagi used by N7BHC in V5 to try to make contact with ZD8BI.  The wind was blowing 80 km/h, with gusts to over 100 km/h when this picture was taken.  The wind was deflecting the middle of the antenna about 50 cm even with more than 200 kg of tension on the antenna. N7BHC used 3mm Kevlar for the boom wires to minimize stretch and keep element spacing accurate over a wide range of tensions. The Kevlar rope was obtained from West Marine.  The yagi has a 40m boom.

UPDATE!

Lionel has redesigned the antenna to have a 50 ohm driven element.  That means it can be a split dipole fed with 50 ohm coax and you can use either ferrite toroids around the coax to choke the RF on the shield, or use some other method such as a Pawsey stub to match it to the balanced 50 ohm dipole.   Below is the revised design data received from VE7BQH for this new design on January 3, 2013:

VE7BQH Rope Yagi with 3.175mm (1/8") el.
144.000 144.100 145.000 MHz
43 elements, millimeters
              3.1250    8.0000
    0.0000  1024.9750   0000.0000   0000.0000   
  401.7890  0000.0000   0987.7792   0000.0000   
  583.8506  0946.5488   0000.0000   0000.0000   
  976.3783  0940.1720   0000.0000   0000.0000   
 1381.3430  0933.6112   0000.0000   0000.0000   
 1877.2152  0922.3234   0000.0000   0000.0000   
 2489.4309  0917.7544   0000.0000   0000.0000   
 3103.3643  0909.3950   0000.0000   0000.0000   
 3735.2500  0904.0172   0000.0000   0000.0000   
 4457.3101  0902.1806   0000.0000   0000.0000   
 5204.1118  0899.2042   0000.0000   0000.0000   
 5942.3325  0893.8304   0000.0000   0000.0000   
 6695.3433  0888.8312   0000.0000   0000.0000   
 7487.8125  0886.0774   0000.0000   0000.0000   
 8320.8760  0885.3904   0000.0000   0000.0000   
 9166.8096  0885.0514   0000.0000   0000.0000   
10025.3779  0882.0188   0000.0000   0000.0000   
10887.9912  0879.1972   0000.0000   0000.0000   
11729.7295  0873.8140   0000.0000   0000.0000   
12482.5117  0866.2224   0000.0000   0000.0000   
13227.0840  0864.9466   0000.0000   0000.0000   
13974.4619  0871.7912   0000.0000   0000.0000   
14725.5820  0866.9242   0000.0000   0000.0000   
15472.4951  0857.2578   0000.0000   0000.0000   
16218.2900  0861.2754   0000.0000   0000.0000   
16967.8906  0867.8694   0000.0000   0000.0000   
17717.4727  0858.2322   0000.0000   0000.0000   
18463.9629  0850.5968   0000.0000   0000.0000   
19210.2070  0862.2996   0000.0000   0000.0000   
19960.2676  0862.8776   0000.0000   0000.0000   
20709.9199  0852.2834   0000.0000   0000.0000   
21454.8945  0849.7156   0000.0000   0000.0000   
22202.3027  0860.6222   0000.0000   0000.0000   
22953.4902  0860.4088   0000.0000   0000.0000   
23701.3848  0847.0908   0000.0000   0000.0000   
24446.1094  0848.3580   0000.0000   0000.0000   
25194.9004  0865.6212   0000.0000   0000.0000   
25946.1660  0861.5302   0000.0000   0000.0000   
26693.0508  0843.6596   0000.0000   0000.0000   
27436.9668  0858.0192   0000.0000   0000.0000   
28187.4902  0882.5146   0000.0000   0000.0000   
28940.1953  0875.6558   0000.0000   0000.0000   
29683.9805  0884.6826   0000.0000   0000.0000   
  0000.0000   0000.0000   0000.0000   

The prototype 6M8GJ I used on the E51SIX 6m EME DXpedition also used an adaptation of a Pawsey stub, and it worked quite well.   Below is a photo of that, just to give you some ideas.  Of course, you would not need a hairpin match with the rope yagi because it was designed for a 50 ohm split dipole from the start.

This page last revised on  3 January, 2013