Published 21/8/2014

A Super-quiet 11 element EME and Weak signal antenna for 222MHz

Model: 11-222-WS - LFA Yagi

Download the EZNEC files for this antenna HERE

If you wish to buy this antenna ready-built, find it HERE

The LFA Yagi is designed to be very low noise and thus, allow the user to receive weak signals that could otherwise not be worked. As a result, performance with modes such as MS and EME is exceptional.

Note this is wideband and thus stable in wet and icy weather too!

 

The only place you can buy this antenna is InnovAntennas no other company has permission to sell 222MHz LFA Yagis!

 

 Performance Plots

 

Note the very fast drop off to high suppression either side of the antenna from the 45 degree line backwards. This is key in ensuring you receive no unwanted noise (from directions other than which your antenna is facing).

 

 Azimuth

 

Elevation plot

This super-clean antenna when placed 10m above ground is a serious performer.

 

A nice flat, SWR curve as I am sure you have come to expect from me!

 

Performance

Gain: 14.92dBi @ 222.050MHz

Gain: (1 antenna 10m above ground): 20.81dBi

Gain (2 stacked 10m above ground): 23.19dBi

F/B:   43.32dB  @ 144.050MHz

Peak Gain: 15.02dBi

Peak F/B: 44.72dB

Power Rating: 4kw

SWR: Below 1.1.1 from 221.000MHz to 224.00MHz

Boom Length: 4.01m

Stacking Distance Vertically: 1.5 -2.2m (best trade-off  1.8m)

Stacking Distance Horizontally: 1.6 - 2.2m (best trade-off 1.95m)

 

2 Stacked Vertically @ 1.8m Gain: 17.55dBi

2 Stacked Vertically @1.8m F/B: 38.21dB

 

2 Stacked Horizontally @ 1.95m Gain: 17.61dBi

2 Stacked Horizontally @ 1.95m F/B: 37.53dB

 

4 Antennas 1.8m V x 1.95m H Gain: 20.28dBi

Sky Temperature: 212.7 Kelvin

G/T Figure: -2.99dB

 

Notes: The lower the temperature figure, the better but it is. The G/T figure is the most important attribute in the above specification (more positive the G/T figure, the better the antenna is for receiving weak signals) and as you can see, this antenna is better than anything else listed of the same or similar length. 1MHz bandwidth normalised to best 1MHz bandwidth (143.8Mhz to 144.8Mhz) not 144Mhz to 145Mhz. If the antenna is very narrow band, it is more likely to shift in wet weather conditions.              

So here are the details for this one if you want to go build it yourself.

Boom positions in mm, dones this was as mm mean more precise measurements!:

Ref: 0

DE: 98mm (this is the drive part of the loop See notes below)

DE2: 205mm

D1: 356mm

D2: 594mm

D3: 861mm

D4: 1276mm

D5: 1780mm

D6: 2325mm

D7: 2896mm

D8: 3493mm

D9: 4025mm

 

Element Lengths - (All parasitic elements 1/4'' diameter with the exception of the driven loop which is 1/2'' and has 3/8'' folded dipole ends). See note below on potential correction factors and tuning.

Ref: 663mm

DE: 517mm (This is the length the 1/2'' sections need to be cut to)

DE2: 517mm (see notes below on loop preparation)

D1: 616mm

D2: 582mm

D3: 585mm (this is correct, D3 bigger than D2)

D4: 579mm

D5: 568mm

D6: 556mm

D7: 541mm

D8: 521mm

D9: 518mm

 

Driven element Notes:

• With a folded dipole/LFA loop this design is direct feed, 50Ω and needs no matching device
• While you will read elsewhere to the contrary, a choke or balun (1:1) IS required see here
  
• The above listed dipole length has had 50mm removed to achieve the length required for the straight sections in the diagram below and to account for the radius of the trombone-style end sections of the loop.
• This is required to allow for correction due to the curves in the loop-ends, the step-down in loop-end diameter and correction due to the loop being earthed opposite the feed point
• A tool to bend loop ends to exactly the right size required can be purchased here
• It is best to have absolute minimum contact with the drive element itself so use the shortest/smallest form of insulators possible. Avoid feed point enclosures where possible and only use coaxial cable joins that maintain impedance. 
  
• Once the loop is together, measure its complete width to the above mentioned dipole length plus 30mm and adjust for best SWR from that starting point
  
• The overall height of the folded dipole can vary if you wish it, but the length of the folded dipole will change. For example, if you change loop height from 46mm to 40mm, the width if the FD will need to be longer then the above stated in order to achieve a perfect SWR. The opposite applies if you increase loop height. The construction of the loop allows for easy SWR adjustment be means of a Trombone type adjustment. See here for more details

 

 Antenna Layout using recommended Stauff clamps and 1.25'' square boom

Download the large-layout version of this diagram HERE

 

 

Pitfalls and Cliffs

If you have any questions or want an antenna of a different size, Email me.

There is NO CORRECTION added to any element lengths. If you follow my mechanical construction guidelines, nothing will need to be added at all. DO NOT use any insulators where bolts pass through the boom and element without establishing correction factors, your antenna elements will need to be lengthened should you chose to go down this route.

Any questions just ask. Within this next few weeks, I will add this antenna to as new category and will add another version.

COMMERICALLY AVAILABLE FROM INNOVANTENNAS. NO OTHER COMPANY HAS COMMERCIAL USE RIGHTS OF ANY KIND

Copyright G0KSC 2013 all rights reserved