MY NEW LOW NOISE AND WIDEBAND 4x8EL EME ANTENNA SYSTEM

my goal for this work:

WSJT from Joe Taylor K1JT made it possible to work also EME with small antennas and low power.
Thats why I decided in december 2005 to design an optimized antenna system for my purposes.

For weak signal operation my needs are the following for an optimzed antenna system:

1. good gain
                   2. low noise to prevent man made noise from monitors and computers
(low sidelobes,low TVI)
3. moderate bandwith for use in bad wheater (snow,ice) and also for SAT work
4.easy handling (because of not to big & complex mechanical construction)
5.payable material

 So i started my work and analyzed....to find
the optimal solution for my purpose

the result was my new 8EL Design with 3.62m BOOM 11dBd Gain

(many thanks for the help and conversation with Steffen DD0VF and Pop YU7EF)

simulation results of the single 8EL antenna:
TYPE
 L
GAIN
 FWD
 SIDELOBE
 BACK
 Tlos
 Ta
 G/T
 frequency
 remarks
DG0OPK_8EL
 1.74
 10.98
 177.17
 66.84
 2.73
 4.67
 251.52
 -10.88
 144.0 MHz
DG0OPK_8EL
 1.74
 11.03
 176.85
 67.31
 3.51
 4.65
 252.33
 -10.84
 144.5 MHz
DG0OPK_8EL
 1.74
 11.04
 175.83
 69.30
 5.34
 4.76
 255.23
 -10.88
 145.0 MHz
DG0OPK_8EL
 1.74
 10.99
 173.08
 75.34
 8.99
 6.47
 263.89
 -11.08
 145.8 MHz
 

						L    		= Length in Wavelengths
						FWD 	 	= Forward Lobe Noise Temperature 
						SIDELOBE	= Sidelobe Noise temperature
						BACK 		= Antenna Noise made from backside lobe 
						Gain 		= Gain in dBd of antenna (without losses)
						Tlos 		= The internal resistance of the antenna in degrees Kelvin (high losses means critical design)
						Ta  		= The total temperature of the antenna in degrees Kelvin. This 
			       		  			  includes all the side lobes, rear lobes and internal resistance of the antenna. 
						G/T  		= Figure of merit used to determine the receive capability of the antenna
      		 			  			  (Ga + 2.15) - (10*log Ta). The more positive figure the better.

simulated horizontal and vertical pattern

simulated SWR over frequency

simulated impedance over frequency


measurement results of the single antenna - first prototype (JULY2006):
(with Vectronics SWR-584B antenna analyzer and phasing line)
frequency
 impedance
 SWR
140
 46+j16
 1:2.1
141
 38+j17
 1:1.8
142
 35+j11
 1:1.5
143
 36+j0
 1:1.3
144
 41+j0
 1:1.1
145
 48+j4
 1:1.1
146
 46+j0
 1:1.1
147
 37+j15
 1.1.7
measurement results of the 4 antennas for the system (December2006):
(with Vectronics SWR-584B antenna analyzer and phasing line)

frequency ANTENNA 1 SWR
 ANTENNA 2 SWR
 ANTENNA 3 SWR
ANTENNA 4 SWR
142
 1:1.3
 1:1.3
 1:1.4
 1:1.4
143
 1:1.2
 1:1.2
 1:1.3
 1:1.2
144
 1:1.1
 1:1.2
 1:1.2
 1:1.1
145
 1:1.1
 1:1.2
 1:1.2
 1:1.2
146
 1:1.0
 1:1.2
 1:1.1
 1:1.1
147
 1:1.6
 1:1.5
 1:1.6
 1:1.6


mechanical sizes for the elements
Element
 Length
 Distance
 Diameter
reflector
 1024
 0
 5
driven
 988
 344
 8
director 1
 962
 577
 5
director 2
 935
 1071
 5
director 3
 918
 1703
 5
director 4
 904
 2411
 5
director 5
 876
 3050
 5
director 6
 830
 3616
 5

mechanical sizes for the elements
Element
 Length
 Distance
 Diameter
reflector
 1024
 0
 4
driven
 988
 344
 8
director 1
 966
 577
 4
director 2
 940
 1071
 4
director 3
 923
 1703
 4
director 4
 910
 2411
 4
director 5
 882
 3050
 4
director 6
 838
 3616
 4


the first array is up in our portable location in jo50an and working fine (click for picture)

the second array is up in my home location in jo50gq (since 19.feb.2007)

stacking parameters for an array of  2x 2  for low sidelobes and moderate gain
(that could be my use in the city or in my home location)



calculatet noise temperature parameters for the complete system (Tsky=200K,Tearth=1000K)
stacking distance H = 2.3m , V = 2.3m

Gain @ 144 MHz = 16.18dBd  (18.43dBi)
forward noise temperature of the system @ 144MHz:      187.8K
sidelobe noise temperature @ 144 MHZ:          35.16K                    
backside lobe noise temperature @ 144 MHZ:          2.36K                    
loss temperature @ 144 MHZ:          4.52K       
overall antenna noise temperature @ 144 MHz: ca. 230K

G/T value calculations (using Tant  by YT1NT, and help from Boban YU7XL)
   
frequency gain
 noise temperature (without losses)
 G/T value
144.0 MHz
 18.43dBi
 224.2K
 -5.08 dB
144.5 MHz
 18.50dBi
 223.8K
 -5.00 dB
145.0 MHz
 18.54dBi
 225.0K
 -4.99 dB
145.8 MHz
 18.56dBi
 231.8 K
  -5.09 dB
        

stacking parameters for an array of 2 over 2 for maximal gain (thats the use on the /portable location)
stacking distance H = 2.8m , V = 2.5m

Gain @ 144 MHz = 17dBd  (19.15dBi)
forward noise temperature of the system @ 144MHz:      182.83K
sidelobe noise temperature @ 144 MHz:          49.41K                    
backside lobe noise temperature @ 144 MHz:          3.48K             
loss temperature @ 144 MHz:          4.71K         
overall antenna noise temperature @ 144 MHz: ca. 240K
  G/T value regarding to VE7BQH chart : -4.65dB

      
mechanical details
feed lines,driven element connection,antenna holder,element holder

  
IF YOU WANT TO USE HIGHER POWER  ... USE 75 OHM TEFLON CABLES FOR THE FEEDLINE.
(for my purposes QRP  < 200W at the single antenna in a group of 4 , RG59 will do it)

  
Special Note:
This design is the work on many simulations and measurements over some month.
The mechanical work costs a lot of money and time of my friend Pit DM2CKK.
Special thanks also to  Karsten DM2CT and Jens DO6JE.
Distribution and publishing of these data and information is permited ONLY
for radioamateur purposes and construction.
Use of these information and data for any commercial purposes is strictly prohibited
without the written authorization of the author.

if you are interested in some special parts or complete antennas write me an email ....


info

Back to main page



  last change: 27.june 2007 (DG0OPK)