Transcript Antenna Measuring Contest - Cheltenham Alumni Association

Propagation and Antennas
Net Frequency Selection
Antenna Contest Cook-Off
Tony Fusco
AFE3TM/AFA3TF
Illustrations from open internet sources
Some MARS Tales?
 “RC” always works.
 A low antenna is good for NVIS.
 Verticals make good DX antennas.
 Your tuner tunes your dipole.
 A feed-line can be any length.
 Low SWR indicates a good antenna.
 The propagation is going long.
What’s going on up there?
How do you know?
Millstone Hill Digisnode
The numbers that matter most
foF2 F2 layer Critical Frequency, MC (FOT <10-15%)
foF1 F1 layer Critical Frequency, MC (FOT <10-15%)
foE E layer critical frequency, MHz
fmin Lowest frequency at which at which echoes are received
MUF(D) Maximum Usable Frequency for D=3000 km
C-level Confidence level: 11=very good, 22=good, 33= moderate,
44=questionable, 55=bad
D
MUF-AM
MUF-PM
100 200 400
4.5 4.5 4.7
7.8 7.8 8.2
600 800 1000
5.1 5.6
6.3
8.7 9.4 10.5
1500
8.4
13.7
3000 (km)
13.9 (mc)
21.8 (mc)
When selected net frequency is
below the Critical Frequency (foF)
When selected net frequency is
above the Critical Frequency (foF)
 This is what happens when we operate our station above
the foF (FOT)
SSN Graph
Net Frequency & Propagation
 Lets go to our VOACAP crystal ball to see how critical
frequency and antenna selection can affect our nets.
J0G VM HD
RC “
“
RB
“
“
RA “
“
 Note: VOACAP area plots represent 10% of month days.
Actual conditions will be much worse for the 90%.
Ant & Prop Summary
 Station Examination:
Where do I go from here?
Am I ready for the Solar Minimums?
Money, time and space constraints?
“Space” the last frontier!
 A dipole is a dipole until it meets mother earth!
 EZ-NEC - a 65 ft dipole for gain and impedance
 7.30 mc
Gain 2.04 dbi / 73.4 ohms
 3.65 mc Gain 1.60 dbi / 13.5 ohms
 1.82 mc Gain 1.12 dbi / 3.4 ohms
 0.91 mc Gain .09 dbi / 1.1 ohms
J
-J
-J
-J
0
1K
2K
5K
- ½ wl
- ¼ wl
- 1/8 wl
- 1/16 wl
But bring it back to Earth!
The same dipole at 26 ft over ground gives us:
- 7.3 mc gain +6.08 dbi / 71.2 ohms REZ
- 0.91 mc gain -9.32 dbi / 1.6 ohms –J 5.3K
Now elevate it to the same <1/4 wl (220’) gives us:
- 0.91 mc gain is now +5.24 dbi !
“Its not the size of your dipole but where you hang it!”
Feeding your Antenna See Jun QST
 Details 40 meter dipole feed-line heat loss
@14mc with 100’ feeds, tuner and 1500w
* 600 ohm ladder line loss = 175w
* 450 ohm window line loss = 541w
* RG-213 coax loss= 1376w!
 Magic tips for mismatched feed lines:
- ¼ wave - transforms antenna impedance
- ½ wave - reflects antenna impedance.
“Only when both ends of a transmission line terminate
in its characteristic impedance is the system is happy!”
What can we expect from our antennas?
 Lets look at 8 antennas in the perfect EZ-NEC world.
GMV - 35 & 50 ohm
PMV - 50 ohm
Dipoles - at ¼ & ½ wave hi
Inverted Vs – at ¼ & ½ wave hi
V Dipole - at ½ wave hi
 Caution Tag Line - using HF verticals
GMV 35 ohms on 2.5” lawn
GMV 35 ohms on 2.5” lawn
GMV 35 ohms on 2.5” lawn
GMV 50 ohms on 2.5” lawn
GMV 50 ohms on 2.5” lawn
GMV 50 ohms on 2.5” lawn
PMV 50 ohm
PMV 50 ohm
PMV 50 ohm SWR
Dipole at ¼ wave – 17 ft
Dipole at ¼ wave – 17 ft
Dipole at ¼ wave – 17 ft
Dipole at ½ wave - 35 ft
Dipole at ½ wave - 35 ft
Dipole at ½ wave - 35 ft
Inverted V Dipole ¼ wave high
Inverted V Dipole ¼ wave high
Inverted V Dipole ¼ wave high
Inverted V Dipole ½ wave high
Inverted V Dipole ½ wave high
Inverted V Dipole ½ wave high
V Dipole ½ wave high 35/23 ft
V Dipole ½ wave
V Dipole ½ wave high
Antenna cooking by the numbers
TYPE
GAIN dbi
ANGLE deg
IMP ohms
GMV 35
-.18
25
35
GMV 50
-1.24
27
50
PMV
+.64
20
50
Dipole ¼ hi
+5.79
65
78
Dipole ½ hi
+7.3
25
69
Inv V ¼ hi
+4.02
90
50
Inv V ½ hi
+6.22
30
50
V Dipole ½ hi
+5.71
35
50
Enough said about that!
 That was an antenna eye-full!
 If you have antenna questions – please see me later!
 And now – what we’ve all been waiting for…
NED Antenna Cook-Off
 Seven members submitted ideas
 A few are real in use antennas
 Most are lets see - what ifs’- or old ideas
 The review was objective, participants were not part of
the selection process.
Entry 1 – A Loop 140 ft sides @40 ft
Entry 2 - Inv V 40’ hi – 51’ sides
Entry 3 - RC/RB Dipole @ 18’ hi
Entry 4 - Fence Rider 102/5 FT
Entry 5 – Broadband Antenna 40’hi
400 ohm loads into 8 ft gnd rods
Ver2 with counterpoise on grass
Entry 6 the AS-2259 15 Ft hi
Entry 6/2nd – Sloped TFD 40’/6’hi
Entry 7 142’ Dipole 40’ high
Cooking our gain by the numbers
ENTRY
RA
RB
RC
J0G
Total Gain
#1 Loop
4.79/55
8.64/60
10.93/35
10.77/15
35.13
#2 Inv V
1.49/65
3.8/90
4.19/90
7.49/90
16.97
#3 Inv V
NA
2.6/90
1.66/90
NA
NA
#4 Fencer
-11.14/90
-5.01/90
-2.09
.65/60
-17.59
#5 Broad 1
-12.36/90
-8.94/90
-14.82/45
-.68/25
-36.35
#5 Broad 2
-10.04/50
-8.48/90
-1.83/45
-.95/25
-21.2
#6 AS-2259
-8.28/90
-2.11/90
1.87/90
3.17/90
-5.35
#6 TFD
-7.07/85
-.32/85
-.34/80
2.65/30
-5.08
#7 Dipole
6.04/90
6.78/90
7.99/45
9.21/25
30.03
Note:
Gain/angle
dbi/deg
Igor the envelope please
 “All MARS” category antenna winner is the Grand Loop!

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

AFA2DO – NY’s - Paul Conway
“Trans Global” winner is – again – NY’s the Grand Loop!
“Regional” winner is the Big Dipole!
AFA3TF - PA’s – Me
“Restricted Antenna by CC&R” winner is the Fence Rider!
AFA2QD – NJ’s - Bob Harrision
“Wet Noodle” Antenna award goes to the WB Worm Warmers!
AFA3PB – VA’s - Ken Heitner
 Kudos to: AFA3WD - Dennis Welch, AFA3QP - Skip Masker, and
AFA2PD - Paul Dukette . Dennis’s tuner fed Inv-V may actually
be called the “most practical” of the bunch. A new category!
The Net Triad
Traffic
Capability
NET FREQ
Finally!
 Summary: What’s really important to MARS?
Its “US” – its team and how we accomplish the mission.
Future shock is here – in time, I hope that all members
can adapt to the new procedures to make our corner of
the D0D/MARS Trans-Global Network a better place to
connect and move traffic.
 After my 16 months of observation…our critical task:
- Generate/Move USMTF Traffic (can you?)
- Air/Army Net Frequency Agility (can we?)
- Mission Ready (are we?)
BL: Take the Initiative and Practice, Practice, Practice!