Clackamas Amateur Radio Emergency Services (CARES)

Transcription

1 Presented by: Clackamas Amateur Radio Emergency Services (CARES) 4/25/2015 1

2 NVIS Near Vertical Incident Skywave 4/25/2015 2

3 Introduction In this class the basic techniques in the theory, use, and making of a NVIS antenna will be presented Instructor: David Kidd, KA7OZO Emergency Coordinator (ARES) Clackamas Co, Oregon 4/25/2015 3

4 Training Points What is NVIS? How will it work for us? How hard is it to use? Why should I use it? What does it really do for us? What materials are needed? 4/25/2015 4

5 What is NVIS NVIS is a combination of radio hardware, sky wave radio propagation, operating procedures, cooperation, and knowledge used by a group of radio operators who need reliable regional communications. NVIS fills the gap between line-of-sight ground wave and long-distance "skip" sky wave communications. 4/25/2015 5

6 Propagation Theory 4/25/2015 6

7 NVIS Effect 4/25/2015 7

8 300 Mile Coverage 4/25/2015 8

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14 Dual Band Yes; you can remove the 60 Meter elements! 4/25/

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17 How It Went Together Materials Construction Modifications 4/25/

18 Parts List 1 - Feed point - 50 Ohm #14 insulated stranded wire ½ x 10 PVC cut to length 2 Insulators Tie wraps 3/16 rope cut to length Coax to the shack 4/25/

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20 Spreader Lengths 2 17 Next to center insulator nd from center insulator End of 40 M element End of 60M element Another spreader could be used between the center insulator and the end of the 40M element 4/25/

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22 Element Lengths 75 Mtr legs = ft 60 Mtr legs = 45.4 ft 40 Mtr legs = ft Prune these lengths to meet your ground conditions 4/25/

23 40 Meter Tension 4/25/

24 Tensioning method for 40M 4/25/

25 Spreader keepers 4/25/

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27 UV resistant line 60 Meter tension 4/25/

28 60 Meter Tension 4/25/

29 Beamwidth 75 Mtrs 38 deg. To 142 deg. 60 Mtrs 36.5 deg To deg. 40 Mtrs 34 deg. To 146 deg. 4/25/

30 Night Time Ionosphere (300 mi.) 4/25/

31 Hints & tips Solder wires at the feed point Solder feed point pigtail to all other wires Dipole insulator has an eye bolt in the top for suspension from a tree or skyhook Coax should be perpendicular to the antenna 4/25/

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33 Choke balun 18 coiled 9-10 turns 4/25/

34 Hints & tips (cont.) Ground conditions will drive element lengths Wet vs.. dry Use an antenna analyzer!!! Tune 75M first, then 60 then 40M There is interaction between the 60 & 40 meter elements 4/25/

35 Reflectors Ground wires laid directly under the antenna 5 Total! 1 on 75M and 2 each on 60 & 40M Spacing is important M on either side of 75M & 40M on the outside of 60M 4/25/

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37 Tri-band Reflector Lengths 75M 65 60M M /25/

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41 Dual Band Element Lengths 75 Mtr legs = 59.7 ft 40 Mtr legs = ft Prune these lengths to meet your ground conditions 4/25/

42 Dual Band Reflector Lengths 75M M /25/

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44 60 Meter Considerations USB 2.8 khz bandwidth limitation 5 Channels (Window freq khz) 100W ERP limitation Antenna gain Feedline loss QST Feb or ARRL FAQ 4/25/

45 Regional 60 Meter Agreement 5405 Nation/International 5373 Washington 5368 Idaho 5348 Montana/Oregon 5332 Regional coordination between states/sections 4/25/

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47 NVIS Antennas are nondirectional, Antennas designed for High angle, beamwidth may be 30 degrees or more, greatly determined by antenna height Refracted back in circular pattern Radius depends on strength and D/E layer absorption Ground wave can help/hinder NVIS skywave, due to phase relationship 4/25/

48 Omni Pattern 4/25/

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50 What is NVIS German ground forces first documented NVIS techniques in WW-II NVIS was more fully documented, studied, and used by US forces in Vietnam NVIS is still used by today s military in combat operations 4/25/

51 What is NVIS NVIS propagation is generally considered to be F-layer ionospheric reflection at angles of degrees 4/25/

52 How will it work for us? Emergency groups such as ARES and RACES are studying NVIS propagation, techniques, and equipment deployment for emergency preparedness. NVIS is the tactical communication system of choice in mountainous areas, any areas without complete repeater coverage, and all situations where repeater-based systems have failed or might fail. 4/25/

53 How will it work for us? (Cont) With the recent release of manufactured mobile and even portable HF radios, HF, and antennas employing NVIS propagation, it should become much more popular and useful for disaster tactical communications. 4/25/

54 What can NVIS do? This is a mode of HF radio equipment deployment that allows for reliable communications within a range of miles, and depending on condition even farther out. NVIS can be viewed more as a "Systems Concept" and not just what antenna to use. The concept of NVIS is to have reliable communications anywhere within an 800 mile diameter circle. Your station would be located at the center of this circle. 4/25/

55 How hard is it to use? NVIS is not just an antenna type or a propagation mode -- it is a tactical communications system that was designed by military radio operators in the field. The NVIS antenna is only part of that system. The other part is the knowledge and cooperation of the operators, which must be accurately applied to achieve the best results -- particularly when used in life-and-death situations. Training and coordination is a key factor in making it all work properly. 4/25/

56 How hard is it to use? (Cont) Emergency communications should be driven by clearly written procedures that have been well-designed and tested. The procedures should be drilled on a regular schedule. The drills should be followed by debriefings attended by everyone, so that all can learn to avoid future mistakes. Suitable procedures are available in books, Field Manuals, and on the web. Look for ARES and RACES web sites and capture their procedural documents. Other excellent sources are FEMA and MARS sites. 4/25/

57 Why should I use it? To talk close in: under 200 miles To have good overall state coverage To have multiple frequency capabilities To have a system that will work under poor band conditions 4/25/

58 Main Reason To Use It First and foremost, to completely eliminate the skip zone. This enhances all forms of local and regional HF communications, for all practical and experimental purposes. Most of all it can be used effectively for emergency operations within a local geographic area. 4/25/

59 Among the many advantages of NVIS NVIS covers the area which is normally in the skip zone, that is, the area normally too far away to receive groundwave signals, but not yet far enough away to receive sky-waves reflected from the ionosphere. NVIS requires no infrastructure such as repeaters or satellites. Two stations employing NVIS techniques can establish reliable communications without the support of any third party. Pure NVIS propagation is relatively free from fading. 4/25/

60 More Advantages Antennas optimized for NVIS are usually low. Simple dipoles work very well. A good NVIS antenna can be erected easily, in a short amount of time, by a small team (or just one person). Low areas and valleys are no problem for NVIS propagation. The path to and from the ionosphere is short and direct, resulting in lower path losses due to factors such as absorption by the D layer. 4/25/

61 Still More Advantages NVIS techniques can dramatically reduce noise and interference, resulting in an improved signal/noise ratio. With its improved signal/noise ratio and low path loss, NVIS works well with low power. 4/25/

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63 Disadvantages of NVIS operation For best results, both stations should be optimized for NVIS operation. If one station's antenna emphasizes ground-wave propagation, while another's emphasizes NVIS propagation, the results may be poor. Some stations do have antennas which are good for NVIS (such as relatively low dipoles) but many do not. 4/25/

64 A Few More Disadvantages NVIS doesn't work on all HF frequencies. Care must be exercised to pick an appropriate frequency. The frequencies which are best for NVIS are those where atmospheric noise is a problem, antenna lengths are long, and bandwidths are relatively small for digital transmissions. Due to differences between daytime and nighttime propagation, a minimum of two different frequencies must be used to ensure reliable around-the-clock communications. 4/25/

65 What materials are needed? Materials are dependent on which antenna type you want to use Dipole fixed or portable position Ham stick rotating dipole Military type 2- band version We will discuss material required for each type All are simple to make and use 4/25/

66 N6VNG s NVIS Antenna 4/25/

67 Parts List N6VNG s NVIS 2 ea. 1.5" PVC pipes 7.5' long 1 ea. 1.5" PVC coupling 1 ea. 1.5" PVC cap 4 ea. Egg type insulators 5 ea. Brass Screws, nuts and washers to fit coaxial fitting 1 ea. SO-239 or UG-266 female panel-mount connector with solder pot center pin 5 ea. Stakes (One at the mast center) 4 ea. Heavy solder lugs to fit brass screws 150' Antenna wire 60' Nylon rope Coax to rig. As much as you need. Run it up the center of the PVC pipe mast and connect to the panel-mount 4/25/

68 Construction Notes: N6VNG s NVIS Drill PVC cap to accept SO-239 and 4 screws and nuts Mount SO-239 to PVC Cap with screw heads down Cut off the head of a brass screw Solder a brass screw to center post of SO-239 Cut antenna wires to length plus a little Fit one end of each wire with solder lugs Fit the other with the egg insulators Install wires to SO-239 using brass nuts and washers {as shown in the figure} Erect antenna (2 men ~ 5 minutes) Tune antenna match for minimum VSWR (also could adjust mast height and wire lengths) 4/25/

69 Dual "Ham Stick" version Configuration that shows promise for ARES/RACES is to take two mono-band mobile antennas and mount them base to base, with one being the driven. element and the other being the ground side. Care must be exercised in tuning this configuration that the elements are the same length. They are light weight, portable, fairly inexpensive, and easy to put up. 4/25/

70 Dual "Ham Stick" version This antenna is available at HRO. Antennas are Ironhorse IHF80's and IHF40's (two each) and the Ironhorse IH- DAK-AD adapter Total cost for four antennas and the mounting bracket is $ (as of 2/21/06). You can use a Radio Shack tripod and five foot mast sections for simplicity or 4 sections of cammo poles. Plus a run of coax 4/25/

71 40m Rotating Dipole KC7TOF s rotating 40m dipole and masting configuration Very easy to set up and get on the air 4/25/

72 Frequency Possibilities & Modes 40 meters during the day 80 meters at night 160 meters at night if 80m is out The new 60m band with it s power & antenna limitations can be very effective using NVIS techniques. Desired modes: SSB, RTTY and PACTOR 4/25/

73 Multi-Band NVIS 40m, 80m, & 160m 170 #14 stranded 30 with a tuner Budwig Hye-Que type connector - HRO Insulators - one $1.95 UV resistant rope for support as needed for antenna site 4/25/

74 Real Life NVIS Use Fixed dipoles at appropriate height Rotating portable dipoles using Ham Sticks Military styled X version with 2 band capability - portable/fixed position 4/25/

75 In Reality... Groups of operators using NVIS must understand and cooperate on the basics. All must be using NVIS antennas (defined as any horizontal antenna well under a quarter-wave high), as well as the radio hardware and propagation theory. All must understand that the frequencies used must stay between the total absorption and vertical MUF ranges. The group must decide whether it will equip itself to use 160. Calling frequencies and other procedures should be established, in writing, with contingencies clearly stated. 4/25/

76 Actual Field Operation & Test SET - 9/25/04 In parking lot adjacent to new county office building on Kaen Rd. KC7CJO s military version antenna on loan to CARES Worked great! 4/25/

77 Personal Experience 80 meter horiz loop Using on 75 Meter at & with tuner. Work regional nets Net controls in: Seattle 200 miles Hermiston 180 miles Coeur d alene, ID 380 miles Kelowna, B.C. 480 miles 4/25/

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89 What This Means NVIS works It is simple to make and simple to use NVIS will fill the gaps during poor propagation and conditions Minimum NVIS capability will cover the entire state of Oregon NVIS can reach the capitals of the adjoining states of CA, NV, WA, & ID from our county 4/25/

90 Next Steps Since you now know the basics of NVIS, it is time to put your knowledge to use You can make one, buy one, or borrow one... Just try it and I know you will become a believer 4/25/

91 Links to NVIS URLs age1.htm G%20AS2259.htm 4/25/

92 Presentation Credits What s the deal about NVIS? By Dean Straw, N6BV, QST Dec 2005 NVIS Operations by Ed Farmer, AA6ZM, QST, Jan 1995 The NVIS - A Low Antenna for Regional Communications by Albert Pion, KK7XO, QST, Jun 2002 NVIS by Norm Fusaro, W3IC, internet PPP Understanding NVIS Antennas & Propagation by Harold Melton, KV5R, 2002, /25/

93 Just about the end Questions? Thank you showing interest in NVIS antennas! I look forward to helping you get started with your NVIS antenna project 4/25/