51 Foot Non-Resonant RV Antenna

I own a Jayco 23 foot camp trailer. I often go to RV camp grounds and I like to get in some hamming away from my home QTH. I've always been concerned about hazards to the other campers such as guy wires or wire antennas that have fallen down. As a result I been searching for alternatives that minimize these potential hazards. Some of my RV'ing friends use Buddy Poles others use mobile whips mounted on their RV's. The most common method it to permanently mount a mobile mount on the ladder used to access the top of the RV. Once their camp is set up they attach the mobile whip and feed line to the mount.

My trailer does not have a ladder. So my solution was to put a second spare tire mount (available at Harbor Freight) on the rear bumper of the trailer.  I "rigged up" a couple of eye bolts and a locking hitch pin to hold a mast. A short piece of PVC protects the fiberglass from damage when it moves because of wind. See Picture 1 and 2 below. I prefer a Jackite 30 foot fiber glass telescoping pole available at jackite.com or amazon.com. I use a Jackite 20 pole strapped to the gas bottle cover in the front to hold the far end of the antenna. That way everything is over the trailer. These poles are not fishing poles with the very flexible top section. These poles are designed for wind socks and flags. The top section is not hollow tube but rather sturdy solid rod.

The antenna is 51 feet of #22 AWG stranded wire used in aircraft construction. This is just wire I had in the "junk garage". Yes my junk box is one side of a three car garage. The only thing I'd recommend on the wire is that you use something quite flexible. I pull the wire up to the top of the 30 foot pole on a halyard. The far end goes to the 20 foot pole to make an inverted L with the vertical leg 30 feet and the horizontal led 21 feet running downward at about 30 degrees. This downward angle is of little significance in the antenna's performance. I use a light chalk line type cord throughout.  The horizontal leg does not reach the 20 foot pole so I use the same cord to make up the need length to reach the wire and then down to pole.

Picture 1

Picture 2

I wound a 9 turn unun on 2 1/2 inch PVC pipe with about 1/2 inch spacing. The wire is bare #14 AWG. I used hot glue strips at interval 1/4 the way around to hold the wire in place. See  the Picture 3 below. I tapped the unun as shown in the table below.

Picture 3

UNUN Tap Data

Turns above         |     Turns below         | Turns ratio        |  Impedance       |   Matches 50 Ohms
ground                 |      the antenna         |                          |   ratio                 |   to the following

1.75	7.25		4.14	:1	17.16	:1		858
2.00	7.00		3.50	:1	12.25	:1		612
2.25	6.75		3.00	:1	9.00	:1		450
3.00	6.00		2.00	:1	4.00	:1		200
3.50	5.50		1.57	:1	2.47	:1		123
4.00	5.00		1.25	:1	1.56	:1		78
4.50	4.50		1.00	:1	1.00	:1		50

I used four large mix 31 snap on ferrite beads distributed around a two turn 6 inch coil of the feed line about a foot away from the unun to suppress RF on the feed line getting into my RV. See Picture 4 below.

Picture 4

I ran this setup for nearly a month this summer while out and about with good results. I did not use that data because I felt it was better to use the Winter Field Day data. The Winter Field Day data is the same mode and power throughout. The resultant date will be a better representation of the antenna's performance and not a function of applied power or operating mode.

Antenna design model

The grounding scheme is a closed loop around the perimeter of the trailer. It is a 68 foot long loop made of 2 inch wide aluminum/mylar tape. ("Mutual Industries 17774-25-2000 Polyethylene Underground Water Line Detectable Marking Tape, 1000' Length x 2" Width, Blue" available at Amazon, about $30 last I checked). This works like a non-resonant counterpoise or ground mat. It just provides capacitance to ground. That is the wires you see in the model labeled 4, 5, 6, and 7. I loop it around the trailer to keep people from tripping on it.

The "on the air" performance for the antenna is documented below with data from my Winter Field Day log. I was running 25 Watts on PSK31 for the entire time using battery power. The radio was my IC-7300. I used my LDG Z-11PRO tuner with 20 feet of RG8x feed line into the trailer. The tuner in the 7300 does not handle wide range of impedance presented by the antenna.* 

 ------------------------------------------------------------------------------------------------------------------------

Winter Field Day Log Data

    Call                   UTC      Freq       Distance
    ------                 -----        -----   --------
Begin 01/25/20
    W7D                19:15     7.071    671.1
    KN4FRG         19:43   14.070      1076.7
    N5OAK           19:51   14.071      1092.9
    W0ARC          19:56   14.070      1057.8
    KC5LVW        20:02   14.070      1077.3
    KD5ILA          20:10   14.070      1042.0
    KI4ITI            20:30    14.071      1444.9
    K9BY             20:52    14.070      1190.9
    N4MZ             21:22    14.070      1541.8
    N4ZC             21:25    14.071      1728.8
    W5AWL         21:52      7.071      1014.0
    KB9REV        22:04      7.071      1251.8
    W7A               22:06      7.070      707.2
    NV7AV          22:15      7.071      392.0
    WA5WRL      22:27       7.071      1022.0
    W0BLK         22:30       7.071      493.4
    K7SI              22:46       7.072      285.9
    W4CVY         22:56      7.071      1606.6
    WB6AGE       22:58     7.071      662.0
    K5LRK          23:02      7.071      1001.4
    KC8QDP        23:09     7.071      1582.5
    K5OQ             23:47     7.071      1133.6
    N7YIQ           23:51     7.070      415.7
    W0IZ              23:56     7.071      266.8
Begin 01/26/20
   AD0ND            00:02    7.071      804.3
    W7GBU          00:07    7.072      514.8
    KD5ILA          00:16    7.070      1042.0
    W9UUU          00:22    7.072      1301.1
    W4GR             00:26    7.070      1603.4
    KC3FL            00:31    7.071      1872.5
    W3GQ             00:34    7.071      1719.7
    NV1O              00:38    7.070      531.7
    K6EI                00:44    7.071      589.8
    WD6RAT         01:02   7.070      556.7
    W7PIG             01:07   7.071      317.8
    N4MZ              01:49    7.070      1541.8
    W2OW             01:51   7.071      1851.3
    K5IJ                 01:53    7.071      1477.5
    W2SO              02:01    7.071     1711.2
    W8VVL           02:14    7.071     1453.9
    W8VA              02:14    7.071     1576.5
    KD9IPZ           02:31    7.070     1333.9
    VA3TPS           02:56     7.071   1694.3
    NT7H              03:26     3.581    673.0
    W6ZE              03:40     3.581   596.0
    NV7AV            03:42     3.581   392.0
    K7KY              03:46     3.581    632.7
    W5RRR           03:50     3.582 1242.8
    WB6AGE        03:55     3.581   662.0
    W7PIG            12:51     3.581   704.9
    K7UVA            12:53    3.580   59.6
    W5PDO           12:59    3.580   477.6
    W9LRC           13:05    3.581   1248.8
    KE8RV            13:07    3.580   1500.0
    W4SHL            13:23    3.581 1480.6
    KB9REV          13:28    3.581 1251.8
    K1KRN            13:50    7.071 2020.5
    VE3YRA          14:12    7.071 1660.1
    K5LRW            14:39    7.072 660.1
    K5WXV            15:06   7.071 1007.9
    K7IRA               15:26   7.070 511.6
    KE6SHL            15:40   7.071 507.5

Callsign, date, and time from my Winter Field Day Log
Distance from QRZ.com
Total QSOs         62

Distance
1041 miles average
2020.5 longest
59.6 shortest

73,
Keep On Ham'n
______________

* - High SWR has little to do with how well an antenna radiates RF. The losses experienced due to high SWR are losses in the feed line especially coaxial cable. The primary reason for keeping the SWR low is to keep the finals in the transmitter from overheating and being damaged. That is why I have kept my coax to 20 feet. And yes there are losses in the tuner due to adjusting for the miss match. I try to look to "on the air" performance when judging an antenna.

FEED LINE CHOKE FROM COAX

Over the years coiled coax has been used to choke off RF from the outside of coax feed lines.  Sometimes these are called 1:1 baluns, choke balun, but technically a balun is an impedance transformer while these coils are chokes.  (NOTE:  This discussion is limited to air core chokes only.)  The reason for a choke is to stop RF from coming down the coax, causing distortion of the antenna’s radiation pattern and RF problems in the shack. 

Coax line chokes work well if they are used correctly.  However, there are some things one needs to know about using this type of coax line choke.

1      1.       They are most effective on one band only below 40 meters.

2      2.       If carefully designed, they will perform on more than one band 40 through 10 meters (see chart below).

3      3.       Always “flat” wind these chokes.  Scramble winding adversely impacts their performance.

The most important performance limiting factor is inner turn capacitance, called parasitic capacitance. 

Remember that any time two conductors are next to each other, even if there is a DC electrical connection between them, there still is some capacitance between them at radio frequencies (RF).  

NOTE:  Do not confuse parasitic capacitance with the capacitance between the shield and the inner conductor of the coax.   The capacitance between the shield and the inner conductor does not contribute anything of significance to this discussion.

As parasitic capacitance gets larger the choke starts to look more and more like a capacitor to RF.  Remember that a capacitor's or an inductor's resistance to alternating current (AC) varies with frequency.  

Experience over the years has shown that 10 times the feed line resistance for a well match antenna is a good number to use for a coaxial line choke's reactance.  I used 500 Ohms for creating the chart below.  In the real world up to 25% either way is acceptable.  That is 375 to 625 Ohms.  A choke will remain effective so long as both its coil and parasitic capacitance remain in the acceptable range for the expected operating frequency.

The following chart gives a list of coaxial line chokes for various ham bands. 

      Turns         Diameter         Height     Coax type         Band Coverage

      13             8                   3.25           RG-174           160 meters only

                                                              RG-58

                                                              RG-8x

      9              9                    3                RG-174           80 meters only

                                                              RG-58

                                                              RG-8x

      8              6                    2                RG-174           40 meters only

                                                              RG-58

                                                              RG-8x

      9             4                    2.25            RG-174          40 – 30 meters

                                                              RG-58

                                                              RG-8x

      8            4                    2                  RG-174         30 – 20 meters

                                                              RG-58

                                                              RG-8x

      5            5                    2                  RG-174         20 - 15 meters

                                                              RG-58

                                                              RG-8x

     6             4                    2                  RG-174         17 - 10 meters

                                                              RG-58

                                                              RG-8x

     4             3                    1                  RG-174         6 meters only

                                                              RG-58

                                                              RG-8x

     Height and Diameter are in inches.

Be sure to match the length of the coil keeping the spacing even between turns.  This may require using a spacer between turns while winding the coil.  Once the coil is wound the spacer should be removed and the turns need to be glued in place.  Deviating very far from either length or diameter will chance the frequency at which the coil will work.

Here are three graphs that will help you see why a coaxial line choke is limited.  Note how rapidly the inductance and capacitance very with frequency.  Notice that on each graph inductive reactance and capacitance reactance cross on 500 Ohms.  Remember from above that this is the design criteria.

Notice the higher the band, larger the range of frequencies the choke covers.

Other coil sizes and coax types will work.  However, they are too numerous to post.  

73

Dave, K7PDW

SMALL BACK YARDS - THE BANE OF HAMS

It seems that there is an assumption that if you have a small backyard you are doomed to some sort of compromise antenna.  My response to that dire prediction is, “It isn’t necessarily so.”

If you have 70 feet in a straight line that you can put up a wire even at 15 feet above the ground, you have what it takes to make a simple (no traps, no ground radials, no compromise) antenna that will work well from 40 meters through 10 meters and even 6 meters.  (Please remember to be cautious of power line when installing any antenna system.  They’re real killers.)

It turns out that the simplest antenna to build is one of the best radiators of RF.  Sixty seven feet of #14 copper wire with a convenient length of either 300 Ohm TV ribbon or better 450 Ohm ladder line for feed line will do the job very nicely.  Bring the feed line down as perpendicular to the antenna as possible.  It does not have to be perpendicular to the ground as long as it stays 8 feet or so above the ground.  When you get to where you want to enter your house install a balun.  Here a 4:1 balun will work with most tuners and 450 Ohm ladder line, but I prefer a 9:1.  In my experience more tuners, both built in and stand alone, perform better with 450 Ohm ladder line and a 9:1 balun.  If you use 300 Ohm TV ribbon then a 4:1 is a better choice unless you can find a 6:1 balun which would be ideal.  You should be aware that TV twin lead has more loss than ladder line, but both beat an all coax feed line in this application by a country mile.

This antenna performs as a common ½ wave dipole on 40 meters.  On the higher bands it behaves as a collinear.  That is why you want to feed it with twin lead or ladder line.  Ladder line is preferable because it has significantly less loss than TV lead.  You may be tempted to put the balun right at the feed point of the antenna and then run coax all the way back to the transceiver.  That will work but the loss in the coax will be very high especially 17 meters and up. 

Here’s why.  There is a common misconception that by putting a balun in the feed line even when there is a high SWR that somehow the balun will correct the mismatch.  This is just not true.  The balun only transforms the mismatch to another value that may or may not match the feed line impedance. The feed point on this antenna and most collinear runs from 20 Ohms to 800 Ohms depending on the frequency you are running.  The following table compares the loss between a balun at the antenna feed point and 70 feet of RG58 and 60 feet of 450 ladder line between the feed point and a 9:1 balun then 10 feet of RG58 to run through the wall to the tuner and transceiver in the ham shack.

BAND                                    60 ft ladder line and        70 ft RG58 with a balun                  70 ft RG58

                                                10 ft coax w/balun           at the ant feed point                      no balun

---------------                       ------------------------        -----------------------------      --------------

6 meters                              8.52 dBi ERP                        5.84 dBi ERP                                3.93 dBi ERP

10 meters                            7.84 dBi ERP                        4.89 dBi ERP                               -2.66 dBi ERP

12 meters                            8.24 dBi ERP                        6.10 dBi ERP                                0.21 dBi ERP

15 meters                            6.96 dBi ERP                        4.65 dBi ERP                                4.50 dBi ERP

17 meters                            8.34 dBi ERP                        5.79 dBi ERP                               -1.58 dBi ERP

20 meters                            6.83 dBi ERP                        4.02 dBi ERP                               -3.14 dBi ERP

40 meters                            5.71 dBi ERP                        4.37 dBi ERP                                5.67 dBi ERP

ERP – Effective Radiated Power for the antenna system

Note – I did not have the necessary loss specs for TV twin lead for this comparison, but it will fall somewhere between 60 ft ladder, a balun with 10 ft of coax arrangement and the all coax with a balun arrangement.

Another misconception is that an antenna must be resonant to radiate.  This is also not true.  The loss of signal strength in a non-resonant antenna system is almost always due to high loss in the feed line caused by mismatch between the feed line and the antenna’s feed point.  A low loss feed line such as ladder line, TV ribbon, or open wire feed line carries the transmitter’s power to the antenna where it is radiated efficiently despite high SWR cause by non-resonance.  The performance of a non-resonant antenna will be comparable to a resonant antenna when feed line losses are kept to a minimum.  However, you must still do something to prevent the high SWR from damaging the transmitter.  This is the job of a tuner.  For multi band antennas that do not have provisions for achieving 50 Ohm feed point impedance at all the expected operating frequencies, a low loss feed line and tuner arrangement is a reasonably inexpensive solution.  Another solution is a remote auto-tuner at the feed point of the antenna.  This is effective, but considerably more expensive.  And it is often difficult to manage the weight of the auto-tuner at the antenna’s feed point unless it also happens to be at one of the antenna’s support points.  If an auto-tuner is available, it will work just as well at the end of the ladder line where it enters the house.  If you use an auto-tuner be sure it has provisions for feeding a balanced line.  If not, then a balun will be necessary between the balanced line and the auto-tuner.  It would be best to check with auto-tuner manufacture about how to implement that.

Some will note that this antenna looks suspiciously like a G5RV and that is a valid observation.  The major difference is that the balanced line can be any convenient length and the coax can thus be kept to a minimum length.  In this type of antenna one should always try to achieve the shortest run of coax possible and thus reduce the feed line losses to a minimum.  It is true that the balanced line that is cut to a specific length on the G5RV does act as an impedance matching device.  But again it will provide a good match at some frequencies and not so good at others just like a balun.  The loss that occurs in the coax will still be present. So always keep the coax as short as possible and the balance line as long as is sensible so as to reduce the loss in the antenna feed system to a minimum.

Happy HF’n and 73

K7PDW

PS - By the way, this antenna can be bent or sloped but its efficiency will drop some and often the bandwidth will get narrower making it difficult or impossible to tune some bands.

Back To Back Mobile Whips For Portable Stations

Back to back mobile whips have long been used to create rotatable portable dipoles.  You may have heard varying reports on how well they work.  Some folks even claim that they are nearly unusable because of high SWR.  My experience working contests while portable QRP with them has been good.  My setup has good SWR and I don’t seem to have problems making contacts with my FT-817 on SSB.  I was actually please with the ability to turn the dipole in null out strong signals.  The one disadvantage I found was that my setup only covered about 100k on the 20 meter band at less than 2:1 SWR.   I expected that because it is the nature of wound antennas to have a narrow bandwidth.

I began to wonder why others had such bad experience with this type of antenna.  I believe I discovered the reason when I began to consider buying a commercial mount design for back to back mobile whips.  I noticed that the commercial version simply grounded one whip to the mount while insolating the other one as in a standard mobile installation.  My home brew setup uses insolated mounts on both whips.  I connect the feed line, coax, as any other dipole.  Shield to one side and center conductor to the other side.  I use a coaxial wound choke to control RF on the outside of the coax.

 That got me to thinking.  I decided to experiment with grounding one whip, the one connected to the coax shield as the commercial mounts are designed.  I used a short jumper for the connection.  I usually use about 18 inches of PVC as an interface between top of my mast and the antenna mount.  I went ahead and set up the antenna as usual with the PVC as usual.  I didn’t see any difference. 

I next decided to try doing away with the PVC and connect directly to the mast still leaving the antenna and coax shield connected to the mount and thus now connected to the entire mast.  The mast I was using is 4 foot sections of the military mast I bought off the surplus market.  I have both aluminum and fiberglass sections.  I had use the aluminum in the previous tests and did so this time.

This time the SWR exceeded 5:1 which is well out of the range of many automatic tuners.  I grabbed my MFJ Travel Tuner Model MFJ-902 and was able to tune the antenna to an acceptable SWR.  However, tuning the FT-817 more than a few kHz required retuning the tuner.  I decided I was onto something but just to satisfy my curiosity I replaced the top two section of the mast with fiberglass sections.  The SWR dropped down to where it was when I still had the PVC between the mount and the mast.  I decided to confirm my result.  I put the PVC back in place and went back to the aluminum mast section.  The SWR remained low as expected.

 So if you are considering back to back mobile whip, I would avoid commercial mounts that simply ground one whip to the mount unless you plan to use non-conducting mast material or at least 18 inches of PVC between the metal mast and the mount.  I also recommend that you make provisions for keeping the RF off the outside of the coax.  A 1:1 balun, ferrite beads, coax wound on a ferrite core or a coiled coaxial choke are all solutions for this.  The coiled coax is the least expensive but if it is not constructed correctly it will not be as effective as one would like.  This will be the topic of a future post.

73

K7PDW

VHF/UHF Dual Band Antenna "Feature" You Should Know

Most dual band antennas available for VHF/UHF have a little discuss “feature”. 

Maybe you have noticed that very few antenna manufactures ever give their angle of elevation[1] information for each band.  They are very happy to share the maximum gain in dB for each band.  However, there is a characteristic of most antennas that causes the higher frequency signal to leave the antenna at a high angle.  It is not unusual for the major lobe on 2 meters to be less than 10 degrees while the 70 cm major lobe to be higher than 45 degrees.  The truth of the matter is that there will usually be a secondary lobe on 70 cm that is lower than 10 degrees.  But that lobe is not the maximum gain lobe.  Now as far as operational performance, this is seldom a problem.  The only time this may be noticeable is if you find that 2 meter signals are getting difficult to copy and change to 70 cm expecting to get an improvement in signal strength.  You may still find that the signal is easier to copy, but this will most like be due to better signal to noise ratio[2] rather than a stronger signal.

So is this a problem to be concerned with.  Generally speaking I’d say no.  However, you should be aware of it and understand that the gain numbers you see in advertising are necessarily representative of an antennas performance in the real world.

There is one antenna, in my experience, that does have low angle at both VHF and UHF.  It is the ARROW OSJ 146/440.  See http://www.arrowantennas.com/osj/j-pole.html.  It is one of the best antennas for the money.  It is rugged build from aluminum rod not tube.  It has good SWR on both bands.  It is heavier than antennas made of tubing but still not unreasonable.  I have one that I use for portable operation with my RV and just “out in the field”.  It has been blown over while up on a 20 foot mast and didn’t even bend when it landed on a parking lot.  I know a number of ham locally that own one of these and I have not heard one complaint.

---

[1] - Angle of elevation is the angle above the horizon at which the strongest lobe leaves the antenna.  The smaller the angle number is the better for reaching maximum distance.

[2] - Signal to noise ratio is a measure of signal strength to the background noise, i.e. noise floor.

Some Antenna Do’s

There are some things that one should avoid when planning or working an antenna installation.

SAFETY CONSIDERATIONS

-  Keep away from power lines.  They are deadly.  There is any number of ways to come into contact with power lines and your chances of survival are slim to none.  This also means masts or towers that can fall over onto power lines once erected or during erection.
-  Always wear gloves when handling rope, cable, coax, antenna wire, etc, while putting up antenna installations.  A small slip of any of these can remove quickly remove everything to the bone and beyond.
-  Always wear a qualified safety harness every time you set foot on a tower and hard hats all around.
-  RF exposure must be taken into account.  It is a FCC rule.  The Amateur Radio RF Safety Calculator on DX-Zone’s website will help you perform the RF exposure study required by the FCC. 
                                http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=11352  

LOCATION CONSIDERATIONS (To make it easier on me, this posting will not consider HF antennas.)

-  Generally speaking the higher you can put an antenna the better.  This is especially true for VHF/UHF antennas. 
-  Keep your antenna away from trees.  Trees will absorb RF signals both inbound and outbound again especially at VHF/UHF frequencies.
-  Whenever possible get above buildings.  Metal buildings will act like a reflector to inbound and out bound signals.  Metal siding and roofs, electrical wiring, metal window screens, metal Venetian blinds, E glass windows, etc, can cause problems with your signal.  You may experience a signal that is coming in strong, but the voice is so garbled you cannot understand it.  This is usually caused by something called multipath.  The inbound signal is bouncing off a metal surface somewhere between you and the transmitted signal.  It can often be solved by moving the antenna on one end or the other by as little as a quarter wave length.
- Orient your antenna with the radiating element in a vertical plane for FM work and in the horizontal plane for SSB and CW.  These are conventions use by ham radio and other radio services.  Tilting the antenna or wrong orientation will cause your signal to drop off in strength.  This is easy to forget when using a hand-i-talky.

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NOTES:  All of these considerations apply to mobile antennas and portable operations.

                       See Antennas in the topic list and read “Using the Amateur Radio RF Safety Calculator”

Using the RF Amateur Radio RF Safety Calculator

DX-Zone has posted an Amateur Radio RF Safety Calculator for hams to use to make it easy to comply with the RF safety requirements of the FCC.  See link at the bottom of this posting.

Calculate Radio Frequency Power Density

Top of Form

The average power at the antenna: In watts
The antenna gain in dBi: Enter 2.2 for dipoles; add 2.2 for antennas rated in dBd
The distance to the area of interest: From the centre of the antenna, in feet
The frequency of operation: In MHz

My user notes:Bottom of Form

A – Enter the maximum RF output power your radio can run.  This will not take into account feed line loss or loss due to possible mismatch but it will not get you into trouble either.

B – This information is usually available from the antenna manufacture for commercial antennas.  For home brew (ham speak for home made) antennas, you may have to do some research to get an estimate of what a similar antenna’s gain might be.

C – This is the closest point that a person might come to the antenna during transmitter operation.  That means if someone 6 feet tall is standing under an antenna whose center is 18 feet above the ground, that person is 12 feet from the antenna.  This includes people inside a building where the antenna is mounted.

D – If the antenna is a multiband you must run the calculation for each band.  Use a frequency near the center of each band.

This calculator is the easiest one I have found to use.  There is a lot of good information on RF Safety on the DX-Zone website.  Once you are on DX-Zone website run a search for RF Safety using their site search.

Links –

DX-Zone   http://www.dxzone.com/

RF Amateur Radio RF Safety Calculator   http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=11352

Quick Antenna: Wire Ground Plane

The quick and easy first antenna is a wire ground plane.  This antenna is probably the most affordable and rugged antenna you could have.  It will serve as a base station antenna and will also come in hand for portable use when you get another for your base station. 

You will need a SO-239 connector 8 ½ feet of #12 or 14 wire and four ½ inch by 6-32 bolts with 8 washers and 4 nuts to fix.

Cut 5 pieces to 20 ½ inches long.

Solder one piece of wire to the center conductor where it sticks out of the insulation on the bottom of the connector.   

Bend a loop in one end of each of the remaining wires to fit on the bolts. Put a bolt from the bottom up into one hole on the connector and slide on one washer. Slide on one of the wire followed by another washer then put a nut on top and tighten. Repeat for the other 3 holes.

Once the wire are attached as shown, bend the 4 wires downward about 45 degrees.

Now you’re ready to build the mast.  This will be a piece of ¾ PVC of any convenient length.  Mine is about 5 feet long.

About 6 inches from one end of the PVC, cut an oval shaped hole just large enough to slip the coax connector on the end of your coax cable into the PVC.  Slide the cable up and out the closest end and connect antenna.

Slide the cable up and out the closest end and connect antenna.

Slide the coax back down until the antenna sit down onto the end of the PVC.  You are ready to tune the antenna.  Note that winding the coax around the mast helps hold the antenna in place.

The antenna in the pictures has served me for many years now.  It has fall over while on a 30 foot mast.  The mast was damaged by the antenna was not.  It spends much of its life behind the seat in my truck where it gets bent and banged.  I did originally solder the 4 radial wires on the connector but that proved to be a weak point.  The radials keep breaking off so I went to bolts and have not had one break since.  Maybe it was just bad soldering but bolts work for me.

Antennas: What’s Important?

This question will garner a wide range of responses.  I am kind of a simplistic guy so my answer will sound that way especially to the crowd with degrees in engineering.  Here’s the simple of it in two parts.

One – An antenna should not damage your radio.  Keep the SWR below 2:1.  Even lower is better.

Two – You are able to talk to other hams.

Once these two have been met you are on the air.

It does not mean that you have done all you can do to improve you signal, but unless you can more than double your signal’s effective strength^*, it is unlikely anyone will notice a difference.

So what are some things to keep in mind when you are ready to put up an antenna?

SAFETY FIRST!   Where are the power lines?  Too many hams have been killed by a mast or wire coming in contact with overhead power lines.

Generally the higher an antenna further your signal will reach.  This is especially true on 2 meters and up. 

SWR adjustment will be the subject of future posts.

^* - This refers to Effective Radiated Power (ERP).  ERP is effected by a number of thing.  This will be the subject of a later post.