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.