N4JTE 6 BAND "RIBBON" ANTENNA
This antenna article is geared towards new Hams and antenna
builders looking for a very inexpensive 6 band antenna that can be
efficiently fed with 50 ohm coax without a tuner.
The inspiration for
this design resulted from a visit to my 82 year old neighbor's home who
had asked me for some help in dismantling his amazing and extremly
beautiful model train set, and box up for his grandson. During this
process I was intrigued by his use of 5 and 10 conductor 18 gauge flat
insulated ribbon cable for all of the L.V. switching and action
So Begins the
Antenna shown resting on the driveway. Colored
lines show each section.
5 conductor computer ribbon cable
honest I am getting more and more frustrated with some of the latest
marketing ploys being used by commercial antenna manufacturers and their
incredible, misleading and unsubstantiated miracle "all band" antennas
that will sucker in some poor unsuspecting new ham who will spend his
money on a heavily marketed, over priced, and in some cases, amazingly
reviewed antenna // Toaster.
My plan was to use this relatively cheap
insulated wire and find out if was actually possible to get 6 bands
cleanly matched to 50 ohm coax. As this antenna was basically built for
testing and performance evaluation the construction details are limited
and somewhat primitive by most standards so I will leave it to others to
refine, hi. When I envisioned this concept my only real concern was how
all the close spaced wires would interact. The shorter dipoles will all
present high impedance at the feed point when they are not driven forcing
the feed line to pick the path of least resistance and best match for the
The 40 meter wire will serve well on the 15 meter band
as a center fed 1.5 wl wire.
I am aware that a fan
dipole uses the same single feed concept but I believe the ribbon antenna
eliminates all those extra tie off points while maintaining the resultant
extra effective radiated height, especially if used in a flat top
configuration. Certainly less obtrusive and much less work. Below is the
basic layout with lengths for each half of the
Final lengths per side of each dipole:
40 meter length 32ft (also used on 15 meters)
meter length 16ft
17 meter length 12ft
10 meter length
you have to start somewhere, so I chose the OMISS net
available at http://omiss.net/,
as my starting point for the band frequencies and wire lengths.
built more than enough monoband Inv. Vees at this location with insulated
wire so I use my own formula of 450/ freq, to
achieve what I'm after with minimal pruning.
You need to approach
this antenna one side at a time. The ribbon wire I purchased was only
available in 50 ft. lengths so I knew the 75 meter wire would need about 8
more feet added to each end to reach 75 meters. It's best to unroll and
stretch the wire out to remove the "wire memory".
accomplished, measure out your 5 chosen 1/4 wl lengths and mark or tape
As the 75 meter wire is pretty much done after adding the
required wire, separate the next wire, and carefully peal back to the
taped off marker and cut off excess. Continue this process for the
remaining wires up to the 10 meter point. Yeah I know it seems like a lot
of wasted wire but at 6 cents a foot you'll get over it
Repeat the process with the other half of your
antenna. I just laid them along side each other and matched all the
lengths. Be careful to use a dull knife or fingernail file to separate the
wires so as to not break the insulation.
After cutting all your
wires to length you will need to have some kind of center support and
feedline connector in mind before stripping and soldering the 5 conductors
together. In my case I pushed each one thru a ceramic insulator and then
carefully stripped and soldered together in preparation for feedline
The ends of half wave dipoles are at high rf voltage
and if too close to others will add unwanted capacitance and tuning
problems. For starters I just separated the adjacent wires by about a foot
and let them dangle down.
My goal with this initial attempt was to see basically
where or if, I would get full power out. This would give me the best
indication of what was actually radiating and at what frequency. You
cannot expect, nor limit yourself, to a 1 to 1 swr as being your goal.
The meter will serve only as a guideline to where your wire length and
height works in the real world of your backyard.
A quick look at
any antenna book will show the relationship between height above ground
and radiation resistance in ohms. This inv. Vee at 43 ft. is even a little
more tricky to predict especially when the 75 meter antenna is only at
.175 wl high and the 10 meter antenna is at 1.2 wl above real
All 6 antennas (the dipoles) should range between 20
and 90 ohms with the ends at 10 ft. above ground. The results of the first
attempt were very interesting in that at least I was getting full power
out somewhere close to the 6 bands of interest.
I had my doubts because
of introducing the 17 meter antenna into the mix which is not an even
multiple of the lowest band, usually considered a no no on multiband
I use an eye hook stuck into the
top of the fiberglass pole with a masonry string to allow easy up and down
access for the cutting and tuning process.
I started by adding about 4
ft to each end of the 75 wire and after some diddling ended up with around
3.95Mhz. The only band affected by this change when scanning thru the
bands was the 40 meter wire which changed it's apparent resonant frequency
to 6.9Mhz and the 15 meter wire also dropped in frequency.
trip to the backyard to shorten each end of 40 meter wire by one foot
made no change on the resonance. I then separated the 40 from the 75 by
dangling about 3 ft. at each end. Obviously the end effect was kicking in
because I ended up at 7.1Mhz, close enough for my needs and the 15 meter
wire was happy in the middle of the SSB
The only bands left to fine tune
were the 17 and 10 meter wires which were still too long, so I cut off 6
inches from both ends of each antenna. The 17 meter ended up at 18.135Mhz
and the 10 meter at 29.5Mhz in the FM portion of the band which I actually
prefer these days.
THIRD, FINAL TRY, I'm
The whole tune/recut
exercise took about 6 hours and resulted in a 6 band antenna that will
radiate full power out without a tuner.
Due to the fact that
there are no traps, no loading coils, no tuners and no ladderline needing
a balun to match, the only losses will be in the feedline due to it's
length and not the result of any mismatch at the antenna feedpoint. I do
not have the necessary brain power to model this design and would
appreciate a peer review on the modeled radiation resistance and resultant
interest; The 60, 30 and 12 meter bands had around a 3 to 1 swr and
were showing 60 to 70 watts out without a tuner. Probably will work well
with an auto tuner.
IF YOU BUILD
1. A simple Plexiglas T, or equivalent with double slots for
the ribbon wire and two small holes to tie wrap the coax should be more
than enough after waterproofing to ensure stability and strength for a
center supported light weight antenna such as this.
2. The 75
meter wire ends up holding the whole antenna up, so I would attach
some masonry string to the center insulator and tie wrap at the dipole leg
end dangles and a couple more at the 40 and 80 wires with the string going
to tie off points. By tie wrapping you will also prevent the wires from
separating at band junctions.
3. Attach small non conductive weights at
the drop wires after final tuning.
4. Use a tuner at
higher powers to attenuate harmonics and any possible spurious transmitter
5. If 10 conductor wire is available you can double up the
wires for each band providing an increase in bandwidth and power handling.
FYI, I had no problems with the 5 wire at 500 watts
I am not
going to waste everyone's time by recounting all my log entries while
testing this antenna. I will tell you it is a joy to run from 75 to 10
meter fm and be able to hear what is going on and respond to a cq without
fumbling around with antenna switches and tuners. This antenna is nothing
more than 6 inv vees at 43 ft. that perform to the laws of physics and
will serve you well if you are committed to a little sweat equity to get
it working efficiently.
You will not be disappointed with this $35
BUILD.... DON'T BUY !