marcot
Well-Known Member
I've built a rope antenna for my Icom M710 but How long should it be ? I will measure it from the tuner AT130.
Rope antenna
- Thread starter marcot
- Start date
DavidGrieves
Well-Known Member
Not too sure what a rope antenna is or what frequency you are transmitting on. But assuming you are wanting to make an antenna for 156Mhz (chn 16) you need to divide the speed of light by your frequency. If you are calculating in megahertz you need to divide 300 by 156 this will give you one full wave length of 1.92m (192cm) so half wave would be 96cm. This calculation is a bit rough and ready but near enough as a starting point.
When you say "tuner" are you referring to your radio or an ATU? The 1.92m wavelength would be measured from the exposed section of the antenna and not the length of coax from the back of the radio. you could start at 1.92m and use an SWR meter to check your antenna.
No doubt there will be a radio ham expert along shortly to cross the I's and dot the T's but that's what makes the forum great.
When you say "tuner" are you referring to your radio or an ATU? The 1.92m wavelength would be measured from the exposed section of the antenna and not the length of coax from the back of the radio. you could start at 1.92m and use an SWR meter to check your antenna.
No doubt there will be a radio ham expert along shortly to cross the I's and dot the T's but that's what makes the forum great.
sarabande
Well-Known Member
ICOM seem to recommend a folded dipole of 80.3 ft. !
http://www.airadio.com/Icom-MF-HF-Marine-Transceiver-IC-M710*productID_285-products_details (see the download)
They do however say the M710 has an automatic antenna tuning facility.
There is also some comment about the need for a ground plate...
The commerciial Rope Antenna has
35 Ft
45 Ft
48 Ft
54 Ft
lengths, whch should give you a clue.
http://www.airadio.com/Icom-MF-HF-Marine-Transceiver-IC-M710*productID_285-products_details (see the download)
They do however say the M710 has an automatic antenna tuning facility.
There is also some comment about the need for a ground plate...
The commerciial Rope Antenna has
35 Ft
45 Ft
48 Ft
54 Ft
lengths, whch should give you a clue.
Last edited:
tawhiri
Well-Known Member
I have 9m, seems to work for me
rogerthebodger
Well-Known Member
I have a ICOM 700 with a AT130 tuner and I have a 7 meter whip antenna which gives me OK range. So anything over 7 meters will be OK and the AT130 will compensate at non matching wave lengths
VicMallows
Well-Known Member
In my amateur radio days we used electric fence 'tinsel' cord and flew it from a kite or sometimes a balloon. Length immaterial as long as tuned by an ATU. (usually on 1.8MHz or 3.5MHz). Fun days
William_H
Well-Known Member
As far as I could make out a rope antenna is just a way to hold a piece of wire up towards the top of the mast. The length is optional as the ATU will tune the antenna by adding inductance in series or capacitance in parallel to make the whole thing resonant at the huge range of frequencies used. As said a ground plane is vital to success of the antenna.
I don't know much about the ICOM ATU but in the old days of building and adjusting tuners for small aircraft HF used from 3.4mhz to 9 megahertz we found that about 27 ft was an ideal length. This meant that the wire was shorter than self resonant at 3.4 and 6.6 megahertz so a coil in series tuned it OK and was too long at 9 meghertz so a capacitor was switched in parallel with the antenna then coil added in series to tune it. What was really difficult was when the antenna was naturally close to resonance at the frequency used. It was difficult to get the tuner to match it correctly. I mention all this because using your AT130 it may have trouble tuning some frequencies. The answer may well be to shorten the antenna by a metre or so. Then check all the needed frequencies again.
Rogershaw's whip antenna while 7 metres long is most likely a coil of wire around the f/glass pole so tuner will see a lot longer than 7 metres.
With the rope antenna try to get it as far away from the stays as possible. This is why insulated backstays are used as an antenna because it is so far from the mast and side stays. You might also have noticed the old MW radio station towers always had stay wires that were insulated at various points to break up the long wire which can soak up the radiation. After all that SSB is such an improvement on the old amplitude modulation (double sideband) ( who rmemebers that) that almost anything will work. good luck olewill
I don't know much about the ICOM ATU but in the old days of building and adjusting tuners for small aircraft HF used from 3.4mhz to 9 megahertz we found that about 27 ft was an ideal length. This meant that the wire was shorter than self resonant at 3.4 and 6.6 megahertz so a coil in series tuned it OK and was too long at 9 meghertz so a capacitor was switched in parallel with the antenna then coil added in series to tune it. What was really difficult was when the antenna was naturally close to resonance at the frequency used. It was difficult to get the tuner to match it correctly. I mention all this because using your AT130 it may have trouble tuning some frequencies. The answer may well be to shorten the antenna by a metre or so. Then check all the needed frequencies again.
Rogershaw's whip antenna while 7 metres long is most likely a coil of wire around the f/glass pole so tuner will see a lot longer than 7 metres.
With the rope antenna try to get it as far away from the stays as possible. This is why insulated backstays are used as an antenna because it is so far from the mast and side stays. You might also have noticed the old MW radio station towers always had stay wires that were insulated at various points to break up the long wire which can soak up the radiation. After all that SSB is such an improvement on the old amplitude modulation (double sideband) ( who rmemebers that) that almost anything will work. good luck olewill
SimonJ
Well-Known Member
There are indeed some lengths which should be avoided. I suggest you google to find them if you are that concerned noting they will be different for each range of frequencies.
I use a rope antenna with my ICOM 706 rig and tuner and have not worried too much about avoiding the 'wrong' length. I get excellent results. My antenna is about 45 ft. I may have just been lucky but the performance even with a lower powered ham radio usually is as good as or better than higher output marine HF sets used in many other boats with whom I am often in contact. I believe this to be because of the use of a coated copper wire aerial (sheathed in rope) rather than a twisted stainless steel wire (SS is a poor emitter) and the avoidance of extra connections noting the aerial connects directly to the tuner.
Hope yours works well!
funk-an-bord.de
Active Member
When you use the M710 on a boat you have to take care of the GMDSS distress frequencies on the 2,4,6,8,12 and 16 MHz bands.
You should avoid to use a length that will be resonant on one of these frequencies.
Wilhelm
funk-an-bord.de
Active Member
You find a background for the calculation at
http://www.hamuniverse.com/randomwireantennalengths.html
That is dedicated for HAM bands.
If you are on marine bands you have to consider the 2,4,6,8,12 and 16 MHz bands.
Wilhelm
http://www.hamuniverse.com/randomwireantennalengths.html
That is dedicated for HAM bands.
If you are on marine bands you have to consider the 2,4,6,8,12 and 16 MHz bands.
Wilhelm
KellysEye
Well-Known Member
A wire antenna should be about 34 feet which makes up half the antenna the other half is the ground get that wrong transmission will be bad. The ATU tunes the wire to the required frequency it should be connected by copper strip to as close as possible the exit point inside the boat then to a wire up to the back stay where the wire is clamped on above the isulator.
As said if a wire is holding up the antenna then keep it well away from the mast and rigging otherwise the signal will jump to those and make them live. If you hold a live wire it will cook your hand from inside and for fun you can light a cigarette from a live wire. Personally I wouldn't bodge the antenna and use an insulated backstay it's much safer, it's why all long distance boats have them.
As said if a wire is holding up the antenna then keep it well away from the mast and rigging otherwise the signal will jump to those and make them live. If you hold a live wire it will cook your hand from inside and for fun you can light a cigarette from a live wire. Personally I wouldn't bodge the antenna and use an insulated backstay it's much safer, it's why all long distance boats have them.
