Here's a great starting out link to go to if you just want to learn about the construction of a lot of antennas or even if you want to buy antennas because there are several listed. -
Antennas, Grounds, Tuners, Baluns, and Test Equipment
Note that this is not an exhaustive treatment of the subject. It’s just a starting out point. I have listed some antennas that are very easy to build and use and if done right they will compete with commercial antennas. Most of the antennas listed here are fairly compact. Many of us are living on small plots of land, some are in condos or townhouses and need a little help. In any case restrictive covenants are a challenge to overcome. A search of the web will bring up lots of ways amateur radio operators have overcome such things, it just takes some creativity and a bit of knowledge. It’s also a willingness to live with less. Having shortened antennas means having less capture area and that usually comes back as lower signal strength or poorer transmit capability. Many people use their vehicles as ham shacks and use screwdriver antennas such as made by High Sierra andTarheel and have acceptable DX on the HF bands even though their antennas are relatively small. Antennas are one area where both Advanced and Basic amateurs can still get in and do some hands on experimenting. Don’t forget – “this is fun even if you fail with the first few attempts.”
The very best antenna you can have is one that matches the output of your radio and does not require any adjustment to work on your particular frequency of choice. Most of us want to work on more than one frequency and to do that we need some sort of “antenna tuner”, also more accurately called a trans-match. There are antennas claiming to not require tuning and can cover all HF bands without a tuner. With those sort of claims it’s buyer beware. Some of those antennas, like my Windom off-centre-fed antenna come close to that claim but even with that it depends on how it’s mounted. Mine is too close to the earth and that detunes it so that it requires a tuner to be able to operate successfully.
Before going further it may be a good idea to have a look at this article on antenna gain. It makes many good points about real and unreal manufacturer's promotional (boasting) discussions about "their" antennas.
Constructing antennas is a really fun challenge but there are some things to be aware of. For instance - that shiny new radio you just spent several hundred dollars for, it can be damaged by reflected power coming back from a mismatched antenna. There's a post sticker shock for you.
Even a brand new antenna can be defective, maybe from the factory, maybe in transit. In any case when you connect your radio up to your antenna with a piece of coax you should insert a suitable VSWR meter (is also usually a power meter) in there between the antenna and the radio. A VSWR meter looks at the signal going out and compares it with the signal coming back. If the signal going out is completely absorbed by the load (antenna) there will be no reflection back and everything is rosey. The ratio on a VSWR meter would be 1:1 on the scale. If there is some mismatch there will be some deflection of the meter needle. Generally speaking you should not use a meter designed to work HF frequencies for work in the VHF and UHF area. It's usually best to use one designed for the bands you are using. Many people belong to clubs and often the club has basic test equipment. Once a VHF or UHF antenna is set up such as in a car or truck it doesn't need further adjustment. If you have a long wire antenna or a big dipole or loop you usually need to reajust things everytime you make a frequency change. For that you need an antenna tuner also called and antenna match or a trans match. It makes the radio see a 50 ohm load. The VSWR meter needs to be between the radio and the transmatch. Most modern transmatches have VSWR meters built right in. In most instances VSWR meters and transmatches were separate. How to use a VSWR (SWR) Meter:
Use a short, suitable, coax cable to connect an SWR meter "transmit" side to the output of the transmitter. By short I mean somewhere around 3 to 6 feet.
Connect your antenna coax to the "antenna" side of the meter.
Select a low power range on the SWR power range switch (most have at least 3 power ranges).
Set the transmit power of your radio to a low range (most mobile radios and hand helds allow you 2 or 3 power output ranges).
Now here is a difficult thing because manufacturers have some differences in the way they lable things. You may have a switch that says "POWER", "FWD", and "REF" or "CAL".
Select a frequency on your radio that may be used for simplex in your area. Listen to the radio and see if it is busy.
Select REF (Meaning reference not reflected) and push the transmit switch on your mic button . You should get some deflection. You should have a knob called "PWR SET". While transmitting adjust the SET knob and see if you can get the meter needle to go full scale to a point usually labled "set".
Switch the meter to FWD and key up the transmitter again. If the needle barely deflects then your antenna is a good match. Less than 1.5:1 is considered pretty good. If less then its excellent. If it's more than 1.5:1 then some tuning is required. It's a good idea to adjust the transmit frequency to each end of the band of interest and go through this procedure. If the antenna is great at one end and not so great at the other you may want to adjust it to improve transmission.
If you are working on HF and are only interested in one part of a band such as SSB in the 80m band then you may be able to get away with adjusting the antenna for that and be able to use your antenna without the help of a transmatch. In the following section on Slim Jims please know that Slim Jims can be difficult to tune. Once set up they work well but many finals in brand new radios have been destroyed by new amateurs not realizing that antenna mismatches can hurt their gear. Start with low power to do your testing. Be good hams and realize that you are surounded by hundreds or even thousands of other hams your experimenting could interfere with. Even on low power you should identify yourself with your call sign and ask if the frequency is in use before going ahead with your tests. After your tests you should identify yourself again and pass on that you have finished and are turning the frequency back for general use.
i1wqrlinkradio - (http://www.i1wqrlinkradio.com/) The best web site I have seen to date Oct 2011 listing antennas for do-it-yourself construction. Quantity of information is unbelievable and it is indexed in several different ways so that you have no trouble finding an item you wish to search for. Give it a try!
HAM Universe. A really good listing of various antennas.
VA7DH dual band Slim Jim - This is one made from Radio Shack 300 ohm twin lead. Complete instructions are in this file. Canadians please note that Radio Shack is not willing to ship into Canada. If you want to construct this antenna you will need a friend to buy some 300 ohm foam insulated flat line from Radio Shack USA and ship it up or find an alternate source for the same kind of flat line. Any other type of flat line will have a different velocity factor and so measurements will need to be different. Well worth the effort, this is a great antenna for emergencies, back packing, stealth (hide it in an attic or closet in one of those condos that don't allow antennas outside). Great bandwidth and good gain.
2 meter Slim Jim 300 ohm twin lead antenna. You can roll them up and put them in a back pack. Slim Jims tend to be wider bandwidth and higher gain than an equivalent in a J-pole type 300 ohm twin lead antenna. They can also be more difficult to tune.
Copper Slim Jim Made with small diameter copper tubing. No explanations about tuning but good diagrams.
Note: the article suggests using a fibreglass bicycle safety flag as a support for this antenna. I looked for them and all I could find were two piece ones with a metal joint in the middle. Recently I was walking through Canadian Tire, in the automotive department, and came across fibreglass driveway marker poles with corner reflectors on top. The units were quite inexpensive and came in various lengths. I picked up a telescopic version which is approximately 6 feet long when extended. The bottom has a sturdy metal spear point for pushing into the ground. It can have the end reshaped and holes drilled to mount it to a bike.
Arrow J146/440 Dual Band Antenna (Stealth Antenna)
A very durable medium gain antenna for a reasonable price. Can be mounted on a bathroom drain vent stack on the roof and coax run into the house through a roof air vent. Can be purchased ready made (kit to assemble) from Radio World or you can make one yourself: http://www.arrowantennas.com/
Radio World: http://radioworld.ca/index.php?cPath=193&filter_id=21
Moxon Antennas
Moxon antennas are easy to construct. You merely have to follow the instructions, use non conductive supports, and can use PVC, fibreglass, wood for a supporting structure. It all depends on what is available and sometimes what you can afford. You can make them for just about any frequency/wavelength/band. They are fairly wide bandwidth, high front to back ratio (as high as 40 dB) and somewhere I read that the gain off the front is similar to that of a 3 element Yagi. I have been considering using one where I am getting a considerable amount of interference from a trunk repeater. The repeater is causing havoc with some 2m radio frequencies I wish to use. The level of the signal is high enough to cause saturation in my transceivers receiver section and therefore I get mixing between that and other frequencies, some of which punch through my radio where I can hear them. Anyway, nice antenna as long as you don't need a full omnidirectional antenna.
Here are a few links to the Moxon antennas. A Google search will reveal even more.
NVIS means Near Vertical Incidence Skywave. When we bounce a radio signal off the ionosphere we are often going for as much distance as we can get, something wen refer to as DX transmission. To do that it is necessary to transmit at a fairly shallow angle to the ionosphere and from that we get the longest bounces. That’s all well and good if we are contesting and attempting to check off exotic grid squares. What if we are trying to just communicate a couple of hundred miles or so without using VHF radios and radio repeater networks? Well, you can use HF but you need to send most of the signal upwards where it can get reflected back down and cover only a few hundred mile radius. The antennas are simple. The antennas only need to be a few feet up and need to be horizontal. Even the support structures can be much more primitive than usual for DX antennas. Soldiers in the Korean and Vietnam wars discovered that they could get better local HF radio coverage (up to about a 200 mile radius) by taking their long whips on their 4X4 vehicles and turning them sideways so that they became parallel with the ground. If they wanted to reach out for communicating using ground wave or DX they would reallign the antennas vertically.
- This is a very well written article worth reading by those involved with emergency communications and who would like to get involved in the HF side of things (no repeaters necessary to cover a small area up to 200 hundred miles radius, more or less)
This antenna makes use of a Buddi Pole support underneath. This antenna could make use of a telescopic fibreglass window washing pole as a support though the telescopic sections would not collapse down quite as short. Still, a much more affordable way to go.
HF Wire Antennas
If you are working in emergency communications you will likely be asked to participate in 80m nets, sometimes 40m nets, and rarely but sometimes 20 m nets. You may wonder why this is. A big old 80m dipole is also very wide beam width meaning the signal is physically spread wide with small nulls off the ends. This means that it may not need to be rotated to be able to be used to contact all parties. It’s not that hard sometimes to build two and have them cross at right angles and that way everyone is covered fairly well. Wire can be insulated or bare. Bare wire is lighter. Insulated wire has some resistance to noise from static charges. Many consider that it makes no difference. 80m dipoles about 10 feet above the ground make great NVIS antennas too. 40m is not as good for NVIS and 20m is a dead loss for NVIS.
Buxcomm 7 band Windom - Good information on the very popular Off Centre Fed Dipole (OCFD) antenna. There is a very good table in that article listing what impedance to expect at various heights the Windom is installed above ground and what balun ratio is most suitable.
If you have small yard space, as many of us city dwellers do, then one antenna you may want to look at is a ground mounted vertical. Most of them require radials though a few don’t. The transmission pattern is omni directional meaning they transmit equally well in 360 degrees. The energy is also sent out relatively low and so DX (long distance) can be worked. Radials are basically 1/4 wavelength pieces of wire, either insulated or bare, buried in your lawn or garden and represent the missing half of a dipole antenna. It's not necessary for the wire to be in straight lines if you don't have the space. Many people bury their radials in a zig-zag fashion a few inches below the roots of their grass. Some have been known to press the wire down hard against the crass and pin it down with "U" shaped bits of stiff wire a few inches long somewhat like staples, then let the grass grow over it. Whatever works for you. There are some vertical antennas that make claims they don't need radials. Often that is the case for upper bands but still need radials to help cover the lower bands (80m and 160m) properly.
Novice 4 band vertical. This is an easily constructed, home built, antenna and does require radials which can be shallow buried under the lawn. Not necessary for the radials to be in straight lines, do the best you can. Wire can be bare or insulated.
Screwdriver Antennas
Screwdriver antennas do not need an antenna match, that is taken care of by the motor driven adjustable loading coil in the base section. There are automatic tuners such as the Turbo Tuner you can use to tune the screwdriver antenna. Just put out low power so that the Turbo Tuner has a signal to work with. All HF radio installations should have an SWR meter to help you to understand what is going on with your radio. I use a double needle one from Daiwa , model CN-101L because it does not require calibrating. You can manually tune the antenna with a forward/neutral/reverse switch while watching the SWR meter. When you get to the correct tuning you will see the swr drop to 1:1. The tuning is very narrow on the screwdriver antennas and so most remote tuning switch arrangements have a high speed/low speed setting. You need to watch closely for a dip when on high and then switch to low to zero in. VE3EDY (see below) has been promoting a novel use for his screwdriver antennas. He has been attaching the main base unit to a long vertical piece of pipe in his back yard and using that as a long range HF DX antenna with great results.
VE3EDY Canadian made (made in Ontario) Stainless Steel screwdriver antennas (80m or 160m) Note the use of the screwdriver base unit to drive a vertical 48 foot piece of fence pipe. See: More
The maker of these antennas is a chap named Larry Parker, very nice guy to talk to. I asked Larry how much his antennas are and he said $350 for the 80m and $650 for the 160m unit but these prices are subject to change. They are very ruggedly built and designed to deal with the winter storms found across Canada. Larry does not make these antennas for a living, it's more of a hobby so you won't find them listed in ham radio magazines. Some of his screw driver antennas are on their second owners. It's not a question of wearing it out and having to replace it with another. If there is a defect you can send it back to Larry for repair if you can't repair it yourself.
Larry's web site has some interesting installation suggestions. You can mount the screwdriver antennas on vehicles but you can also fabricate up a mount for it and a long piece of pipe, load the pipe as a long whip, and then have a really awesome vertical DX antenna for 80 or 160m depending on the screwdriver antenna assembly you choose.Great to use for Field Day. One of Larry's Field Day setups took 5 minutes for him to be on air as was done this year - 2009. Click on the link and you will find lots of pictures of setups using his screwdriver antennas. If you already have a screwdriver antenna and its sitting around you may be able to use some of Larry's suggestions to put it to use in a way you had never considered before.
Note that the combination of a device like the Turbo Tuner plus the motor adjusted loading coil in a screwdriver antenna constitutes something like a conventional vertical antenna or dipole connected to an autotuner. The Turbo Tuner circuitry senses the SWR and drives the screwdriver mechanism while it searches for a dip in the SWR. Once the dip has been found, and centred on, the Turbo Tuner stops feeding power to the screwdriver antenna until you make an adjustment to the transmit frequency at which time the tuner will again hunt for a "Best Tune Spot" on the screwdriver antenna.
HF YAGIs
I mentioned that YAGIs are generally too difficult to construct in an emergency. The following item contradicts that by being very economical to build and not too difficult to construct if an emergency situation demanded it.
Baluns are used to either adjust the antenna impedance to the feed line or the feed line to the tuner or radio. Balun means balanced to unbalanced. Dipole antennas are balanced output and coax feed line is unbalanced and generally either 50 ohm or 75 ohm impedance. Baluns can also be used to adapt balanced pair transmission line to the unbalanced input of an antenna tuner. There are several styles of baluns. There are voltage baluns, current baluns, coaxial baluns, air core baluns, ferrite core baluns, something for everyone’s needs.
RFA-4005 Crimp tool for installing connectors on coax(I have one of these and like it). On PL-259’s I solder the center pin rather than crush the pin with the crimper. If you do the job right the fitting will be water tight.
Fastening PL259 connectors to RG-8 and RG-213 This describes a good method for attaching the larger coax such as RG-8 and RG-213. Other descriptions I have read refer to a method folding the braid back over the outer sheath of the cable and then threading on the body of the connector over that. It works but it can twist. This method solders the connector in place on the braid and so cannot twist. It works and is the way I prefer to do my installations. This also describes how to install smaller cables into PL259 connectors, cable such as RG-58 and RG-8X and RG-8 mini foam. I prefer to to solder the braid where it is bent back over the sizing adapter. Once again, it won't twist where the standard approach defined on the is video can allow for twisting.
Antenna Supports
This is a big subject and sometimes it’s a touchy subject. I have friends that live in condos or townhouse complexes. People are thrust in close proximity to one another and so to reduce chances for confrontation rules are put in place. One of those usually stipulates that the members don’t put up wash lines, antennas, towers, that sort of thing. It’s amazing what people have come up with to resolve some of this in amateur radio so that they can still get on the air. Obviously they have antennas but where and how they are concealed is often worthy of a Sherlock Holmes mystery.
My antenna supports are a variety. I have a short Radio Shack tower recovered from a relative who wanted to get rid of it. It’s three ten foot sections tall which makes it 30 feet. On top of that is a piece of heavy duty antenna mast pipe. Antenna mast pipe has a wall thickness of around 1/8” of an inch. That may not sound like much but when you’re holding 10’ of it you know it. That’s considerably heavier than an equivalent diameter of EMT electrical tubing. A piece of EMT supporting a large antenna risks crumpling in a heavy wind. I also have an old Alliance rotor recovered from the widow of a Silent Key (a ham who has past away). I tried it out and found that it wouldn’t turn. I took it apart, cleaned out the old grease and put in fresh and put the ball bearings back in their correct track positions. Works like a charm. I currently have 2 Yagi antennas up top. There is a 3 element 6m and an 11 element 70cm. In the future I will be taking those down and will be putting up a decent HF Yagi. I have a used 2m Isopole antenna hung off the side of the tower with pipe standoffs. Isopoles are one of the niftiest antennas. For one – they look impressive, something space age. My neighbours say so anyway. Isopoles look like a couple of large upside down aluminum ice cream cones with a whip antenna out top. They have reasonably good gain and bandwidth that nicely covers the 2m band. I was given mine by a ham in the Okanagan who moved into a trailer court with some of those restrictions I mentioned.
Antenna Insulators
Insulators are required at both ends and the middle on wire dipole antennas. A traditional insulator is an egg insulator. They are quite strong and fail safe meaning if they were shot and shattered the antenna wire would still be captured though shorted. A fault of egg insulators is additional capacitance at the ends between the ends of the antenna and end support wires. One place that they are useful is in breaking up support wires into small , meaningless bits which don’t come close to resonating. That’s handy when you are trying to support a pole that’s the centre support for an inverted V antenna.
The dogbone insulators can be longer and therefore less capacitance problems. Any of these insulators are found in a variety ofmaterials, glass and various plastics. Glass can last a long time exposed to UV from the sun whereas plastics are subject to degradation over time. Still, the plastic ones can last for a very long time. I often use a strip of Plexiglas (acrylic) as an insulator. I just drill a hole at each end and tie my wire to it. They usually last longer than the length of time the antenna stays up before I try out another design. I’ve heard of people using short lengths of plastic pipe or even pieces of pop bottle as insulators. Many times I have just used a piece of poly or nylon rope. That’s already a good insulating substance, especially if it’s dry.
Building antennas takes some work and the antennas usually must be tuned to work on the wavelengths they were designed for. It’s fairly rare to construct any kind of antenna and be totally happy with the results on completion of the project. There are some bare minimum pieces of equipment necessary.
One item is a VSWR meter. Basically it is inserted into a coaxial feed line at the output of the transceiver with the feed going to the antenna off the other side of it. When you transmit the signal goes through the meter and if the antenna is a good match all of the signal will be taken up and radiated. If the match is less than perfect some of the energy will be reflected back. The VSWR meter compares the outgoing with the reflected and gives you a reading corresponding to that ratio.
The problem is that the meter will not tell you whether your impedance is too high or to low or whether the antenna is cut too long or too short. By making adjustments (shortening and lengthening) to your antenna and observing the changes you can tune it in. When you are making an antenna, especially one made from tubing, always leave a little extra length. You can always shorten but its more difficult to lengthen.
Antenna analyzers are another very useful tool. They generate their own signal and so don’t require a transmitter. They have sensitive circuitry to measure the reflected signals from the far end and can usually provide readings of VSWR plus actual impedance. The signal from the oscillator within the meter is low enough in signal strength at it does not pose a problem to other hams who may be working on the same frequency.
One such antenna analyzer is the MFJ-259 or MFJ-269 and others in that series. You can look them up on the MFJ web site. Most of the ham radio stores in Canada sell the more popular items in the MFJ line. Some can be found on swap-and-shops or on eBay as used equipment. It’s buyer beware though. A common problem with antenna analyzers is that unfamiliar users sometimes connect the output of their transceivers to these analyzers and hit the transmit key. It instantly destroys some of the sensitive electronics making for an expensive repair bill. Analyzers allow you to see what frequency the antenna is tuned to and when it's the right length they will tell you the impedance and VSWR.
Another type of analyzer is theminiVNA or mini antenna network analyzer. Some software is loaded into a laptop or desktop computer and the analyzer is connected to it via a USB cable. The analyzer is connected to an antenna or a filter and the software run. There are various setups that can be made in software but basically what you get is a sweep of an antenna over a selected piece of frequency spectrum. You get lovely traces on your computer screen showing how the antenna is performing. You know exactly where to trim or lengthen for tuning. My experience with the miniVNA was that it performed well at HF on my HF antennas but was limited when doing tests on my VHF antennas. It’s hard to throw stones at it because it was doing a job. My problem relates to the fact I am in an area where there are many cell towers, pagers, and other commercial transmitters. The antenna was feeding that into the miniVNA and ruining my traces. Still, it can be used to analyze VHF filters and so not a total loss. I recently analyzed a VHF antenna in another part of town and the miniVNA worked very well.
Sept 28 2009
I just helped out with an amateur radio upgrading course in Surrey BC. My part was to talk about propagation and also some on antennas (types, polarization, etc). I used my miniVNA hooked to my laptop and it to a digital mulimedia projector. When we made adjustments to demonstration antennas the students could immediately see the result. It worked very well as an educational tool. I highly recomend it. The miniVNA is now available for sale in the US.
http://www.w4wb.com/Misc/miniVNA.htm According to the web site today's price is: $398
Also: http://www.ssbusa.com/minivna same price.
Coaxial cable loss for 100 feet of cable at 400 MHz
RG-8/U mini 4.32 dB50 ohm470 watts max.242” OD foam
RG-8X7.7 dB50 ohm90 watts max.24” OD foam
RG-589.384 dB50 ohm140 watts max.195” OD solid
RG-596.9 dB75 ohm130 watts max.242” OD solid
RG-17417 dB50 ohm50 watts max.1” OD solid
RG-2134.4 dB50 ohm490 watts max.405” OD solid
Note that the maximum power calculation here is for 400 MHz (near the 70cm UHF ham band). In the case of RG-58 coax the max at 400 MHz is around 140 watts but at the much lower frequency of 1.8 MHz (80m band) the loss would be much lower at .6 dB (that’s decimal 6)and the maximum power would be much greater at approximately 2.3 KW. What I’m telling you, if it’s not already obvious, is that the frequency you will be using has a great bearing on how you will make a choice of your coaxial feed line
Also note that some of these coax cables have solid dielectric insulation in them between the centre conductor and the shield and the coaxial braid while others have foam plastic. The coax with solid dielectric can withstand some rough use such as being stepped on. The coax with foam is somewhat fragile because it can be damaged by being crushed. For the same reason one should be careful when lashing it to a tower. Don't pull it down so tight with zap straps that you change the cross section size. It's a saw off. If you go for foam insulated you will have almost half of the loss of solid plastic dielectric.
For Those who would like to embrace HF radio and build wire dipoles, that sort of thing, at some point you will have to connect up your radio to the antenna. Typically you will use some make of an SWR meter plus an antenna match device between your transceiver and antenna.
Many of the newer antenna matches have the convenience of an SWR meter already built in. You can couple up to the antenna via a length of coax or via a ballanced line. Coax is fine if the impedance you will have from the antenna is 50 ohms at resonance. Many of the comercial antennas have a balun at the antenna to convert over from the ballanced pair of wires to the 50 ohm impedance of unbalanced coaxial feed line. If you are putting up just a pair of wires for a dipole without a balun at the antenna then you can couple to that with a ballanced line. By ballanced I mean two wires running parallel with one another. It could be a length of 300 ohm TV twin lead if your intention is to not run high power (not over around 150 watts). If you want to run higher than that you may want to use 450 ohm impedance ladder line or wider.
The nice thing about 450 or 600 ohm ladder line is that the conductors are beefy compaired to those usually found in TV twin lead. TV twin lead is usually supported by special stand off insulators all the way from the antenna to where it enters the house. You must keep it away from metal surfaces or soaking wet surfaces because that will influence the impedance at those points. The wires are fairly fine and are usually stranded. 450 ohm ladder line is usually dancing away in the breeze between the centre point of your dipole antenna and where it is attached to the house with some sort of home made stand offs. The wires in 450 ohm and 600 ohm ladder line are usually copper coated steel solid single conductor. I have a partially filled pop bottle hanging from a spot near the middle of my 450 ohm feed line to keep it from flapping around in the strong winter/spring winds. I tell people it is a scientific meteorological device for determening weather conditions (if its bouncing around it's windy, if it casts a shadow its sunny, you get the picture).
Some amateur operators make their own parallel line. It's not difficult, you need two wires and something to act as spacers to keep the wires evenly appart. The more spacers the better. Some people use plastice rod, some use plastic tubing, still others use lengths of wooden dowel that they have notched in the ends with a saw and have then soaked in hot parafin wax to water proof them. Short length of wire are wrapped around the ends to hold the wire in place. I prefer the manufactured line.
Why would you want parallel feed line anyway, coax is so easy to set up? Well, for one thing the transmission loss over parallel line for HF is negligible, your line could literally be hundreds of feet long. For another, you can put up a dipole that is not a resonant length and still be able to use it. The antenna match you would be using will compensate for odd ball impedances you will get at off resonance. The parallel line doesn't care about the fact it may be 300, 460 or 600 or whatever impedance, it will still work just fine. The width (size) of the parallel line just determines the maximum voltage that it can carry. Off resonance antennas can sometimes create some fairly high voltages across the feed line. You need to be aware of that if using a linear amp. Coaxial line is much fussier. It likes to see a terminating load (antenna) the same impedance as it's rated for.
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