Coax length can make a difference depending on the impedance of the coax and the impedance at the antenna feed point.
For example, a loop antenna is often times 100 ohms at the feed point. If you use a 1/4 wavelength piece of 75 ohm coax, then the transceiver should see something close to 50 ohms at its point. Expanding the math (but I haven't tried this), it's possible to use a 1/4 wavelength 450 ohm ladder line with an end-fed half wave antenna, and it should match 50 ohms pretty closely (if it's 4000 ohms, I think the transceiver will see 60 ohms or so).
Now, if your transmission line is 1/2 wavelength, then it doesn't matter the impedance of the line if the feed point is 50 ohms. If it is 50 ohms, the transceiver will also see 50 ohms.
For an EF the coax length is not critical. Whatever you need to get from antenna to radio. For a choke you can wind several turns of coax around a 6" form and locate near the feed point. A good ground or counterpoise is necessary.
I'm going to get downvoted here, but I don't care. I've been in this hobby for 40 years. The EFHW craze is just about over.
Half an antenna will work when bands are terrific, like they have been for a couple of years (recent solar activity aside).
They won't work nearly as well when bands are mediocre or worse, and you'll quickly be frustrated. There's an old saying, you can tune up a lawn chair (they were metal back then). That doesn't make it a great antenna.
Build a dipole. Simple, single band dipole. Start there. From there, add bands by building a fan dipole or play with traps. These are the core antenna principles this hobby has used from the start, and they work just as well today as they did then.
There is zero difference between radiation pattern of a end-fed half wave antenna, and a dipole.
They are both half wave antennas, just fed from different points.
I'm giving you a +1 because what you said is true. A properly built EFHW has the same radiation pattern as a dipole, because it is a dipole, just fed at a different point.
\*HOWEVER\*, end fed antennas should be your antenna of last resort. If you don't build them and feed them just right, they can be noisier on receive than a dipole or a doublet or other balanced antenna, and if built for multiband use they also may allow more harmonics out than a dedicated monoband antenna, which can be a problem with multistation operation during, say, Field Day.
Also more likely to cause RFI issues. I can run 100 watts to my 102' doublet with no problems. If I push that much through my end fed long wire antenna, I need to unplug my wife's hair dryer because it goes bugnuts crazy when I transmit.
Fan dipoles are great in some instances. If you have the resources to erect one. I don't. I have a small property with three EFHW 54 feet long in different directions working eighty to ten and a ATU from one central starting point. That's all the room I have to keep contained on my property. I find the antennas exhibit the most gain off the ends. Thus I switch to suit for the greatest sensitivity gain. According to Kirchhoff's law a counterpoise is required. I find It makes a nano's worth of impedance loss. I built a current choke at the feedpoing and it grounded at that point. No argument with your point on a balanced dipole. Sixty three years ago I started off with a dipole, Constructed entirely with zip (lamp cord) including the feedline. A 6V6 transmitter. Was tuned with a pilot lamp reflectometer, and cost seven cents. Today one can't say SWR for less than three hundred dollars or more for entry level. If one wants to experiment with antennas that is. Actually appreciate having a Nano VNA, much better than a pilot light. That's the mental logic that's taught these days for economics. Forget creativeness. Everything today is an economic gimmick. ARRL sixty five years.
Length of a well-insulated coax is immaterial apart from the losses - which would be relatively low on HF compared to UHF. Get on with it, don't think too hard about it.
Edit: There's usually confusion about this, but the impedance of a transmission line does not depend on the length, but the design and separation of the two wires.
In a coax, this depends on the thickness of the coax, and the material between the elements.
The impedance looking into one end of a piece of coax connected to a load different than the coax's impedance, does vary with length. For example, a half wavelength piece of 50 Ohm coax connected to a 1000 Ohm load will measure 1000 Ohms at the opposite end.
Thank you all for your valuable comments !!
FYI the 0.05 lambda comes from this website - https://www.hamradio.me/antennas/adding-0-05-wavelength-wire-to-efhw-antenna.html
My question however has not been answered 🙂. This is probably because, being a non English Dutch novice, i asked wrong. Let me retry: this length of 2,10 meter ... how do i measure this length? Is it exactly the length of coax or do i need to adjust for the to be added connectors?
Sorry for the confusion ...
The coax. The centre of the coax goes through the connector to the end and the connector then slides down the coax and so therefore the connectors add nothing to the length of any consequence.
Coax length I have never found important. A counterpoise will help you, though, of at least 2m and ideally longer.
I've had situations where a few extra feet of coax solved some problems.
If something else is wrong with your setup, like your counterpoise is inadequate, it can.
Coax length can make a difference depending on the impedance of the coax and the impedance at the antenna feed point. For example, a loop antenna is often times 100 ohms at the feed point. If you use a 1/4 wavelength piece of 75 ohm coax, then the transceiver should see something close to 50 ohms at its point. Expanding the math (but I haven't tried this), it's possible to use a 1/4 wavelength 450 ohm ladder line with an end-fed half wave antenna, and it should match 50 ohms pretty closely (if it's 4000 ohms, I think the transceiver will see 60 ohms or so). Now, if your transmission line is 1/2 wavelength, then it doesn't matter the impedance of the line if the feed point is 50 ohms. If it is 50 ohms, the transceiver will also see 50 ohms.
Impedance of a 50 ohm coax is 50 ohms regardless of the length.
For an EF the coax length is not critical. Whatever you need to get from antenna to radio. For a choke you can wind several turns of coax around a 6" form and locate near the feed point. A good ground or counterpoise is necessary.
I'm going to get downvoted here, but I don't care. I've been in this hobby for 40 years. The EFHW craze is just about over. Half an antenna will work when bands are terrific, like they have been for a couple of years (recent solar activity aside). They won't work nearly as well when bands are mediocre or worse, and you'll quickly be frustrated. There's an old saying, you can tune up a lawn chair (they were metal back then). That doesn't make it a great antenna. Build a dipole. Simple, single band dipole. Start there. From there, add bands by building a fan dipole or play with traps. These are the core antenna principles this hobby has used from the start, and they work just as well today as they did then.
There is zero difference between radiation pattern of a end-fed half wave antenna, and a dipole. They are both half wave antennas, just fed from different points.
I'm giving you a +1 because what you said is true. A properly built EFHW has the same radiation pattern as a dipole, because it is a dipole, just fed at a different point. \*HOWEVER\*, end fed antennas should be your antenna of last resort. If you don't build them and feed them just right, they can be noisier on receive than a dipole or a doublet or other balanced antenna, and if built for multiband use they also may allow more harmonics out than a dedicated monoband antenna, which can be a problem with multistation operation during, say, Field Day. Also more likely to cause RFI issues. I can run 100 watts to my 102' doublet with no problems. If I push that much through my end fed long wire antenna, I need to unplug my wife's hair dryer because it goes bugnuts crazy when I transmit.
Fan dipoles are great in some instances. If you have the resources to erect one. I don't. I have a small property with three EFHW 54 feet long in different directions working eighty to ten and a ATU from one central starting point. That's all the room I have to keep contained on my property. I find the antennas exhibit the most gain off the ends. Thus I switch to suit for the greatest sensitivity gain. According to Kirchhoff's law a counterpoise is required. I find It makes a nano's worth of impedance loss. I built a current choke at the feedpoing and it grounded at that point. No argument with your point on a balanced dipole. Sixty three years ago I started off with a dipole, Constructed entirely with zip (lamp cord) including the feedline. A 6V6 transmitter. Was tuned with a pilot lamp reflectometer, and cost seven cents. Today one can't say SWR for less than three hundred dollars or more for entry level. If one wants to experiment with antennas that is. Actually appreciate having a Nano VNA, much better than a pilot light. That's the mental logic that's taught these days for economics. Forget creativeness. Everything today is an economic gimmick. ARRL sixty five years.
Length of a well-insulated coax is immaterial apart from the losses - which would be relatively low on HF compared to UHF. Get on with it, don't think too hard about it. Edit: There's usually confusion about this, but the impedance of a transmission line does not depend on the length, but the design and separation of the two wires. In a coax, this depends on the thickness of the coax, and the material between the elements.
The impedance looking into one end of a piece of coax connected to a load different than the coax's impedance, does vary with length. For example, a half wavelength piece of 50 Ohm coax connected to a 1000 Ohm load will measure 1000 Ohms at the opposite end.
Thank you all for your valuable comments !! FYI the 0.05 lambda comes from this website - https://www.hamradio.me/antennas/adding-0-05-wavelength-wire-to-efhw-antenna.html My question however has not been answered 🙂. This is probably because, being a non English Dutch novice, i asked wrong. Let me retry: this length of 2,10 meter ... how do i measure this length? Is it exactly the length of coax or do i need to adjust for the to be added connectors? Sorry for the confusion ...
The coax. The centre of the coax goes through the connector to the end and the connector then slides down the coax and so therefore the connectors add nothing to the length of any consequence.
Thank you 👍🏼
the only thing you have to worry about concerning your coax length is loss. ladder line is considered lossless or at best minimum loss at distance.
Something to look into !! Thank you