One more thing to consider in choosing the antenna type: A simple dipole or inverted V can be used on both odd and even harmonics, with a tuner. But a folded dipole or V will not work on even harmonics.
You got me thinking because I have ALWAYS heard "odd harmonics only", so I did a little experiment here. Just from a frequency perspective ... I tried 80/75m frequencies first as the fundamental. Only even harmonics hit other ham bands with the exception of the 17m band and the antenna would have to be tuned to the LOW end of the band to make this work. So, I retried assuming a 40m antenna. From a frequency perspective, this was more promising. See these results in the document link below. From an SWR perspective on a *real* antenna ... Next, I connected my VNA up to my 40m inverted vee and scanned it from 7MHz to 50 MHz. Yes, I know it is tuned a bit high in the band, so this just verified what I already knew. I am looking for SWRs at harmonics of the fundamental. Here is what I discovered: Harmonic Freq (MHz) VSWR 1 7.250 1.30 40m band 2 14.50 5.95 20m band 3 21.75 2.78 15m band 4 29.00 3.78 10m band 5 36.25 2.52 -- nowhere -- 6 43.50 2.90 -- nowhere -- Here is a link to the document with the results: docs.google.com/document/d/1ZD5ibBJV9QnHSeQH7TFLW_5p9lPWEPzo/edit?usp=sharing&ouid=113004549152926472999&rtpof=true&sd=true So, I suppose it is possible to use the even harmonics, but the antenna's radiation efficiency has got to be abysmal. Additionally, with SWRs in the 6 range (20m band), we have 51% of our power being reflected back at the transmitter. The antenna tuner might make the transmitter happy, but it will not change the fact that we are throwing away 51% of our power in heat somewhere. Thank you for your thought inducing comment.
@@eie_for_you I disagree that you are "throwing away" any power due to SWR when the line is matched to the transmitter, except for the slight additional loss in the feedline due to SWR. Reflected power is reflected back and forth between the source and the load, and most of it ultimately reaches the load. I have a rotary dipole 10m long, fed through about 10m of homemade open wire line, no. 12 wire spaced 10cm. It is matched to the transmitter by a link-coupled tuner, an old Johnson KW Matchbox. It works very well on all the bands from 40m to 10m (I had to make a slight mod to the matchbox so it would resonate on 30m). On 40, I calculate the loss due to the astronomical SWR as about 2 dB; on all other bands it's negligible, due to the low inherent loss of 10m of open line.
I had to noodle on this. True, the power does reflect back in the direction of the antenna and from the antenna back to the transmitter ("rattling back and forth"). 51% of all of the power arriving at the antenna comes back at the transmitter due to the mismatch; this is the re-reflected power + the transmitter power. It is also true that there is loss for each trip through the feedline. In the end, there is still appreciable loss which cannot be ignored. We cannot forget the abysmal radiation inefficiency of an antenna at the even harmonics. While we *could* use an antenna on an even harmonic in a pinch, I would *never* recommend this as normal operating.
@@eie_for_you If the antenna is fed with low loss transmission line like open wire line, the loss can be very small. My dipole acts as two half waves in phase on 10 meters and it even has a little gain over a dipole. The extra loss in the feedline due to the SWR is negligible. It even works on 40 meters, where the SWR is about 90:1! But since the feedline is short (only about 10m) and very low loss, the additional loss due to SWR is only about 2 dB. In fact, the 1/4 wave feedline translates the impedance of the antenna, which has low resistance and is very capacitive, to a high resistance plus inductive reactance, which is much easier to efficiently match to the transmitter. I agree with you that this would not work very well with a coax feedline.
Aaaaaah ... I am speaking to the average person who only feeds their antennas with coax and does not care to, or have the knowledge how to, do any such transformations. They just want to connect their antenna with some coax and be done with it. The setup you describe is very different than this scenario.
Aaaah! How well does that work for you? I have a folded inverted vee for my 75/80 antenna. I created it because I was tired of the bandwidth limitations of the simple inverted vee (ruclips.net/video/McbDL1GxbqI/видео.html). I've heard of doing the termination thing, but I decided to keep it this way because I have the space for dedicated, single-band antennas. 🙂
Hello - I find the T2FD one really great antenna, with a very low VSWR from 80m to 10m. There are one or two spots where the VSWR goes above 2.5:1 but my ATU easily sorts that out. I've been on the air for 40+ years and I have to say that the T2FD is the best antenna for restricted places.
Very interesting from my perspective also!
I thought so, too! 🙂
One more thing to consider in choosing the antenna type: A simple dipole or inverted V can be used on both odd and even harmonics, with a tuner. But a folded dipole or V will not work on even harmonics.
You got me thinking because I have ALWAYS heard "odd harmonics only", so I did a little experiment here. Just from a frequency perspective ...
I tried 80/75m frequencies first as the fundamental. Only even harmonics hit other ham bands with the exception of the 17m band and the antenna would have to be tuned to the LOW end of the band to make this work.
So, I retried assuming a 40m antenna. From a frequency perspective, this was more promising. See these results in the document link below.
From an SWR perspective on a *real* antenna ...
Next, I connected my VNA up to my 40m inverted vee and scanned it from 7MHz to 50 MHz. Yes, I know it is tuned a bit high in the band, so this just verified what I already knew. I am looking for SWRs at harmonics of the fundamental. Here is what I discovered:
Harmonic Freq (MHz) VSWR
1 7.250 1.30 40m band
2 14.50 5.95 20m band
3 21.75 2.78 15m band
4 29.00 3.78 10m band
5 36.25 2.52 -- nowhere --
6 43.50 2.90 -- nowhere --
Here is a link to the document with the results:
docs.google.com/document/d/1ZD5ibBJV9QnHSeQH7TFLW_5p9lPWEPzo/edit?usp=sharing&ouid=113004549152926472999&rtpof=true&sd=true
So, I suppose it is possible to use the even harmonics, but the antenna's radiation efficiency has got to be abysmal. Additionally, with SWRs in the 6 range (20m band), we have 51% of our power being reflected back at the transmitter. The antenna tuner might make the transmitter happy, but it will not change the fact that we are throwing away 51% of our power in heat somewhere.
Thank you for your thought inducing comment.
@@eie_for_you I disagree that you are "throwing away" any power due to SWR when the line is matched to the transmitter, except for the slight additional loss in the feedline due to SWR. Reflected power is reflected back and forth between the source and the load, and most of it ultimately reaches the load.
I have a rotary dipole 10m long, fed through about 10m of homemade open wire line, no. 12 wire spaced 10cm. It is matched to the transmitter by a link-coupled tuner, an old Johnson KW Matchbox. It works very well on all the bands from 40m to 10m (I had to make a slight mod to the matchbox so it would resonate on 30m). On 40, I calculate the loss due to the astronomical SWR as about 2 dB; on all other bands it's negligible, due to the low inherent loss of 10m of open line.
I had to noodle on this. True, the power does reflect back in the direction of the antenna and from the antenna back to the transmitter ("rattling back and forth"). 51% of all of the power arriving at the antenna comes back at the transmitter due to the mismatch; this is the re-reflected power + the transmitter power. It is also true that there is loss for each trip through the feedline. In the end, there is still appreciable loss which cannot be ignored.
We cannot forget the abysmal radiation inefficiency of an antenna at the even harmonics.
While we *could* use an antenna on an even harmonic in a pinch, I would *never* recommend this as normal operating.
@@eie_for_you If the antenna is fed with low loss transmission line like open wire line, the loss can be very small. My dipole acts as two half waves in phase on 10 meters and it even has a little gain over a dipole. The extra loss in the feedline due to the SWR is negligible.
It even works on 40 meters, where the SWR is about 90:1! But since the feedline is short (only about 10m) and very low loss, the additional loss due to SWR is only about 2 dB.
In fact, the 1/4 wave feedline translates the impedance of the antenna, which has low resistance and is very capacitive, to a high resistance plus inductive reactance, which is much easier to efficiently match to the transmitter.
I agree with you that this would not work very well with a coax feedline.
Aaaaaah ... I am speaking to the average person who only feeds their antennas with coax and does not care to, or have the knowledge how to, do any such transformations. They just want to connect their antenna with some coax and be done with it. The setup you describe is very different than this scenario.
I use a T2FD due to restricted space.
Aaaah! How well does that work for you?
I have a folded inverted vee for my 75/80 antenna. I created it because I was tired of the bandwidth limitations of the simple inverted vee (ruclips.net/video/McbDL1GxbqI/видео.html).
I've heard of doing the termination thing, but I decided to keep it this way because I have the space for dedicated, single-band antennas. 🙂
Hello - I find the T2FD one really great antenna, with a very low VSWR from 80m to 10m. There are one or two spots where the VSWR goes above 2.5:1 but my ATU easily sorts that out. I've been on the air for 40+ years and I have to say that the T2FD is the best antenna for restricted places.
@@EI6DP That's cool! Thanks! 🙂