unun

[Crowling]

I get kind of a kick out of the venerable ~130ft end-fed being referred to as an end-fed half-wave for 80-10. It's only a half wave on one band and it has the radiation pattern and performance you would expect. On 40m it's an end-fed full-wave and is still "ok". But things go downhill from there at any higher frequency than that its radiation pattern starts to look like a cauliflower and it is no longer a "good" antenna.

The only purpose of the transformer is to reduce the impedance to something your tuner can handle - the antenna has to be used with a tuner to make it an "all-band" antenna. So, like you say, it can be tuned for 80m and used without a tuner. But adding a cap to make it wideband just because you don't have a tuner is an exercise in futility because that makes it low-Q and less efficient on the fundamental. Just use the tuner on it instead and you'll enjoy a highly efficient antenna on the fundamental and get the same result on 75 as making it wideband with a cap.

Some hams seem to think that using an antenna tuner is "bad". It's not. I've always said the antenna tuner is the single most useful piece of equipment in the shack. It adds inductance and capacitance to your antenna system as needed, because all you need to do is make the radio happy with its 50-ohm output. Many hams think that reflected power beyond that is "lost" and just goes up in smoke. It's not. If you look at what goes on on the feedline with standing waves on it, the feedline itself becomes a transformer and you can tune the length of the feedline to get the desired result to hit the radiating element in-phase. Any losses on the feedline with standing waves at HF is so minimal you can't even measure it if you can get the feedpoint impedance and associated SWR of the radiator to something reasonable like <5:1. You obviously don't want to try to tune a 25:1 antenna system with an in-shack tuner because the voltages in the tuner will be quite high. But if you have a good tuner that can handle the voltage, you can still do it and it works as well as going to great lengths to tune the antenna itself.

My last monster Unun.

 

[AC9KH]

My last monster Unun.

What was the purpose of that? To build an inductance monster? Unfortunately, that's not gonna work.

 

[Crowling]

View attachment 184077

I though I mentioned the band width of the 80m EFHWs that I have modified with a capacitor in the middle have the same BW, therefore the same Q with or without the capacitor, its just the resonant frequency on 80m that has shifted upwards. Its still a high Q antenna with the same roughly 200KHz BW on 75/80m.

So you want to spar with Danny Horvat on antenna theory? Good luck with that.

Why would I spar with Danny Horvat when I don’t know him?

Adding what I like to call "magic capacitors" to antenna systems is non-productive, and sometimes downright deceptive. If you want to move the resonant frequency of your 80m EFHW up, then just shorten the wire.

The same holds true with the unknown capacitance of using a bifilar primary winding, or adding a capacitor across the primary to get a deceptively low SWR on 20 or 10m. As with any LC resonance, you’re introducing a frequency-specific item. Many commercial sellers (and even the tutorials on the internet) advertise this as a "feature". It’s not. Your 80m EFHW is not a good radiator @ 10 meters. Period. You’re seeing a good match, not good performance.

Same with cores. At lower frequencies the cores can experience higher losses due to increased hysteresis and eddy currents. The reactance of the windings is lower and you need high-permeability cores. Cores that work good at 80/160 don't work good at 20m. At 20m the cores suffer from skin effect and increased resistive losses, stray capacitance and leakage inductance. So you actually need a different core mix for 80 than you need for 20, and saying one core fits all is another compromise. What you really need is two different antennas and transformers.

So the 80m EFHW, advertised as an "all-band" antenna gets a bad rap as a "compromise antenna" due to transformer losses, which it really is, but it doesn't have to be be that way. All you have to do is reach the realization that it's only really good on one band, and that building wide-band transformers is a bad idea from the word "go". And, unfortunately, on the one band that it's really good on, most hams don't have the resources to get the antenna high enough off the ground.

Oh yeah, some people like Danny Horvat have had great success selling these things for ridiculous prices to unsuspecting hams, even some who should know better, but it still doesn't make the misconceived concept of an "all-band" antenna valid. I realize some hams don't have the room or resources to put up different antennas for the different bands, and they are probably the primary buyers of these things. As long as you realize that there's inherent limitations to trying to cover 27,000 KHz of radio spectrum with one piece of wire, all is fine.

Shortening the wire won’t bring the 75 meter portion of the antenna into acceptable range. Example:…. Let’s say that the entire hf spectrum of the antenna has good swr readings EXCEPT 75 and DEFINITELY 80 meters it’s ok. I found 125-130 feet is the length when using # 14 gauge wire. If then you shorten or lengthen the wire length to bring 75/80 to a decent swr THE REST OF THE HF bands swr’s change….for the WORSE. In my experience. I have seen that My Antenna company has a capacitor/coil kit to add on and the more $$ expensive models come WITH “the kit” as part of the complete antenna assy.

 

[prcguy]

Adding what I like to call "magic capacitors" to antenna systems is non-productive, and sometimes downright deceptive. If you want to move the resonant frequency of your 80m EFHW up, then just shorten the wire.

The same holds true with the unknown capacitance of using a bifilar primary winding, or adding a capacitor across the primary to get a deceptively low SWR on 20 or 10m. As with any LC resonance, you’re introducing a frequency-specific item. Many commercial sellers (and even the tutorials on the internet) advertise this as a "feature". It’s not. Your 80m EFHW is not a good radiator @ 10 meters. Period. You’re seeing a good match, not good performance.

Same with cores. At lower frequencies the cores can experience higher losses due to increased hysteresis and eddy currents. The reactance of the windings is lower and you need high-permeability cores. Cores that work good at 80/160 don't work good at 20m. At 20m the cores suffer from skin effect and increased resistive losses, stray capacitance and leakage inductance. So you actually need a different core mix for 80 than you need for 20, and saying one core fits all is another compromise. What you really need is two different antennas and transformers.

So the 80m EFHW, advertised as an "all-band" antenna gets a bad rap as a "compromise antenna" due to transformer losses, which it really is, but it doesn't have to be be that way. All you have to do is reach the realization that it's only really good on one band, and that building wide-band transformers is a bad idea from the word "go". And, unfortunately, on the one band that it's really good on, most hams don't have the resources to get the antenna high enough off the ground.

Oh yeah, some people like Danny Horvat have had great success selling these things for ridiculous prices to unsuspecting hams, even some who should know better, but it still doesn't make the misconceived concept of an "all-band" antenna valid. I realize some hams don't have the room or resources to put up different antennas for the different bands, and they are probably the primary buyers of these things. As long as you realize that there's inherent limitations to trying to cover 27,000 KHz of radio spectrum with one piece of wire, all is fine.

Most of what you posted here is opposite of what the antenna industry knows as true. The 100pf or so across the 50 ohm side of a 49:1 or 64:1 transformer helps counter some inductive reactance on 10m and does help the match on 10m with no negative effects. That has been measured and posted for years. Adding a 250pf capacitor in the middle of an end fed 80m to raise only the 80m resonance has been known for many years and well before anyone started using ferrite transformers. Adding a 150pf in the middle of an 80m OCFD to raise the 80m frequency has been done for decades and works great with no ill effects.

You say the EFHW is a compromise due to transformer losses but the better commercial designers measure two of their transformers back to back and losses are very low like .37dB worse case across 3 to 30Mhz. .37dB is literally no loss and much less than using an outboard antenna tuner at the radio end. Their higher power transformers designed for the lower bands like 160 through 40m have even less loss like advertised .2dB loss across that range.

I've been building and using EFHW antennas with 64:1 and 49"1 transformers from about 2005 and I've built and thoroughly tested maybe 30-40 of them, I cant even keep track and have not experienced anything you have mentioned. Antenna mfrs like MyAntennas publish their test procedures and results that contradict your claims. They have sold tens of thousands of units with no problems and tens of thousands of happy users.

So I might ask to see some of your contradicting test info and how you came up with your claims if you don't mind. Besides having a ham license do you have any credentials in antenna design or manufacturing?

 

[Crowling]

What was the purpose of that? To build an inductance monster? Unfortunately, that's not gonna work.Here’s about 2-3 minutes of reading my rants about my experiments LOL! It was comprised of (4) 240/43 cores and (2) unknown core. I flunked algebra and never tried trigonometry obviously. All (98%) of the formulas you guys use might as well be written in Latin. I never went to college for electronic engineering, or anything else for that matter. However I am self taught in electronics at a technician level. I repaired consumer electronics as a living for over 40 years. I have countless successfully completed courses and completed analog and digital training from the biggest company names in the business… before Y2K which shortly after marked the end warranty repairs. Toshiba,Sony,Rca/Ge, Samsung,Mitsubishi,NEC,Pioneer, NAP North American Philps (Philips magnavox sylvania) Funia etc,etc. Now it’s the customers responsibility to save the box the product came in and send it back in warranty. Even Walmart won’t accept returns on certain brands. I like to experiment sometimes. I built but never patented a jig to perform digital convergence of 46-60 inch Rca/Ge projection tv’s. Using my jig only required the technician to bring the d-con pcb to the shop and leave the giant tv in the customers home and removed the need of 2 people to load and unload the tv from a van. By using a program from Rca to upload the digital parameters then download to the new empty memory on the d-con. My jig supplied the necessary 3.3 vdc, +5vdc, clock, data, +12vdc, and PWM signals. I also was told by the all the manufacturers engineers (tech assistants) that removing an EEPROM and swap it from a defective d-con board to transplant onto a new d-con pcb would NOT permit correct alignment of convergence. They were wrong. I started getting new d-con’s and removing the NEW eeprom then replacing the old, original eeprom from the defective pcb. The results were NOT SPENDING 3-6 hours doing a complete convergence alignment !!!! Again all because of my experimental tendencies lol.

 

[Crowling]

I forgot to mention that there was NO convergence necessary at all using my homemade convergence jig. Sometimes a tv might need a tiny touch up but not an alignment

 

[AC9KH]

Shortening the wire won’t bring the 75 meter portion of the antenna into acceptable range.

It won't? I've done it many times and it works fine with dipoles, EFHW's and 1/4 wave verticals on 75 meters. I've run 'em all in the phone portion of the band and when you build an antenna for 75 you normally do the calculations and cut it and it's too long. That's because of velocity factor in the wire (or in the tower in the case of the vertical). So you cut it to where the electrical length (not the physical length) resonates.

Now, after you do this, it doesn't mean you have perfect SWR. So you tune it with a LC network either at the antenna, or at the in-shack tuner. You can fine tune it with feedline length. In the case of an EFHW, if the impedance is so high it won't tune you can fix that with a step transformer.

SWR does not mean good performance and/or radiation efficiency. It just means the radio is happy and that's what they make LC networks and tuners for. I got a dummy load that has perfect SWR on all the bands. But put it on a 50ft pole and try to contact somebody with it (I've done this too with an old cantenna on 160 and managed to get 30 miles out of it). Just because it has nice SWR don't mean it's a good antenna. Go visit your local AM radio station - they likely got a tower loaded up that's electrically resonant on their broadcast frequency. But the SWR on that tower is horrible. That's why they got a big antenna tuner (matching network) on it to make the transmitter happy.

 

[AC9KH]

Most of what you posted here is opposite of what the antenna industry knows as true.

I think you just like to argue. Anybody who thinks a 130ft piece of wire makes a good 10m antenna is delusional. You can throw some stuff at it and make it usable. But usable and good are two different things and that's the fallacy of the 80-10m end-fed wire.

 

[Crowling]

It won't? I've done it many times and it works fine with dipoles, EFHW's and 1/4 wave verticals on 75 meters. I've run 'em all in the phone portion of the band and when you build an antenna for 75 you normally do the calculations and cut it and it's too long. That's because of velocity factor in the wire (or in the tower in the case of the vertical). So you cut it to where the electrical length (not the physical length) resonates.

Now, after you do this, it doesn't mean you have perfect SWR. So you tune it with a LC network either at the antenna, or at the in-shack tuner. You can fine tune it with feedline length. In the case of an EFHW, if the impedance is so high it won't tune you can fix that with a step transformer.

SWR does not mean good performance and/or radiation efficiency. It just means the radio is happy and that's what they make LC networks and tuners for. I got a dummy load that has perfect SWR on all the bands. But put it on a 50ft pole and try to contact somebody with it (I've done this too with an old cantenna on 160 and managed to get 30 miles out of it). Just because it has nice SWR don't mean it's a good antenna. Go visit your local AM radio station - they likely got a tower loaded up that's electrically resonant on their broadcast frequency. But the SWR on that tower is horrible. That's why they got a big antenna tuner (matching network) on it to make the transmitter happy.

I’m referring to NOT using a tuner. Meaning reading the swr directly at the feed point with a 2 foot coax between the NanoVNA and Unun.

 

[prcguy]

It won't? I've done it many times and it works fine with dipoles, EFHW's and 1/4 wave verticals on 75 meters. I've run 'em all in the phone portion of the band and when you build an antenna for 75 you normally do the calculations and cut it and it's too long. That's because of velocity factor in the wire (or in the tower in the case of the vertical). So you cut it to where the electrical length (not the physical length) resonates.

Now, after you do this, it doesn't mean you have perfect SWR. So you tune it with a LC network either at the antenna, or at the in-shack tuner. You can fine tune it with feedline length. In the case of an EFHW, if the impedance is so high it won't tune you can fix that with a step transformer.

SWR does not mean good performance and/or radiation efficiency. It just means the radio is happy and that's what they make LC networks and tuners for. I got a dummy load that has perfect SWR on all the bands. But put it on a 50ft pole and try to contact somebody with it (I've done this too with an old cantenna on 160 and managed to get 30 miles out of it). Just because it has nice SWR don't mean it's a good antenna. Go visit your local AM radio station - they likely got a tower loaded up that's electrically resonant on their broadcast frequency. But the SWR on that tower is horrible. That's why they got a big antenna tuner (matching network) on it to make the transmitter happy.

Shortening a stock 80m EFHW to resonate higher like 3.9MHz to cover roughly 3.8 to 4.0MHz works great for 75m and the VSWR will be very nice. Its no different than making a half wave dipole for 3.58MHz then shortening it for 3.9MHz. The problem doing this with an EFHW is all other bands will then resonate way outside the ham bands. This is because 75m phone is not harmonically related to any other ham band and the EFWH works on half wave resonances or even harmonics. The capacitor mod in the middle of the antenna is the fix for 75m phone as it will not detune any other band.

 

[prcguy]

I think you just like to argue. Anybody who thinks a 130ft piece of wire makes a good 10m antenna is delusional. You can throw some stuff at it and make it usable. But usable and good are two different things and that's the fallacy of the 80-10m end-fed wire.

Hams have been using a 135fft center fed doublet on all bands since before you were born and have worked all states on 10m with it and the radiation properties of that is nearly identical to an 80m EFHW. No its not the best 10m antenna, I never said it was. Yes its handy as heck to have one wire antenna work just about all bands 80 through 10m without needing a tuner.

 

[AC9KH]

I’m referring to NOT using a tuner. Meaning reading the swr directly at the feed point with a 2 foot coax between the NanoVNA and Unun.

Of course it will, due to harmonics. But if 75 is your primary operating band, tune the antenna for that and just use the tuner on the rest of the bands if you want to try to use the antenna on them. Or better yet, if you have the room and resources, put up a shorter antenna for the higher frequency bands. This aversion that some hams have to using an antenna tuner is almost like a plague. But it is true that the commercial antenna industry has made millions selling wide-band antennas to hams who don't want to buy a tuner.

 

[AC9KH]

Hams have been using a 135fft center fed doublet on all bands since before you were born and have worked all states on 10m with it

That's great. Here's real-world results on 30 meters. 127' end-fed vertical vs 32' 3/8 wave vertical @ 2.2 watts using JS8Call to a local station that's about 10 miles away.

5dB better SNR on tx (-08 to -03), 8dB improvement on rx (-13 to -04) with the shorter antenna. Simply due to antenna efficiency. I can repeat the demonstration to somebody on the east coast and the results are even more dramatic if propagation is poor. I can pick up signals at -24dB on the 32' that the big EFW can't even hear on 30m. So hams can continue using their 135' wires all they want on 10, ignorance is bliss since they don't know what they're missing out on.

 

[prcguy]

Of course it will, due to harmonics. But if 75 is your primary operating band, tune the antenna for that and just use the tuner on the rest of the bands if you want to try to use the antenna on them. Or better yet, if you have the room and resources, put up a shorter antenna for the higher frequency bands. This aversion that some hams have to using an antenna tuner is almost like a plague. But it is true that the commercial antenna industry has made millions selling wide-band antennas to hams who don't want to buy a tuner.

But that will incur noticeable coax loss when operating on all bands besides 75m. Trimming an 80m EFHW to 75m will put the other bands in the 3:1 and up range and when coax is operated with a high VSWR its loss goes way up compared to advertised matched losses. If you stick the capacitor in the middle of your 80m EFHW then 75m phone works great and all harmonic bands will have a nice match with no tuner, you will have no additional losses and life is good. Why use a tuner if you don't have to? And why put up a second EFHW when the first one with a capacitor mod will do everything?

 

[prcguy]

My last monster Unun.

There is a reason you have never seen a commercial version of this.

 

[AC9KH]

But that will incur noticeable coax loss when operating on all bands besides 75m. Trimming an 80m EFHW to 75m will put the other bands in the 3:1 and up range and when coax is operated with a high VSWR its loss goes way up compared to advertised matched losses. If you stick the capacitor in the middle of your 80m EFHW then 75m phone works great and all harmonic bands will have a nice match with no tuner, you will have no additional losses and life is good. Why use a tuner if you don't have to? And why put up a second EFHW when the first one with a capacitor mod will do everything?

Why the second antenna? Because of the efficiency differences I can easily demonstrate at higher frequencies as in my previous post. Even at 30m you're already behind the curve of where a 80m EFHW is efficient.

Noticeable coax loss due to VSWR? I've only ever seen about 1dB @ 80 meters even at 5:1. It will be higher at 10m but I've never measured it.

Why the tuner? A shack tuner sees a complex impedance that has been transformed by the transmission line. This is dependent on the length and impedance of the transmission line, of course, and will normally be completely different to the complex impedance at the antenna. The beauty of the shack tuner is that it presents a purely resistive 50 ohm load to the transmitter finals with no reactive components from the feedline transformation.

 

[Crowling]

Shortening a stock 80m EFHW to resonate higher like 3.9MHz to cover roughly 3.8 to 4.0MHz works great for 75m and the VSWR will be very nice. Its no different than making a half wave dipole for 3.58MHz then shortening it for 3.9MHz. The problem doing this with an EFHW is all other bands will then resonate way outside the ham bands. This is because 75m phone is not harmonically related to any other ham band and the EFWH works on half wave resonances or even harmonics. The capacitor mod in the middle of the antenna is the fix for 75m phone as it will not detune any other band.

That’s what I thought too

 

[Crowling]

There is a reason you have never seen a commercial version of this.

I bought a 4 core stack “commercial” version

 

[Crowling]

Well, all I know for sure is that when Ac9kh finishes the winding to his satisfaction i know I will be satisfied with it too. He seems to have a lot of experience with winding different types for different purposes. He will be certain it’s the best it can be for what I need

 

[prcguy]

I bought a 4 core stack “commercial” version

From???