unun

[AC9KH]

If anyone is interested in making a high power 49:1 transformer this guy has figured out the recipe and has a good video on the details. Notice he is not using 43 mix cores when stacking three.

That's fine for higher frequencies. But if the desired band of operation is 80m, I'd tend to stick with -43's due to their higher inductance. They magnetize easily @ 3500-4000 KHz with no eddy current losses and run cool even with the amp on them. If you plan on running 7000 KHz and above, then -52's (or even -61's) are a better choice. -61's are not going to work for 3500 KHz, -52's are marginal because they don't magnetize as easy. What the guy in the video built is a transformer primarily for 7000 KHz as the fundamental.

Again, in my experience there is no such thing as an "all band" antenna that works good. Building a low-Q antenna system just to get SWR dips on all the bands is the wrong way to go about it because the bands are not exact harmonics. The bottom end of 80m lines up with the bottom end of 40m, for instance, but the top end of 75m does not line up with 40m because the 75/80m band is 500 KHz wide. So if building a EFHW for 80m, make it high-Q so it's efficient, but expect to use an antenna tuner for 75m. If you build it with lots of capacitive coupling in the transformer just to get a flat SWR across 80/75, it's not going to be as efficient and expect to get considerable core heating even at 500 watts.

This is why I offered to wind a transformer for Mr. Crowling. He can't seem to get the desired result, so he's either got unreasonable expectations of a no-tuner "all-band" EFHW, or his cores are no good. I can wind a test transformer, throw the scope on it tell you within minutes if those cores are -43's just based on the phase shift between primary and secondary.

 

[prcguy]

That's fine for higher frequencies. But if the desired band of operation is 80m, I'd tend to stick with -43's due to their higher inductance. They magnetize easily @ 3500-4000 KHz with no eddy current losses and run cool even with the amp on them. If you plan on running 7000 KHz and above, then -52's (or even -61's) are a better choice. -61's are not going to work for 3500 KHz, -52's are marginal because they don't magnetize as easy. What the guy in the video built is a transformer primarily for 7000 KHz as the fundamental.

Again, in my experience there is no such thing as an "all band" antenna that works good. Building a low-Q antenna system just to get SWR dips on all the bands is the wrong way to go about it because the bands are not exact harmonics. The bottom end of 80m lines up with the bottom end of 40m, for instance, but the top end of 75m does not line up with 40m because the 75/80m band is 500 KHz wide. So if building a EFHW for 80m, make it high-Q so it's efficient, but expect to use an antenna tuner for 75m. If you build it with lots of capacitive coupling in the transformer just to get a flat SWR across 80/75, it's not going to be as efficient and expect to get considerable core heating even at 500 watts.

This is why I offered to wind a transformer for Mr. Crowling. He can't seem to get the desired result, so he's either got unreasonable expectations of a no-tuner "all-band" EFHW, or his cores are no good. I can wind a test transformer, throw the scope on it tell you within minutes if those cores are -43's just based on the phase shift between primary and secondary.

No, three 52 mix cores are good from 80m through 10m. Three 43 mix cores are not good above about 40m. I've used a single 62 mix core down to 80m. If you look up some of the other videos from the guy in my link you can see where he started with three 43 mix cores and had all kinds of heating and other problems at high power. I eventually learned with three cores you need much less permeability when stacking three and he found 52 mix the best.

I don't know what MyAntennas uses but they have two and three core versions that are very low loss 80 through 10m and work great, better than anything I have been able to make. MyAntennas does not use 43 mix in their 64:1 or 49:1 transformers.

 

[AC9KH]

If your goal is a broadband low-Q step transformer I would agree. But higher permeability provides higher inductance per winding, so a particular design for the lower frequencies using -43's will require more copper with -52's. I'm not familiar with -62's, I've only ever used -61's before.

As usual, with ferrites, there is no "one fits all". The different mixes are for different applications and provide different frequency response depending on what you need for your application.

 

[Crowling]

I’m gonna try to get the package out tomorrow. Here’s 2 sweeps of my single core 49:1 from Ultramax. I.do not know what mix the core is. It’s swr is pretty good from 80-10. People I know that own My Antenna j1k and 3k models have 80 meter high swr. MA makes a kit for them to improve 75-80 meter swr’s. 1st one on left is measured at the radio end of 100 feet of 8u flex. Right is coax going through all of my equipment.

 

[Crowling]

Btw sweep is 2-32 mhz if I remember correctly. Craig

 

[prcguy]

I’m gonna try to get the package out tomorrow. Here’s 2 sweeps of my single core 49:1 from Ultramax. I.do not know what mix the core is. It’s swr is pretty good from 80-10. People I know that own My Antenna j1k and 3k models have 80 meter high swr. MA makes a kit for them to improve 75-80 meter swr’s. 1st one on left is measured at the radio end of 100 feet of 8u flex. Right is coax going through all of my equipment.

An 80-10m EFHW will resonate around 3.58MHz on 80 and will have high SWR in the 3.8-4.0MHz phone band. If you measure 67ft from the insulator end, cut the wire and insert a 250pf HV capacitor that will bring the resonant frequency up to about 3.9MHz covering 3.8 to 4.0Mhz with a very good VSWR and will not affect any other band. I use a doorknob capacitor around 10kV and bridge it with an insulator like this. Ignore the capacitance value in the picture, it was for another antenna.

 

[prcguy]

If your goal is a broadband low-Q step transformer I would agree. But higher permeability provides higher inductance per winding, so a particular design for the lower frequencies using -43's will require more copper with -52's. I'm not familiar with -62's, I've only ever used -61's before.

As usual, with ferrites, there is no "one fits all". The different mixes are for different applications and provide different frequency response depending on what you need for your application.

A single FT-240-43 is fine for an 80-10m EFHW but when stacking two or more you have to go with lower permeability otherwise the transformer will have too much inductance. A single 52 mix will not work down to 80m with the typical windings but three of them stacked will work better 80-10 with less loss than using 43 mix.

If you have time and parts and build a pair of three stack out of 43 mix and a pair of three stack 52 mix then put them back to back and measure loss 80-10m on a network analyzer you might be shocked how bad the 43 mix is.

 

[AC9KH]

An 80-10m EFHW will resonate around 3.58MHz on 80 and will have high SWR in the 3.8-4.0MHz phone band.

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.

 

[prcguy]

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.

I own and operate several MyAntennas 40 and 80m EFHWs and have built dozens for others and there is no need for a tuner on any band they cover. The 40m version has a great match on 40, 20, 15 and 10 but the 80m version also has a very useable match on a few WARC bands. I run a 1.2kW amp with no tuner. The radiation pattern is the same as a center fed dipole of the same length as in the old favorite 135ft doublet fed with ladder line and yes on higher bands there are a lot of gain lobes and nulls, but the antenna is doing what its supposed to do. Placing a capacitor in the middle of the 80m version to resonate on 75m does not make it low Q or reduce its efficiency at all, it just shifts the resonant frequency up and it has the same BW on 75m as it did on lower 80m. Maybe you should have a chat with Danny at MyAntennas to set you straight on some facts.

 

[Crowling]

I’m gonna try to get the package out tomorrow. Here’s 2 sweeps of my single core 49:1 from Ultramax. I.do not know what mix the core is. It’s swr is pretty good from 80-10. People I know that own My Antenna j1k and 3k models have 80 meter high swr. MA makes a kit for them to improve 75-80 meter swr’s. 1st one on left is measured at the radio end of 100 feet of 8u flex. Right is coax going through all of my equipment.

As seen in the photos the swr on the allocated “ham bands” have mostly less than 2:1 swr’s. Again it’s a single core 49:1. I’m terrible at judging heights and will guess the antenna is 40-50 feet at it’s highest.

 

[AC9KH]

Placing a capacitor in the middle of the 80m version to resonate on 75m does not make it low Q or reduce its efficiency at all

Actually, it does. Antenna Q is given by Q=fc/(f2-f1) where fc is the center frequency and (f2-f1) is the bandwidth over which the antenna maintains <1.5:1 SWR. High-Q antennas have a very narrow range where input impedance does not change, they tune very sharp, have lowest radiation resistance and highest efficiency. Low-Q antennas are broad-banded, have higher radiation resistance and lower efficiency. A dummy load is an example of a broad-banded, low-efficiency, low-Q antenna that converts most of the energy fed to it to heat (although a dummy load does radiate). If Danny disagrees with that I could set him straight on some facts.

 

[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.

Mr. Olson. I’m going to try to get to the usps before they close today. In the box is a brand new

 

[AC9KH]

As seen in the photos the swr on the allocated “ham bands” have mostly less than 2:1 swr’s. Again it’s a single core 49:1. I’m terrible at judging heights and will guess the antenna is 40-50 feet at it’s highest.

Which I'd say is pretty normal for an end-fed wire with a step transformer at the feedpoint. Unless you purposely design the antenna system to be low-Q, expect to use a tuner with it.

 

[prcguy]

As seen in the photos the swr on the allocated “ham bands” have mostly less than 2:1 swr’s. Again it’s a single core 49:1. I’m terrible at judging heights and will guess the antenna is 40-50 feet at it’s highest.

View attachment 184077

Actually, it does. Antenna Q is given by Q=fc/(f2-f1) where fc is the center frequency and (f2-f1) is the bandwidth over which the antenna maintains <1.5:1 SWR. High-Q antennas have a very narrow range where input impedance does not change, they tune very sharp, have lowest radiation resistance and highest efficiency. Low-Q antennas are broad-banded, have higher radiation resistance and lower efficiency. A dummy load is an example of a broad-banded, low-efficiency, low-Q antenna that converts most of the energy fed to it to heat (although a dummy load does radiate). If Danny disagrees with that I could set him straight on some facts.

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.

 

[Crowling]

Mr. Olson. I’m going to try to get to the usps before they close today. In the box is a brand new

A brand new Carlon 4x4x4 pvc box. Also (4) each 240/43 cores. Also an SO-239 with a 100pf @20KV capacitor soldered to the center pin. That way the cap won’t get lost inside the box.

Which I'd say is pretty normal for an end-fed wire with a step transformer at the feedpoint. Unless you purposely design the antenna system to be low-Q, expect to use a tuner with it.

I’m on my way to the usps after this email. I put o note with all my personal info including my phone number INSIDE the pvc box. All 4 cores and so-239, with the 20kv cap soldered to so-239 are inside the box as well. The radios built in tuner is all that’s necessary for my Unun. I have a mfj-989 3KW/ roller inductor but seldom use it.

 

[AC9KH]

A brand new Carlon 4x4x4 pvc box. Also (4) each 240/43 cores. Also an SO-239 with a 100pf @20KV capacitor soldered to the center pin. That way the cap won’t get lost inside the box.

I’m on my way to the usps after this email. I put o note with all my personal info including my phone number INSIDE the pvc box. All 4 cores and so-239, with the 20kv cap soldered to so-239 are inside the box as well. The radios built in tuner is all that’s necessary for my Unun. I have a mfj-989 3KW/ roller inductor but seldom use it.

I'll be looking forward to getting it in the mail. I'll for sure have questions about what your antenna orientation is, what type of ground system you have, etc.. It'll be much easier to talk about that stuff on the phone than via an internet forum.

 

[Crowling]

I'll be looking forward to getting it in the mail. I'll for sure have questions about what your antenna orientation is, what type of ground system you have, etc.. It'll be much easier to talk about that stuff on the phone than via an internet forum.

I looked again at qrz but I don’t see any email for you. This is my only way to communicate with you. Anyway here’s a picture of the tracking number.

 

[Crowling]

I looked again at qrz but I don’t see any email for you. This is my only way to communicate with you. Anyway here’s a picture of the tracking number.

I would have shipped earlier but other things happened lol. I got a new “used” motherboard for my PC. The box had BIG FRAGILE stickers on it. The usps employee literally THREW THE BOX onto my porch and landed with a loud THUD!!! Miraculously it didn’t crss as kv or break the PCB!! So for $17.00 I now have a pc that the audio inputs and outputs work. I can enjoy mmsstv again, along with playing music etc. USPS lady said the package should arrive Wednesday.

 

[AC9KH]

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.

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.

 

[AC9KH]

I looked again at qrz but I don’t see any email for you. This is my only way to communicate with you. Anyway here’s a picture of the tracking number.

I don't put my email on the zed to keep the spammers at bay. I'll it to you via private msg here.