THE UGLY BALUN choke

[northern35s]

My take on the CB no radial EFHW is that they work because the feedline isn't choked, however if the choke were to installed in such an installation then the mast supporting the antenna would carry the common mode current, isolate the antenna from the mast, choke the feedline and then you'll probably see the antenna's performance drop off, add the ground plane kit and you'll probably see it's performance return. In effect, not choking the coax on a no radial EFHW puts the antenna at the short end of an off centre fed dipole

As I said previously, these type of antennas (EFHW) rely on common mode current in order to perform as well as they do, most people using them don't realise this and probably wouldn't care if it did. An often reported fault of the fibreglass radome antenna is the high levels of static noise that some people suffer, my question is this; is it the fibreglass antenna, or the lack of a current choke that's causing the problem? If fibreglass was such a noisy material then the SteppIR antenna, one of the most popular multiband HF antennas, just wouldn't sell in the numbers they do, the amateur forums would be awash with reports of noise problems.

 

[Marconi]

There's no need for a choke on a Sirio Gainmaster because Sirio built one into the design.
What is it about a Super Penetrator and a V4K that negates the need for a choke?

I agree 35, what is it.............?

Several times in my experience I've found a structural problem with some of my antennas that were really acting bad. I've talked about it too, but I doubt seriously anybody ever gave this idea a second thought, because I've never heard anyone else chime in with a similar experience or a question about the idea.

Most suggest that folks...just have their mic turned up too high. I remember I use to say that too...until I found out it could be other things going on.

Most guys are just lucky if something detectable doesn't happen, and other's are just not aware, period. If something is wrong with how the antenna works, most will likely just bad mouth the antenna, and do something else instead of trying to figure things out, learning nothing in the process and caring less.

Some never consider a possible worst case scenario as a result of installing their antenna badly, while some other's proudly boast of destroying their antenna.

 

[Robb]

Certainly not advocating anything here - even though it may sound like it. Just my own personal experiences and the steam it left behind. So, don't take down your EFHW and burn it just because i don't like them! Keep it and use it if you like it or must use it.

Many of us who have stations - do so from urban areas. I do. When I did run EFHWs, I had complaints from the neighbors (ESPECIALLY with the BigStick - ugh!). Didn't even run an amp either. Ran an old Archer 5/8w in its place and the complaints stopped. Same feedpoint height and location. I must assume the the ground planes of the 5/8w organized a better radiation pattern and focused the energy higher in the near field.

The Imax doesn't seem to have a problem with the neighbors; just CMCs in my own shack - due to proximity to the antenna. On 15m and 17m, the antenna uses more of the coax and there are massive CMCs with same amount of power output being used on 10m or 11m. Needless to say, I don't use it on 15m or 17m often - just because I like keeping peace in the neighborhood.

Local op recently changed from using the Imax to the Sirio GM. Lives in an apartment complex too. No complaints now and he enjoys much better TX/RX from that vertical dipole SGM. Another local op went from using a non-GP 1/2w antenna to the Vector 4000 - and the complaints he once got also vanished. Evidence the antennas with better organized polar pattern are better than the EFHW? Not necessarily; just anecdotal evidence. But I buy into that.

No chokes used on either of those antennas either - of course . . .

 

[Marconi]

Certainly not advocating anything here - even though it may sound like it. Just my own personal experiences and the steam it left behind. So, don't take down your EFHW and burn it just because i don't like them! Keep it and use it if you like it or must use it.

Many of use who have stations do so from urban areas. I do. When I did run EFHWs, I had complaints from the neighbors (ESPECIALLY with the BigStick - ugh!). Didn't even run an amp either. Ran an old Archer 5/8w in its place and the complaints stopped. Same feed point height and location. I must assume the the ground planes of the 5/8w organized a better radiation pattern and focused the energy higher in the near field.

Local op moved from using the Imax to the Sirio GM. Lives in an apartment complex too. No complaints now and he enjoys much better TX/RX from that vertical dipole SGM. Another local op went from a non-GP antenna to the Vector 4000 and the complaints he got also vanished. Evidence the a better organized polar pattern is better than the EFHW? Not necessarily; just anecdotal evidence.

Robb, what if your Big Stick was a SP two piece model, and you found out it was really a center fed sleeved dipole and not an EFHW?

Would that make any difference in your thinking or the concerns you had?

Center fed dipoles are supposed to be very mellow acting antennas, and you typically hear few complaints of this sort. I had a Super Big Stick that worked fine if I got it up about 35'-45' feet.

I believe you are correct however, the A-99, and the Imax need something that provides conductive material for the return currents...every antenna does. The issue here is what is providing that need. The Big Stick probably uses coax shield material inside the fiberglass bottom of the antenna, and that provides the path for return currents. There may well be a small capacitor inside there also.

IMO, the A99 effectively does not need radials to work, and I think there is enough evidence out there to support that conclusion. The traditional 5/8 wave antennas mentioned are more in need of a physically large current return path to work. This is in part because the bottom portion of those radiators can possibly show 100% more current flowing at the base than at the base of the A99. They also typically use a differnt matching system compared to the A99/Imax.

My Eznec models of the A99 vs the Imax tends to show there are more of an effect on the pattern when adding radials to the Imax than there are when adding radials to the A99.

I've claimed for sometime, if we don't have much current flowing near where the radials are mounted, how much current will you have that can flow on the radials.

I've had A99's that showed obvious CMC's before, and I've had several that did not. One was really bad, and I opened it up and fixed the solder problem I found. It work fine after the fix, even though it was now just a wire angenna fairly close to the ground, and not very useful for my purposes. Without the fiberglass support I could not get it up as high.

My good acting A99's also seemed a lot quieter as I recall.

So Robb, are you sure this problem is associated with EFHW's or could it possibly be some badly constructed A99's or Big Stick out there.

A time or two when I had my I-10K up over the years, it acted bad too, but most installs I made with that bugger...it worked fine. One time a radial came loose an slid inside the other element making that radial very short. That I-10k was really acting bad when that happened.

We're just talking here, and this is why I'm on this forum...to talk about my antenna experiences hoping it might be of some help to someone with a similar experience, or that I can learn something new.

Even though I have Eznec models that I think support my thinking, I don't know enough to really prove anything here otherwise. I could show my models, but I don't believe most understand sick'em from come'er about the models I post, and for sure when the issue is complicated by currents flowing, such efforts are typically in vain.

 

[Robb]

I've claimed for sometime, if we don't have much current flowing near where the radials are mounted, how much current will you have that can flow on the radials.

I agree; because this is obvious enough.

Whether or not these EFHWs were defective or not; I don't think so. There is plenty of anecdotal info that the the BigStick is a BigNoiseStick - for one. Dunno if it because the radiation angle is parallel or straight to ground; but suspect as much. Don't think that a rf choke would help this problem either - if I'm right about the radiation pattern. No wonder yours worked best when elevated up to 45 ft.

Other than that, I will stay tuned to this thread and be learning what I can gather - too . . .

 

[northern35s]

Marconi, if I'm understanding you correctly, you believe the EFHW A99 doesn't necessarily require radials because of the low current at its base? How does that then fit with Kirchoff's current law, the base of the antenna may be a low current node, but what of the mid point of the radiating element?

At any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node.

If we consider a fire engine hose pipe and the flow of water from it, the only way water can flow is if there is water entering the pump, let us consider our PA section as the pump, the feedline must carry equal and opposite current, just like the water pump must have an equal amount of water entering as it does exiting, the pump merely adds the pressure, just like our PA

This current within our feedline has to come from somewhere, with the no radial 1/2WL it is either the coax or the mast, or a combination of them.

 

[Marconi]

Marconi, if I'm understanding you correctly, you believe the EFHW A99 doesn't necessarily require radials because of the low current at its base? How does that then fit with Kirchoff's current law, the base of the antenna may be a low current node, but what of the mid point of the radiating element?

At any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node.

If we consider a fire engine hose pipe and the flow of water from it, the only way water can flow is if there is water entering the pump, let us consider our PA section as the pump, the feedline must carry equal and opposite current, just like the water pump must have an equal amount of water entering as it does exiting, the pump merely adds the pressure, just like our PA

This current within our feedline has to come from somewhere, with the no radial 1/2WL it is either the coax or the mast, or a combination of them.

Good point 35. I agree that this setup is not likely to show good balance at the feed point.

I can't imagine how all this electric stuff works in the matching area either. So, I can only assume it's doing what it does and following the laws of Kirchoff and others in order to work. I'm not saying it doesn't follow the laws of electronics, I'm just wondering how radials can be effective working to return currents in an area near the open end of a radiator, a current node.

Then again, maybe it is as Steve Yates - AA5TB found when he reported in his article, that the EFHW only requires .05/WL of wire to provide this necessary return path: AA5TB - The End Fed Half Wave Antenna.

In his tests he says he did it both ways and it didn't seem to make any difference. In my tests of the A99 with radials or not, I found simlar results using my analyzer right at the feed point, little to no difference noted. If you try this same test on a 1/4 wave, you'll see a considerable difference in the match, so much it is unbelievable, even though CBr's report trying it and saying it works fine.

I can't argue with Kirchoff's current law, I don't understand circuits that well, if at all. It seems to make sense to me, if the radiator of an EFHW (A99) works as a 1/2 wave radiator then both ends should show very low current flow at both current nodes. Currents may not be zero maybe, but it should be very low. I can only guess, but this is why I think we find a rather large capacitor in this area of the circuit.

I think one thing is for sure is going on however, if the bottom end of the wire somewhere near the bottom of the A99 is not a current node with very low current flowing, then whatever is above this point as the radiator will not be a resonant 1/2 wavelength long.

I've heard it argued that feeding a 1/2 length wire at the end will not work, so I figure even the experts on these matters can't agree on that far more important issue than radials.

In the article above Yates tells us that the EFHW only requires a returns current path that is about .05 of a wavelength long in order to fulfill that need by such an antenna. I consider that maybe that pigtail coax inside the A99 from the coil to the SO239 may do all that is required to provide this return current path.

I was thinking about this one day and had a thought...what if I used my analyzer and a short length (14') of coax to my A99, and I recorded the results. Then I put the analyzer right at the feed point and did the same. Would I see any difference? I thought if it is true that the feed line serves as the ground return path for the A99, them maybe such a comparison test would indicate some difference.

35, I saw very little difference, but this was way before I knew about Yates' ideas, and I didn't make any notes about the test, or I can't find them.

Maybe I should try that again. I don't know what this says, but my thinking is...if the A99 really needs the/a feed line to work right, then removing the feed line might somehow prevent it from working right and it would show up in such a test. Then again maybe it won't show up, because of the difference in the way capacitors, AC, and DC works.

I wish I knew enough to give a good argument, but my referring to this report from Yates or some law of electricity does not seem like it is enough either.

 

[northern35s]

I've just asked locally if anyone has an A99 I can run some tests on, I intend attaching my VNA at the base of the antenna, the antenna won't be attached to any mast so there will only be the antenna and VNA in the circuit, I'll take some screen grabs and report back, however that'll be later this week.

I've seen the AA5TB article before, he even links to this article by W8JI:

End fed vertical

He makes this comment:

Can we end-feed a halfwave antenna, or end-feed any antenna, without a ground or counterpoise?

The answer depends on what we want to call a "ground". This simple rule applies to all end-fed antennas, and this rule cannot be broken. The rule is:

Current flowing into the antenna's end must be equaled, at that end point, by the same amount of current flowing into a ground or counterpoise of some type.

I've highlighted a very important point, which is founded on Kirchoff's current law.

It's important to remember the word 'law' it's not Kirchoff's good idea, or Kirchoff's suggestion, it is a fundamental law.

 

[Marconi]

35, I hope you can get hold of an A99, and check the idea out. It would be interesting to see if my results could be duplicated.

I still don't understand well enough what the link is saying. You're lucky to be as well informed to understand all that suff. I have to go mostly by the seat of my pants ideas.

 

[northern35s]

I wouldnt go as far as to say I understand it all, just trying to make sense of it all like everyone else This site is a great place for discussion, some clever people on here sharing their ideas and experience.

Edit: picking up an A99 on Thursday,;I'll carry out as many tests as I can think of, I wont be testing it at height though as I've sold my 12m mast and the 18m replacement isn't installed yet.

 

[Marconi]

I wouldnt go as far as to say I understand it all, just trying to make sense of it all like everyone else This site is a great place for discussion, some clever people on here sharing their ideas and experience.

Edit: picking up an A99 on Thursday,;I'll carry out as many tests as I can think of, I wont be testing it at height though as I've sold my 12m mast and the 18m replacement isn't installed yet.

I understand 35.

Except for the effects on the feed point impedance maybe changing due to a little variation in height, comparatively I can't see the end results changing much either.

Back then I was thinking, if the A99 appreciably needs the feed line, it might be effecting the match in a positive way by being attached. If so, and the feed line was not included, would that then ill-effect the match?

I was really even expecting to see a big difference in the match, because I believed all the stories I was hearing...that the A99 used the feed line for its radials/counterpoise.

I haven't tried this with the A99, but you may even be able to test this idea with the A99 lying on two wooden or plastic saw horses. The tune may change a little, but it shouldn't go to heck in a hand basket as compared to it being vertical.

Does my thinking here even make sense to you 35?

Do you believe removing the feed line from an A99 might show a corrupted match or a noticeable difference in the match...if the FL is missing from the mix while using an analyzer?

 

[northern35s]

Hi Marconi, now here's the thing, an antenna will find a ground/counterpoise even if it has to make that up via stray capacitance to anything surrounding it.

As I've said before my main interest in the hobby is amateur radio rather than CB radio, and in my line of work I get the opportunity to work abroad for extended periods of time, when I do this I take my FT817 with me and a multitude of home brew and small commercial antennas, one of which is the miracle whip antenna, this is a 57" antenna with an impedance matching device at it's base, the manufacturer describes this as a no counterpoise antenna, but it is an end fed antenna, if we are to accept Kirchoff's current law, then this statement can't be true, however there are many people that use this tiny antenna from 40m and up with mixed success, in fact when I was on the Island of Crete I made around 400 contacts using one, with many into the US, East, Mid West and West Coast, with as little as 500mW.
The thing is, this antenna does require a counterpoise and will use the person holding it, the case of the radio, and the dirt the rig is resting on to form that counterpoise, I did two things with my rig whilst in Crete, add a counterpoise and sit the rig on the roof of my car, that why I managed to work the US with 500mW (SSB) and had I not done this then I wouldn't have been so lucky, I tried it without, it was poor!

What does this have to do with the A99, it means I have to be very careful how I site the antenna if I want to get some reasonable measurements, one way I'll overcome this is that my VNA has a bluetooth facility, that means I don't have to be anywhere near it, and the antenna can be far removed from anything conductive in order to carry out the tests. I'll attach the VNA direct to the antenna socket and take it from there, I'll also add a 0.05WL counterpoise and see what happens to the readings, I'll also add different lengths of coax between the antenna and VNA to see what changes take place, I'll also add a good current choke to the feedline and see what happens there, and ultimately I'll attach the antenna to my 7' trailer hitch mount on my car and work a bit of 10m DX, well it would be rude not too

ps. I plan to post what I think will happen and then carry out my tests, I'll follow this up with my findings, I hope they match, but if they don't I'll still be happy because I'll have learnt something. For what it's worth I believe the antenna will prove to have ground losses without a coax.

 

[Marconi]

35, I've heard plenty of stories that indicated using a 102" whip without any ground plane, just a support, and it was said to work fine.

There were no matching devices noted to be on these 102" antennas either, but these guys swear it works fine and that it was using the mast.

Here are four models of a simple 1/2 and 1/4 wave radiator with a mast, and with and without radials. I don't know if/how these jive with Kirchoff's laws, but this is what I base my idea concerning the 1/2 wave radiator needing radials or not, end fed or not.

I do see the radials on the 1/2 wave helping to decouple the mast however, but it doesn't look to make enough difference to really matter, as long as we can get the antenna to match for the radio. According to these models, it looks like the A99 should work fine without radials.

View attachment 35's discussion.pdf

Good luck with your testing and be sure to keep some good records that I can hopefully copy.

 

[Robb]

Since it is an experiment to see the coax being affected; then you should probably use a 10 ft fiberglass section at the top of your mast - so that the antenna will use the coax and not the mast as a ground plane.

Would you agree?

 

[Marconi]

35, I've heard plenty of stories that indicated using a 102" whip without any ground plane, just a support, and it was said to work fine. There were no matching device noted to be on those antennas either, but these guys swear they work fine and the antenna was using the mast as the radials/counteroise.

Here are four models of a simple 1/4 and 1/2 wave radiator, with and without radials. I don't know how this jives with Kirchoff's laws, but this is what I base my idea concerning the 1/2 wave radiator needing radials or not, end fed or not.

I added some notes.

View attachment 10251