The 5/8 and .64 debate!

[Marconi]

I understand your point DB, and I believe your model is probably correct. I too am disappointed but not surprised to learn the fact that if we could just add matching to models correctly...probably made just as small difference in real world results too.

Again, this information confirms for me what my old antenna mentor use to tell me about trying and working hard to get my SWR on a 1/2 wave dipole down to 1.01:1...we don't likely gain a thing except the bragging rights in doing so.

For years I've heard CBr's and others claim how bad the matching device is on the A99 (about like a dummy load they say) and how undesirable it is to have to work a fiberglass antenna...even while maybe 8 in 10 contacts made in CB probably are made using at least one side of the contact using such a design.

If you had used the 5/8 wave antenna models to demonstrate the differences in matched and no match models...we probably would have seen even less of a difference in gain since the natural match is much less of a problem to transform to 50 ohms at the feed point for a 5/8 wave vs. an EFHW.

You are correct DB and the proof is in the pudding, so-to-speak. I agree there just isn't much more to talk about concerning modeling.

Thanks again for bringing this all to light.

 

[Marconi]

Eddie, you are completely missing the point of why I add matching networks to my models. You see it as an ends, and see a minor change in my demo models and quickly jump to calling it irrelevant, or nearly so.

DB below is your quote regarding your own observations on adding the matching device to an EFHW model. I did not say your model is in error, I'm just agreeing with you. Here is what you said below.

As you can see, the plots are the same, except one is attenuated slightly.

DB again, above is you direct quote. Why you added the matching is not the point, I agree that the difference matching makes to your model's results are slight, just like you claim. I just added my long felt comments as to why I expected the difference to be slight. My point is that just adding matching to a model changes the results very little, but I could not prove it.

You did prove it for me, so thanks again.

 

[Needle Bender]

Thanks guys, that was awesome effort!
I bet a combined graph of a 1/2λ, 5/8λ & .64λ - all at both 36' & 54' would be very revealing.
Notice how at 58.5' both the 5/8 & .64 fill in the null around 45° left by them at 72'.

And to get away from matching networks, what about direct feeding the 5/8 with a 1/4 wave of RG62 (84% VF) (and with the shield connected to the 1/4 wave radials) for lower power applications?

 

[The DB]

what about direct feeding the 5/8 with a 1/4 wave of RG62 (84% VF) (and with the shield connected to the 1/4 wave radials) for lower power applications?

93 ohm coax? Interesting, don't see that referred to every day... An electrical 1/4 wavelength section of that would transform a 50 ohm coax input to near 173 ohm resonant output. Such a setup will not correct for any reactance present in a 5/8 or .64 wavelength antenna, nor is it high enough to match to the high impedance of a half wavelength end fed antenna...


The DB

 

[The DB]

DB below is your quote regarding your own observations on adding the matching device to an EFHW model. I did not say your model is in error, I'm just agreeing with you. Here is what you said below...

So what you are saying here is one example of one particular type of matching network for one antenna that uses fairly good quality (essentially ideal) components and doesn't have much of an effect, so obviously no form of matching that this modeling software can produce will have a noticeable effect in any possible circumstance?

That is quite a jump... And it isn't the first time you have made such a jump with something I was referring to that you clearly know nothing about. Actually, it isn't the second time either...

Here, read this again...

Eddie, you are completely missing the point of why I add matching networks to my models. You see it as an ends, and see a minor change in my demo models and quickly jump to calling it irrelevant, or nearly so. I, on the other hand, see it as a means to an end that I am working towards.

Another important part of the same message right here...

To me it is a step in the process of further improving my modeling technique.

And pay special care to what was stated here.

We are obviously at a point of disagreement. Due to our past on such discussions, I have no interest in discussing this with you further.

At this point I will let you believe whatever you want to believe as I really don't care. Good day sir.


The DB

 

[Needle Bender]

Years ago I made a 5/8 from bare 12ga copper wire & a 105" radial, saw 176Ω direct feeding it w 24' of 213.
I've always presumed a typical unmatched 5/8 w/counterpoise was about 150Ω-200Ω.
Time for more research

 

[Needle Bender]

I just found this on another forum:

"The following quote is from the A.R.R.L.'s Antenna Compendium Volume 1, page 105

"The input impedance of a 5/8-wave whip above a ground plane 1/2 wavelength or more in diameter has a resistive component close to 50 ohms, and a capacitive reactance that depends considerably on the whip diameter, typically in the range of 50 to 150 ohms." "
The problem I see with just direct-driving a 5/8 with 93ohm coax is a lack of DC ground shunt. I imagine one could be incorporated.

 

[vkrules]

Here is a coax match for you with a shorted stub.

 

[The DB]

The problem with direct feeding a 5/8 wavelength antenna with a set of 1/4 wavelength radials is you will have reactance present, just like that ARRL article you quoted said.

That being said, you can shorten the radials and find the resonant point. At that point, if memory serves, you should have an R that is close enough to your 93 ohm coax transformer output idea you posted above to be very useable...

I'll have to model it to be sure, but not right now, its been a long day...


The DB

 

[Marconi]

Thanks guys, that was awesome effort!
I bet a combined graph of a 1/2λ, 5/8λ & .64λ - all at both 36' & 54' would be very revealing.
Notice how at 58.5' both the 5/8 & .64 fill in the null around 45° left by them at 72'.

And to get away from matching networks, what about direct feeding the 5/8 with a 1/4 wave of RG62 (84% VF) (and with the shield connected to the 1/4 wave radials) for lower power applications?

NB, in my real world experiences I don't think I see much difference in real world performance between the use of an EFHW compared to a 5/8 wave. You may see some difference on your radio's meter in some situations, but generally speaking I don't think you will see a difference...where the EFHW fails to communicate and the 5/8 wave starts to excel.

In my last Signal Report dated 12/03/10 - 05/14/11, noted below, you will see less than 1 Sunit difference on the average signal report over several months of reporting for a group of antennas I tested and compared.

I just found this on another forum:

"The following quote is from the A.R.R.L.'s Antenna Compendium Volume 1, page 105

"The input impedance of a 5/8-wave whip above a ground plane 1/2 wavelength or more in diameter has a resistive component close to 50 ohms, and a capacitive reactance that depends considerably on the whip diameter, typically in the range of 50 to 150 ohms." "
The problem I see with just direct-driving a 5/8 with 93ohm coax is a lack of DC ground shunt. I imagine one could be incorporated.

NB, I encourage and commend folks to develop their own ideas and to experiment. Many of such articles as you note above...show folks doing just that. However, if you read the 4 pages of the article before page 105, and then read the heading "Where the 5/8-Wavelength Pays Off" near the top of page #105, you will note the following conclusion thus far in the article,

It seems that up to this point, except for its use as a broadcast antenna, the 5/8-wave monopole has little to offer.

This is in spite of the fact that the chart Fig. 2, shows a 5/8 wave is 3 db over a 1/4 wave, but this chart is over perfect ground too and that fact should not be ignored. Only when I started to model these antennas was I sure all these CB Monopole antennas were about the same and except for within reason...raising them up higher will we see the advantages we seek in performance.

After all these years I still find all of the CB antennas I own perform pretty much the same. However, when I put my homemade horizontal 4 element yagi beam up in the air...I see notable differences.

Your mileage may vary.

 

[Needle Bender]

NB, in my real world experiences I don't think I see much difference in real world performance between the use of an EFHW compared to a 5/8 wave. You may see some difference on your radio's meter in some situations, but generally speaking I don't think you will see a difference...where the EFHW fails to communicate and the 5/8 wave starts to excel.

In my last Signal Report dated 12/03/10 - 05/14/11, noted below, you will see less than 1 Sunit difference on the average signal report over several months of reporting for a group of antennas I tested and compared.



NB, I encourage and commend folks to develop their own ideas and to experiment. Many of such articles as you note above...show folks doing just that. However, if you read the 4 pages of the article before page 105, and then read the heading "Where the 5/8-Wavelength Pays Off" near the top of page #105, you will note the following conclusion thus far in the article,

This is in spite of the fact that the chart Fig. 2, shows a 5/8 wave is 3 db over a 1/4 wave, but this chart is over perfect ground too and that fact should not be ignored. Only when I started to model these antennas was I sure all these CB Monopole antennas were about the same and except for within reason...raising them up higher will we see the advantages we seek in performance.

After all these years I still find all of the CB antennas I own perform pretty much the same. However, when I put my homemade horizontal 4 element yagi beam up in the air...I see notable differences.

Your mileage may vary.

Now try a Quad!
I've run numerous beams over the years, many were Yagis but only when I tried a Quad did I find incredible performance, especially on receive.

But, I'm not certain of anything anymore.

Where I lived before my move, two weeks ago, I lived for over 30 years and quite possibly due to the lay of the land, (being a 210' ridge in most all directions from there) I may have had skewed test results due mostly to the extra height of the 5/8s & .64s which I used compared to the 1/2 waves and AP I tested, all of which fell quite short of the performance of the .625s & .64s, possibly because the tops of the 5/8s & .64s just made it over the ridges from my 160' elev.

Earlier today I tested a Penetrator500 against an Imax and the Imax won every comparison... Low area + low installation? Who knows.

I'm gonna try Shock's favorite, the Vector, and hope for a couple more dB over everything.

And Marconi, I doubt you were able to give the GainMaster what it requires, (in my experimentation anyway) that being real height and NOTHING around it for 50'-100'. I saw mine come alive once I got EVERYTHING out of it's near field. - Again, that was at the old QTH.

I'd like to see you test it again, but at least 50'+ above the ground and well away from all other antennas. I received more S9+10 & S9+20 overs from Europe on the GM with only 100w from the FT-990 than any other vertical I've had up, even with more power.

 

[Needle Bender]

The problem with direct feeding a 5/8 wavelength antenna with a set of 1/4 wavelength radials is you will have reactance present, just like that ARRL article you quoted said.

That being said, you can shorten the radials and find the resonant point. At that point, if memory serves, you should have an R that is close enough to your 93 ohm coax transformer output idea you posted above to be very useable...

I'll have to model it to be sure, but not right now, its been a long day...


The DB

You know, DB, I wonder if that reactance could be 'shunted out' by adding the correct DC ground shunt?

Perhaps an 1/8 wave matching circuit ain't so bad after all.

 

[Marconi]

NB, my antenna days are over and for sure with beams.

Earlier today I tested a Penetrator500 against an Imax and the Imax won every comparison... Low area + low installation? Who knows.

Were you testing local contacts?

Was DX working during your testing?

I'm gonna try Shock's favorite, the Vector, and hope for a couple more dB over everything.

I have a S4. My models of this design shows the New Vector works a little better than my S4 model, and the New Vector Kit comes a few inches shorter by design.

And Marconi, I doubt you were able to give the GainMaster what it requires, (in my experimentation anyway) that being real height and NOTHING around it for 50'-100'. I saw mine come alive once I got EVERYTHING out of it's near field. - Again, that was at the old QTH.

When I first got my GM, I was very anxious to test it, and I mounted it right away. I think it was at 18' feet, and I was also terribly disappointed at its performance at that height. I had the thought right away that the GM needed space to work well. Mine is currently mounted at nearly 50' feet to the mount, but I have a small back yard...so I have obstructions nearby within about a wavelength.

IMO the GM is all around the best antenna I have, however you will notice that it only came in at the middle range of the signal report ratings I posted above, and that was several months of signal reports from a select group of local contacts out to about 30-60 miles at the time.

Good luck and keep us posted.

 

[Needle Bender]

NB, my antenna days are over and for sure with beams.



Were you testing local contacts?

Was DX working during your testing?



I have a S4. My models of this design shows the New Vector works a little better than my S4 model, and the New Vector Kit comes a few inches shorter by design.



When I first got my GM, I was very anxious to test it, and I mounted it right away. I think it was at 18' feet, and I was also terribly disappointed at its performance at that height. I had the thought right away that the GM needed space to work well. Mine is currently mounted at nearly 50' feet to the mount, but I have a small back yard...so I have obstructions nearby within about a wavelength.

IMO the GM is all around the best antenna I have, however you will notice that it only came in at the middle range of the signal report ratings I posted above, and that was several months of signal reports from a select group of local contacts out to about 30-60 miles at the time.

Good luck and keep us posted.

To address your beam questions, I was amazed by the Quad with both local & DX. A three element compared to both Wilson 3 & 4 element 'Moonraker-style' Quagis, and a Hy-Gain Long John tried both vertical & horizontal.

I'm now curious as to the lay of the land in your area. And how about DX contacts on the GM? Though you can't really do a good DX test of several differing antennas, how does it 'feel'? Seem to outperform most others or just hang in there with them - somewhere in the mix?

 

[Marconi]

I haven't used a beam in several years.

The GM works DX well, but conditions are spotty now. Local contacts are almost non-existent, and have been since DX started up last.

Land is flat in my area and I'm about 75' feet above sea level in my area of Houston and Houston shows an average near 50' feet, so I'm sitting high in the forest.

I use a barefoot Gaxaxy DX 2547 on ssb, and at times I have little to no problems making contacts.