-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
5/8wave vs .64wave
- Thread starter bob85
- Start date
"In a few years it will not have mattered what you babble about today"op:
LMAO,
I am going to use that next time some of my rag chew guys on 75 meters start running their lips.
Thanks Mack
I see in all the years since Bob asked this question, that nobody has yet provided a link to anything that tries to explain the advantages of a .64 wave antenna. My simple Eznec5 models for these two design lengths don't show that the .64 has any advantage, except when mounted on or near the ground. So, I still think the Japanese RF engineers, back before WWII, were just trying to discredit the American made study that reported that .625 wavelength showed to be the longest length radiator suitable for ground mounted vertical antennas used for local commercial radio of the times. So, maybe this is why we can't find the proof that Bob requested, because the .64 wavelength idea has been totally discounted by the broadcast industry.
I've said it before and I say it again, IMO the Wolf .64 wave is not a typical .64 wave ground plane. If it works as designed, it is a vertical collinear that may just happen to physically be about .64 wave in overall length.
If I could figure out how to model the phasing inductor at the top of the first 1/4 wavelength, I might be able to support my claim that the Wolf probably is a true collinear and works as such. The phasing coil idea is pretty simple, but I can't quite figure it out with the Eznec5 software.
I've said it before and I say it again, IMO the Wolf .64 wave is not a typical .64 wave ground plane. If it works as designed, it is a vertical collinear that may just happen to physically be about .64 wave in overall length.
If I could figure out how to model the phasing inductor at the top of the first 1/4 wavelength, I might be able to support my claim that the Wolf probably is a true collinear and works as such. The phasing coil idea is pretty simple, but I can't quite figure it out with the Eznec5 software.
Marconi, ctstallion modeled them on eznec and got a better performance graph from the 64 then the 5/8 at both 10 degrees and 27 degrees. There wasn't much difference at 10 degrees but at 27 degrees it showed more db improvement on the 64 over the 5/8 (and 5 degrees lower) than the sigma4 and vector have over the 5/8. I don't know when that 27 degree gain would come into play but half a db is half a db and the sigma4 -vector is only about 1/3db better than the 64 at 10 degrees. I don't see why the 64 should not always be considered better than the 5/8 unless EZNEC is wrong for him but right for you, plus I found a website that said the 64 is a closer length to a 50 ohm 3/4 wave so it has a lower impedence than a 5/8 making the matching network supposedly a little more efficient. I wonder why your models don't agree with the ones ctstallion did?
Last edited:
NB, I noted above that my models showed the .64 was a slight bit better when the antennas were placed on or near the Earth, so we need to know how CtStallion set his models. I never saw any modeling details, but for his simulated version of a Starduster which was done in Eznec's Demo version. The Demo version is very limiting in its scope. Regrettably I did not save his file, so I can't go back now and try and figure out why or what the differences might be that account for our results being so different...except to say my current models are done in the feature rich environment of Eznec5. I may have this file in all its details printed out on paper somewhere, and if I find it I may try and decipher what could have caused such differences, when compared to my model of the Starduster. Off the top of my head, I would think this issue may have to do with Segmentation settings for his models.
Regarding your last statement above. I think technically you may be right, the closer the antenna is to the perfect match the less loss and the easier the matching would likely be. However, in my modeling experience I don't typically see big differences in results due to mismatches when such mismatches are within the range of difference we might see among the CB antennas we are discussing here. I have not tested this idea out to the limits of any real world mismatch that I might have experienced, but within reason I find very little ill-affects in performance due to mismatch...assuming the construction is properly done.
B
BOOTY MONSTER
Guest
ok . either i have some really good chit or i'm miss-understanding the pics .
i see the .64 having a higher angle and stronger top lobe , a lower but similar strength middle lobe , with the 5/8 having a slightly stronger and lower bottom lobe .
the sigma looks to have a bottom lobe @ 10 that's definitely stronger , middle lobes just a hair behind but a little lower angle and slightly sharper top lobes .
put those 3 antenna in 3 different installs and either one could be the best for each one . i'm very happy with my sigma wanna-be so far .
but we all usually recommend what we have
i see the .64 having a higher angle and stronger top lobe , a lower but similar strength middle lobe , with the 5/8 having a slightly stronger and lower bottom lobe .
the sigma looks to have a bottom lobe @ 10 that's definitely stronger , middle lobes just a hair behind but a little lower angle and slightly sharper top lobes .
put those 3 antenna in 3 different installs and either one could be the best for each one . i'm very happy with my sigma wanna-be so far .
but we all usually recommend what we have
Attachments
Marcomi, this is where the models are http://www.worldwidedx.com/cb-anten...ur-favorite-citizens-band-radio-antennas.html
I opened each one in a new tab and it allowed me to click on each and immediately see from one to the others how the model shapes differed. Booty if you read on the right it says what the zero db line is and the 64 is higher then the 5/8by a little more than half a db . the sigma4 -vector is a little better then the 64 at 10 degrees by .37of a db. The 64 shows 3.37 db so it's the highest gain of all but its higher at 27 degrees. Marconi can you repost your modeles?
I opened each one in a new tab and it allowed me to click on each and immediately see from one to the others how the model shapes differed. Booty if you read on the right it says what the zero db line is and the 64 is higher then the 5/8by a little more than half a db . the sigma4 -vector is a little better then the 64 at 10 degrees by .37of a db. The 64 shows 3.37 db so it's the highest gain of all but its higher at 27 degrees. Marconi can you repost your modeles?
NB, my models compared to CTS would be like comparing apples to oranges. I took one of my 1/4 wave models and adjusted it to produce similar results to CTS's 1/4 wave with horizontal radials, using no more than 20 segments, and with 5 wires only. Just as was the case when I began using Eznec Demo, all of my work was full of errors...that were easily noted by the software.
If it were me, I wouldn't use these models for comparisons until the Eznec errors were all corrected...if at all possible. And, I don't think that will happen until CTS buys one of the updated versions of Eznec5. So, I won't be posting my models as you request. I did however reproduce one of my models trying to emulate what CTS did with his 1/4 wave example. It is not the antennas that you are interested in, but as a result maybe you'll be better able to see that I right in what I said in my earlier post to you regarding them being meaningless. For me to repost my models here again, and for them to be meaningful to your inquiry, I would have to modify and tweak each model attempting to emulate the inputs that CTS did with his models.
Maybe these following examples of a 1/4 wave radiator with 4 horizontal radials 20' feet high, with no mast support, or feed line will allow you to visualize what I'm trying to say. The first model is my idea of what CTS did in the first model he presented. The second set is my version of the same model using Eznec5 instead of the Demo version. Take notice of the small green dots which represent the segments for each wire element. Also note the error message in his model. That is not present in my model because my Eznec5 allows for far more segmentation than the Demo version. I believe this is the difference you will see among all of these models that CTS made compared to my models.
View attachment CtStallions models vs. mine.pdf
I have also included the wires display in case you have and can use Eznec5.
Last edited:
I dont know. it looks like your models have a higher swr with too low a take off angle for a 1/4 wave and too much gain on yours, looks more like a 64. the lobes on his look more like a classic 1/4 wave pattern.
Needle bender, thats a wrong assumption.
The stallions model could indeed be improved.
But so where those of marconi and mine when i started.
(to CST) Dont be "irritated" you have already shown your willingness to deal with it..but it takes quite some time to do things rigth.
NB, your interpertation about the gain and lower take-off angle is based on a freespace model in which the gain will be less..however marconi is showing us a "real world" where a small effort from ground gain comes in place and the take-off angle is influenced by earth.
Another thing is as often people refer to SWR as it is often the only thing one can measure..but there is much more going on..
A groundplane can show a perfect 1:1 where at large portion is radiated in the earth. Where a good efficient groundplane can show a much higher SWR but in that case allmost all energy is actually radiated into the sky where it should be.
Ill give a examle:
The efficiency of a antenna is:
The antenna impedance/total impedance x100 procent.
The antenna impedance (in this case a 1/4 wave vertical) is 36 ohms:
Say we have a earth ground system of 14 ohms:
36/36+14x100 = 72 procent efficiency
BUT THE SWR WILL BE 1:1 as we have 36+14 ohms = 50 and matched to 50 ohms will show 1:1
Say we have the same vertical but now a efficient groundsystem in the order of 3 ohms.
36/36+3x100 = 93 procent efficiency!! but the SWR will be 50/39 is about 1.3
Oke, so what we have found out that a bad groundplane antenna can show a good SWR but will radiate poor.
We need to see 36ohm for the radiating element en preferbly a 0 ohm resistance in the groundsystem. In that case we have a high swr but a efficient system.
This is also the reason people claim high impedance antennas dont need radials.
Example: halve wave vertical (i take 1000 ohms as impedance could be a coulpe hunderd off though).
1000/1000+50= 95 procent. In this case i used 50 ohms for the groundsystem which is quite poor.
So, for the full quater wave vertical users...dont tune for 1:1 swr tune for that 36 ohms and more power will be transmitted in the air. (add to the groundsystem in order to lower that impedance).
As a perfect groundplane will show a SWR of about 1.3..1.4
Oke, so yes we have "reflected" power but thats only about 2..3 procent much less loss than the 1:1 system in which we were broadcasting about 20..30 procent in the earth.
Kind regards,
henry 19sd348
All about antennas
The stallions model could indeed be improved.
But so where those of marconi and mine when i started.
(to CST) Dont be "irritated" you have already shown your willingness to deal with it..but it takes quite some time to do things rigth.
NB, your interpertation about the gain and lower take-off angle is based on a freespace model in which the gain will be less..however marconi is showing us a "real world" where a small effort from ground gain comes in place and the take-off angle is influenced by earth.
Another thing is as often people refer to SWR as it is often the only thing one can measure..but there is much more going on..
A groundplane can show a perfect 1:1 where at large portion is radiated in the earth. Where a good efficient groundplane can show a much higher SWR but in that case allmost all energy is actually radiated into the sky where it should be.
Ill give a examle:
The efficiency of a antenna is:
The antenna impedance/total impedance x100 procent.
The antenna impedance (in this case a 1/4 wave vertical) is 36 ohms:
Say we have a earth ground system of 14 ohms:
36/36+14x100 = 72 procent efficiency
BUT THE SWR WILL BE 1:1 as we have 36+14 ohms = 50 and matched to 50 ohms will show 1:1
Say we have the same vertical but now a efficient groundsystem in the order of 3 ohms.
36/36+3x100 = 93 procent efficiency!! but the SWR will be 50/39 is about 1.3
Oke, so what we have found out that a bad groundplane antenna can show a good SWR but will radiate poor.
We need to see 36ohm for the radiating element en preferbly a 0 ohm resistance in the groundsystem. In that case we have a high swr but a efficient system.
This is also the reason people claim high impedance antennas dont need radials.
Example: halve wave vertical (i take 1000 ohms as impedance could be a coulpe hunderd off though).
1000/1000+50= 95 procent. In this case i used 50 ohms for the groundsystem which is quite poor.
So, for the full quater wave vertical users...dont tune for 1:1 swr tune for that 36 ohms and more power will be transmitted in the air. (add to the groundsystem in order to lower that impedance).
As a perfect groundplane will show a SWR of about 1.3..1.4
Oke, so yes we have "reflected" power but thats only about 2..3 procent much less loss than the 1:1 system in which we were broadcasting about 20..30 procent in the earth.
Kind regards,
henry 19sd348
All about antennas
Yes NB, IMO the big difference in the patterns and results we see here are probably due to the height difference and the segment limitation when using Eznec Demo version. Among other things, I could have lower my model from 32' down to 20' feet above the Earth, made the wires diameter equal those of CtS, and made the segment count and distribution the same, but then the results would look more like his model...just as noted in the model I posted as "CtStallion's Model". This is not what I was trying to demonstrate however.
I should not have interjected my models into this nice presentation that CtS went to a lot of work to produce. I should have stopped after I claimed you can't compare apples to oranges, and leave it at that.
BTW, I want to thank CtStallion for being the only person to ever really help me get started in my modeling efforts, and to help give me the understanding that got me over the hump, so-to-speak. I'm pretty sure a lot of you guys have faced this hump before...trying to get started using this modeling product.
I tend to agree with you Henry, and thanks for your comments. If you have any tips regarding my #4 .25 horizontal radials 108 model that will make it more accurate, then please advise. I appreciate all the constructive help I can get.
BTW, regarding you comment near the bottom of your post talking about tuning a full 1/4 wave vertical to its natural resistive match near 39 ohms. My old antenna mentor, long gone now, always told me that tuning a 1/4 wave ss whip to an SWR of about 1.5:1 was better than seeing a 1.1:1 with the same setup. He was not one to elaborate much, but he would say that making such a setup, however you did it, to show a 1.1:1 SWR was just adding loss to the system. I agree with you Henry, even though I did not fully understand it back then.
Don't forget, I need your tips if any come to mind.
BTW, regarding you comment near the bottom of your post talking about tuning a full 1/4 wave vertical to its natural resistive match near 39 ohms. My old antenna mentor, long gone now, always told me that tuning a 1/4 wave ss whip to an SWR of about 1.5:1 was better than seeing a 1.1:1 with the same setup. He was not one to elaborate much, but he would say that making such a setup, however you did it, to show a 1.1:1 SWR was just adding loss to the system. I agree with you Henry, even though I did not fully understand it back then.
Don't forget, I need your tips if any come to mind.