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To 7/8 or NOT to 7/8, that is the equastion
- Thread starter Needle Bender
- Start date
Not the same mast, location or coax, irrelevant comparison.
A 5/8 is about 3-4dB stronger than a 1/4 wave, and in tests I've conducted, it only takes a dB or so to be heard over someone else, when both stations are:
1) On frequency
2) Similarly modulated
3) Same mode
4) Similar Filter widths
5) ?????? - and any other secret hidden tiny detail no one there could've possibly imagined
I'll take even a partial dB gain over an argument any day. This was put to rest clear back when we were teenagers in the '70s.
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Hi again Eddie,
Well I've been "Horn-swaggled" into building several more .64 for local ops and helping them install & tune, so it's waiting, patiently, for a new hub & gamma from Sirio, unless I decide to fudge it but I fear that would be what was blamed for any loss of signal in comparison to any other antennas against which it would be tested so I think it best to do it right and get a new one. I'll order that Monday if I remember and can find their info, AND if they will sell me just that part.
If not, I'll manufacture one, even cast it with a friend's help who has experience in that.
Too bad some gorilla had to snap off the connector & mounting plate before I got it.
Would you like to recommend lengths & diameters of gamma rods that should function correctly? - I'm open to suggestions, except cutting it down
to a high-performance 1/4 wave
Needle Bender.......no offense but if you are seeing that much gain over a 1/4 wave then you should patent the antenna and make millions because even professional antenna design engineers can't do that simply by changing out the antenna and leaving all else the same. If the signal is in a null and the null moves with a change in antenna design then YES it can make that much difference but that is not really because of gain overall. Gain should always be measured at the horizon and that will make very little difference in gain figures from a quarter wave to a 7/8 wave. As for the 1dB making the difference, it would on FM with the capture effect but not so sure on AM or even SSB unless the signals were barely there on a quiet band. Back in the 70s and early 80s there was a bunch of us all around the province that would get on late at night and try various antennas and comparing omni verticals never did show much difference at all over paths of 75 to 100 miles.
Well I guess that means those plots which show tall, rounded 1/4 wave pattern dying out around 30-35 miles, whereas the much flatter, extended 5/8 pattern continues for up to 75-80 miles must be in error, along with about 97% of those on every radio forum who swapped out their 1/4 wave or even 1/2 wave droopy-drawers for a 5/8 decades ago and were pleasantly surprised at the noticeable improvement, including hearing distant stations that simply were not there before on the other (inferior) antenna.
I am actually rather amazed that anyone would've experienced no improvement in performance when switching from a 1/4 wave to a 5/8, but perhaps the lay of the land/sea is the explanation.
You are confusing radiation patterns with absolute gain. Sure the patterns hug the ground further out but the DIFFERENCE in gain figures is not that much.
On edit: What you are essentially doing is lowering the angle of radiation to better cover the horizon without a big difference in gain. I and many others have always said not to worry about the gain or where the peak is but worry about where the nulls are.
On edit: What you are essentially doing is lowering the angle of radiation to better cover the horizon without a big difference in gain. I and many others have always said not to worry about the gain or where the peak is but worry about where the nulls are.
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LOL
Last time I checked, no antenna produces RF, only radiates the RF which the power amplifier provides it, and in a pattern and/ or at an angle which provides "gain" (over a different antenna design) where you want/ need it.
It appears to me you're renaming gain so gain isn't gain but another type of gain showing gain which is a gain different from the gain we want to see as gain at the other end.
LOL
Last time I checked, no antenna produces RF, only radiates the RF which the power amplifier provides it, and in a pattern and/ or at an angle which provides "gain" (over a different antenna design) where you want/ need it.
It appears to me you're renaming gain so gain isn't gain but another type of gain showing gain which is a gain different from the gain we want to see as gain at the other end.
And it appears to me you have no idea about what it is you think you understand. You obviously do not understand the term "absolute gain". There is relative gain which compares two things and there is absolute gain which is the gain of a single item and neither term has anything to do with your silly "It appears to me you're renaming gain so gain isn't gain but another type of gain showing gain which is a gain different from the gain we want to see as gain at the other end." statement.
http://www.atis.org/glossary/definition.aspx?id=10
Nowhere did I say anything about an antenna producing RF and have no idea where you even got that notion or why you would even mention that. What I DID say was that the radiation pattern and thus the take off angle can be different between two antennas and yet not exhibit a great difference in gain. In case you missed it read it above again. And again and even again if you have to.
Here is an example of what I am talking about. I had a 1/4 wave 2m antenna on my truck and it worked very well for local repeater use and when working some of the 2m FM satellites. I travel thru a long narrow valley and thought I would try a 7/8 wave antenna, the Diamond SG-7500,which has an absolute gain of 5.5 dB on 2m and 7.5 dB gain on 440MHz. This means it had about 3.4 dB gain RELATIVE to the 1/4 wave. It worked great as long as I was out of the valley and working repeaters or simplex a long distance away but it actually performed worse than my 1/4 when in close to the base of the mountain where the repeater was located and it really sucked when working the satellites except when they were low on the horizon.Did this antenna somehow magically vary it's gain? Of course not. It had a much lower angle of radiation and only a few dB more gain than the 1/4 wave. The problem was the antenna had much deeper nulls in the high angle radiation that the 1/4 wave did not have. When measured at the angle of maximum radiation, where all antennas are measured at, it did however exhibit gain over the 1/4 wave yet would perform worse in many cases hence my statement about not worrying about the gain you have but worry more about where the nulls are in the pattern.
Trust me man, I have more experience in antenna patterns, both azimuth and elevation angles, than you realize. I cut my teeth tuning and phasing AM broadcast arrays as well as multi-bay FM stacks.
Excellent! I wasn't certain you understood.
Thank you for making my point, and No, I'm not going to enter into a pissing contest with you.
Perhaps in a year or two you'll realize that you absolutely echoed the point of my prior posts.
73
From your attitude and post it appears that you will NEVER understand what I said because it in NO WAY echos your point . I'm not looking for a pissing match either but when someone makes posts in an attempt to make me look like an idiot,such as claiming I said antennas create RF, or when they make absurd posts in mockery of something THEY don't understand, then I will attempt to educate and if that fails then I shall ignore them as a lost cause. Since you have NOT been educated in this matter I shall ignore you in this matter UNLESS you make further posts trying to make it look like it is I who does not understand what it is I am talking about.
No, not at all. Actually my posts were politely in response to what I perceive as a condescending tone from you as you argue against my points & against long-known & established antenna designs which yield gain at differing distances & angles ("on the horizon" also) over other designs, plus, having minored in psychology, I understand the term, "Projecting".
If the shoe fits...
73
Okay. It's a little while since I have had this antenna up. It has seen some good storms. But yesterday took the cake. We had what many call a microburst or several of them actually and some heavy rain and a lot of lightning. Lost a large tree limb. Pretty much the whole neigborhood basically got it pretty good.
At any rate I am happy to say my Sirio vector is still standing straight and is performing same as usual. I have truly been impressed with the beating this antenna has taken thinking many times "it's coming down I know it LOL"! But it has done well. The only mods I did was too add some HD hear shrink at every joint from the top whip to the bottom mast pipe. I did double up all of my paracord and Dacron rope and also added several more guy ropes. Was it worth the effort. IMO, heck yes it was. Only the top 5-6ft of the mast is not supported by any guy ropes. This has worked well for me so far. I also have 2 ratchet straps, one a 1" and the other an HD 10k rated one, a 2". They hold the antenna to the chimney, then I have an L bracket at the base as well that holds the mast pipes. Yes I have 2 mast pipes going up to about 15ft or so. Just added security. Also mast pipes are bolted to house and dug into ground about 3-4ft. No concrete was used at the bottom. Just diug out the area and dropped the pipe in. It's supported in so many places the entire chimney would have to fly off LOL. At any rate, the antenna has done a hell of a job handling some bad winds. 40+ mph sustained for a while. Here is a pic of it now. It's still raining and a little breeze at the moment. Please don't laugh at my guy ropes. They work and do what they are supposed to. I get by with what I have laying around as well. But anyways here are some pics as of this morning 8:45am.
Again it's no work of art, but it works. No failure of any ropes yet. Anyways, to those that say this antenna is fragile, I don't know about all that. It's been through some bad stuff here around my area. Daytona Bch., FL. It's not even summer yet! And it's 91 for daytime highs and almost 100% humidity!!
Anyways. Just some real experience with the new Sirio Vector 4000, and the mods I performed which was to add some HD heat shrink to every single pipe joint including the whip. And I used no-ox over the entire antenna. A very light coat. Nothing special, but it works!!! Have a good day.
At any rate I am happy to say my Sirio vector is still standing straight and is performing same as usual. I have truly been impressed with the beating this antenna has taken thinking many times "it's coming down I know it LOL"! But it has done well. The only mods I did was too add some HD hear shrink at every joint from the top whip to the bottom mast pipe. I did double up all of my paracord and Dacron rope and also added several more guy ropes. Was it worth the effort. IMO, heck yes it was. Only the top 5-6ft of the mast is not supported by any guy ropes. This has worked well for me so far. I also have 2 ratchet straps, one a 1" and the other an HD 10k rated one, a 2". They hold the antenna to the chimney, then I have an L bracket at the base as well that holds the mast pipes. Yes I have 2 mast pipes going up to about 15ft or so. Just added security. Also mast pipes are bolted to house and dug into ground about 3-4ft. No concrete was used at the bottom. Just diug out the area and dropped the pipe in. It's supported in so many places the entire chimney would have to fly off LOL. At any rate, the antenna has done a hell of a job handling some bad winds. 40+ mph sustained for a while. Here is a pic of it now. It's still raining and a little breeze at the moment. Please don't laugh at my guy ropes. They work and do what they are supposed to. I get by with what I have laying around as well. But anyways here are some pics as of this morning 8:45am.
Again it's no work of art, but it works. No failure of any ropes yet. Anyways, to those that say this antenna is fragile, I don't know about all that. It's been through some bad stuff here around my area. Daytona Bch., FL. It's not even summer yet! And it's 91 for daytime highs and almost 100% humidity!!
Anyways. Just some real experience with the new Sirio Vector 4000, and the mods I performed which was to add some HD heat shrink to every single pipe joint including the whip. And I used no-ox over the entire antenna. A very light coat. Nothing special, but it works!!! Have a good day.
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Uhm, wow?
I'm a bit amazed it survived without folding the mast below the NV4K and above the guy lines, unless that's not just a single section, single-wall standard TV antenna telescoping mast.
If so, I'd definitely add guy lines to right up to the base of the antenna, or at least double-up on the number of sections, at least double-layer it or add a 6'-8',
1" - 1.25" solid fiberglass rod inside if you're not going to guy up to the NV4K base.
Some people even guy the center of the NV4K radiator!
Otherwise it looks nice & straight, and I'm glad for you that it survived, though a 40mph gust is relatively minor.
______________
Oh and how much improvement have you noticed on the NV4K compared to the 5/8 you had up, and what was the mounting height difference?
73
The antenna has double walled pipe. The top pipe is doubled up with smaller pipe inside. It's not a push up mast. It's 2" to 1 5/8" pipe. And yes all my guyed ropes are doubled up. The antenna has has 2 pipes up to 20ft bolted together and both are reinforced. As well as the antenna being bolted to the house and chimney. Also ar the chimney there are 2 ratchet tie downs.
Antenna is only up to about 26-27ft to the base of the antenna.
This is compared to the 28-30ft that I had the tornado up.
And yes I have noticed a large difference in RX and TX over the Sirio Tornado.
I am able to regularly talk to about 70 miles locally. This is pretty well in all directions.
And yes a 40mph sustained gust for 5-10 minutes at a time. Winds may have been higher then that. We had what appeared to be a small tornado or a damn good couple of micro bursts. I've not seen the wind blow like it did the other day for a long time NB. Beleive me I even thought the antenna was going to fold. Told myself if it's going it's going now LOL.
But seriously, IDK if adding the heat shrink on every joint helps or if it's just my antenna isn't very high up and the fact I have quyed off at the 20ft mark with several guyed ropes now. The antenna doesn't move much at all now. I am pretty sure that the antenna isn't coming down at this point. I am always checking my stuff and I do mean constantly.
But like I said it survived some winds that I believe most would have thought it would have folded the radiating element. I can't confirm the winds were just 40mph. But I know it was at least blowing that fast and most likely more as there was quite a lot of tree damage on my steer the the one behind me. I am talking whole trees got knocked down! And many large branches including one in my front yard! Big enough to total a car!
At any rate this antenna has proved to be a winner in my book. Maybe not up at 100ft. But at the height I have it or even up to 35-40ft I believe it would have been fine. Just would need to guyed off some another section if I ever went that high. I am pretty happy with it where it's at as no one in the HOA has said a word about it being up. Not pushing my luck. If I do go higher I will have to pull permits from the city and I hate to give them any more money than I have too.
But like I said it has been a greet antenna for me and has definitely made me a believer that it's one of the best vertical antennas out there.
All this being said. Yes there are some areas that could be made to be stronger, like adding another support for the cone at or near the top of the ring itself and not so low on the radials that hold it. Add another 4 way ABS plastic piece at or near the top of the cone/ ring, whatever you want to call it.
But for what it has been through here and what improvements I have as far as RX/TX and DX as well. If I can hear them I can talk to them majority of the time. I just haven't been getting on the air. I listen, sandbagging more than anything at the moment on the weekends and days off.
But anyhow, just my experience with the antenna and my opinion of it after having it up for a bit now. It still looks like the day I placed it up and is still showing the same readings on the MFJ analyzer. Like I said, I am a happy camper. For a while I thought about buying another to mess with and beef up some, but this one has proved thus far anyhow that it will survive most bad weather we have other than a hurricane. If one comes this way best believe the antenna will be lowered down as far as possible!! Only time will tell as to the durability of the antenna. Until then I will keep posting every so often with updates if anything should happen to it.
But for now it's all good with this antenna and like I said, it was a heck of a storm it went through the other day. I am just glad the antenna held up and didn't have any issues after the storm. At any rate, thanks for the reply and I'll keep everyone updated as to how it holds up through the summer T-storms we get here
around Central FL.
Have a good one NB.
Sean.
Antenna is only up to about 26-27ft to the base of the antenna.
This is compared to the 28-30ft that I had the tornado up.
And yes I have noticed a large difference in RX and TX over the Sirio Tornado.
I am able to regularly talk to about 70 miles locally. This is pretty well in all directions.
And yes a 40mph sustained gust for 5-10 minutes at a time. Winds may have been higher then that. We had what appeared to be a small tornado or a damn good couple of micro bursts. I've not seen the wind blow like it did the other day for a long time NB. Beleive me I even thought the antenna was going to fold. Told myself if it's going it's going now LOL.
But seriously, IDK if adding the heat shrink on every joint helps or if it's just my antenna isn't very high up and the fact I have quyed off at the 20ft mark with several guyed ropes now. The antenna doesn't move much at all now. I am pretty sure that the antenna isn't coming down at this point. I am always checking my stuff and I do mean constantly.
But like I said it survived some winds that I believe most would have thought it would have folded the radiating element. I can't confirm the winds were just 40mph. But I know it was at least blowing that fast and most likely more as there was quite a lot of tree damage on my steer the the one behind me. I am talking whole trees got knocked down! And many large branches including one in my front yard! Big enough to total a car!
At any rate this antenna has proved to be a winner in my book. Maybe not up at 100ft. But at the height I have it or even up to 35-40ft I believe it would have been fine. Just would need to guyed off some another section if I ever went that high. I am pretty happy with it where it's at as no one in the HOA has said a word about it being up. Not pushing my luck. If I do go higher I will have to pull permits from the city and I hate to give them any more money than I have too.
But like I said it has been a greet antenna for me and has definitely made me a believer that it's one of the best vertical antennas out there.
All this being said. Yes there are some areas that could be made to be stronger, like adding another support for the cone at or near the top of the ring itself and not so low on the radials that hold it. Add another 4 way ABS plastic piece at or near the top of the cone/ ring, whatever you want to call it.
But for what it has been through here and what improvements I have as far as RX/TX and DX as well. If I can hear them I can talk to them majority of the time. I just haven't been getting on the air. I listen, sandbagging more than anything at the moment on the weekends and days off.
But anyhow, just my experience with the antenna and my opinion of it after having it up for a bit now. It still looks like the day I placed it up and is still showing the same readings on the MFJ analyzer. Like I said, I am a happy camper. For a while I thought about buying another to mess with and beef up some, but this one has proved thus far anyhow that it will survive most bad weather we have other than a hurricane. If one comes this way best believe the antenna will be lowered down as far as possible!! Only time will tell as to the durability of the antenna. Until then I will keep posting every so often with updates if anything should happen to it.
But for now it's all good with this antenna and like I said, it was a heck of a storm it went through the other day. I am just glad the antenna held up and didn't have any issues after the storm. At any rate, thanks for the reply and I'll keep everyone updated as to how it holds up through the summer T-storms we get here
around Central FL.
Have a good one NB.
Sean.