antenna comparisons/tests

[bob85]

Hea Blanket, what about your I-10K test results?

When I compared my I-10K at 40' to several other verticals including a Starduster at 50' I saw very little difference. For sure not enough to crow about anyway. That included mostly local RX signal reports.

Sometime back I even posted this report in a thread here on this forum. It was pretty busy and messy, but it was all that I had to supported my words on the subject and included about 25 stations around the Harris county Houston area here in Texas. I am not saying that it was the best test and I don't make any claims about results.

Two antennas were installed at the same time using a switch box to see results. The antennas were about 30' apart and when I reversed the antennas on these two locations I never noticed a difference due to a particular location.

marconi i find that very odd,
i do see differences between antennas and interaction when 2 antennas are mounted in close proximity,
there is a huge difference to some stations between the 10k and my imax when mounted at 12ft but less difference when mounted over 30ft,
the 7/8 sigma easilly outperforms them both when mounted at 12ft,
my buddies 10k outperforms his old sirio 827 5/8 antenna when mounted at about 36ft,
i made a local a choke from 1/2 wave of coax for his a99 isolated the antenna from pole with a short piece of hardwood and put 1/4wave wire radials sloping down his guys,
his signal improved to everybody in the circle he talks to,

i think it is a pattern under a certain set of circumstances/surroundings deal rather than outright gain differences but the differences are there and not hard to detect on hf or cb S meters,

are you sure your antenna switch aint slipping on the shaft :twisted:

 

[Master Chief]

You and your friends must be wrong Bob and only trying to justify spending the money on the I-10K.

......or how about this one......

Radio waves work different in England and what you see there is NOT what we see here!

:twisted: :twisted: :roll: :roll: :roll: :roll:

 

[W5LZ]

bob85,
Got a question about your friend's 'A99'. What kind of guys were they, metal or non-conductive?
About antenna comparisons. There are almost always variables that for some reason can't be eliminated. Those variables will always introduce some error as far as the 'accuracy' of that testing is concerned. Maybe 'relevancy' would be a better description, since 'accuracy' tends to point to the truthfulness of the test, which I don't mean to impugn. One of those variables is the proximity of two frequency 'related' antennas during "A/B" testing. Unless you happen to be doing the test in the middle of nowhere, that 'nearness' is hard to get around. The only way I know of doing that is by swapping the mountings of the two antennas and doing it all again. That just doesn't happen very often (MY excuse is that I'm just too lazy). Then there are all the 'other' variables that always creep into a test. One of those 'other' variables during 'on the air' comparison testing is the 'subjectiveness' of the one doing the listening. It's always subjective and only objective by a miracle (me included). I hate to say it, but the only way I can be really objective is by not knowing what antenna(s) are being tested, a 'blind' test. Some times a 'double-blind' test with a 'placebo' thrown in for good measure is a very good idea! Not just on the 'CB' radio, but on ANY radio system. The testing is still very 'subjective' by nature. Doesn't tell you why one seems better than the other, just that one might be better than the other, --> under those exact conditions.
Can you see why I don't put much 'faith' in 'on the air' testing? Has nothing to do with the tester's honesty or ability. Do I do that 'on the air' testing? Of course I do. But I still have to figure out why one appears to 'do' better than the other. Then it's a matter of which does what I want it to do in the first place.
- 'Doc

 

[bob85]

doc his guys were polyrope with stranded coated copper wire taped to the upper 1/4,
i agree on not telling folk what antenna im using and sometimes pretend to swap antennas while i sit scratching my nuts for a while just to make sure any reported difference is real,

the cost issue is simple enough for me and untill the 10k breaks it wont change,
IN THE UK WE CANNOT BUY ANY DECENT CB ANTENNA at any price,

the best is the vector 4000 without any doubt in my mind but its so weak you cannot even think of using one long term, they can be made durable by shortening them to 3/4wave but you still need an apropriate sellection of old good quality antenna parts in the shed to modify it and double skin the lower section,

the next best is the sirio 827 which is pretty strong but rarely last more than 2 years from new before they either snap or start having connection issues on the coil and tapping point,
( converting the 827 to a trombone match would be well worth the effort if you also swapped the upper sections for an old gp sections you would have a strong good performing antenna ),

the rest are just plain junk some (cte's) are made from recycled corrugated something masquerading as antennas of old,
they look like the old antennas if you close one eye and squint with the other but not worth a carrot in our weather, heavy soft bendy,
the way i see it over here is the most expensive cb antennas are less expensive than they were 25 years ago but the quality of tubing now sucks,

there is a market over here for a better constructed antenna but the large jump in price between a 827 and the i10k is too large for most folk once shipping and duty are figured in, i think its worth it but people have become accustomed to not paying much for a cb antenna round here, if there was a ladder of prices rather than a gaping wide hole i think things would be different,

building a replica of any one of the old good antennas would cost more than you would imagine even using off the shelf seamless tubing,
when chief sends me the top bracket i am going to build a replica astroplane,
the legs and hopefully the hoop will be one piece to save time and better structurally, i dont intend shipping it anywhere so it dont need to break down into manageable parts,
lets see what it costs me,

i have another antenna in the making, 3/4 to 7/8 radiator with flared 1/4wave radials following ideas in the sigma4 patent,

i have the vertical which is vector 4000 and a 25year old 1/2 gp grafted together ( gets rid of the weak upper sections )
the 4 flared radials will be from my cushcraft 10-d4 so they will be pretty strong, i just need to find some suitable box section and a aluminum welding buddy

oh and the name of my antenna,




it will be called the "Mc HAMMER"
or should it be the "jack" hammer :twisted:

 

[bob85]

blanket i agree the imax suffers badly when mounted low and the signal differences cannot reflect actual gain differences because the signal increase was too large, it must be a distortion of pattern deal given a certain set of surroundings, the 10k is less effected and the sigma suffers the least under those conditions,

the 827 is already a good performer outdoing all the other 5/8 sirio or the other italian makers produce in both performance and strength so any improvement is a big bonus,
im not claiming a big improvement 1/2 s unit on my jrc meter,
he is about 40mtrs above me on a hill, does that mean the 10k puts out more signal at low angles than the 827 when mounted at the same height?

hmmmm

 

[Marconi]

Bob, earlier I talked about my I-10K compared to the Starduster which according to most should be no contest even with the SD about 8' higher to the feed point.

Below you will see a similar signal report comparing my Wolf .64 to my I-10K. I have also included a photo of the two antennas tested. The push up pole with the .64 was pushed out to 33'. The other pole with the I-10K was pushed out to 35' according to my notes.





These station operators work 27.395 lsb and are all around me in the Houston and outlying areas. I have also compared signals from the radio that I used with several others around here and the signals were generally the same.

 

[bob85]

you do see differences between the two, granted it aint all in the 10k's favour,
what about a 10k vs astroplane test with the antenna tips at the same height and the astro on a pole insulated from the support mast 8-9 feet below the hoop as stated in the patent for best takeoff angle ????
that would put the tip about level with the 10k

 

[Master Chief]

doesnt sound very scientific for you to try sticking your chest out like you are.

Bob and I have a long history and I was ribbing him...no problem with the chest sticking out.....the gut is another issue.

Marconi, I love the test sheet! You always seem to have a solid test procedure that is repeatable. I have four questions.

1. How far apart are the two antennas?
2. What are their orientation to North and South?
3. What compass degrees are the receiving stations?
4. Is the off-air antenna grounded when testing the other antenna?

My thought is that the antenna orientation in relation to the receiving stations may favor one antenna over the next in a particular direction. What do you think?

 

[bob85]

 

[Marconi]

Marconi, I love the test sheet! You always seem to have a solid test procedure that is repeatable. I have four questions.

1. How far apart are the two antennas?
2. What are their orientation to North and South?
3. What compass degrees are the receiving stations?
4. Is the off-air antenna grounded when testing the other antenna?

My thought is that the antenna orientation in relation to the receiving stations may favor one antenna over the next in a particular direction. What do you think?

You might be right MC, but it should not be much. I have checked this before, but maybe the antenna to the north is adding something to the antenna in the back.

Bob is right also, I did record some small differences.

1. The pushup poles are about 32 feet apart at the base. The antennas would effectively be a bit less than that so they could be affecting one another in some way, that is possible.

2. The I -10K is directly north of the other antenna in this case. In the picture I am due east of my home shooting almost midway between the two antennas.

3. The degrees are not handy, but most of these stations are north, and northeast including Splendora 36, Tomball 35, N. Houston 11, Decker Flats-40, Magnolia 44, Spring 25, Conroe 50, 1960 area 8, New Waverly 60, Plantersville 60 and this station switches from a beam to a GP quite often. Acres Home 5-6 due north is closest station to me in the list. The Heights station is about 6-7 miles south of me. New Caney 35 a little more to the northeast, Richmond 50 miles Southwest. Adams Flats, and Katy are due West about 50 and 30 miles, and Boerne is about 200 miles due West when close in skip is working and is later in the evening.

4. I use a grounded Alpha Delta 4.

This was all RX signals in the report. The reports were not all at one time and at some point when we were discussing signals, I received a report from one station noted that the audio between the two antennas was more clear and robust when I was on the .64 antenna. The other two stations noted, chimmed in with similar remarks. My radio was a KW570D with
all filters off.

 

[Marconi]

you do see differences between the two, granted it aint all in the 10k's favour,
what about a 10k vs astroplane test with the antenna tips at the same height and the astro on a pole insulated from the support mast 8-9 feet below the hoop as stated in the patent for best takeoff angle ????
that would put the tip about level with the 10k

Bob, I would really like to do as you suggest, but I'm not up to it right now. I'm still recovering from knee surgery and don't feel comfortable working at heights since my surgery. I developed a bit of vertigo and I’m not getting any better fast. I have the poles up and the antennas, but I’m just not up to it anymore.

Could you answer a few questions or anybody add comments?

In your post above, you noted that the patent indicates that the mast #14 needs to be 8-9 feet below the bottom hoop. This suggests this is the optimum length possible for best TOA and it is true that the patent states those words. However, I sense you also feel that 8-9 feet is the only length for the mast period, in order for the antenna to show the optimum TOA. In the same vain you speak about insulating the mast at this 8’ point from any supporting structure in order to maintain this optimum length if you plan to elevate the antenna. Do I understand you correctly?

I read the patent differently and I don’t think this is what the patent states or implies. I read it a though this length of 8-9 feet is just the minimum that should be used or else the TOA will rise up. See section 3 lines 42-55. IMO, when Avanti scaled down the antenna to 2 meters as noted in sections 4 lines 46-75, and section 5 lines 1-14, they verified that making element #14 shorter than 1/4 wavelength would tend to raise the TOA, but said nothing definitive about making it longer. So I guess this does raise a question. In section 5 lines 11-14 there is mentioned a 20-foot mast to be used with this antenna as designed. Your idea suggests a mast length of about 16-feet, while Avanti suggests in the patent using a 20-foot mast for #14. When I read it, I am not persuaded that 20-feet is the best way to go here either, because a 20-foot mast does not provide for the maximum tip height under FCC, Part 95 rules, which provides for an omni directional antenna and supporting structure not to exceed 60 feet above ground level. Under this rule an AP could be supported on a 56-foot high mast and a typical half wavelength ground plane would need to be on a 42-foot mast.

In section 6 lines 9-14 it is suggested that the use of a 4 foot top loaded element #46 including 4 feet of capacitance cap adds bandwidth. Thus for me, this suggest that if this element were replaced instead with a full 1/4 wavelength monopole it would show some improvement in efficiency for the antenna as the bandwidth was reduced somewhat. Sounds like to me that adding a cap hat was a reasonable compromise, allowing the antenna to be elevated an additional 4 feet higher within the FCC limitations and providing added bandwidth in the CB band. I think most CB operators would prefer a broader bandwidth, but within reason I believe antennas, operated at resonance, will typically show a somewhat better signal as the bandwidth were made more narrow as apposed to made very broad. Maybe the idea of full 1/4 wavelength monopole on top of an AP, as use with the AP Beam, would perform better in the stand-alone version too. And, that if one really wanted to raise the TOA and elevate the antenna far above the earth, then decreasing the length of #47 to less than 1/8 wavelength and increasing the length of wire elements #48 and #50 in order to maintain an electrical 1/4 wavelength for element #46 on top would be the way to go in order to raise the TOA a bit. Additionally it is also noted in the patent that the flare of elements #16 and #18 has an affect on impedance, as well as an affect on TOA. See section 5 lines 56-61 for explanation.

The clincher for my opinions here are in section 6 lines 14-25, where the term at least on line 16, is used to describe the length of mast #14 below the bottom hoop, and the words are omitted on line 23, are used to discuss the consequences of removing the capacitance hat radials at the top of #47 and make the top element #46 longer at a full 1/4 wavelength.

I remember somebody wanted to check out the TOA somehow using a modified AP, but cannot recall who it was and if they did that project. I have been off the forum for about 6 months doing my 50th reunion events. Bob, do you know anyone that can modeled the AP and maybe check out these ideas?

 

[bob85]

i dont know anybody that would model it and tell us what the results are ,
i would imagine height above ground and soild type would also effect t/o angle but its just a guess, maybe the optimum is a combination of height/soil/mast length before isolation i dont know,

the deal with the cap hat i have read several times usually late at night when im half asleep but they seem to contradict themself,
i cant decide if they mean the cap hat lowers t/o angle at the expense of bandwidth or is it the other way around,

i always thought cap hats helped even out current distribution at the expense of bandwidth,

what do you make of what they say on the subject??

when my sparring partner MC sends me the bracket i will be trying to build one and i will try a full 1/4 vs caphat and i will if i can get the tubing at sensible cost try a telescopic mast section so i can test different lengths before isolation while mounted at the same tip height,

i understand the not up to it part,
i used to shin 50ft up a scaffold pole carrying another 20ft pole and whatever antenna i was errecting,
a while back i went to retreave what was left of my poles from the tree at my parents house,
i can tell ya i will never climb that tree again and no way could i climb it then shin up a pole stuck out the top with or without the antenna and 20ft pole in my spare hand,
old age sucks and it creeps up on ya way faster than you realise once you stop doing stuff for a number of years.

 

[Marconi]

I think you might be right about a contradiction concerning the Cap Hat and the affects on bandwidth. Read section 3 lines 28-32, where it suggest that if a larger bandwidth is desired element #47 may be increased in length while conductors #48 and #50 be reduced or eliminated. This seems to be the opposite of what I said in my previous post starting with the words "In section 6 lines 9-14...." I will have to check this out further, but I think the fact about Cap Hats bring about big arguments and discussions also.

Personally, I think a Cap Hat should help increase bandwidth in an antenna and when replacing it with a full 1/4 wave element, as in the top of an AP, the gain should be improved at the expense of some bandwidth. More or less like happens with any longer radiator apposed to a shortened radiator at the same frequency. I also believe bandwidth is typically affected mostly by element cross-section (width) and a Cap Hat may well effectively add electrical width to an element. If you will notice the shortened top element in the AP is already twice as wide as the other elements, and this too may add more to the bandwidth. It surely was not an accident in design.

 

[W5LZ]

"Capacitance hats at the open ends always help bandwidth and efficiency."

Sorry, just not true. Depends on the constraints you are operating under. Capacitive hats do radiate. Nothing exceptional in that. Again, it depends on the 'where' and 'shape' of that capacitive hat as to how much it radiates. And since they are only used on antennas that are shorter than 'normal', they effect efficiency in a positive way. They certainly increase an antenna's efficiency compared to the same antenna with out one, but that doesn't make it 'better' than not needing one to start with. Bandwidth always has a 'cost' in efficiency.
- 'Doc

 

[Master Chief]

Define, "BETTER". No no...just kidding...ha ha ha