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Hey Bob, I just posted my last three Signal Reports comparing my Sigma IV to my I-10K and my AstroPlane in my post above. I don't believe you have seen these yet. I was really surprised to see how well the AP performed when the tips were close to equal heights. Conditions are better now and DX has been sparse to non-existent up until today and conditions were just terrible. All the locals were sounding like they were off frequency and DX was so strong the locals sounded like they were 100's of miles away. Tonight conditions are very good and now I'm copying stations nearby up to a 100 miles or so. That is nice.

I also just added the choke to my Sigma that I described to you earlier. I sense less noise when it is quiet, but according to the Signal Reports I have just recorded and comparing them to signals back in August---I am not seeing improved signals---and that confuses me considering I seem to be hearing better.

I agree that TX/RX are supposed to be reciprocal, but I can't figure out why I'm not seeing better RX signals also. I would think that should go along with what seems like a lower noise level. So, if I have eliminated some of the CMC that may have been emanating from my Sigma, then I'm hoping the reciprocal idea is also doing its thing. Of course I will repeat these comparisons just in case I was experiencing bad conditions.

Our weather is changing dramatically so changes in signals may be occurring and maybe that is why my recent signals are not as good as they were back in August. I'll plan to get back to my antennas soon. I have ordered some delrin material to better insulate my antennas and when that arrives I'll get started. Then I can raise the insulation idea up above the mast as both you and Master Chef suggest. I do think that is important to help prevent passive radiation between the radiator and ground even if I don't end up seeing results similar to you and Multimode 200. I'm going to first try it out on the A99, cause I can't find any of my Antenna Work Sheets on my A99, so I'll be starting over with my testing again. Sooner or later I will get it right, as practice makes perfect, so I hear.

Hang loose,

hello eddie,
its good to finally see the results for your sigma4 vs other antennas, i was kinda waiting with baited breath to see how it turned out, i dont know why as i was pretty confident if you got the sigma tuning even half right it would beat the other antennas mounted at the same feedpoint height, still good to see it where it belongs though lol

i dont doubt the astroplanes performance when mounted as the designers intended , i found a nice 60" piece of .070" wall 6061-t6 tube for my homebrew astroplane,
the hub you sent me will live to fight another day, i thank you,

if your choke is reducing receiver noise id suspect it is reducing common mode noise or other noise thats getting onto your coax and back into the antenna, if the sigma is still electrically connected to the mast i would not expect the choke to do much if anything for received or transmitted signals but as always i could be wrong,

keep us posted

__________________
the blind lead the blind but the enlightened will lead you to the sigma4

Well like I said some where today, I have some plastic coming and then I'll be able to insulate the Sigma and some of the others the right way.

I have been studying my Antenna Work Sheets and I am seeing the I-10K "R to X" problems with other antennas as well. I hope to get to the bottom of why that is too, but it will take more work and testing. I plane on trying to solve that issue if I can first, and then see how the insulation idea works out.

Stay tuned.

marconi,

if what we are presuming about how the A99 works by using the coax shield as a counterpoise; then if you were to isolate it from its mast, and use the RF choke at the feedpoint, but did NOT use the groundplane kit in this install, then you should see a high SWR right?

or am i confused again? LOL

LC

__________________
"Man shall never reach the moon, for such a quantity of gunpowder would be needed as to gravely injure the crew."
~ Children's Encyclopedia, 1926

LC, as I understand this issue concerning the A99, CMC, Isolation, Chokes, and no GPK, the choke and isolation alone would only have minimal responses in such a configuration if we excluded proper GP radials. This is because the system needs a return path for these currents and without the GP radials to provide that path, the CMC would just defeat the choke and flow on the shield anyway. I'm sure it is much more complicated that this, but others will have to speak to that.

In my limited experience on this issue I am lead to believe that the SWR may in fact show to be a bit higher if we are able to curtail the flow of CMC if we start out with a system that shows a very low SWR. I see this as if we might expect the feed point impedance to be reduced a bit from say 50 ohms when we stop CMC if they are bad enough to matter. These current might be exhibiting a better match at the feed point due to losses and if we reduce those losses, we might see the SWR go up a bit due to an increase in reactance creeping into the system. I've also been told that if we have a low loss system, feed line, and resistive load---that most of this type of problem will not happen. I'm still waiting for someone to be able to prove that to me and be convincing.

It is really hard to predict what a feed point impedance might be when we make a modification of some type to our antenna system and I can only guess that the SWR could also start out in a system a bit high and end up actually lower as a result of curing the CMC problem also. Just a guess though.

My mentor in radio, the man that got me started in all this business, was a retire Army Master Sgt. in charge of field communications training for nearly 25 years. He use to tell me when installing a 1/4 wave whip on an auto to always strive to achieve at least a 1.3:1 VSWR. He explained the natural match for such an element under proper installation conditions is approximately 38 ohms of resistance at resonance and with a suitable ground plane the effects would be to generate an approximate VSWR of 1.3:1, and if you pushed the system to show more than 38 ohms somehow you are just adding losses that show up as increased impedance via reactance and that part of the feed point impedance (reactance) does not radiate. You all have heard that from our friend 'Doc as long as I can remember, but you have to be paying attention to understand that.

I tend to believe that idea although, I like most prefer to see my SWR as low and as flat as possible with at least 1- 2 megs of bandwidth. I just wish I could definitively measure and prove that idea, because most will not even consider such an idea.

I had a .64 and a "ring of fire", same as the starduster but firestick whips,(not loaded).

The .64 was better in 80% of contacts, but for some reason, I could get the guys in bellingham and everett better on the ring of fire.

The .64 was 40ft to base and the ring of fire was maybe 25ft to tip.

LC, give us and update on how you're coming along with your new AstroPlane installation.

i put the top one up this past friday.

all went pretty well, and no major setbacks.

the last time i installed one of these antennas, i bent the hoop sections so they were more circular.

this time i didnt bother with that, and while i know it does not have any effect on the signal radiation, i dont like the way the bottom has sort of a "clover-like" appearance to it. LOL

SWR ended up being about 1.3 across the regular 40.

it sits on a 30 foot push up pole with a 5 foot mast on top.

the push up pole is held up by a tripod bolted to a heavy metal base plate.

i did this because i am renting a house right now and cant attach anything to the house.

i push it up when i want to use the radio, and lower it down when i am done.

works well, but i havent made any DX contacts with it yet.
i blame the sun. LOL

LC

__________________
"Man shall never reach the moon, for such a quantity of gunpowder would be needed as to gravely injure the crew."
~ Children's Encyclopedia, 1926

LC, thanks for the update. The following may be a lot more than you want to know, but I just completed some testing during July and Aug and have now studied what the results might mean and for sure one of my best performers was the AstroPlane, so here goes.

I have no doubt that you will be doing some DX when it returns with a furry, but DX is not a very good indicator of an antennas effectiveness in my opinion. I don't know about your area, it may be different, but I have not really heard any DX here for maybe a month, so why not check out your local traffic while you wait. I think you will find the AP will DX for you very well at just about any height and you might not even be able to tell the difference with different heights, but your area may be different.

Have you done anything ahead of time that will give you some basis for comparison---are will you just be flying by the seat of your pants (opinions and recollections only from the past)?

For some reason I did not attach my AstroPlane Antenna Work Sheet dated 080309 to my album for work sheets in my profile or I would link you there to see all my recent reports. This attached report will show the Band Width curve for my standard AstroPlane @ 37' feet and it is noted as #4 at the top.

This report is a analyzer scan thru my feed line for the antenna at the time, because it is not practical to scan at the feed point of an AP. I say this to let you know that I find some line effects to the scans when using the feed line with all the antennas I compare, so consider that as a variable. This report looks pretty good none-the-less, so I don't think any thing significant will be found to be a big problem.


You will see that your SWR readings and mine are very close across the CB band---see the measurements at the bottom under "Inline Meter." You can also compare these SWR results to the Autek readings above on the chart.

I'm scanning way wider than the CB band to get a bandwidth curve <2:1 SWR, but notice how the antenna is not nearly as flat as the Inline meter indicates and that the resonance shown in the scan was right near the middle of the CB band and the SWR was a bit higher. More importantly, check out that at resonance the match and resonance is fairly good, but not nearly perfect at R=50, X=0, SWR=1.1, Z=50. So the numbers on the report are the numbers I get with a completely stock AstroPlane. This is what I will have to live with unless I modify the antenna somehow. When you guys work your SWR meters only within even 40 channels up and 40 channels down tuning your antennas you are not really seeing much bandwidth and every thing to you might look flat.

Antenna Work Sheet AP #04 080309.jpg

Now below is my final Signal Report for the AP vs. Sigma 4 at the same tip heights. If you look at the smaller numbers below the actual report you will find my recap data---comparing all the signals in each column for both antennas where I add up the values and divide the values by the number of contacts to get average S units. I also used two radios to get my RX signal reports in this case.

Surprisingly, you will notice---the AP modestly out did the big old 30' foot long Sigma 4 antenna even with the small mismatches note above and the AP is only about 12' feet tall.

Another point to notice is that I tuned my Sigma4 at 27.205 resonance and that is also by design where the AP is tuned to resonance. All of my signal reports were recorded on channel 39 where all of my buddies hang out that talk often. So, I'm operating a little away from center frequency. In my next round of tests, I plan to try and tune both resonance and match as perfect as I can and see if that makes any difference in the signal responses on channel 39 and on channel 20 to see if tuning can actually show me a difference when I'm perfect compared to beign just close.

Signal Report 080309 Sigma vs. AstroPlane Tips =.jpg