Buying An Astroplane

[HomerBB]

I'll want to try it out on the same tilt over mast with additional pole at the top to get it to the same over all height.
I will not be expecting too much, however I've heard both good and not so good from different sources, so it should answer questions for me about the AP.

 

[Marconi]

I'll want to try it out on the same tilt over mast with additional pole at the top to get it to the same over all height.
I will not be expecting too much, however I've heard both good and not so good from different sources, so it should answer questions for me about the AP.

Thanks for trying this setup Homer. Verification of the AP, one way or another, is exciting for me. It is not often that happens, and I'm interested when others choose to check for similar results to my own. Sometimes I feel like I'm by myself with some of my results.

 

[CDX-007]

I thought of another good reason to consider the Top One / AP design, IF it's as good as your tests have shown, Marconi...

When your limited to a maximum height by local statute.

If it's as close to the SGM as your test show, then getting it's high feed point within 4' of the maximum ceiling height just might provide close to the best performance 'ALLOWABLE BY LAW'!

...and that's the best this Tequila hang over can offer this morning

 

[HomerBB]

Got the Astroplane in the air. The bottom of the loop is @ 38' The coax feed point is @ 45.5' and the top of the antenna is about 49'.

SWR: ---------- @50W DK ------- @5W DK
28.855 -------------- 3+ ------------ 1.9:1
28.305 ----------- 3.0:1 ----------- 1.5:1
27.855 ----------- 1.9:1 ----------- 1.2:1
27.555 ----------- 1.7:1 ----------- 1.1:1
27.405 ----------- 1.6:1 ----------- 1.1:1
27.205 ----------- 1.3:1 ----------- 1.1:1
26.965 ----------- 1.1:1 ----------- 1.0:1
26.515 ----------- 1.3:1 ---------- <1.1:1
26.065 ----------- 2.9:1 ----------- 1.5:1
25.615 -------------- 3+ ----------- 2.3:1
25.165 -------------- 3+ ----------- 2.0:1

 

[CDX-007]

Hi Homer,

Odd it goes so high with only 50w. You have your swr meter after the amp, correct?

Maybe try a 3' - 10' patch cord in line between the coax from the AP and the meter to see if you've happened upon an unfriendly length of coax for that specifically fed antenna design.

I'm wondering how's the performance? Good you've got it above a wavelength from ground.

Looks good.

 

[HomerBB]

I do not have the jumper that ships with the antenna, nor have I put a parallel 75 ohm x 6' jumper in line, yet. I think if that is required then I'll get it done soon.
With skip running like it is I can't say what local performance is like, but it seems to do just fine with DX.

186 -------------------------- NY Winchester Radio
125 -------------------------- NY
Black Magic ----------------- Quebec, Canada
RC427 ----------------------- Niagara Falls, Canada
373 -------------------------- Canada
606 -------------------------- Canada
265 -------------------------- Ontario, Canada
577 -------------------------- Ottawa, Canada
8620 ------------------------- Toronto, Canada
579, Dr Smooth ------------ Ontario, Canada
427, Mark ------------------ Lake Erie
489, Frank ----------------- Lake Erie, Canada
355 -------------------------- Ontario, Canada
130 -------------------------- PA
751 -------------------------- Canada
323 --------------------------
392 -------------------------- PA
441 -------------------------- Lake Erie
#29 -------------------------- PA
136 -------------------------- PA mobile
290 -------------------------- PA
8017 ------------------------- Central OH
105, Kenny ------------------ NJ
357 ---------------------------
123 --------------------------- Cleveland, OH
210 ---------------------------
579 ---------------------------
462, Cowboy ----------------- OH
138 ---------------------------- Columbus, OH
Hotrod ------------------------ KY
357 ---------------------------- KY
Bright Eyes ------------------- Hartford, KY
Gate Keeper ------------------- MD
33 ------------------------------ KY
Moonshiner ------------------- KY
Waterboy --------------------- KY
205, Hotrod ------------------ VA
499 ---------------------------- VA
420 ---------------------------- KY
252 ---------------------------- KY
214 ----------------------------

 

[HomerBB]

Homer, I did write you a nice long post over on the other forum, but when I attempted to save...I got the "down for fixin' the WWRF mess" popped up, so I'm not sure if it saved.

Nope. Isn't there.

Great report, and good work.

thanks

You will find most operators are misguided by the simple words Avanti used in their Patent to describe their design idea. They never claimed that the antenna had to be mounted low to the Earth in order to perform well. Their idea did address the FCC height restriction mandate of that time however...when too many guys were getting electrocuted installing all metal antennas.

That's the way I sw it after reading through the Astroplane thread on the other forum.

In fact at one time the antenna was manufactured and promoted as a 10 meter antenna and that often accounted for the antennas tuning a little high in frequency. I know your's tuned lower, but both of my Top Ones tune a little high. Not that it really matters with such a broad bandwidth. I even installed mine with a smaller diameter mast 1" in order to see if the resonance would change. The original antenna you have could even go back to the 23 channel days, and your's may have been from that vintage...thus showing to be a bit lower in frequency. How did you find the dimensions compared to the published ones you got on the Internet?

What I've got it on is a 1 3/8" aluminum mast for the ipper 12' and a 1 1/4" steel mast for another 10'. As for the dimensions, they were spot on to those I got from online. I am not surprised by the 10 meter potential of this antenna. It is reasonably wide banded as it is.

You may try adding a few feet of coax and see if the apparent resonance seems to change. You can do it at the radio for the same affect. I find that both of my knockoff antennas show transformational shifting in the match due to the feed line length, but I'm not sure it is due to CMC's which is typical. Maybe that is what you are concerned about wanting to install a choke. In my experience with excessive CMC's comes increased noise. My TO's are typically very quiet. How is your's? Don't get me wrong here, if you think you need a choke, try it and let me know what you observed.

I'll have to hear it without skip conditions to evaluate its noisiness. I was thinking I might have too much coax inline, now. I am moving my shack location in the house and think I can reduce the amount of coax it takes to get to the antenna when I do. as for the choke, I read where I believe it was Bob85 who recommended one at the 9' below the hoop location. I put ferrites there, but will put in a choke to see how that works out.

I believe the antenna is a well matched 1/2 wave center fed dipole. I could even argue that it is much like the GM...with the exception of being 5/8 wavelength. If you consider that the choke on the GM effectively minimizes the CMC that could be flowing down the feed line and mast and is due to the high impedance field it creates with the choke where it terminates the physical bottom of the dipole: then the coax passing inside the high impedance voltage node on the AstroPlane bottom hoop has a very similar affect. This high impedance point helps eliminate CMC flow at that point below the hoop. I do see RF out from the base and below my TO antennas at my location using a digital field strength meter, but I don't detect any RF on the feed line right below the antenna and no noise convinces me that it shows very little to no CMC's.

You could be right. Putting a choke inline then removing it may clear this up for me. As long as it isn't too windy I can have the antenna over and back up in less than 10 minutes.
[quote name='Old Grandpa' timestamp='1294123575' post='299077']
BTW, that 75 ohm harness you mentioned on the other forum was included with the AstroBeam kit. I don't think you will find it a necessary part for the AstroPlane. The bottom of the AP is long and makes a smooth transition via the voltage nodes at the ends of the 1/4 wave tuner and the end of the 1/2 wave radiator connected by the high impedance hoop at the bottom. The bottom hoop is very sensitive to its surroundings, just like CDX007 and I both feel is true of the New Gain Master. IMO, this is the reason for Avanti's warning about getting stuff too close to the hoop.[/quote]
Good to know. I didn't see much of a need if any given the tune I got without it. I just thought putting it in might make changes. I won't likely bother with it now. Tuned fine, if a little low.

I also see similarities between the AP and the Sigma4 design, the way Avanti uses long smooth transitioning of RF for controlling the feed point match without troublesome ground radials that tend to disrupt the radiated pattern.

I am not so sharp on the exact science of these antennas, but my thoughts do run similar to yours, here. Clearly avanti sees something useful in the similar physical designs of the two antennas.

Good DX. You may be getting a lot of work on that one. It is probably the primary advantage noted for this antenna. The other, not so good comment is noted above. I think you will find this little antenna to be very effective with both local and DX contacts. Keep us posted when you get a chance to compare it to some of your other antennas at any height. Just let us know about the height issues you see, OK?

Will do.

 

[HomerBB]

Two Weeks Later

I continue to be somewhat surprised by this antenna. At a tip-top elevation of 54.5', it seems to have better ears locally than I had expected it would. I have noticed the ability to hear some stations in the 20 to 30 mile range that were lost to me in the noise. This antenna seems to be quieter in receive than the 5/8ƛ I had up before it. I am not saying it upgrades their signals receive wise, but I am saying that they are more readily understood as the white noise is less intrusive, or at a lower level on the Astroplane.
As a note, I am in the Ozarks. Stations at 20 to 30 miles distant in a given direction can be more difficult to contact than those twice the distance in another direction.

Still observing . . . .

I have come to the conclusion that there must be some improvements made in my homebrew 5/8ƛ and Qv4k (homemade Vector 4k) when Spring arrives. Those will be on the order of improvements to the matching systems, and of the components at the connections. I will readdress the dimensions to be especially sure they are dead-on to specs, I will hopefully purchase newer better coax, and will be moving the shack to a different location so my run will be 1/3 distance closer. I am looking to reduce any losses due to fabrication compromises.

After that, perhaps I'll try to build a Q(quasi)SGM.

 

[Marconi]

Two Weeks Later

I continue to be somewhat surprised by this antenna. At a tip-top elevation of 54.5', it seems to have better ears locally than I had expected it would. I have noticed the ability to hear some stations in the 20 to 30 mile range that were lost to me in the noise. This antenna seems to be quieter in receive than the 5/8ƛ I had up before it. I am not saying it upgrades their signals receive wise, but I am saying that they are more readily understood as the white noise is less intrusive, or at a lower level on the Astroplane.
As a note, I am in the Ozarks. Stations at 20 to 30 miles distant in a given direction can be more difficult to contact than those twice the distance in another direction.

Still observing . . . .

I have come to the conclusion that there must be some improvements made in my homebrew 5/8ƛ and Qv4k (homemade Vector 4k) when Spring arrives. Those will be on the order of improvements to the matching systems, and of the components at the connections. I will readdress the dimensions to be especially sure they are dead-on to specs, I will hopefully purchase newer better coax, and will be moving the shack to a different location so my run will be 1/3 distance closer. I am looking to reduce any losses due to fabrication compromises.

After that, perhaps I'll try to build a Q(quasi)SGM.

Homer, again a good report. I have found much the same type results over the years with my AP's. In 2006, I published this link: The Radio Operators Roundtable: AstroPlane . You may have seen it before, but just in case...you might be interested.

I've changed my mind a little on the AP being a 5/8 wave however, and that is because I could never account for the bottom loop in the antenna. I just assumed it was a 90* bent bottom 1/8 section of a 5/8 wave. I now feel certain that it's a 1/2 wave radiator, that is very effectively center fed...similar to the Gain Master in that it has a balanced design. I believe this, because recently when I installed them side by side with the centers of the antennas at the same height, I could not see any RX signal differences. I did not take any readings for TX signals, but guys say all the time that antennas are recipocal in this regard, but I'm not sure that is always true in real world test...I see differences sometimes on a rare occassion when I get a feedback signal report with two antennas up and folks say they see a big difference on their end while I'm seeing the signals about the same. That said however, this may be the same thing going on with my radios, and my location which ever is true.

Fortunately I also discovered that the mount I had the AP mounted on was noisy compared to the new mount I just built next to my shack where I had my GM mounted. I could not detect any significant signal differences between these two locations, but I did notice the noise differences and at first I was giving the GM the credit for being quieter...without knowing it was the locations making the difference. This was sort of like you felt when you noticed the noise differences...albeit your were comparing from the same mount, which is better. I don't know as I would be able to pick up such difference, however, with my hearing problem.

If you can, how would you compare your AP to your other antennas regarding your local contacts at about the same height?

 

[CDX-007]

Hey Marconi, Just a quick thought, (I've given this about 14 seconds of consideration so nothing definitive here) but I recall measuring mine a couple weeks ago and found it too long for a 5/8λ and too short for a 3/4λ but taking into consideration the top hat, I wonder if it could be a direct-driven 50Ω 3/4λ, folded to re-phase the bottom current from causing the typically high angle seen from a completely vertical 3/4λ, with the top hat acting as a true capacitance hat to add back that missing length of a 3/4λ?

Doesn't it measure right about 1/2λ from the feed point down, around & back up to the opposite side of the mounting bracket where the current should be max @ min/zero voltage?

 

[HomerBB]

Homer, again a good report. I have found much the same type results over the years with my AP's. In 2006, I published this link: The Radio Operators Roundtable: AstroPlane . You may have seen it before, but just in case...you might be interested.

Thanks. I'll take a look at the reference.

I've changed my mind a little on the AP being a 5/8 wave however, and that is because I could never account for the bottom loop in the antenna. I just assumed it was a 90* bent bottom 1/8 section of a 5/8 wave. I now feel certain that it's a 1/2 wave radiator, that is very effectively center fed...similar to the Gain Master in that it has a balanced design. I believe this, because recently when I installed them side by side with the centers of the antennas at the same height, I could not see any RX signal differences. I did not take any readings for TX signals, but guys say all the time that antennas are recipocal in this regard, but I'm not sure that is always true in real world test...I see differences sometimes on a rare occassion when I get a feedback signal report with two antennas up and folks say they see a big difference on their end while I'm seeing the signals about the same. That said however, this may be the same thing going on with my radios, and my location which ever is true.

Fortunately I also discovered that the mount I had the AP mounted on was noisy compared to the new mount I just built next to my shack where I had my GM mounted. I could not detect any significant signal differences between these two locations, but I did notice the noise differences and at first I was giving the GM the credit for being quieter...without knowing it was the locations making the difference. This was sort of like you felt when you noticed the noise differences...albeit your were comparing from the same mount, which is better. I don't know as I would be able to pick up such difference, however, with my hearing problem.

I've never had an opinion on the AP, except I thought they performed well when on the receive end of a transmission.
Yes, I'm on the same mount. One thing I've discovered is that I am located on one of the noisiest spots on my street. I noticed this when I was in my mobile. Oh, well, it is what it is. Can't move the house.

If you can, how would you compare your AP to your other antennas regarding your local contacts at about the same height?

So far the AP seems to do as well in terms of the clarity of the audio. What seems different is the S-units are down on the local signals. I know S-units are not proof positive of things given the variety in radios, but this is exactly the same everything, radio included.

 

[CDX-007]

Homer, how much lower, if at all, is the top of the AP than was the top of the 5/8λ?

 

[HomerBB]

If the imagination is allowed to roam unrestrained, the AP somewhat resembles a V4k upside down.

 

[CDX-007]

Homer, again a good report. I have found much the same type results over the years with my AP's. In 2006, I published this link: The Radio Operators Roundtable: AstroPlane . You may have seen it before, but just in case...you might be interested.

I've changed my mind a little on the AP being a 5/8 wave however, and that is because I could never account for the bottom loop in the antenna. I just assumed it was a 90* bent bottom 1/8 section of a 5/8 wave. I now feel certain that it's a 1/2 wave radiator, that is very effectively center fed...similar to the Gain Master in that it has a balanced design. I believe this, because recently when I installed them side by side with the centers of the antennas at the same height, I could not see any RX signal differences. I did not take any readings for TX signals, but guys say all the time that antennas are recipocal in this regard, but I'm not sure that is always true in real world test...I see differences sometimes on a rare occassion when I get a feedback signal report with two antennas up and folks say they see a big difference on their end while I'm seeing the signals about the same. That said however, this may be the same thing going on with my radios, and my location which ever is true.

Fortunately I also discovered that the mount I had the AP mounted on was noisy compared to the new mount I just built next to my shack where I had my GM mounted. I could not detect any significant signal differences between these two locations, but I did notice the noise differences and at first I was giving the GM the credit for being quieter...without knowing it was the locations making the difference. This was sort of like you felt when you noticed the noise differences...albeit your were comparing from the same mount, which is better. I don't know as I would be able to pick up such difference, however, with my hearing problem.

If you can, how would you compare your AP to your other antennas regarding your local contacts at about the same height?

Hey Marconi, I just got to reading that, now I'm wondering how long you needed to make the top tube when you tried the AP without top hat radials? How was it's performance compared to stock configuration?

 

[HomerBB]

Homer, how much lower, if at all, is the top of the AP than was the top of the 5/8λ?

1.5' lower top to top AP to 5/8

AP - 54.4'
5/8 - 56'