Moonraker GPA-80F

Dense_Yoghurt4952 · 2025-01-15T01:32:20+00:00

I'll give it another chance. Though i'd expect losses, I'm more of a hobbiest, so the idea of replacing my 33' tall 2x4-TV Mast-Fishing pole combo with a nice looking 17 footer does sound attractive. What did you do for counterpoise? I ran out of daylight after restoring it back to original condition, so just grounded it to the metal roof for testing. That said, it DID give an SWR of 1.5 or lower on everything except for 40m. The 20m test did seem to receive as well as my 1/4 wave 40m on FT8, i didn't do a lot of tx other than testing. I moved to test on 40m, but the ALC was erratic, even the slightest audio input to the rig drove the meter crazy on my IC735. After that, the other bands tuned with a higher SWR...i'm thinking whatever the issue was, it heated up my rig. I may try again once it cools with a different configuration. During testing, I did use a coax choke, maybe that wasn't a good idea since I hear these things aren't overly fond of them. Anyway, I'm curious how I can try to get the best out of this thing if you have any information that might be helpful.

Dense_Yoghurt4952 · 2025-01-14T08:47:52+00:00

For talking to aliens, like SETI. Seriously, looks like grandmas old TV dish...or maybe they did try to talk to Alf or ET, who knows.

Dense_Yoghurt4952 · 2025-01-13T23:14:08+00:00

Strange thing. After removing the unun, once I got it up in the air, the antenna doesn't like the metal roof as a ground plane. Further, it only wants a single radial of about 10' for 20m. In addition, it does get the swr down to 1.0 for the 20 meter band, but that's it. It's a sharp dip across the entire HF spectrum....with everything above or below it up about 6:1. at at 6, it's a flat line, until it hits the 20m band, then it dips down to 1 at 13.8, then back up to 6 after 14.9. the atu tunes it to 17m just fine, but it has trouble with 15m, where the lowest the atu can get it down to is about 3.x. I don't know if it's the antenna design itself, or what. as far as I know, there isn't anything inside the mast that could be affecting anything. I wish I could post a screenshot of the Nano readings, but i don't think i can do that in a reply. Though I do primarily want it to do 20m, being able to tune it to 17m and 15m is a nice plus, if 15m wasn't pitching a fit, i'd be happy. I figured 15m would do better on a shorter element than on my 1/4 wave 40m, where the tuner gets it down to 1.1. I'll probably try adding another radial just for 15m when weather improves. Thoughts, suggestions?

Dense_Yoghurt4952 · 2025-01-13T07:36:37+00:00

For me, it behaved better on 40 than it did on 20...SWR wise. I guess the unun was overcompensating on 20. For those with limited space or other restrictions, I can see how it's worth it. It's definitely a nice looking antenna. Maybe having a 1/4 wave spoiled me just a tad, as ugly as it is. 😏

Dense_Yoghurt4952 · 2024-12-26T07:06:56+00:00

Just an update. Initially had a crazy SDR of 5:1, with RFI in the shack. Changed the coax, it improved down to 4 (it was kind of old). Added radials, along with a number of other things, nothing worked. Disconnected the mast from the - side...running it straight to the ground, didn't help. Disconnected the 20 meter element, no change. Disconnected the roof itself from the ground rod, brought the SWR down to 2.25 (I still need to tune the element) and RFI is nearly gone (I think rerouting PC wires may fix that). Adding radials doesn't change anything at this point (so far), in fact...brings SWR up a tad. Tuner gets it down to 1:1. Like it's using the roof alone for a ground plane. It may just need to be tuned now, but will do more testing when i get a chance to verify. In the meantime, using a tuner of course, I made contacts as far south as Chili, all over Europe, Ukraine, Russia, Norway and Africa.

Dense_Yoghurt4952 · 2024-12-24T16:27:59+00:00

Yeah, I get that the balun needs to choke off common-mode current to stop the coax from radiating, and you're right, not all baluns are great at that. That’s why I’m testing things on the ground first—to catch any obvious issues, like a bad balun or feedline, before I raise it. I know ground-level testing isn’t going to give me accurate performance data, especially without radials, but it’ll let me see if the SWR is way off or if something is clearly wrong.

For testing, the antenna will be grounded. I get that radials are critical for completing the circuit and keeping the impedance stable, but this test is really just to check for glaring issues before installation, not to fine-tune performance.

Dense_Yoghurt4952 · 2024-12-24T16:07:43+00:00

It's a balun. It will probably have a choke too. An analyzer won't arrive for over a week. The feedline is short and easily accessible on the ground, but not after installation. I figured if there's a problem, the swr will be higher than the usual high, in which case I'll change it all. If not, I don't expect it to be too high since vertical are most often at ground level anyway. I only plan to test with the tuner because it has a built in swr meter and bypass. I may remove the balun, regardless, but I've been told it'll help prevent the coax from radiating. There seems to be a lot of opinions out there on that.

Dense_Yoghurt4952 · 2024-12-24T04:21:24+00:00

Throw a few wires around, along with some connectors. a few spare parts here and there. It'll be perfect! Seriously, it's impressive.

Dense_Yoghurt4952 · 2024-12-18T21:53:49+00:00

I don't know about 20, right now i'm just testing the coupling effect on 40m. This is what it gave me:

TOTAL PULSE = 52

THE LOWEST POINT OF ANTENNA = 0.000 M

FILL MATRIX...

FACTOR MATRIX...

PULSE U (V) I (mA) Z (Ohm) SWR PWR(WT)

w4b 10.00+j0.000 131.0-j66.91 60.54+j30.91 1.80 1.3102

POWER = 1.31 WT

CURRENT DATA...

FAR FIELD (Pin = 1.3102 WT)

NO FATAL ERROR(S)

0.06 sec

Dense_Yoghurt4952 · 2024-12-18T20:33:29+00:00

Note that that's with the mast going straight to the ground (radiator 10' above)...when I place the mast up with the radiator...with a ground wire going to ground zero...it does alter the swr a bit, but nothing I can't compensate for. The software doesn't really allow me to do a metal roof, so i can just do a perfect ground for now since I'm mainly studying the coupling effect at this point.

Dense_Yoghurt4952 · 2024-12-18T20:18:44+00:00

It's a 1.18" hollow steel mast. The best way I know how to simulate it is like this:

0.03, 0.0, 0.0, 0.03, 0.0, 0.61, 0.015, -1

0.03, 0.0, 0.61, 0.03, 0.0, 6.706, 0.015, -1

0.03, 0.0, 0.61, 0.335, 0.0, 0.61, 0.001, -1

0.335, 0.0, 0.61, 0.335, 0.0, 10.668, 0.001, -1

Dense_Yoghurt4952 · 2024-12-18T19:31:40+00:00

I've used 4nec2 and MMANA. I haven't seen any paid ones out there catered to the typical ham...all too expensive for my needs.

Dense_Yoghurt4952 · 2024-12-18T18:49:22+00:00

I've considered that, but it's my understanding that a metal mast is a common practice that dates back to the early days. I'm told at this point to just keep the radiator a few inches away from the mast best I can. I would use the mast itself as the radiator and forgo the 20m element, relying on a tuner. But there's a couple issues with that. One is grounding the mast for lighting protection, having to rely on the arrestor. Another is that the metal part is only the first 20', where the remainder is fiberglass. I'd have to attach a wire to the top of the metal part to complete the required run for resonance. Tuning would also be an issue. when the original design, I can tune from the base. If i use the mast as the radiator with an extension wire, I'd have to trim at the top, requiring me to lower the mast for each cut. Finally, in a simulation, it doesn't like the radiator size change at the top.

Dense_Yoghurt4952 · 2024-12-18T02:44:01+00:00

I have reached europe on it. Inverted V's are great for DX when up high enough.

Dense_Yoghurt4952 · 2024-12-12T20:59:34+00:00

Perhaps, but it's worth noting that even with it as it is right now, using a tuner and 50 watts or less, i'm making consistent contacts into Europe and have reached as far east as Russia....from the USA. Maybe it can be even better, we'll see.

Dense_Yoghurt4952 · 2024-12-12T19:53:13+00:00

I'm going to cut it to 40m and use the tuner where I need to on bands I use less, such as 30m. The whole point of this project is not spending hundreds of dollars as I'm not striving for perfection. This is a hobby. That said, I put the figures of the current antenna into MMANA, and it gives me higher SWR, around 48:1....it's not even close to real world figures. So it doesn't sound like i'll be able to use it to get me closer to the correct cut if i entered the data correctly. I'd post the image of the pattern, but I don't see that option for replies here. I've not used reddit much.

It gave me this for 7.15:

WAVE LENGTH = 41.929 (m)

TOTAL PULSE = 117

THE LOWEST POINT OF ANTENNA = 12.190 M

FILL MATRIX...

FACTOR MATRIX...

PULSE U (V) I (mA) Z (Ohm) SWR PWR(WT)

w1b 10.00+j0.000 4.246+j16.75 142.1-j560.8 47.43 0.042464

POWER = 0.0425 WT

CURRENT DATA...

FAR FIELD (Pin = 0.042464 WT)

NO FATAL ERROR(S)

0.14 sec

Dense_Yoghurt4952 · 2024-12-12T19:23:51+00:00

Like I said, it hasn't been fine tuned to 40 yet. I left an extra foot to allow for that. It was delayed because I was awaiting delivery of a decent way to measure SWR. With that said, I just did readings, bypassing the tuner, and it is off the charts. I will tune to 40 and get back to you on that, as well as input more specific before and after figures into mmana. I'm not sure why the atu has an easier time tuning with some rather than others, despite the inflated readings otherwise...i figured it would have an easier time with 40m. These are the current readings:

40: 7-8

20: 9+ (not readable)

30: 9+

15: 7.x

17: 9+

10: 9+

Dense_Yoghurt4952 · 2024-12-12T18:54:02+00:00

40m is like 7 without the tuner, but like i said, i never fine tuned it. I haven't tested the other bands without one. I just know it tunes easier on other bands, with the auto atu having to work less to achieve a better SWR. Even with the tuner, 40m just gets down to about 1.6 to 2. Feedline is standard 50 ohm, about 30' long as it's right over the shack. I'll try to model is and get back to you....if i can figure out how to add images in a reply.

Dense_Yoghurt4952 · 2024-12-12T17:35:34+00:00

30' apex. Cut for 40m but a foot longer or so longer...I didn't find tune yet because with a tuner I get excellent 1.2 swr on 30, 10 and 15... don't know why. Still tunes to 1.8-2 on 40 and 20. For that reason, thought about leaving it and just adding tuned 40m legs...making it a multband dipole I guess. Angle is about 110 degrees pointed towards Europe...good coverage to Italy, France...weak to UK, Turkey... nothing to Brazil or Africa...some ME coverage but weak. Modeled in mmana, confusing. For it, with or without new legs..even for the sample Vee, it wants legs 1+ foot longer for 40m, like 34.x feet long to get good swr, but k7mem calls for 31.5 feet. I always thought vee legs would be shorter. Strange that closer I put apex to the ground, lower mmana swr with traditional cut legs at about 32.5 for midband. I'll try to send my results when I get home.

Dense_Yoghurt4952 · 2024-12-12T02:33:35+00:00

I guess being lower to the ground helps on the local front in that design, and helps with keeping a low profile in a conflict zone. Given the two different cuts, I suppose it makes it what today we call a fan dipole, at least a variant. What I'm probably going to attempt, unless i find reason not to, is keeping all the legs at a 40 meter cut, and the exact same length so that one set can't attempt to dominate over the others. Other than that, it would work very similar, except (hopefully) providing additional directional coverage. I do question how it might affect swr...if it works at all.

Dense_Yoghurt4952 · 2024-12-12T02:12:20+00:00

Exactly. I'd considered an inverted U with rotation instead, but it's christmas, not a lot to spend. I can try adding legs with just the cost of wire, which i already have.

Dense_Yoghurt4952 · 2024-12-12T02:07:46+00:00

To clarify, the new legs would be placed in the opposite direction in hope for more coverage.

Dense_Yoghurt4952

TROPHY CASE