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Author Topic: Vertical & 1.5Kw VS Tribander & 200w  (Read 5246 times)
AF3Y
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« on: January 08, 2013, 10:10:56 AM »

OK, here is your math problem for today.  

Ham "A" is in Key West, Florida, running 1500 Watts to a 1/4 wave vertical with 36 radials of varying lengths.

Ham "B" is down the street from "A", a few hundred yards. He is running barefoot, 200 watts to a Force 12 Tri-bander up around 100 feet.

Assuming both these guys want to work BS7, WHICH One is going to put the most power in the ears of the ISOTROPE on Scarborough?

Obviously, assume all prop, condx, etc. to be equal for the comparison.
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N3QE
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« Reply #1 on: January 08, 2013, 10:31:35 AM »

On 10, 15, and 20... Ham B will hear BS7 and work BS7. Ham A will be heard by BS7, but not be able to hear BS7.

Ham A can very likely get him by grey line on 40, probably 30 and 80 as well. If he had a receive loop and propogation was in favor, maybe even 160. Ham B cannot.

Tim.
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KY6R
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« Reply #2 on: January 08, 2013, 11:20:36 AM »

I was going to make a wisecrack about it being a trick question - that an isotropic radiator doesn't exist, but . . .

I agree with N3QE, and that the BS7H team wouldn't stay on those scaffolds long enough for the pileups to get anything less than massive. the competition would be HUGE. Even on the West Coast - with a Moxon and 800 watts I had a rough time getting one Q - only on 20M SSB. And BS7H is EASY from the West Coast. Anything in OC-PAC and Asia is easy. P5/4L4FN was very easy for me.

Even my 20M Moxon had 4 dBd gain over a dipole. The vertical has loss - from 3 dBi to [a lot more depending on which band you are using it on]. This means your 1000 watts of power going in will not be what is effectively going out. The yagi users take off angle would also cover the lower angles that your multiband vertical probably won't - and for Florida to BS7H, low angles would be needed - especially if it were (again) activated at the low part of a cycle.

Your vertical also has no F/B - so you will need decent filtering if they run the split only 2 Khz up.

NOW - if you phase TWO verticals using something like the PVS-2 from DX Engineering - you will have gain and directionality end fire and broadside. You will then be on par with something like a Moxon - at least end fire, and would compete well with the yagi users. You could perhaps get a PVS-2 for 20M and do some switching to switch it in or - out - since phasing renders the two antennas as a mono bander. If you have the bucks - Array Solutions has that multiband phase system - but its expensive.

I wouldn't count on the same conditions that happened with ZL9HR - they had a ridge and big hills and an inlet with antennas that favored the East Coast. BS7H is a clear water path to W6-W7, KL7, KH6, JA, VK/ZL, Asia.

« Last Edit: January 08, 2013, 11:34:16 AM by KY6R » Logged
W6DXO
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« Reply #3 on: January 08, 2013, 12:40:55 PM »

Both guys hear the DX, but "B" get's in the log.

It's that whole "laws of physics" stuff I keep hearing about... Roll Eyes

73 de harry, W6DXO
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AF3Y
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« Reply #4 on: January 08, 2013, 05:40:07 PM »

I dont know guys....... Roll Eyes

Using these two stations and running VOACAP predictions to various areas yield some interesting results. But then again, I would never put my $$ on a VOACAP prediction, having seen it be "out of the ballpark" at times.

73, Gene AF3Y
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KY6R
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« Reply #5 on: January 08, 2013, 05:47:23 PM »

there's always the ARRL Antenna Book and Array of Light for real "enlightenment"......
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NU1O
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« Reply #6 on: January 08, 2013, 06:12:23 PM »

Station A has about 8.8 dB of gain solely due to the big difference in power. A tribander has loss on 15 and 20 meters due to the traps. I don't know exactly how much gain one gets by moving from the average height of about 50 to 55 feet to 100 since much of that depends on the path. If both stations are on the East Coast I'd want as much gain as possible at low takeoff angles and station B should have a big advantage in that regard.

If the stations are on the East Coast I'd go with the tribander at 100 feet but if they are on the West Coast I'd go with the vertical and the big power advantage.

73,

Chris/NU1O
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KY6R
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« Reply #7 on: January 08, 2013, 07:42:19 PM »

You will have a much more realistic idea of exactly how much gain you would have with each antenna if you use EZNec and HFTA to model them. Since you are on Flat terrain - EZNec could be used by itself to really know how much LOSS you have with your vertical (make sure you model with your radials). You could then subtract that loss from the gain the amp gives you to see how much less than 1000 watts you would have.

EZNec would also show you the takeoff angle of the vertical - and then you will see how much better it would be with a yagi up 100 feet. EZNec will show you the gain added by ground reflection at that height - and it is significant, possibly a couple dB. EZnec is better than guessing.

Trapped triband yagis have sub-optimal element spacing, and you could assume that trap loss is maybe 1 - 2 dB. On trapped tribanders, 20M suffers the most and it gradually gets better on 15 and 10M. Non trapped tribanders (Force-12, Bencher) do better more so because they use an interlaced design with sleeve coupling, and they have been designed using EZnec. There is no trap loss, but as you add each successive band - none of the bands in the tribander are really "like having 3 monobanders". Not exactly - but far closer than a trapped tribander with sub-optimal spacing. Each successive band degrades and causes at least some interaction. Which is exactly why I went with the 2X2 17M monoband stack - 7 dBd on 17M and 4 dBd on 20M, and a set of stacked rotatable dipoles on 15, 12 and 10 - maybe 2 dBd on each of those bands. No negative interaction between elements at all.

Now - the question didn't specify what bands, and I think most have assumed high bands. On 30M and down - if you can't get a horizontal antenna up 1/2 wl - or more - I would always choose the vertical. My 60' high 40M doublet is WAY better than my old 43' vertical, but when that doublet was only up 35', the vertical and doublet were about the same.
I prefer hatted verticals because they slightly compress the lobes and give you slightly lower take off angle - which from the East Coast - you will need for BS7H . . ESPECIALLY if it gets activated a the next bottom of the cycle - like it was this last time  Grin
« Last Edit: January 08, 2013, 07:50:01 PM by KY6R » Logged
W2IRT
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« Reply #8 on: January 09, 2013, 05:48:36 AM »

Personally, I don't buy the premise. If you can afford to put a triband Yagi up at 100' AGL you can probably also afford at least a kW amp if not legal-limit. And I'd also add that if you're putting a Yagi up that high, you're probably not using some POS trapped tribander, but rather something with some serious gain on 20 and 15 as well as good F/B and F/S rejection.

I can tell you that from my own experience with a C31XR up 70' it's fairly easy to get through with 200W if there isn't a huge pileup. If there is, that extra 7-8 dB out of the amp makes a huge difference. From my QTH, I needed my AL-1200 and the C31XR to get BS7 in the log in 2007.

But if I had to choose, from my QTH, I'd rather have the high Yagi and 200W since the combination of good receive gain to hear the BS7 (doubtful on a vertical), and F/B and F/S rejection to attenuate the lids as much as possible would beat the performance of a vertical like a red-headed stepchild. And since you're not specifying which tribander would be used, I'll pick a Force-12 C49XR (49' boom, 7.6dBd on 20, 8.2dBd on 15 and 9.4dBd on 10), which, if driven with 200W, would yield an ERP of about 1100W on 20m after Heliax feedline loss is taken into account.
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N2RJ
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« Reply #9 on: January 09, 2013, 07:23:48 AM »

I rarely turn on the amp for most of my DXing. The 100w and the MonstIR at 75' beats out a lot of guys running a tribander and 1.5kw.
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W2IRT
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« Reply #10 on: January 09, 2013, 07:51:08 AM »

I rarely turn on the amp for most of my DXing. The 100w and the MonstIR at 75' beats out a lot of guys running a tribander and 1.5kw.
Not to mention being 875' ASL and having a great takeoff angle over about 270 degrees.
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Night gathers and now my watch begins. It shall not end until I reach Top of the Honor Roll.
N3QE
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« Reply #11 on: January 09, 2013, 08:10:08 AM »

I dont know guys....... Roll Eyes

Using these two stations and running VOACAP predictions to various areas yield some interesting results. But then again, I would never put my $$ on a VOACAP prediction, having seen it be "out of the ballpark" at times.

73, Gene AF3Y

I too am dubious about VOACAP but...

I think that running VOACAP for the reverse path would be most useful here. The vertical is very unlikely to be able to hear BS7 above the noise on the high bands unless the BS7 has an enormously massive monobander stack.

The vertical in Florida could work quite well on 40/80 if the HYPOTHETICAL BS7 DXped did more than a token low band effort. I'd quote something about "two guys on the beach" but... what beach?!

Tim.
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KY6R
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« Reply #12 on: January 09, 2013, 08:16:07 AM »

I rarely turn on the amp for most of my DXing. The 100w and the MonstIR at 75' beats out a lot of guys running a tribander and 1.5kw.
Not to mention being 875' ASL and having a great takeoff angle over about 270 degrees.

The good old hills of Sussex County. Grew up there and graduated from Newton H.S. Worked in Franklin, NJ soldering military solid state tube replacement parts at a place called "Tymac Controls" during the summers when I first went to college - and before my family moved to the SF Bay Area - half way through college.

People don't realize how nice NJ can be . . .
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N2RJ
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« Reply #13 on: January 09, 2013, 08:19:13 AM »

Shhhh don't tell 'em... Wink

Yes it is nice out here. But it still is NJ, so this means that you can adore the wonderful rolling hills and scenic countryside including the wildlife while you sit in your car and an attendant pumps your gas.
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W5DQ
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« Reply #14 on: January 09, 2013, 08:34:11 AM »

Bottom line .... you use what you have and hope for the best or 'invest' more $$$ and add capabilities.

With my vertical setup, I have found that by modifying my 6BTV by extending the main antenna mast above the 30M trap and adding a cap hat (DX Eng Hot Rodz setup and replacing the 80M Super resonator with the 40M Super) I can hear better on 80M and 40M with the vertical and results indicate that my TX signal has better presence since I am logging more Qs than before. The bandwidth is wider too, appx 100Khz on 40M and 50+khz on 80M - both tuned at the low end of the band.

I would really like the chance to try for BS7H on any band using my current vertical config against my Force 12 C3S at 13M high. Someday when I move to the retirement QTH, I plan on having some 'real' antennas Smiley

Gene W5DQ
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Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
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