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Author Topic: Trap Vertical (Hustler 6BTV) Trap Losses  (Read 7241 times)
WX7G
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« Reply #15 on: April 18, 2010, 03:09:14 PM »

N3OX, yes each trap was measured for inductance and Q. A NEC model was then constructed with the traps and the tuned tubing lengths. The NEC model gave base impedance and VSWR bandwidth for each band. This was compared to actual base impedance measurements taking into account the ground resistance I have, which is around 15 ohms. This was then checked against paper-and-pencil numbers.

The trap losses quoted are with the vertical placed over perfect ground. Over a ground such as mine the trap losses are lower because the antenna current is lower.

A subscription to AntenneX allows you to view over 10 years of articles. That's over 1000 antenna designs. The CFA, EH, PF, Isotron, Tak-tenna, Room Cap, and other antennas are analyzed. Small antenna designs are featured from a 9" 28 MHz vertical on up.
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WX7G
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« Reply #16 on: April 18, 2010, 03:19:14 PM »

VK1OD, the losses quoated are the "trap" losses with the antenna mounted over perfect ground. Note that the losses on 40 meters occur in the 10, 15, 20, and 30 meter traps and they are operating as loading coils.

With the antenna mounted over a reasonable ground having 10 ohms of ground loss the trap losses will be roughly 1 dB. This will indeed create quite a bit of heat. Don't try to run 1500 watts of RTTY with this antenna.

What really helps this antenna on 40 meters is that it is top loaded with most of the loading occuring 80% up the vertical. This makes for a rather high radiation resistance helping to offset ground and trap losses.  

The traps are nothing to write home about. If one wants to build a low-Q inductor this is how to do it.

Read the article if you would like to dissect the method in greater detail.
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K0BG
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« Reply #17 on: April 18, 2010, 03:24:50 PM »

Assuming that low coil Q relates directly to trap losses is a push at best.


Read what Tom says about this: http://www.w8ji.com/traps.htm
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W5WSS
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« Reply #18 on: April 18, 2010, 05:27:01 PM »

I am in the middle of testing quater wave verticle vs the Hustler mobile system...I know the traps are different anyway 1st test compared the 1/4 wave 10M whip installed on my mobile and tuned properly vs the Hustler installed on my mobile from the same ball mount in the middle of the roof top and tuned properly. 10 miles down range the signal was so close that the operator could not detect any difference there.Not bad for a mo-1 mast and super resonator with stinger...I would say the Hustler products are pretty efficient. I am willing to conduct tests on all the bands down to 40M. I fully expect the 1/4 wave to begin to demonstrate more signal strength by 20M but we will see. 73
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WX7G
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« Reply #19 on: April 18, 2010, 05:57:39 PM »

Upgrading from the BTV to a StepRR, given your ground, can give you 1 dB to 2 dB more signal. An amp may be a better investment.

Does the vertical comparison report support this claim?
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WB2WIK
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« Reply #20 on: April 18, 2010, 06:13:40 PM »

On 10m, the BTV is a "full sized" (1/4-wave) vertical, so I don't see how a different 1/4-wave vertical would be better.

On 15m, it's slightly short.  On 20m, it's slightly "more" short.  On 30m, it's slightly more short, again.  But even on 40m, it's only a couple of feet shorter than a full 1/4-wave vertical.

The HUGE compromise with the 6BTV comes in on 80m, where  it's less than 1/2 sized and very loaded (top loaded).  It's efficient and works well on 80m, but only over a very narrow bandwidth (like 50 kHz).  Off resonance, its performance is severely degraded.
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K0ZN
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« Reply #21 on: April 18, 2010, 07:06:21 PM »

Before you shell out hundreds of dollars on a new antenna, I would suggest you give serious consideration to doing a comparison test between a full size quarter wave vertical (something homebrew and temporary, but a quarter wave and using YOUR ground system!) and the BTV on maybe two bands, say 30 and 20 or whatever and compare the signal strength on a field strength meter. You can build our buy a basic field strength meter. Using YOUR ground system is pretty key to getting a real "apples to apples" comparison. Any calculated answer is THEORETICAL.

You could also consider making a homebrew vertical using individual wires for each band; that totally eliminates the trap question! That would not be a hard antenna project.

You also may want to consider an UNUN at the base to get a good impedance match. They are commercially available.

All the above said, if money is not an issue, the SteppIR is very attractive, no doubt.

73,  K0ZN
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N3OX
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« Reply #22 on: April 18, 2010, 07:29:22 PM »

Quote

A subscription to AntenneX allows you to view over 10 years of articles. That's over 1000 antenna designs.


Yeah, I know.

I have reasons for not subscribing.
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
N5YPJ
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« Reply #23 on: April 18, 2010, 07:33:57 PM »

K0BG, WB2WIK and VK1OD plus W8JI's article all make a good educated argument in favor of the 6 BTV. My argument is based more on experience this antenna for it's price and performance in the multiband trap vertical market is great. I'm not able to get a horizontal antenna more than 35 ft above ground and an inverted vee at that, with this antenna I work DX easily on 40 meters. It wont beat a yagi or a quad at one half to one wave length above ground but it doesn't cost what one does either plus the tower, rotator, installation, etc., etc. do either. I can set my antenna up within about half a day should I decide to change QTHs. Not a cure all but it meets this poor ham's needs.
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WX7G
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« Reply #24 on: April 18, 2010, 08:15:32 PM »

Comparing the BTV against a full size vertical over the described ground system would be a challenge. The biggest challenge is measuring the approximately 1 dB difference on 7 MHz.

We - including me - are using the term "trap" loosely. By trap I mean what Hustler calls a trap even when it is operating as a loading inductor. The only band on which the 6BTV has only a trap is 10 meters. On that band the trap loss is 0.7 dB.

On 15 meters we have the 10 meter trap operating as a loading coil and we have a 15 meter trap.

On 20 meters we have the 10 and 15 meter traps operating as loading inductors and we have a 20 meter trap.

On 30  meters we have the 10, 15, and 20 meter traps operating as loading inductors and we have a 30 meter trap.

On 40 meters we have no traps. We have the 10, 15, 20, and 30 meter traps operating as loading coils.

On 80 meters we have a rather lossy loading inductor at the top. The radiation efficiency over perfect GND is 25%. Over a 15 ohm ground it's 15-20%.

N3OX, do you not prefer AntenneX since L.B. Cebik left it when he became a silent key? It is the only magazne that has debunked all the small miracle antennas.
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NO9E
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« Reply #25 on: April 19, 2010, 07:06:06 AM »

I have full size verticals for 40-30-20 with 15 ground radials, 80 full size vertical with 8 elevated radials, DX-77 that is no-radial trapped 40-10m vertical at 5 ft,  and a few dipoles. DX-77 and full-size verticals are more less equal on 20-30-40, while dipoles beat them up by 5-15 db, local or DX. Some of the difference could be due to GA clay and lots of tall trees but some is due to 6db of ground gain for dipoles.

An issue of 1-2 db pales in comparison to 5-15db. I would first compare a vertical to a dipole in your location. If the vertical is 10 db down, whether it can be improved to 8 db down does not matter much. Good automatic antenna tuners make resonance less important, at least < 200W.
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VO1FZ
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« Reply #26 on: April 19, 2010, 11:05:39 AM »

How high are your dipoles?
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NO9E
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« Reply #27 on: April 19, 2010, 12:04:44 PM »

Dipoles are at 40 to 60ft.
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N3OX
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« Reply #28 on: April 19, 2010, 12:12:32 PM »

40 to 60 foot high dipoles are hard to pull off stealthily unless you've got some REALLY big trees
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
K0BG
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« Reply #29 on: April 19, 2010, 12:44:51 PM »

Quote
It is the only magazne that has debunked all the small miracle antennas.

I might buy this, but that fact alone (if it is one) doesn't mean everything else on the site is kosher. Dan (N3OX) has his reasons for not joining, and I have mine. I'd bet they are one, and the same.
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