My New 10 Meter Antenna - Or, do antennas grow in (er, ON) trees??

[Steve - K4HX]

All other things being equal, the horizontal antenna is going to beat the vertical. If you look at the antenna patterns, nothing indicates the type of contact you are making. It's gain versus angle. The dipole is superior at all elevations angles between zero (or whatever the pseudo-Brewster angle is for your location) and 25 degrees and again from 35 right up to 90.  Want full azimuth coverage? Put another dipole up at right angles.

And, if you really want to go for some easy gain, do what Tom suggested: stack some dipoles. Now that notch in the pattern between 25-35 degrees is gone! No single vertical will come close at any useful angle.

This is very interesting - I've tried a variety of antennas, both verticals and 10 meter dipoles.... over the long term, nothing outperforms the "magic" 75/160 meter dipole.  Yes, when switching back and forth, sometimes the "other" antenna (whatever it is) is better than the "magic" antenna, but not for long.  Fading absolutely makes a difference - usually, when one antenna is "down" the other is quite a bit stronger, but overall the "magic" antenna is better.

I'm wondering if it's simply the height.  The big antenna is WAY up in the air - and it is perched on the top of a hill that goes down fairly quickly in all directions, giving additional effective height.  In fact, to the east, south and particularly west, the drop-off is quite significant, and occurs within 20 feet (or less) of the tower base.

I think the next experiment is to place the I-max 2000 atop the tower.

[ke7trp]

Acording to your your computer programs

[KC4ALF]

Read the obituaries and pay my last respects, and make sure I left something with the Dearly Departed.

[Steve - K4HX]

My computer programs?  NEC was written by Jerry Burke and Anthony Poggio while they were working at at Lawrence Livermore Labs in 1981, under contract to the US navy. The accuracy of the program has been proven time and again. It is the basis for numerous commercial programs used by hams and industry. If you have some information on errors in the general method of moments modeling approach or NEC2 and NEC4 specifically, please let us know.

Acording to your your computer programs

[ke7trp]

Steve, I dont need computer programs.  To choose an antenna. I prefer real world tests.

Here is a video I took today doing back to back tests of actualy real world 10 AM meter from the east into AZ.

The vertical typicaly wins over the wire as you will see.  However, Sometimes the wire is better. 

If anyone gets a $59 vertical and throws it up at 10 to 15 ft, They will work some great 10 meter AM. 

QIX,  Something is not right with your vertical. I think the tuning is off on the rings or you need to cut it down and tune it. 

http://youtu.be/KVc6z1SRcu0

http://youtu.be/RsAKDmBDwWQ



C

[Steve - K4HX]

FYI, I'm using a homebrew vertical dipole on 10 meters right now, so don't think I'm down on them. The reality is that when 10 meters is open, any antenna will work. That's the beauty of the band. 

I've used numerous antennas on 10 meters over the last three sunspot cycles. The horizontal ones were always superior. I will be putting up a horizontally polarized antenna for 10 meters soon, so I will be able to do direct comparisons with the vertical. I'll bet you your iMax 2000 super bee buzz killer antenna that the horizontal antenna will be better. Or you can just send me the $59.   

[K1JJ]

Steve/QIX and company:

There is a significant difference between an 80M dipole (122') used on 10M and a  standard half-wave dipole used on 10M. (16')    (This assumes they are both matched well on 10M too)

On 10M, the 80M dipole has no less than EIGHT horizontal lobes, much like an octopus - four to the ~east and four more to the ~west.  The problem is there are big nulls in-between these lobes that can be down as much as -20db or more from the peak lobes. Thus, if one of these narrow lobes is not on the desired station, the signal could be down significantly or not there at all.

So unless this 80M dipole is rotatable or the lobes have been carefully plotted to know when they favor a particular station, comparing against a vertical as apples to apples is difficult.

In contrast, a standard 10M 1/2 wave dipole has a broad, predictable, figure eight pattern. It is relatively easy to know if the desired station is within its broadside coverage or not. This is why a 1/2 wave dipole for a particular band is important for comparisons. It is called the "reference dipole" for a reason.

That said, an 80M dipole will perform fine as long as the desired station is within one of the narrow eight lobes.  Though, a 1/2 wave dipole for 10M is really a great way to go for broad, DX coverage, especially if it is up 40' or more. Additionally, a turnstile pair (fed 90 degrees out) would cover omni-directional within 3db.

I would have to model it, but contrary to popular opinion, an eight lobed pattern probably does not have any gain over a 1/2 wave dipole since the lobes are all spread out and not focused such as, for example,  two half-waves in phase would be.

T

[ke7trp]

I dont have the IMax anymore.  I used to but it died with the old tower in a big monsoon here.  My vertical is an A99 that was given to me for free.  

10 meter is hot right now, Coast to coast.  32v3, rangers 2s, FT101s and robert on his 4-400 by two 813 rig blasting in.  Lots of fun for all on any antenna!

The more antennas the better.  

C
 

[W2VW]

Steve, I was able to detect your carrier an hour or so ago while you were working K0RZ. Maybe we can take up CW.

[ke7trp]

ja1ifd on 10 meter AM 29.050.  Vertical beat wire.

C

[Steve - K4HX]

QSL TNX OM HI ES FB 73

Steve/QIX: Tom had previously mentioned stacking 2 or more dipoles. These are simple and are hard to beat. Below are the patterns for just two stacked (17 and 34 feet) compared to a vertical dipole at 35 feet. The stack has a lower take-off angle and almost 10 dB more gain! That's like turning on your maul leanyar and it's much cheaper than an iCrap 2000!

Steve, I was able to detect your carrier an hour or so ago while you were working K0RZ. Maybe we can take up CW.

[K1JJ]

Vely impressive difference, Steve.

Just to be clear for those who are not familiar with the plotting and software.... the blue dotted line, marked "reference" is the vertical's plot and the red is the two stacked dipoles.

The second plot says it all. The stacked dipoles show an aggressive low angle lobe that is 10 db more than the vertical in the bi-directional broadside directions. 10db is God-awfully louder.

If one wanted to grab the tiger by the tail, then consider THREE stacked dipoles. The top dipole is at 51'. Lower vertical angle, slightly more gain AND: The advantage here is by adding a simple relay that puts a 1/2 wavelength length of coax in series with the middle dipole, the WHOLE array would now be fed out-of-phase and generate a new vertical take-off angle that is higher than the angle of the original in-phase shown. This capability has been demonstrated by Chuck/K1KW using his quad stacked logs over the last few weekends on 10M.  The ability to match our antenna's vertical angle with changing conditions is invaluable.

This can be accomplished with just three 10M coaxial dipoles, a relay and  11' 2" of extra RG-213 coax for the phasing line.

Steve, how about modeling three dipoles in phase and then out of phase to show these vertical angles?  

BTW, I'm in the process of adding a phasing relay to my three stacked 10M Yagis. Might as well have some fun with it too.

T

[KX5JT]

It's true a high dipole rocks.  However for me, I have no trees to tie off too and towers are not an option so the vertical ground plane is a great antenna.  I've been doing VERY well on 10 AM with it... it plays whirlwide with not much scrote (barefoot ricebox for ssb and digital) on 40 through 10. 

[Steve - K4HX]

Here ya go. Three dipoles stacked at approximately 17, 34 and 51 feet all in phase. The TO is 12 degrees and the gain is 13 dB over a vertical dipole!

[Steve - K4HX]

The first is with the bottom dipole out of phase with the other two. The second is with the middle dipole out of phase with the other two.

[K1JJ]

The 13 db gain over the vertical and the FORM of the take-off angle on the three-stack is truly amazing. And that's with simple wire dipoles...  

The cool thang about the triple stack is that lowered TO angle is about right for serious foreign DXing as well as covering USA "DX".  The out of phase position looks perfect for closer in when the band goes higher angle. You'd have it all.

It would have to be determined which dipole to feed out of phase. The middle produces a much higher angle than the bottom one.  Using Yagis for modeling, I've always thought the middle was best to switch OP.


If that antenna was put up, a simple reference dipole at the same height and orientation, but a few wavelengths away would make the A/B switching a blast.   Nothing like reminding ourselves of how well it works. There's no doubt if I didn't already have an antenna up and had a 60' tree available, I'd hoist up a triple set here.

TNX for the demo, OM.

T

[Steve - K4HX]

I wonder what you mean by high. The two-stack heights are 17 and 34 feet.

It's true a high dipole rocks.  However for me, I have no trees to tie off too and towers are not an option so the vertical ground plane is a great antenna.  I've been doing VERY well on 10 AM with it... it plays whirlwide with not much scrote (barefoot ricebox for ssb and digital) on 40 through 10. 

[KX5JT]

I wonder what you mean by high. The two-stack heights are 17 and 34 feet.

It's true a high dipole rocks.  However for me, I have no trees to tie off too and towers are not an option so the vertical ground plane is a great antenna.  I've been doing VERY well on 10 AM with it... it plays whirlwide with not much scrote (barefoot ricebox for ssb and digital) on 40 through 10. 

Anything more than 30 feet is high for someone without trees or a couple towers right? 

[Steve - K4HX]

If you can get something up 30 feet you are in the ballpark.

I wonder what you mean by high. The two-stack heights are 17 and 34 feet.

It's true a high dipole rocks.  However for me, I have no trees to tie off too and towers are not an option so the vertical ground plane is a great antenna.  I've been doing VERY well on 10 AM with it... it plays whirlwide with not much scrote (barefoot ricebox for ssb and digital) on 40 through 10. 

Anything more than 30 feet is high for someone without trees or a couple towers right? 

[KX5JT]

If you can get something up 30 feet you are in the ballpark.

I wonder what you mean by high. The two-stack heights are 17 and 34 feet.

It's true a high dipole rocks.  However for me, I have no trees to tie off too and towers are not an option so the vertical ground plane is a great antenna.  I've been doing VERY well on 10 AM with it... it plays whirlwide with not much scrote (barefoot ricebox for ssb and digital) on 40 through 10. 

Anything more than 30 feet is high for someone without trees or a couple towers right? 

Yeah,  maybe an aluminum dipole so that only one support is required.  Heck then a  60 dollar rotator might be desired!

[K1JJ]

More info - just to be clear for those considering the phased stacked dipoles..

The in-phase/ out-of-phase switching can be accomplished just as well with TWO stacked dipoles.  Just add 11' 2" of coax length to the top or bottom dipole feedline length to get the pair out of phase. (for higher TO angle)

To be in-phase, (lowest TO angle) just connect the two equal length coaxial feedlines together and feed them as one.

To match the lower impedance of two dipoles (~25 ohms)  use a simple homemade coaxial 2:1 step up balun. (Or even a real 2:1 ferrite transformer)

For three dipoles,  (~16 ohms) a 4:1 step up is close enough, especially if 75 ohm hardline is used to the shack.

There is mutual coupling involved between the dipoles, so I went with 50 ohms for each instead of 70 ohms.  The swr wil be less than 2:1 in most cases with these recommended matches.  If not, then try a different balun step-up ratio.

Make sure both dipoles are identical in length and construction.  

John/JT -  How about a guyed 40' telescoping mast?   These dipoles can be inverted Vees and still work reasonably well, as long as the dipole leg angles are >90 degrees.

T

[KX5JT]

JJ - The telescoping mast with guys is definately an idea I will kick around... I'm having a ball with the vertical though!!  As much as AM is my favorite mode, I do kick around in other modes too and I've been working some digital (mostly Hellschreiber) and even FM.  My TS-570 does a pretty amazing job on FM and FM Simplex "DX" is kinda neat on 10 meters. "DX" is in quotes because it's all stateside that I've done so far but 1K mile plus.  The vertical has proven to be very versatile for my purposes.  I can QSY 40 through 10 and am very impressed with it's simplicity and effectiveness.  (I said the same thing about the G5RV but then when I put a resonant dipole it was quite a bit better... but only in a small WINDOW centered around 3.885)

[Mike/W8BAC]

Dumb Question time, Tom, Is the balun or transformer in the shack and not at the dipole feed points?

If your using 3 dipoles the feed line length is still equal on all three unless you want to change phase?

I'm interested to hear more about inverted V construction and how much that will effect the impedance and transformer values. Only 50 ohm feed line here.

Mike

[K1JJ]

Hi Mike,

The three dipoles each use a convenient and equal length of coax that gets joined together at a juncture. Inners to inners, shields to shieds.  You can just strip them and solder them together. This juncture can be outside at the dipoles or in the shack. It is easier outside cuz the coax lengths will be less if you run ONE coax out to the junction of the three.  Once connected to the unun, seal this junction well for the WX.  You can also use S0-239's connected together in a box and PL-259 connectors. Though, I usually solder them together with short leads and see swr no worse than 1.1:1 as a result.  On 6M and above it will become more significant.  Depends how much of a perfectionist you are... :-)

I should have said the "balun" is really an unun, unbalanced to unbalanced, since all coax is being used.

Also, it is a good idea to put some large ferrite beads at each dipole/feedline junction, and add 4-5 turns of coax there too to eliminate any feedline radiation. Feedline radiation will affect the phase to each dipole and should be suppressed.


Yes all three lengths are exactly the same so that the phase to each dipole is the same.  By adding an 11' 2" coax length to the bottom or middle dipole, this will increase the vertical TO angle of the three array. According to Steve's modeling, the lower fed with the coax length produces a middle angle lobe, while feeding the middle with the extra length gives a high lobe. All three the same length gives the lowest angle and the one you will use 85% of the time.

The inverted vees vs: flat dipoles will have to be modeled to be sure, but this will usually lower the impedance of the dipole a little (not really significant here cuz they will be matched later)  and there will be a some slight pattern cancellation. IE, as an extreme example picture the legs pulled straight down and you have an OW feedline with full cancellation.  

I have used inv vees for Yagi els on 75M and they still do FB. Just pull the legs up as high as possible knowing a flat dipole is best.

Hope this helps, OM.

T

[Steve - K4HX]

You can also feed the dipoles with the appropriate length of 75 Ohm coax so when you combine them your are at 50 Ohms.

For the phase switching, just use a relay to flip the feedpoint connections.

The in-phase/ out-of-phase switching can be accomplished just as well with TWO stacked dipoles.  Just add 11' 2" of coax length to the top or bottom dipole feedline length to get the pair out of phase.