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

[steve_qix]

I finally got a "real" antenna up for 10 meters.  First reports are at least 10dB stronger than the 75/160 meter coax fed dipole I was using.

This antenna is up at the 70 foot level (the sturdy part of the tree is at 70 feet), and the antenna sticks up over the top of the tree by whatever its height is (about 20-something feet - a 5/8 wavelength).

The antenna itself is a commercial IMAX 2000.  We'll see how it works out 

[steve_qix]

I suppose a few more details are in order!  The antenna is attached to a mast approximately 45 feet long. A rope runs from an attachment point at the 40 foot level of the mast, to a pulley that I pulled up into the top of the tree.  The rope holding the pulley goes right over the top of the strongest part of the tree and I pulled the pulley up right up to the top.

Then, the whole mast with the antenna and feedline attached to it started out laying on the ground.  I pulled the mast up into the tree, right up to where the attachment point (5 feet from the top of the mast) reached the pulley.  This puts about 5 feet of mast above the pulley, sticking out a little over the top of the tree.  The Imax 2000 is attached to the top of the mast, so the base of the Imax 2000 is about 5 feet over the top of the tree. 

The mast is there largely for balance, keeping the antenna more or less vertical.  There is also a rope tied to the low end of the mast, allowing for some control over the mast at that end.

[KX5JT]

Are their radials with that vertical Steve?


Here's an interesting page on the antenna: http://www.video-observer.com/imax/imax2000.htm

[K1JJ]

The mast is there largely for balance, keeping the antenna more or less vertical.  There is also a rope tied to the low end of the mast, allowing for some control over the mast at that end.

That's a novel method of raising and supporting a vertical.  

I was going to axe you who risked their neck to climb the tree that high.  This is the equivalent of a tilt-over tower.  Good idea, OM.

T

[WB2CAU]

The antenna is attached to a mast approximately 45 feet long.  

The mast is there largely for balance, keeping the antenna more or less vertical.  There is also a rope tied to the low end of the mast, allowing for some control over the mast at that end.

What does the mast consist of?  Is it one piece?  What material?  A 45' mast is not something off the shelf at Radio Shack.

Eric

[steve_qix]

Hi Eric,

The mast is that military stuff - diameter approximately a little less than 1.5 inches in 4 foot sections.  They fit rather tightly together.  You can easily walk up 40 feet of the stuff to vertical - it's quite strong, although not at all self supporting - guys are definitely required at regular intervals.

Anyway, that's what I used.

The antenna does not have any radials, although a "radial kit" is available.

[K6JEK]

Heard you on yesterday.  Were you on the trevertical?

Somehow while raising the trevertical you managed the guy lines.  Did you use trained squirrels or something?

[steve_qix]

Wow - it would be great to talk with you on 10 meters!  I was using this very antenna.

There actually aren't any guy lines.  There are three ropes visible in the picture.

The attachment point of the mast is about 5 feet from the top (this allows 5 feet to protrude above the pulley), and the remainder hangs straight down.  

This is how the three ropes are set up:  1 goes over the tree top and holds the pulley in place.  The 2nd goes through the pulley and is tied to the attachment point on the mast (5 feet from the top) and is used to actually raise the mast itself.  The 3rd is attached to the bottom of the mast to give some control there.

It's kind of a neat way to get good height     I've used this method for endpoints of wire antennas as well.  In this case, another couple of ropes are used to counter the force of the antenna.

[Jim, W5JO]

I heard you too Steve.  You were about S9 and sounded good.  I called one time but someone else called the station you were working and started a conversation so I didn't press it.

If it is easy to do, attach copperweld to the base of the antenna then run it about the length of the antenna for radials.  At the end of the wire attach insulators then enough rope to hold the antenna as you presently have it.  You had a nice signal the way you are.

[WA1LGQ]

Steve, I was mobile on the way home from work today and heard you working KF0OW. I could just barely hear you in the mobile, but you were there. Couldn't pull out good audio, but could hear a little. Heard you again working John KX5JT up freq a little.  .........Larry

[ke7trp]

Neat antenna and great idea on raising the mast Steve.

The neat thing about this antenna is that it will run 10, 12, 15 and 17 meters.  If you add the Ground plane kit, You loose all the other bands.  I used to talk to Timtron  from AZ on mine on 17 meters every day. 

C

[W2VW]

Neat antenna and great idea on raising the mast Steve.

The neat thing about this antenna is that it will run 10, 12, 15 and 17 meters.  If you add the Ground plane kit, You loose all the other bands.  I used to talk to Timtron  from AZ on mine on 17 meters every day. 

C

Your feedline works on the other bands.

[ke7trp]

NO RF on feedline.  I have a 1 to 1 balun at the base of the antenna. A real one. Not an air choke.  Did not change the bands at all when I installed it.  The COAX shield is cold.
C

[KX5JT]

Steve, it was neat to work you on 10 meters the other day.  I was quite surprised that the dipole was 2 S units better than the vertical. 

I would love to see the schematics if you ever work them out for the modulator on the Valiant.  (Was it a Valiant? I think so.)  It sounded great.  I have to say Steve, you have the most consistent superb audio across different rigs.  Doesn't matter if you're running the class E stuff on 75 with the cheap rat shack condensor or the B-1.  You always have that great broadcast sound and I would be hard pressed to be able to tell which rig you're on.

73 John

[steve_qix]

Thanks, John - it was good to work you as well!  I'm sure we'll hook up again during this cycle.

I am going to have to document the audio driver.  It is actually very simple, and is DC coupled end-to-end. 3 ICs, 5 MOSFETs, some zeners and resistors, a couple of pots to set the bias and one for the feedback, and that's about it.  I can get hundreds of volts peak-to-peak out of it.

The 10 meter antennas need more experimentation.  I haven't figured out what's up.  In other sections of the band, the vertical is 20 dB better than the 75/160 meter dipole - consistently.  It is not the case at 29 mHz, however. A bit odd for sure.

[ke7trp]

Steve Where are your rings?   For the top of 10, You need all the way up then come down 1 to 2 turns. 

I always thought it would be best to cut the top radiator down a bit then come off the rings a bit

[Steve - K4HX]

Expect 3-6 dB for comparable heights. Don't know how many dB your S-units represent.

I was quite surprised that the dipole was 2 S units better than the vertical. 

[KX5JT]

Expect 3-6 dB for comparable heights. Don't know how many dB your S-units represent.

I was quite surprised that the dipole was 2 S units better than the vertical.  

It was on the NC-300.. really about 1.5 to 2 S units difference when he did rapid switches between the antennas.  Now this was the vertical and the dipole was his 75 meter dipole which was beating out the vertical.  It was just about dark there in Townsend so the band was probably stretched and maybe that vertical would have been much better for longer haul stuff at that time.

[ke7trp]

I ran some tests here today on 10 meter AM.  I am not using the same antenna as steve, I am using an old CB vertical that was given to me.  Its an A99.  Its mounted at 15 ft. 

The open wire antenna is 70 feet.  75 meter length with 600 ohm line to a KW match box.

I learned today that you cannot do back to back comparisons as the vertical interacts with the Wire antenna and vise versa.  If I reach up and flip the KW to 15 meters, Then the vertical wins most of the time.

If I do not detune the KW to another band or spin the caps, The vertical looses every single time.

The only way to test is to ground the vertical out when using the wire, or detune the wire when using the vertical.   I had an alpha delta switch handy that grounds out the vertical when on the wire.  But you still need to change the bandswitch on the KW when transmitting on the KW, Even though the alpha delta grounds the intput on the KW.

Having two resonant antennas in the same near field can do some odd things.

I did have the wire beat the vertical on one station. He was loud here.  K2ust (I think that is right).  He was much stronger on the wire. He said he had a "Plate modulated johnson thunderbolt using outboard 811s and speach amp and Johnson navigator for drive, Sounded nice)

On the lower portion of the band down where the SSB DX is 28.300 to 500.  The vertical is far superior to the wire.  Not even close.  I think this is because the vertical I use was really intended for 11 meters and up at 29000 its stretched. 

I am going to go outside now and make a simple 10 meter wire dipole, Coax fed and pull it up the tower. I expect that might actualy beat both other antennas. I will pull it up to 36 ft.

C

[steve_qix]

That's very interesting on the antenna interaction.  I don't get that here, probably because the antennas are over 400 feet apart, and on different supporting structures.  I will be very interested in your further testing.

So far, the 75/160 meter dipole generally outperforms the vertical, and often by so much that I can't hear a station on the vertical that I can on the 75/160 antenna.  That seems a bit odd, but maybe polarization is rather well preserved on 10 meters.  I would actually expect the vertical to do better, as a low angle radiator - and it's up in the air plenty high.  Maybe not high enough, however.....  I may put it up on the tower.

[K1JJ]

So far, the 75/160 meter dipole generally outperforms the vertical, and often by so much that I can't hear a station on the vertical that I can on the 75/160 antenna.  That seems a bit odd, but maybe polarization is rather well preserved on 10 meters.  I would actually expect the vertical to do better, as a low angle radiator - and it's up in the air plenty high.  Maybe not high enough, however.....  I may put it up on the tower.

It's hard to beat a dipole, Steve  - especially if you matched one 1:1 for 10M.

For DX, the polarization tumbles to random, so should not be a factor.

You have the vertical up plenty high already.  A good test is to raise a 10M dipole fed with coax to the same 70' height as the vertical. You may be surprised at the low angle performance at that height.  For A/B tests, the two antennas must be separated by several wavelengths at least. Yes, a vertical can easily couple into a vertical run of feedline. I've seen this many times and essentially makes two antennas act as one with characteristics of both. Usually NG.

Another thing you may be seeing when comparing the 75M dipole against the vertical is simple S/N ratio.  The dipole may be quieter, just like a Bev does.  Today I noticed a lot of noise coming from the west, especially when the sun was sinking to the west. Solar noise can occur along with cumulative digital hash and power line noise that propogates in from major cities just like radio signals.  The Yagis were beaming right into this and some signals were heard better on my 75M dipole as a result. The signal was down -20db on the dipole, but the S/N was better due to this noise from the west..


T

[Steve - K4HX]

I've been using the 40 meter loops as a secondary receive antenna on 10 meters. Often when a signal fades on the vertical dipole, reception is FB on the 40 meter loops and vice-versa.

Tom, I heard both you and Chuck on 10 meters today. You were both PW but just about 100% copy. It did not have the backscatter sound.

[Steve - K4HX]

This  topic came briefly on 75 meters last night. From the antenna modeling plots below, you can see that a horizontal dipole is superior to a vertical dipole (at least in the broadside direction of the horizontal dipole). The horizontal dipole has more gain and a lower take-off angle. The differences will vary some at different height, but I haven't seen a case at any reasonable height where the horizontal dipole wasn't better.

The center of both dipoles is 35 feet, the ground parameters are "average" - dielectric constant of 13 and a conductivity of 0.005 mho/m.

The solid red plot is the horizontal dipole and the dashed, black plot is the vertical dipole.

[steve_qix]

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]

I had very good luck with my Imax when it was on the old tower. 

now that I have compared the dipole, A99 and 75 meter OWL antenna I can simply reinforce what we already know.

ITs best to have all three. There is no one antenna that will win over the others.


Sometimes the vertical is far better.  In fact, Most of the time on SSB portion of the band the 10 meter Vertical wins.

The Horizontal 10 dipole is directional so that limits its usefullness to me.  Its also completely 100% useless for instate contacts or 10 meter AM, or SSB nets or rag chew.  Its so far down people cannot hear me.

All three have had there moments where the signal was significantly better then the other.

C