The AM Forum

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  ;D

(http://www.classeradio.com/imax.jpg)

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.

Are their radials with that vertical Steve?


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

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

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

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.

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?

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  8)   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.

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.

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

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.

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

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

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.

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

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

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.

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

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.

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

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.

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.

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.

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

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.

Acording to your your computer programs :P

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

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.

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

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.  ;D

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.   ;)

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

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
 

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

ja1ifd on 10 meter AM 29.050.  Vertical beat wire.

C

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!

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?   :D

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

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. 

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!

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.

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

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

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

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

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

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

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)

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

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

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.

Yes, good idea using 75 ohm coax for two dipoles to eliminate the 2:1 matching unun.     1.4:1 swr is acceptable.


About 180 degree reversing the connections using unbalanced coax, though...  how would you avoid the shield to inner connection problem?    That would unbalance the system I wud think.... no???

T

I think a delay line would be better

ok just because im lazy how about modeling 2 and 3 vertical dipole with the bottom element 10 feet off the ground inline with quarter wave spacing
 

I would think flipping the connections at the feedpoint of one dipole.

Yep, that would work. Just need to support a relay at the center insulator with a control wire pair coming down with the coax.   OR use RF chokes to isolate and send the DC up the coax.

T

With a 30 foot mast, you could put up the antenna below. It's nothing more than a full wave loop but configured in a 2:1 vertical to horizontal ratio. Feed it at the center of the bottom wire and you have a 50 Ohm impedance. It has a 1-2 dB more gain than a horizontal dipole. This means you'll have more like 8 dB gain over a vertical dipole (as shown in the plots below). The horizontal portions are only 6 feet. The supports could made out of PVC.

Single loop will be 100 ohms but not to worry a quarter wave section of 75 ohm transforms to 50 ohms very well.

No it won't. The 2:1 height to width ratio yields a 50 Ohm feedpoint.  

I didn't catch the W/H ratio. I wonder if you could corner feed and get some directivity?

Pretty cool using the W/H ratio to get 50 ohms for a single loop.  EZ to support with the reduced 6' horizontal span at the top.  PCV pipe at the top sounds FB.

Taking it a step further, I'll bet a pair phased ~120 degrees out would look pretty choice.   It would help suppress some of that high angle stuff and give a nice F/B to boot.

There will be an optimum height to give the cleanest high-angle suppression pattern as determined by the modeling.

T

Lots of possibilities. I brought it up as an option for JT. He could put this thing on his mast. Make it with wire and PVC and it would be very light. I might make one this afternoon for a quick and dirty replacement for my JS vertical dipole.

And it even has a little gain (almost 2 dB) over a horizontal dipole. See the plots below for a comparison at 35 feet (red is the loop, dashed is the dipole).

Completed the rectangular loop. I used 36 feet of #12 insulated wire. The thing is 50 Ohms at 28.1 MHz. I figured it would be a little low with the insulated wire, so some trimming is required. But it works FB. SWR is below 2:1 up to about 28.4 MHz. And it is much quieter on receive than the vertical dipole. The S-meter almost goes to zero. It never went below 2-3 with the vertical dipole. I can copy AM stations that do not even move the S-meter now.

Pretty cool, OM.

You may be picking up neighborhood power line noise or digital crud due to the vertical polarization of the vertical.  The horizontal sounds like it's working FB.

Can you add a second one to phase or as a reflector?  


I'm about 20% into my new homebrew 10M monoband amplifer right now. Even built a relay system to switch the 10M Yagis out-of-phase. Still need to climb up there and install it.  Kinda excited to see how well that works.  Gonna be loaded for bear on 10M AM soon.  

Try to get some directivity into Eur with your new system. I can't wait to have a "court" session working the Euro AMers like we did on 75/40M... ;)

T

Did some trimming on the loop. Moved the resonant freq up to about 28.6 or 28.7 MHz. So, with a little more trimming and I'll have it where I want it.

I could hear any electrical motor in the area on the vertical. Someone was running a grinder or sander last weekend. I could hear it all over the band. The noise would go away when switching to any horizontal antenna.

I could put a parasitic reflector behind the loop. I may have to model that. I have a few other options in mind too.

I doubt we could hold court since we would probably not hear each other.

Looks like you'll be the big maul on the band!

Gee, I need to fire up the log and join you guys. 80 meter ant off the ground so just need some wind to shake it loose and go up to full height. Hopefully next weekend. 40 feet of property line cleared 105 feet to go.

I've trimmed 8 inches off so far. If I had to do over, I would have made the loop 35 feet in total length and put a 6 inch stub with a shorting bar at the top of the loop (opposite the feedpoint). Sliding the shorting bar would allow for setting the center frequency almost anywhere in the band quickly and easily.

Yep, as long as that slider will let you move it to 37' 7" when you need to, you be Whorl-Wide!  ;D


The more I's thinks abouts it, I'll bet you could make an "I boom" out of strong 2.5" PVC tubing from Home Depot. They have all kind of "T" fittings, etc. Glue them and put a 1/8" bolt thru each joint too.  

Then suspend two loops, one driven and the other a reflector.   If you suspend the center of the "I" with a rope from a high tree limb, you could use the four loop corner ropes as the stays as well at giving you the ability to rotate it.

If you put some strategically placed stakes in the ground, you could rotate it quite quickly to cover USA or Eur. That wud work about as well as your 40M loops.


Hey, I still use the Armstong method to rotate my Yagis, so WTF, join the club.

(Or you cud take a trip up here and pick up my 5el 10M Yagi with your name on it)

T

That hanging rectangle bottom fed as shown above is what I have been using for the last few weeks on 10M - Simple and it worketh and the match is great. I use a small coil of coax at the feed as a choke. I made it out of # 14 copperweld and pulled it up in between two pine trees. Works great into Europe. Fairly omnidirectional and quiet although it seems to favor broadside to the loop.

Mike WU2D 

Below is a pix of my JS wonder. I built it and put it up in less than an hour. Glad to see yours is working well too Mike.

I listened in the 37' 7" range today. Man was it busy! Lots of whirlwides and back outs.  ;D

If I do a second  loop, I'm thinking of putting 90 degree elbows on the ends of the two horizontal PVC pipes. Then I can attach pipes at 90 degrees. These will connect to the horizontal pipes for the second loop. Thus, the spacing is achieved and I can turn both loops as one.

How about two of them orthogonal and fed with a 90 degree phasing harness for an eggbeater?

I guess that would give you more or less and omni pattern.

I would expect you two to be able to hear each other via backscatter.

Separate antennas are fun for diversity reception. Fades happening at different times. Listen in stereo.

A good check for folks in the area (within 200 miles) is the KQ2H 10 meter FM repeater. The 10 meter hardware is located in the Catskill NY area. The receive site is about 20 miles North of the transmit site. Their antennas are very well placed.

Receive antenna is horizontally polarized and transmit is vertically polarized. 29520 kc input/29620 kc out.

When the band is closed this repeater is an excellent way to check antennas for locals. I'm 150 miles away from the receive site and can access it most of the time with 100 watts and a horizontal antenna. I have only modest capability here compared to some.

2 element quad with a reflector rocks. I ran one for years worked very well.

I could almost copy you last night talking to VK2BA.

I hear Tom sometimes via backscatter on 40 meters.

Once I get a second antenna up for 10, I'm going to do the diversity thing. It's incredible on 80 and 40, so I would imagine it will be FB on 10 meters too.

  Homely Despot has 10' of 1/2 PVC Sked. 40 pipe fer $1.68.

      http://www.amwindow.org/tech/htm/tenmant/tenmant.htm

 You too can make the HuzMan Loop. Sock it to a bit of #14 AWG, 'fore supper time.  You'll do all right.

 klc

 

I think I heard your call on 10 meters in the last few days, Kevin.

I used 3/4 inch PVC but 1/2" should work FB.

BTW, the dimensions for the rectangular loop shown in the article at the link below are different than the ones I'm currently using. I'll have to model those dimensions to see if they are OK. The loop I'm currently using is about about 70.5" wide and 141" tall.

Had several nice AM QSOs with EU stations this morning and then talked to Victor, E51CG (South Cook Islands, north east of New Zealand) on slopbucket.

With ice loads, I'd think at least 3/4" PVC. I would even use 1.5"- 2" if you make that 3D structure for a 2el quad, Steve.

Here's why:  I once built a 6' square telescope shelter out of 2" PVC. I glued the structure together and covered it with a canvas skin.  It worked FB until the temp dropped below freezing. The PVC joints started cracking and splitting from the strain produced by small snow loads.

I found that the joints are definately the weak points of any PVC structure. If you look at them carefully, you will see that the thickness in certain places on the joints is not comparable to the thickness of the straight PVC tubes.  So keep this in mind when using PVC for antenna supports. Use a size bigger than you think.

The joints have little "overlap" with the pipe, thus a little leverage will easily split them.

I also found an 1/8" bolt thru each joint helps to keep it from splitting/ breaking apart too.

T

Good points Tom, especially if the structure is bigger. There are no  joints or fittings. For a single loop, the PVC has very little load. The two horizontal members are not much more than spacers. The top one does support the weight of the wire, the bottom PVC and the coax, so it would be the one to to worry the most about. It can be trussed overhead with rope that is also part of the support to hoist/hold it in the air. A rope down the middle of the structure would eliminate any bowing on the bottom PVC.

A local ham has built these loops and used the rope truss. He even made one for 17 meters.

http://kt4qw.com/acan1bu.htm


I see little or no flex in the 3/4" pipe on mine. We rarely get snow or ice here. For those in the northlands though, it's a different story.   ;D

The  ARRhhLLL has dimentions of 73" X 146".

Maybee ya can model a 10m loop fed with the Crappy Brown stuff.  Or better yet, the crappy brown stuff with 50 ohm feedline.  --- a g5rv ---   I would think tat would be groovey.

And yes, I've bean active on 10m lately.

Yea, that will resonate lower in the band. I'm skewing mine higher for the AM coverage at 29 and above.

Maybe catch you on 10.

Yes, the vertical ropes appear to support the wires very well - like Venetian blinds.

When you mentioned making a structure for 2els, I pictured something different.

All in all, this thread should give those interested in a nice 10M antenna system, something to think about.

T

Here's one option for mast mounting. Larger PVC is recommended for harsh environments. A mast on the top could be added for overhead trussing if needed or desired.

Why not mount the loop in diamond configuration so wire helps support spreader. Feed at center of bottom. I would not use a glue joint in the middle use a plate and muffler clamps. Heck you could even use wood.

I made some SWR measurements on the loop a few days ago. I've trimmed it for about 28.8 (turns out to be 28.820)

Freq          SWR

28.3          2.55
28.33         2.5
28.4          2.3
28.47         2.0
28.5          1.85
28.6          1.6
28.7          1.35
28.8          1.0
28.9          1.2
29.0          1.5
29.1          1.7
29.15        1.8
29.2          2.0
29.3          2.35
29.4          2.52
29.5          2.9
29.55         3.0

The 2:1 SWR range is smaller than the vertical dipole I was using previously.

Wow that SWR curve looks nothing like my loop! By the way my feedline is 100" of Belden 8214 (RG-8). I am using a 4 turn 6" diameter coax choke made of the coax itself at the feed and my loop is #14 copperweld steel and it is pulled up between two pine trees. My rectangle is 6' wide top and bottom (Skinny). Mine is tuned low in the band. The low part of the loop at the feedpoint is at 25 feet.

28.000  1.2:1
28.100  1.2:1
28.200  1.1:1
28.300  1.1:1
28.400  1.0:1 - best point
28.500  1.1:1
28.600  1.1:1
28.700  1.3:1
28.800  1.5:1
28.900  1.7:1
29.000  1.8:1
29.100  1.8:1
29.200  2.0:1 - 2:1 point    

Yes, it looks like your curve is more broad. The measurements I made were at the end of about 60 feet of LMR400. The top of the loop is at about 45 feet, so the bottom is at 32 feet. I used a W2DU style balun (some beads on the coax) at the feedpoint.

how about a moxon  about the same size round about 6 db gain and 15-20 FB  or did i miss something in steves design

Different antenna. I've looked at the Moxon. I have a design that can be held up with a single rope. It may be the next antenna I try.

It has a few dB more gain than the loop and, of course, is unidirectional. The downside (at least in some cases) is that it has a big high angle lobe. The loop's high angle response is less.

It's another good choice and can be built simply.

Plots: red is Moxon, dashed is rectangular loop.

Why not build a second loop and switch directions like the 40 meter antenna?

did you model that as a vertical or horizontal ant

Horizontal - the "normal" Moxon config.

Looking at the modeling numbers, my real life numbers match up pretty close. The model SWR bottoms out at about 28.830 compared to 28.820 as measured (within the error range of the MFJ box).


Freq         SWR Measured      SWR Modeled

28.3             2.55                     2.56
28.33           2.5          
28.4             2.3                       2.16
28.47           2.0
28.5             1.85                     1.82
28.6             1.6                       1.52
28.7             1.35                     1.27
28.8             1.0                       1.0
28.9             1.2                       1.13
29.0             1.5                       1.35
29.1             1.7                       1.61
29.15           1.8              
29.2             2.0                       1.91
29.3             2.35                     2.25
29.4             2.52                     2.64
29.5             2.9                       3.08
29.55           3.0

I was talking to Chuck, W3FJJ a few weekends back. The subject of 10 meters came up. He is now running a Bisquare. It looks like a loop but is actually 2 full wavelengths and it's open at the top and fed at the bottom. It's more like an inverted-V version of a Lazy H. It has 3-4 dB gain over a dipole and could also be held up with one support.