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

[Steve - K4HX]

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.

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!

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.

[KB2WIG]

  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

 

[Steve - K4HX]

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.

[K1JJ]

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

[Steve - K4HX]

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.   

[KB2WIG]

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.

[Steve - K4HX]

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.

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.

[K1JJ]

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

[Steve - K4HX]

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.

[WA1GFZ]

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.

[Steve - K4HX]

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.

[WU2D]

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    

[Steve - K4HX]

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.

[ab3al]

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

[Steve - K4HX]

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.

[WA1GFZ]

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

[ab3al]

did you model that as a vertical or horizontal ant

[Steve - K4HX]

Horizontal - the "normal" Moxon config.

[Steve - K4HX]

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

[Steve - K4HX]

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.