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

[K1JJ]

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

[WA1GFZ]

I think a delay line would be better

[ab3al]

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
 

[Pete, WA2CWA]

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

[K1JJ]

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

[Steve - K4HX]

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.

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)

[WA1GFZ]

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

[Steve - K4HX]

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

[WA1GFZ]

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

[K1JJ]

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

[Steve - K4HX]

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.

[Steve - K4HX]

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).

[Steve - K4HX]

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.

[K1JJ]

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

[Steve - K4HX]

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!

[WA1GFZ]

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.

[Steve - K4HX]

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.

[K1JJ]

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


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

[WU2D]

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 

[Steve - K4HX]

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.  

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.

[WU2D]

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

[Steve - K4HX]

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

[W2VW]

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.

[W2VW]

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.

[WA1GFZ]

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