My 160 antenna

[ke7trp]

On my old tower I had a simple inverted L.  On the new setup, I wanted the L to be dc grounded. I cobbled this current setup so I would not have to use an antenna tuner.

Dont laugh a the coil. I had it lying around for free so I used it

This antenna has been putting out ONE HELL of a signal.  Typical 10 to 20 DB over other L's in the state.  Every one asked me what antenna I was using so I made this video.  I am told this wont work.. and its wrong. LOL  But that signal is brutal from this thing.

What did I do?  I wonder if the tower is hot.  The coax is RF cold. No feedback.  The match is Flat and j is 0 on it. I also used half inch hardline for the feed.

http://youtu.be/SfvmwCgjjJo

Either way I am enjoying 160 nightly.  Alot less SLOP buckets to get in the way.

C

[DMOD]

Interesting.

I think what you have is simply a base-loaded Inverted-L with DC grounding provided by the bottom of the shunt coil and its connection to the bottom of the tower.

In most shunt-fed verticals, you simply angle the center of the coax up to the 50 ohm feed point impedance.

Schematically, it appears that the 60' run of vertical wire is forming a capacitor which adds to the horizontal top-hat capacitance.

Glad it works so well for you.

BTW, Clark, how close are you to Waddell? My son lives there!

Phil - AC0OB

 

[ke7trp]

I looked on a map phil and wadell seems to be about 45 miles from me.  I live 10 to 15 miles south east of phx in chandler. Is your son a ham?

That makes sense on the antenna.  It really kicks but.  I am so pleased with it. Its putting almots 60 db into northern AZ at night.

C

[flintstone mop]

OK Clark
Tell us when you're calling CQ and the freq and I'll start listening and see how far you can throw some fire my way...
Need a little advance warning.
No problem waiting for your time zone.
I see a ladder line heading near the top. Is that a separate antenna system?

It looks like an L antenna. The wire distance from the tower wouldn't be exciting the tower. L's are super antennas.
Glad you did it. Looking forward to some RF from you.

Fred

[ke7trp]

we get on 160 at 8pm on 1885 Fred.  Not sure if the band is open on that hour.  There is not much traffic down there these days.   

On the antenna. The thing that is different from an L is that the vertical wire and the tower itself are both the same ground.  I took a signal strength meter out and the entire tower is hot with RF. So I have a 70 ft vertical I guess.
I am thinking of tuning the thing for 80 also.

The open wire line is 600 ohm and it heads up the tower to a fiberglass military mast section, as an insulator, stck into the metal mast.  This feeds the inverted V.

[DMOD]

Hi Clark, son not a ham yet but we will get him there eventiually.  
Waddell's at the foot of White Tank Mountain.

I took a signal strength meter out and the entire tower is hot with RF.

I doubt one can prove the tower is hot using a signal strength meter. One normally needs an insulated loop mounted on the tower for that.

I think your measured signal is coming mostly from the vertical vector (E-vector) of the vertical section of the Inverted-L.  If the setup was a series fed (bottom-fed) tower with a base insulator, yes it would be hot.

Grounding the inverted L makes sense for sure. I have seen some truly remarkable lightning storms out there in 7 land.

Phil - AC0OB

 

  

[ke7trp]

Ok. Makes sense.  Still learning about this stuff.  The old antenna was a coax L.  It worked great. But this works much much better.  Every one was asking what it was so I made the video.

C

[ke7trp]

This gets even more odd then it already is!

I was on 15 meters today talking to N1Ahx Mike to phx on the wire.  I wanted to retune the FT101 into the dummy as I was only getting 13 watts instead of the stellar 20 she normaly makes 

I found that this inverted L is an AZZ kicker on 15 meters!  I accidentaly put the Antenna switch one position off

The SWR is 1.4 to 1 and the RX and TX is 2 SU over the open wire doublet and way over the Vertical.

I am using 20 watts and putting a bit signal into MASS with the L.  Not bad.  Now I have to find out what other bands this antenna is resonant on!

C

[DMOD]

Yep, resonant at a multiple wavelength mode.

I had a 80/160m inverted L one time that was very good on 2m.

Could you do a favor for those of us who might want to reproduce your antenna and do some modeling?

Measure the height and diameter of your three-turn coil and the diameter of tubing from which the coil was made, and the height above ground at which your coil sits.

Thanks

PhilL

[ke7trp]

Yeah. i realize that it will be resonant up the bands. I never thought it would beat the horizontal wire.  Its dead flat on 2 meter.  I might have to try that later on to see how it works. In AZ, We run 2 meter AM on Tuesdays.  I use a colinear 18ft vertical now. I dont expect this to beat that but we will see.

I could get some measurements for you.  Already a few hams have converted there L's to this kind of arangement. One used a coil he had and the other wound his own out of ice maker tubing.  Both reported back that the antenna did tune but no word on before and after.

I was thinking...  Do you think that since the coil is grounded to the antenna it has better coupling to the ground, rods, wires and radials?  Maybe more then it would if it was floating above that same ground system with no imediate contact?
C

[WA1GFZ]

Many years ago we needed a 1 MHz antenna 2 feet tall. The tapped inductor to ground worked much better than just a series inductor.

[Bill, KD0HG]

Cool! Will look for you on 1885 this evening.

Bill

[ke7trp]

We get on around 8PM Bill. 

C

[k4kyv]

I would put a shelter over that coil, so it doesn't self-destruct in a couple of years.  I believe even in AZ you have wet periods from time to time, plus a lot of sun.  Or even homebrew a coil out of copper tubing, using all weather-proof and UV-proof material. It wouldn't take many turns; just use trial and error to make a coil of convenient dimensions with the same inductance as the active  portion of the broadcast coil.

[ke7trp]

I dont see anything that can fail. Its a piece of copper and I put antiseize on the connections.  Its probably not a bad idea though Don.  Maybe I will build a little cover out of wood or a plastic wash bin.

C

[k4kyv]

What about the insulative strips that support the copper tubing?  If they are  made of  ceramic, they would probably be OK.  But composition materials like miclex and bakelite tend to deteriorate when exposed to the elements.  Plexiglass would probably be OK, but that doesn't look like what I see in the photo.

[flintstone mop]

I gotta note in my shack to keep trying to catch you on the air, Clark.
Seems we have Spring conditions in January and ma nature is making a lot of noise.

[ke7trp]

due to the Sun spot storm, the band was very dead.  I talked to mexico and to norther AZ, Barely. 


C

[k4kyv]

Seems we have Spring conditions in January and ma nature is making a lot of noise.

And most of the thunderstorm activity this winter has moved right through here as the fronts make their way south or east.

This is what I was afraid of back in the fall when I heard the NWS prediction that we were in for an "abnormally warm and wet" winter this year, due to the prevailing pattern of the jet stream.

All winter I haven't dared to exit the shack for the night without making sure the main power switch is pulled "off" and the antennas and control cables disconnected, just as I do in spring and summer. The main power switch is a large buzzardly open-air knife switch probably from the 1920s, so a lightning surge would have to jump across several inches of gap to hit the equipment.

The one night I failed to shut everything down, a few months ago, we had a surprise 2 AM thunderstorm, and it wiped out my very expensive industrial-grade remote antenna control indicator meter.

Oh well, at least we are saving some money on heating fuel.

[ke7trp]

Update. 

I have been using this antenna on 160 and 15 meters AM with out a hitch. 

On 15 meters this antenna beats the dipole by 2 full SU into the east.  Nobody can really understand how or why. It must have some good gain there since it is 3 wave lengths.

On 160 it puts out a big signal.  I only wish I had more then 80KC of bandwidth.  I ended up hooking a dentron super super tuner to the L. 

Had No RX.  Tore open the SST and found a lightning strike had blown the taps off the inductor switch. I scrubbed it with Deoxit and a brush to remove the carbon.  Then soldered the Ground lead and the damaged lead back. I added some corona dope around the contacts to make sure the any remaining carbon would allow a path for an arc.

With the tuner in line, I expect some loss.  However, I dont see much. I tested it back and forth on the air and it seems its about a wash on the two resonant bands.  I can now tune the Antenna on all bands.  160 is flat across.  I use it to stretch the L up to 1945 so I can talk with the CA guys.

On 15 meters, I dont see any change.  The SWR was below 2 to 1 anyways. 

In direct comparisons to the Open wire 80 meters doublet (70 ft) with balanced tuner, I see only 5 DB loss on instate contacts. But some are exactly the same.  Suprise, those where vertical stations or end fed wire stations.

Now 5 DB is pretty heavy loss.  But had you not had the 70 ft open wire line and this big massive tuner sitting here on the table You likely would never miss the inverted V. 

I really like this L.  I wish I could model it.

C
 

[DMOD]

Glad to hear you're I-L is serving you well.

Some time ago I put up a new Inverted-L with the horizontal portion about 15 feet above the ground (physical restrictions here). I made some measurements and it showed a highly inductive antenna with very low resistance.

I too have a shunt coil base loaded system except mine is 8 turns of 1/8' copper tubing with the coax center feeding the seventh turn from the bottom. I drilled a hole in the copper tubing at the best match point and silver soldered the center coax wire to the hole at the seventh turn.

If antenna inductance is high, there are generally two approaches one can use. One is to place a capacitor or capacitive divider at the feedpoint or use a shunt coil. I prefer the shunt coil since it is directly DC grounded. No static drain needed.

At present, I let my Dentron MN-2000 tuner give me the best resistance transformation.

However, I am not through experimenting as yet. I am going to try a 5:1 Unun for a better resistance match.

Phil - AC0OB

[ke7trp]

Sounds good.  Let me know what you find with the unun. 

Today I have been fighting one heck of a head cold.  I did put a few hours into testing the two antennas and taking notes:

Here are my notes:

10 meters not tested, I have a 10 meter vertical.
On 15 meters, the L wins everytime. 2 full SU in most cases.  The band was ON fire due to the contest.
On 20 meters, the v tends to win but its close. WASH.
On 40 meters its a toss up.  Some wins and some losses.
On 80 meters toss up.  If the stations are local in the state, the V is stronger. Station in Arkansas said the L was stronger the then the V.  Again, this is whats expected. The L config has a lower angle and for DX, The L wins.
On 160, the L wins vs the inverted V tuned to 160. The V is 80 meter length and although my tuner will tune the V on 160, its performance is pisspoor.

Further notes:
I am using HALF inch hardline for the feed.  Andrews all the way into the shack. If you use coax, you might get more loss on non resonant bands??

There is NO RF in the shack.  I walked around and pointed the Field strength meter at every connection. Nothing. NO RF on the Coax at all. 

The SWR is the same at the feedpoint with the 259B as it is in the house with the hardline.

I jumped the coil out of line at the base of the tower so the inverted L was  just a standard L.  The shield was grounded to the tower and the L wire was hooked to center.  ALL the tuning changed inside and when I tuned on all bands, the V was 10 times stronger.  The L was not usable in my opinion without the big shunt fed coil. It did however, Seem to work great on 160.  There was limited traffic and weak signal SSB only.

After hooking the Coil back up to the original design I tested to see if the height of the tower changed the tuning.

I then hit the button of the motorized tower and lowered down 5 ft. The resonant point changes!  The resonant point of the 160 band is drasticaly changed by the hight of the tower. This confirms to me that using this coil in the way I have, is in fact shunt feeding the entire tower. 

I am starting to wonder why I even have this ladder line and V hanging over the house.  If I could just improve the L with more radials.  Very odd antenna that seems to really work great. 

I wish I knew more about antennas so I can understand how this can work even close to that huge inverted V.

C