Tuesday, July 19, 2016

Carbon Fiber Pole Antenna QSO

Lunchtime QSO

I had an opportunity to set up my 39.7 foot carbon fiber pole at lunch today for a quick QSO. My outing yielded 3 QSOs into CA, PA, and TX on 14.060.

No Radials

I didn't run any ground radials just attached the black clip lead to the shank of the screwdriver and stuck in the ground. I cutoff about 18 inches of the aluminum section to match the length of the collapsed fishing pole. I stow the CF pole inside the aluminum pole section for protection when transporting it.

Tunes 40-6

When it is set up it basically slips over the bottom section of the CF pole to provide coupling to the bottom section. I don't really know how much capacitance is there but apparently it's enough to tune 40m. It won't tune 80m though but really wouldn't have expected it to.

Video of QSO

Here is a video of the latter part of my QSO with KD3CA, Don out near Pittsburgh running his KX3 at 5 Watts into a TriBander at 55 feet. (That helps).

Needless to say, it still works better than I thought. What a hoot! No wires. None.

video

RBN Hits

Here are the RBN spots.


I didn't work Germany...


73,
Myron WV0H
Printed On Recycled Data

Thursday, July 14, 2016

Carbon Fiber Pole Antenna

Who Said That It Wouldn't Work?

This is the silliest thing. My telescopic pole I use for my Park Portable Doublet is just too handy not to consider its use for anything that needs to be put in the air.

Enter one vertical using only the pole

This shouldn't come as a surprise to you but this thing is conductive! I mean is it conductive enough to allow RF to be launched to and from it?

Really? I have heard of people using saltwater suspended in a PVC pipe and coupled through an antenna tuner or some sort of matching network but I had never considered it myself.



All I did was stick the screwdriver in the ground and slipped the pole over it like normal. Then I took a green aluminum Army camo pole and slipped that over the top of the pole to capacitively couple to it. Then I attached a short clip lead to the BNC to Banana jack adapter on an Elecraft T1 tuner. Hit tune and the 20m band jumped to life! Wow, this is encouraging. Now if they can only hear me. Sent out some CQs and low and behold, somebody answered me. WB2WIK in CA. He was running 500W to a LPDA up 55 feet but he turned his power down to 10W and continued the conversation with some QSB reported both ways. Then I called again and worked NS3C also in CA, then K4ISW in VA using a K3s at 100W. Some QSB out east but not as bad as west.

The pole stands 38 feet tall but can get to 39.7 feet if I want to stick in the tip-top section of the fishing pole. It is very thin and would only be able to support itself but may be worth trying.



The whole thing was amazing actually. I suspect much better than a salt water antenna I suppose.


I had to insulate the metal pipe with a PVC end cap to keep it up off the ground a bit. Also I started out using the T1 but could have easily used the BNC to Banana adapter directly on the KX3 and allowed the internal antenna tuner to take care of the match.

I laid out two 36 foot ground radials. I laid them on the grass and had to shoo the rabbits away in an effort to keep them from tangling themselves up in them.




Oh yeah, I worked K4FB fox as well.

Here are my RBN spots for tonight on this antenna.


73 all
Myron WV0H
Printed on Recycled Data

Sunday, June 19, 2016

2016 ARRL Field Day Dry Run

Murphy Repellant

So I wanted to get the new never used Spiderbeam 12m pole up with the new never used 88 foot doublet with the new never used ladderline before I try to use it at Field Day for the first time. That is a recipe for disaster. The weather forecast called for sunny and 98 degrees! Better get busy. So up at 6:00 am and I am out there pounding stakes. Using a rubber mallet doesn't make a lot of noise to wake neighbors...

I got the base of the pole set with guy lines and added the clamp set.


The next step was to get the rest of the clamps set on the pole and the Ladderline strung through the tip-top.

After that it was all up, guys and all. The guy was place at the bottom of section #8 as per the instructions. (About 26 feet up).


Predicted Data vs. Measured Data

After spending several weeks in EZNEC refining the model I couldn't be more happier with the measured results. Spot on. Gone are the days of cut and try.

SimSmith Predicted Response



SimSmith Measured Response



They are very close. I am pleased.

73 and see you on the air for FD 2016.

WV0H Myron
Printed on Recycled Data


Saturday, June 18, 2016

Doublet Modularity

Using Anderson PowerPoles to Create a Modular Doublet System

In the course of using doublets and ladder line you have a choice to hardwire everything or use the Ladder Lock hanger, both permanently affix the antenna to the transmission line. This doesn't make it very portable or handy because you always have to tote the antenna wire along with the TL.

Enter Anderson PowerPoles

The APP is used for all things DC and surely have yet to reach their full potential. This may just add one to that list.

Use APPs together to create an interconnect system between the tuner, antenna wire and the TL.


If you got it figured out read no further but if you are interested to see how it all goes together here you go.

Construction


I start by laying out 2 - 15 amp and 1 - 45 amp powerpole. I use the 45 amp powerpole to attach a #95 paracord hanger to the center. Then use the 2 15 amp powerpoles to attach each leg of the doublet.



Then I cut the wire sheath back 15mm.


I then slide on a small piece of heat shrink tubing to use as a strain relief.


Once this is done I shrink the tubing and crimp the connection. I slightly over lap the contact and the tubing so the crimped portion of the contact overlaps a portion of the tubing.



Once the contacts are shrunk and crimped all you need to do know is to insert them into the body of the powerpole.


Using It

So when you connect your TL that you have prepared in the same way you have a way to snap together an antenna, TL and tuner.


Another thing. Those little red clips that hold two powerpoles together come in handy when you want the TL securely attached when you hoist the thing in the air, you want it to stay together and what better way to do that than with those little red things you have no use for.

I tied a string through them and around the open window of the ladder line.



73
Myron WV0H
Printed On Recycled Data


Wednesday, June 15, 2016

88 Foot Doublet 20m Patterns

EZNEC Gain Patterns for FlatTop and Inverted Vee Configuration


I have heard it said that inverted vee configurations of an Extended Double Zepp will produce "undesirable" results. Either lobed or skewed patterns resulting from drooping the ends.

EZNEC

The two 20 meter models I created locate the apex up at 39 feet for both configurations, one is a flattop and the other is with the ends down at 20 feet above ground. Both are 88 foot doublets.

Flat Top Results




We can see the "normal" or expected pattern of an Extended Double Zepp antenna, cloverleaf shaping and side lobes. 10.24dBi peak gain at 24 degrees angle.

Inverted Vee Results


So, yes, here we can see some skewing of the pattern going from a nice clover leaf to "jelly bean" shape pattern with the wire ends lowered to 20 feet above ground level. 7.64dBi peak gain at 42 degrees angle. A difference of 2.6dB.

Conclusion

The results are somewhat expected, higher angle radiation is to be expected with decreasing antenna end height. What the model tells us is that the difference is about 3 dB of gain for halving the end height. In fact, getting any dipole or doublet ends up higher will have a dramatic effect on overall gain in the desired direction.

Another attribute of this modeling shows us the decreasing dependence on ground when you get any part of the antenna up higher in general. Which stands to reason, move it further away from ground it has less affect on the antenna.

73,
Myron WV0H


Wednesday, June 8, 2016

88 Foot Doublet Model Construct

EZNEC and SimSmith Guidelines

This is the procedure that I use to model antennas in EZNEC and reveal results in SimSmith.

Set Up EZNEC

I have EZNEC+6.0 and follow the segmentation gain check that Cebik highlights in his 4 part QST series some years back. This is simply setting the ground type to FREE SPACE.



and the wire loss to ZERO,



adjust the segmentation to get the AVERAGE GAIN to equal as close to zero as possible.

I use the SHOW WIRE INSULATION when I know the dielectric constant. It helps to refine the accuracy of the model.


You have to set the PLOT TYPE to 3D to get the AVG GAIN function work.



Hit the FF PLOT button to draw a plot and compute the AVG GAIN.

Don't worry if you are within +-0.1dB, that is close enough.


All of this is necessary to get the model to represent real life as accurately as possible. I have been pretty successful at getting my models to line up with reality in a scary kind of way.

Now that you have the segmentation dialed in reset the WIRE LOSS and GROUND TYPE back to COPPER and HIGH ACCURACY. I use HIGH ACCURACY for any balanced antenna and EZNEC GROUND for verticals.

Place a source on a small segment in the middle of the dipole elements. I have been using +-0.3 feet lately with good results.
When the source is placed at the antenna feed point you are then gathering information about the feed point of the antenna.

Next, set the SWR sweep to 3.5 to 28.5 with 0.1 MHz steps. I do this on all my antennas whether or not they are single banded or not, it keeps the results in SimSmith consistent and it won't puke on you.


Next, click RUN to run the simulation.


EZNEC will populate a file called LASTZ.txt. This file is located in the EZNEC directory. Leave it there and we will tell SimSmith where to look for it. This file is the complex impedance of the antenna feed point for all frequencies from 3.5 to 28.5 in 0.1 MHz increments. SimSmith interpolates in between those points. (I think).

Open up SimSmith and build a file from scratch FILE, NEW. Then drag a transmission line to the elements block area.


The blocks will automatically snap into place and then will allow you to alter the transmission line properties. I have previously measured the properties for the JSC 1318 Ladder Line and have entered them into the block as shown above.

There is a library of transmission lines in SimSmith preloaded and compiled by Dan, AC6LA. To get to this library left click on the "Mdl" block to invoke the TL selection dialog box. (I can't seem to snip it.)

Click on the NONE file area in the LOAD block. It will invoke a dialog box to navigate to your directory that contains the LASTZ.txt file in the EZNEC folder. Load that file by clicking on it to highlight it and hit the LOAD button.



Once that is loaded you will see the response in either the circle or square chart area pop to life and display a trace of something.


Set the V parameter of the G block to "xMtch" to have the generator provide a constant match over the entire frequency band. It's as if you had a continuously adjusting automatic antenna tuner inside the generator.



If it is set to Zo the downstream blocks will affect the power delivered to chain and mess up the gain calculations.

The plot display is determined by the settings of the PLOT boxes. The lines hide the associated plots of the corresponding blocks.



Left click to enable or disable plotting of the LOAD, A-Block, or GENERATOR. You can toggle them on and off as you like. I chose to plot the response at the generator because that is what you are interested in at this point. You can set the SWR and Q to any value you like, I chose 10 for Q and in this case 1.7 SWR.

Click and drag a MARK to place markers on our plot trace. You can click on the MHz block in the marker to numerically enter the exact frequency that you want. The G represents the marker is displaying information for the Generator.



Left click on the small chart icon in the lower left corner.


Switching to the square chart to display the SWR and GAIN across the entire frequency band.

This would not have been possible if you were to add a TL in the EZNEC model because you can't input the K-coefficients (loss coefficients) of the ladder line (or any other transmission line) in EZNEC, a powerful feature of SimSmith.


To obtain a numeric value of interest, place the mouse over the plot line and left click. The parameters will appear in the lower right corner of the screen. The same goes for any plot line.


More to follow.

72,
WV0H Myron


Tuesday, June 7, 2016

88 Foot Doublet

The Ubiquitous 88 Foot Doublet

(In Other Words a 20m Extended Double Zepp) 

My interest for this length of doublet began with playing around with various doublet lengths for 20 and 15 meters. There are multiple 50 ohm resonances that occur with the right length of 450 ohm TL. I managed to make a 20/15m sloper or doublet work with 300 ohm TV twinlead so I thought about why this should be possible with other bands and lines. Might be a candidate for Field Day.

I started with the 40 meter doublet trying to obtain responses that were close to the center of the Smith chart but had to extend the legs to at least 40 feet in order to bring the response somewhat close to the center. Turns out there are many more bands that can come in when you get the leg and TL length just right. This is the same principle that G5RV and ZS6BKW have exploited. It happened to be that 88 foot doublet length was about right to attach a 41 foot piece of Ladder Line and obtain some surprising results.


Not only was I able to bring in 20 and 40 meters but 17, 12 and 10 meters also came in. 15 was out but could be had with an extension of 10 feet of LL to swoop that response around 180 style.


Modeled:

I fired up EZNEC (it's never really dormant on my Surface 3) and created a file that represents an 88 foot doublet up 33 feet in the middle and about 10 feet on the ends. I know this to be an inferior configuration but it was all I could muster given diminishing sunlight tonight.

I fed this doublet with 41 feet of JSC 1318 (Universal Radio 450 ohm TL) and attached my 1:1 microbalun on my AA-600.

Here are the results of the modeling. Oh and the efficiency is pretty good as well.


Measured:

I measured the response with the AA-600 and my microbalun set to 1:1 and clipped to the balanced line input (the transmitter end) and took a sweep. The nulls occur exactly where the model predicts. The SWR seems to be on part with predicted as well. I tested the individual frequencies and the screenshot below doesn't have enough resolution to read between the lines. The actual response when I zeroed into each band was more inline with the SimSmith response.


Thoughts:

I would never operate the antenna in this state because the ends are too low to the ground and it really messes with the pattern. This antenna likes the ends to be up as high as the apex and it really starts to look good when you reach the 35 foot level. There can be some slope to the ends but not more than 10% for a good broadside pattern on 20m.

Supports:

The backyard experiment was performed in haste and I used my 28 foot Jackite on top of my Manfrotto 13 foot lightstand overlapped such that only 6 extra feet were realized in the final apex height making it sit up at 33 feet. I didn't have time to get the ends up and just tied off the rope ends to the fence which resulted in the ends being only up 10 feet.