New POTA/Field EFHW Antenna

This looks like a super easy antenna to deploy in the field. Or even a back up antenna to have on hand in case of emergency needs.

 Links from the video:

Reel-POTA-able Antenna 

Spiderbeams Mast

Hitch Mount for Mast Holder - https://amzn.to/3NQ1eMY

 

Easy And Cheap Vertical - Portable or Permanent

This ham I have posted before, he has great videos and I highly recommend his YouTube Channel. This build is similar to the antenna I first built for portable work and it worked GREAT! I used a "crappie pole", speaker wire and an Altiods Tin as my feed point connectors. Here he demonstrates this kind of build and shows video of his results!

Short Video Discussing Fan Dipoles

Nice short video regarding fan dipoles. Easy to build, multi band and not that costly! Give one a try! Have you built one? What are your thoughts? I built one and it worked well. Made mine for 70, 20 and 40 meters. I used a Balun Design feed point balun and it was up about 25 feet. Worked good but not the best for getting lots of DX due to it's radiant angle.

Back On The Air... With A Twist

Well after 4 months of concrete patio/pergola installation, today I put my tri-band fan dipole back up. New location on the side of the pergola worked great. I began running the coax around the eve of the house and thought that I had better check the SWR on the antenna before I totally hide and attach this coax.

After a cup of coffee and breakfast, I go to the shack and fire it all up. Nice to be on the air fully again right? So I tune radio to 40m, and try the antenna tuner.... rattle rattle kerchuunk over and over and over. I know a lot of you know that feeling. Finally the tuner gives up with SWR OFF the scale. Dang I thought, bad coax? Too close to the new outdoor Wifi outlet? So I tune radio over to 20m... first try was the same thing. rattle rattle kerchuunk over and over and over but this time it stopped and settled in at 1.5 on 14.255. 

Phewww I thought.... switched back to USB and tuned around and actually heard a signal from a station in California. Sweet so ok I guess I need to figure out the 40m issue. Then... the lightbulb went on! Surely I had the coax plugged into the tuner.... right???

Wrong.... so I plug it in and first try it tuned on 40m, 20m and 17m all at 1.1. So I found out that I can tune only my tuner to 20m at 1.5 swr and receive signals still. The Analyzer had it slighty better than before so the tuner easily handled the rest. Sometimes it's the silliest and simplest things that can make your day in ham radio... and mine was made today. like a wise friend of ours always says.... "Welcome to Ham Radio!"

-- 

KAØEGE - Jeff Chancey

How Does A J-Pole Work?

I still am learning about antennas... and I am sure many of you will agree with me. From new hams to long term hams this is interesting. Check it out and Dave does a great job on all of his videos!

Thoughts On Inductively Loaded Dipoles

Or... How To Get 2 Bands On 1 Wire
By Morgan Bailey NJ8M

Having wires strung all over the place on a city lot is not something that the neighbors like seeing done. Keeping the landscape as clean as possible is a good thing, both from a real estate perspective and from an RF interaction consideration between antennas. Also, small lots many times present challenging problems to solve in size and visual impact. Using less wires and giving the amateur operator more bands can be solved by making wire antennas a multiband approach. My solution that allows me to run 1500 watts without problems is to construct an inductively loaded dipole. Alpha Delta antenna products have many products that do exactly that, but why do they work and can they be designed for other frequencies? The following is, I hope, a simple presentation of how to design any dual band antenna using coils to make it fit on your lot. I want to site an excellent website by K7MEM.COM. He has done a bunch of work on shortening antennas but I wanted to take it a simple step further and present my reasoning and how to design any dipole to be a dual band antenna, especially on 80 and 40. This seems to be the problem for most amateurs to solve. 

Questions arise as to how to proceed without using engineering approximations which falls under the heading of a Wild-Ass Guess. Cut-and-try engineering will work but it takes time and many don’t have the patience to succeed. Hopefully, my approach will cut these approaches to a minimum. Problems with inductively loaded dipoles are mainly the ease of construction, the location of antenna and narrowing of bandwidth of the second band. The use of an antenna tuner, matchbox, to increase bandwidth, predicates not using a center balun. High SWR will toast a balun. For this reason AlphaDelta does not recommend a balun and specifically states in their literature that is shipped with the antenna that the “the antenna is designed to not be used with a Balun.” Many would argue that without a balun, the pattern will be changed, specifically, on 80 and 40 meter bands. This is a non-issue because very few amateurs have the ability to put a dipole at 60 feet for 40 meters, much less 120 feet for 80 meters. So, mainly the city dweller will have an NVIS antenna with a center fed dipole up 30 feet and because, most amateurs don’t have 3 supports to make it a flat top, will be using the inverted Vee approach. This is just fine because it gives an omnidirectional pattern and lowers the feed point from 70-72 ohms down to 50 ohms which is what RG213 and RG8X, RG58 and LMR400 coaxes are designed for. Putting up a dipole with an included angle less than 90 degrees falls under the, “ Any antenna is better than No antenna,” category. In general, put a dipole up as high as you can and make the included angle greater than 90 degrees and you will be a happy camper. Don’t worry about DX, I have worked DX from Kansas using an inductively loaded dipole up 20 feet. Is it the best choice, no, but if it is your only choice, you are good to go. Now for the theory, as a general class op, you will have already seen the theory in the test question pool. We will use 2 formulas from that and a third for calculation of an inductor based on turns per inch, wire size and length of coil. 

The first formula is the frequency of a half wave dipole: 

468/frequency in Mhz = Length in feet of a half wave dipole 

This is the pure theory that proves out. Variables are added when you don’t use bare wire. The use of THHN wire from the big box stores is the common go to for antenna building. I use #12 black insulated THHN wire that comes on the 500 foot spools for around $50-60. The insulation adds a velocity factor that shortens the antenna. This is not a factor because trimming the antenna to resonance will be done empirically based on the location and installation of the antenna. In general, it is better to cut longer because it is easier to trim off rather than add because it was too short. I generally add 4 feet to the measured length for 80 meters and 3 feet for 40 meters. This gives me plenty of length to resonate by trimming the length and to terminate the ends and center connections that are necessary. Because of the velocity factor of the wire, it will be longer. Add the length any way. In this case, more is better! That takes care of the basic dipole construction of a single band antenna. Now let's add a second band by using a coil, inductor, and shortening the lower frequency length but keeping the higher frequency un-affected. 

Any dipole can be made into a 2 band dipole by trapping the higher band with an inductor and thereby shortening the lower band length. The added inductance at the higher frequency shorts out the longer wire after the coil. At the higher frequency of the dipole the center dipole does not see the wire beyond the coil. At the lower frequency the inductor adds inductance to the dipole, RF flows through the inductor and by trimming the tail of the antenna, it can be made to resonate on the lower frequency with a greatly shortened length being made possible, thereby making it a dual band dipole with a single feed point. This cuts down on coax runs and decreases cost to the new amateur. So how much inductance does it take to make this magic happen? We need to address how much resistance at a given frequency of operation is necessary to present a resistance to flow of the RF in the wire. I want to simplify the theory of operation by using common sense, which in today’s environment, is rather uncommon. Let us look at data that is easily obtained without any experimentation but just by reading the specs of a product already in production. That being a choke balun used on coax to stop the flow of RF on the shield of coax. Going to BalunDesigns.com and looking at their graphs for these baluns it is found that 3500 to 4000 ohms is enough to get the job done. That was easy. Now lets build a coil that has inductive reactance at that frequency giving the 3500-4000 ohms necessary to get the job done. Ok another formula: 

Inductive reactance in Ohms = 2 x Pi x Frequency x Inductance 

Yes we can solve the equation, but it is easier to just go to a web site, plug in values till you get the right resistance needed, 3500-4000 ohms, and get your answer easily. One such site is: 

http://www.66pacific.com/calculators/inductive-reactance-calculator.aspx

It will give you 2 boxes to fill in. For an 80/40 dipole, you will want to stop the RF of 7Mhz from going beyond the inductor/coil. Entering the frequency of 7Mhz and a random inductance to play with to get to the desired 3500 ohms of resistance/reactance necessary to make the coil, one arrives at 80 microhenries. Because this equation is linear, that is, it scales directly, then by this logic a 20 meter coil will take 40 microhenries and an 80 meter coil will take 160 microhenries to provide the necessary values to obtain the 3500 ohms needed to isolate the end wire from the center dipole. Using a smaller value of resistance, 3000 ohms, and even using 3500 ohms will sometimes cause an interaction between the shortening of the end wire changing the resonant frequency of the center dipole at higher the higher frequency, and vice versa. If one goes to 4000 ohms this does not happen. It is like a switch that is an open circuit to the distant piece of wire. This makes resonating the dipoles easy as they do not talk to each other. First trim the wire on the center dipole then trim the end wire. This will greatly shorten the dipole length on the 80 meter band to around 80 feet over all. The band width will be lower, maybe about 40 Khz on 80 with 200 Khz on 40 meters under 2:1 SWR. 

How does this shortening affect the radiation of the dipole? Since the main current of a dipole is radiated from the center, that is, the current is highest at the center of the dipole and lowest, going to zero at the ends, it has little noticeable effect to the receiving station. Simply stated the receiving station will not be able to tell the difference between 100 watts and 70 watts radiated power. It works just fine. This effect only applies to the lower frequency dipole. The center or higher frequency dipole is unaffected because it, itself, is not shortened. Only the lower frequency is shortened. To decrease this effect of shortening the length of the lower frequency portion of the dipole and increasing efficiency, one can use a value of 3000 ohms and still produce a 2 band dipole, but there will be interaction when you trim either the center or the end wires on the respective dipoles. I settled for the middle ground and my 80/40 dipole is 108 feet long, which is down from 133 feet. It is between 80-90 percent efficient. It fits in my lot. I’m good with that. 

Now for the last equation. How do we make a coil with the given inductance needed to isolate the higher frequency from the lower frequency one? The formula is involved: 

Single Layer Coil D L One Turn - N D2 × N2 L (uH) = ------------ 18×D + 40×L Where: D = Mean diameter of the coil (inches) N = Number of Turns L = Length of the coil (inches) 

Life is too short to do this math. Just go to the web page: 

http://www.k7mem.com/Ind_Coil_Ind_Calc.html 

Plug in the values of inductance, the wire size you have on hand and the coil forms available for the PVC that you have on hand and you are good to go. Happy coil making. 

I have made many coil loaded dipoles and here are some Pix of the coil construction: 

These coils are made for 3.5 Mhz. They were used on a 160/80 meter dipole. Later one of these was used on my home station in the construction of an 80/160 meter Inverted L which is currently in use in my backyard. They are made with regular 3 inch PVC which measures 3.5 inches OD and wound with 14 gauge magnet wire. They laugh at 1500 watts RTTY. 

Once the coils are wound a liberal coating of liquid electrical tape is applied. While this is wet, Scotch 88 electrical tape is applied with over lapping 1⁄2 to 3⁄4 width. Doing this while the liquid electrical tape is wet sort of vulcanizes the tape and makes a very solid construct that is highly resistant to abrasion. It is weatherproof and UV resistant. 

The finished product is on the right with the treatment of liquid electrical tape and Scotch 88

tape. It is ready to be installed. The Inductance did not vary before or after the protective

treatment. It still measured 174 microhenries.

I usually cut and trim the lower frequency dipole for the phone portion of the band I want to

operate. This makes it way too short for the CW portion of the band which is my primary

operating frequency. To solve this, I add an end insulator made out of cheap Sams Club cutting

board.

See below image. I use heavy 10-24 hardware on the insulator. It is what I had and the wing

nuts with a lock washer are easily removed. Using a phillips screwdriver for the phillips machine

head stainless steel bolt helps facilitate tightening the pigtail to the insulator.

This way I can add a pigtail that dangles to adjust the frequency downward. I also use this same

construct if I know that I am going to be moving the antenna and will need to re-resonate it at a

different location. Just soldering on a ring connector and bolting it to the nut makes easy work of

frequency change and tuning.

Conclusions:

Both my son, NS0R and I have used these antennas for years and there have been many 10s

or thousands of QSOs on them running between 100 watts to 1500 watts with no problems. I

made one for Field Day which my son cobbled on to and uses at his home QTH on 80 and 40.

We later added a second wire from the center conductor for 20 meters and made a fan dipole

out of it. No interaction was noted by this modification. This is his only antenna. Using this

construction technique at my home station in the creation of a 160/80 inverted L, has enabled

me to get on 160 meters from my city lot. If you have questions:

Morgan Bailey NJ8M

Cell: 785-554-5561 24/7

 ( If I don't answer right away, I am probably listening to the bottom end

of 40 with my headphones on.) es 73 Cheers!

Easy 2 meter SSB Loop Antenna

Here is a great design and build instructions for a nice 2 meter SSB loop antenna. 2 Meter Halo Antenna by Mike Fedler N6TWW has the detailed instructions on his site. Here are some initial notes from the link...

Project Background & Goals  *CLICK HERE FOR FULL LINK*

Shape Shifting For Antennas

Here is an interesting video! Normally, when you want to adjust the resonant frequency of an antenna, you add electronic components like inductors to the circuit. But you can only go so far with that approach; at some point you’ll have to change the physical length of the antenna. That’s fine if you’re designing something, but impractical to do on the fly—until now. Researchers at North Carolina State University in Raleigh used liquid metal to construct an antenna that lengthens or shortens on electronic command.

CLICK IMAGE BELOW TO SEE VIDEO !!

Simple Tape Measure DIY Antenna

I ran scross this on Romel's KEØAKO facebook page and I thought many of us would have been looking for something like this! I think we should explore building some of these at a meeting. We probably should not do any soldering but I bet we can come up with a method of doing some pre soldering before the meeting.

The club could use some of it's resources to obtain the materials. We would need to find out how many are interested in making one so we know what quantities we would need. The antenna would be great for foxhuning which is on our list of todo's for 2015. It might also be a fun participation activity at Field Day out at Big Brutus! This site lays it out pretty well. There are a lot of ideas and projects for building tape measure antennas so if you know of another good one then send it our way!

Check out the article at the link below....

The Tape Measure Antenna

Technicians & 10 Meters - Build an Antenna

This is an excellent video, especially for new hams and Technician Class license holders because it shows you how to build and test an HF antenna for 10 meters and particularly the 10m portion where Techs can operate using CW, digital like PSK and phone (voice). The 2nd video shows you how to tune the intenna and a nifty formula for calculating how much to take off of length!

Interesting story, my first HF contact was on 10 meters, voice and I had a QSO with a ham near Chicopee Kansas. WØKEU Keith Retzer so my first HF QSO was about 3 miles in distance!! This is a great video for making and testing various componenets and can be used for other bands just by changing the length of the wire!

K7AGE - Antenna Analyzer Tips

Randy K7AGE shows us how to use an Antenna Analyzer and how to calc the changes needed for an antenna check! This video is very helpful...

Great Copper J-Pole Calculator

I found this great little site for calculating the materials and measurements for making a great copper j-pole antenna! If you were looking at making one of these classics, this will help you out !

LINK HERE
J-Pole Antenna Calculator

The Frequency you entered: 146.94 MHz

Measurements(95% Velocity Factor for Copper Pipe):
A: 1.454 meters or 4 Feet 9.24 inches
B: 0.485 meters or 1 Feet 7.092 inches
C: 0.049 meters or 0 Feet 1.932 inches*
D: 0.046 meters or 0 Feet 1.812 inches §

* Adjust up or down to get the best SWR.
§ Measurement not critical.

Antenna Basics from 16mm Film

This is a nice old nugget on antenna basics. It examines the characteristics and dynamics of radio waves emanating from a dipole antenna and is part of the collection: Educational Films

Producer: National Film Board of Canada.; McGraw-Hill Films.
Sponsor: Internet Archive
Keywords: 16mm Film; Educational Film

Loaded Whips and Portable Trips

By David Keath – N0WKZ

Because of my very restricted location, I recently purchased the one of the few antenna's I have ever paid money for.  It is a coil loaded MFJ 1840T telescopic whip for 40 meters.  Granted, I knew it would be a compromise but it turned out to be quite a nice little device.  I have no complaints as it does exactly what it should for what it is.  Nevertheless, time and time again, I continue to find that there is only one true remedy for a bad location.  Portable Trips.  Despite the colder autumn temperatures, I decided to pack up and head out in order to try and get in at least one more trip before mother nature starts pooping all manner of nasty stuff upon us.  As well, I usually get at least one contact out of a trip which is often far more than I get at home.

Portable Copper J-Pole ? Nick Says "Yep!"

Screenshot from YouTube

Nick KEØATH, son of Burke Jones NØHYD in Wichita wanted to make a portable copper j-pole that is portable. Now portable and copper j-pole are not often used together but this is a great idea and video that shows us how to make one! Keep them coming Nick and Burke!

$4.00 Ham Radio Satellite Antenna

Here is a fun project !! Cheap homebrew antenna for working the Satellites on FM !! And this HAM is a Kansas boy. I have used a couple of his projects and he makes some great videos! Be sure and subscribe to his YouTube channel !!

Published on Mar 28, 2014

An easy hand-held dual band 2 m/70 cm yagi satellite antenna

for working the SO-50 and other FM amateur radio satellites.

David's Narrow Copper J-Pole Antenna

This is another post from one of our members!  David sent me a bit of this in an email and I thought it would be great to share with the group!  If you would like to post something here about your projects, experience or thoughts, let me know and we will see if we can post it up!

Narrow Copper J-Pole Antenna
Written by David Keath – N0WKZ

The goals I had in mind for this antenna were relatively simple.  Specifically the low takeoff angle of the Slim-Jim mixed with some of the durability characteristics of the larger cactus copper J-Pole.  Another desirable feature I was seeking that the Slim-Jim does not tend to have due to it's small conductor size is a wider usable bandwidth.  The final result is not a magic bullet, nor does it exhibit miracle performance.  Within reason, it does seem to have the qualities I was trying to achieve.

The dimensions and materials I am listing here come directly from the antenna, which is currently in use at the time of this writing.  I tuned and tested this version using nothing more than the built in VSWR meter on my radio.  Like any other antenna device, this antenna was tuned to my own equipment in my operating environment.  Please be mindful that the J-Pole design is generally somewhat sensitive to environment. Cutting and tuning it on different equipment in a given location may alter the final tuned dimensions slightly. Please also remember that this project was and is an experiment.

Materials Used
• ¼ Inch Diameter Soft Copper Tubing – at least 6.7 Feet
• Common Black Electric Tape
• Small Diameter Nut, Bolt, Washer – 2 Sets
• 1 Card Board Toilet Paper Tube
• Fishing Line – Enough to make a loop for hanging the antenna

Tools Used
• Ordinary Pliers
• Screwdrivers – Phillips and Flathead
• Utility Knife
• Scissors
• Cordless Drill and 7/64 or 1/8 inch Bit

Measurements Approximate
• Long section of the J – 60 inches.
• Short section of the J – 21 inches.
• Bottom section of the J – 0.5 inches.
• Feed-point location from the bottom of the J – 2 inches.

The total length here is long for construction purposes.  It should initially be approximately 81.5 inches/6.7 feet.

NOTE: If you feel confident in working with the copper tubing, you can use lengths closer to the final dimensions which are listed below for reference.  I would however recommend leaving at least an extra 2 inches on the long element and perhaps an extra inch on the shorter one.

Final Tuned Dimensions – Approximate
• Long section of the J – 54.5 inches.
• Short section of the J – 18.75 inches.
• Bottom section of the J – 0.5 inches.
• Feed-point location from the bottom of the J – 2 inches.

Construction
Measure the tubing  and mark off the points where the two bends making the bottom of the J should be located.  Be careful to leave the extra length of tubing on each element before making the bend.

Pliers may be used to flatten the  bottom section of the J.  Being careful to work slowly and carefully, bend the tubing into the J shape.  Used gently, the Pliers can aid in this process.  The average gap or space between the J elements should be approximately 0.5 inches.  This gap is between the tube surfaces, not center to center.

Cut small rectangular strips from the toilet paper tube.  Use a number of them together to create a simple spacer between the elements.  I used electric tape to hold them together and in place.

The area of the feed-point should be flattened and drilled.  Use the feed-point location listed here.  There is no need for the extra holes.  Feed-point holes should be located 2 inches from the bottom of the J.

Choke Balun
5 Turns at about 5 Inches Diameter of RG-58

Handling
While this device is certainly more durable than a Slim-Jim, soft copper tubing can be warped or bent.  Too much rough handling or a good hard drop could damage it.  Some care should be exercised in handling the device.

Mounting
I intended this device for indoor use, either ceiling hung, or installed in an attic.  The main idea is to keep the antenna as far from nearby dense objects or metals as possible, choke the feed-line, and isolate it from direct contact with conductive surfaces within reason.

Feed-Point Polarity
Depending on what publication you read, there seems to be a difference of opinion about which element on the antenna the coax center conductor should be attached too.  Based on most articles I have read, I chose to attach the coax center conductor to the long element on the antenna.  Supposedly this is the difference between having a lower verses a higher takeoff angle.

Tuning
Coax with the choke formed at the antenna end should be attached to the antenna feed-point allowing most of the choke to hang off below and too the side of the antenna within reason.

NOTE:  Before going any further, please remember that trimming off too much Copper cannot be undone.  Certainly an extension can be added but that defeats the whole simplicity idea.  Take your time trimming and tuning the antenna.

• The short element of the J should initially be just slightly longer than my final tuned length.

• The long element of the J should initially be longer by an inch or more.

• The antenna should be initially placed or hung in it's desired location or someplace similar and then check the VSWR at the top, middle, and bottom of the 2 meter band.

• Most of the tuning should achievable by trimming the long element until VSWR is low across the entire 2 meter band.  I would be careful trimming  too much off the short element.

• Trimming is done by grasping the Copper near the top of the long element and using pliers to flatten 1/8 to ¼ inch of copper.  Carefully work the flat copper back and forth with the pliers until it breaks off.

• Check the VSWR between each trim.

• The antenna should initially have a lower VSWR value near the bottom of the band.  Shortening the long element by small amounts and re-checking the VSWR should move the low VSWR region up until eventually the VSWR is acceptable across the band.  That is where I stopped trimming.

When tuning is complete, a small section of copper at the top of the long element can be flattened and formed into a small hook or drilled for a fishing line loop to hang it.  Be certain to hang it securely.

NOTE:  Because I do not own a device to analyze the antenna, it may have positive or negative characteristics I am unaware of.  I would be grateful to anyone who builds the device and tests it with an analyzer to send or share the results.  pu239u235@gmail.com

References:
NOTE: There are more web sites about J-Pole antenna devices and designs than I can list here.  These sites I have listed lead to many others and provide useful information.  Simply searching the word jpole on the Internet will also yield many other sources of information.

Jpoles - Mythbusting and the perils of rogue RF currents. By John Huggins, KX4O
https://docs.google.com/presentation/d/1uJ_INHlJEXUFeDrEiBgRcpQRKZ3TNSx6ahN_lWdX4ms/edit?pli=1#slide=id.p14

JPOLES Handbook, 4th Edition Buck Rogers, K4ABT
http://www.buxcomm.com/jpoles4ever.htm

Web Station, N9TAX
http://www.n9tax.com/Slim%20Jim%20Info.html

I wish to thank the SEKARC Club, Pittsburg KS, USA  for allowing me to submit this project so that others may perhaps use and even improve it.  If errors, comments, improvements, or anything else regarding this antenna comes to light, please do submit that information in the comments below so that others might benefit.

The J antenna design has been around since the time of the rigid airships prior to WWII.  The Slim Jim has also likely been around for some time.  Neither design is my own.  As well, it is unlikely that I am the only operator to attempt to make a rigid narrow J pole.  In essence, I can only state that I constructed this project as an experiment based on existing sound designs.  This is what Amateur Radio is all about.  Experimentation, improvement, and a sharing of those experiences with others.  Of course, there is always the inevitable failures on the way to successes but that is the way of it...

73's
Sincerely, D Keath – N0WKZ – 2013

Element Closeup

Balun Coil

Feed point Closeup

Complete

Hanging Method

Thought I Might Do A Little Tower Climbing...

For those of you afraid of heights, watch with caution. I cannot imagine doing this, especially what seems to be some free climbing WAY up there.