Promised Steve S that I would start a thread when I built my first antenna

[WSKY567]

And....

Turns out it's not that big of a thing.  Used 12 Gauge copper solid wire.  Used the following formula:

 

Used a drill and a vice to straighten the wire.  Ran into one problem, I don't have a hot enough soldering iron/gun for that large copper.  Have one on order but I did manage to get a solid solder connection although not pretty.  Left both legs of the antenna long and trimmed each by 1/8" increments.  Hit 1:1.03 at one point and should have left it alone.  It is now at 1:1.2 which is fine for my first build.  Used micrometers to measure spacing and feed points.  Still have a little work to do on it.  Want to re-melt the solder joints when the hotter gun get's here.  Want to make some "standoffs" out of plexiglass for between the elements for consistency.  Will pick up a chunk of PVC to wrap it in.  Used RGB 8X for pigtail which is fine with me as it is only 6" long with less than 1% loss.  Transceiver is putting out 9.9 out of 10 watts.  

Not sure what I will do with the thing but I just wanted to see if I could make one.  Measurements provided by above plan were very accurate with final build.  My bench is a mess right now but I will take some pictures when I clean up the antenna a little and get closer to finishing the build.  

[WSKY567]

4 hours ago, SteveShannon said:

Are those the measurements for the insulated 12 ga. version or the uninsulated, or both?

Length of both elements are from the inside edge of the base.

Width and connection points are from inside edges of the wire.  

These measurements are from the bare wire build.  That one has a better SWR than the insulated build. 

[WSKY567]

Final step:

Bought 1" PVC pipe.  (Actual ID just over 3/4")  Filled with Great Stuff spray expanding foam insulation to secure antenna in tube.  Put a cap on it.  Left about 1' of extra length on bottom of PVC for mounting.  Pig tail extends from bottom of tube about a foot.  I feel no need to post a pic as it is just a chunk of PCV pipe.  Now I will spend the next 1 to 3 days picking dried Great Stuff off my hands. Think I'll use the antenna for a field base station with a hand held.  

[SteveShannon]

4 hours ago, WSKY567 said:

Final step:

Bought 1" PVC pipe.  (Actual ID just over 3/4")  Filled with Great Stuff spray expanding foam insulation to secure antenna in tube.  Put a cap on it.  Left about 1' of extra length on bottom of PVC for mounting.  Pig tail extends from bottom of tube about a foot.  I feel no need to post a pic as it is just a chunk of PCV pipe.  Now I will spend the next 1 to 3 days picking dried Great Stuff off my hands. Think I'll use the antenna for a field base station with a hand held.  

Did you add the Great Stuff in small quantities or all at once?  When we add it into large rocket nosecones we typically use the two part foam because the can foam depends on atmospheric moisture to cure. I think you should be fine with the length and diameter you’re using. 
I think you will see a change in SWR. Embedding the wire in foam will probably reduce the velocity factor, which has the effect of making the antenna electrically longer. But whether it will be better or worse is yet to be seen. 
The first rule of antennas is that any antenna is better than nothing. 
The second rule is that everything affects everything.

You’re kicking butt!!

[WSKY567]

9 hours ago, SteveShannon said:

Did you add the Great Stuff in small quantities or all at once?  When we add it into large rocket nosecones we typically use the two part foam because the can foam depends on atmospheric moisture to cure. I think you should be fine with the length and diameter you’re using. 
I think you will see a change in SWR. Embedding the wire in foam will probably reduce the velocity factor, which has the effect of making the antenna electrically longer. But whether it will be better or worse is yet to be seen. 
The first rule of antennas is that any antenna is better than nothing. 
The second rule is that everything affects everything.

You’re kicking butt!!

Sincerely appreciate that!  Inexpensive experiments.  The materials are nothing.  The tools are killing me, lol.  Saving grace is that you always have the tool.  I added the foam in a few applications.  Not by plan but because of the way the foam deposited in the tube with a lot of gaps using the can foam.  I'm working today and tomorrow but first of the week I'll test the antenna specs.  

Next build, I'm thinking about using two end caps, drilling one for the coax exit point and using a little JB weld to affix the coax to the cap.  Going to try to concentrate the foam to two points, top and bottom of the antenna just to establish a stable position within the tube.  Obviously this depends on how the current build tests.  If the foam causes too much deviation in specs I think I'll try two rubber disks to stabilize the antenna.  

One point where I'm lacking is understanding when to cut and when to add.  Right now I'm starting long and cutting until I see an adverse effect.  Watching the Tubers is not helping much so far.  I'm convinced that half the tubers haven't a clue and the other half are engineers trying to impress me with their prowess.  Net result so far is I'm wasting a lot of time on YouTube.  One Tuber elaborated on a vector analysis of phase relationships which may be nice to explore down the road but he gave no sense of what is acceptable.  Right now I'm simply interested in SWR, resonant frequency, and loss.  I'm familiar with phase relationships in the audio world but have no idea of the ramifications on a carrier frequency.  

PS....  One big reason I'm "kicking butt" is that I'm retired and only work a couple times a week at a gun range to get out of the house.  It's obviously winter so I have a lot of time to entertain myself with indoor hobbies.  These radios are hitting the spot for that entertainment.  

[WRYZ926]

I like your idea of using end caps. Though I would use some silicon sealer instead of JB Weld. You can always get some dense foam and cut it to fit inside of the PVC pipe. That is how most commercial vertical antennas are done.

And if you don't want to glue the caps on, you can always use some self amalgamating tape with a wrap of UV resistant electrical tape over top of that to seal things up.

As far as knowing when to cut or add lengths, this is where an antenna analyzer or NanoVNA comes in handy. Both will show you exactly where the resonant point (dip) is and you can see if you are long or short right away. 

Yes you can tune an antenna with a SWR/power meter. The problem is that it will only show what the SWR is on the frequency that you are transmitting on. A SWR meter will not show where the resonant point actually is so you are guessing if the antenna is long or short.

[SteveShannon]

2 hours ago, WSKY567 said:

Sincerely appreciate that!  Inexpensive experiments.  The materials are nothing.  The tools are killing me, lol.  Saving grace is that you always have the tool.  I added the foam in a few applications.  Not by plan but because of the way the foam deposited in the tube with a lot of gaps using the can foam.  I'm working today and tomorrow but first of the week I'll test the antenna specs.  

Next build, I'm thinking about using two end caps, drilling one for the coax exit point and using a little JB weld to affix the coax to the cap.  Going to try to concentrate the foam to two points, top and bottom of the antenna just to establish a stable position within the tube.  Obviously this depends on how the current build tests.  If the foam causes too much deviation in specs I think I'll try two rubber disks to stabilize the antenna.  

One point where I'm lacking is understanding when to cut and when to add.  Right now I'm starting long and cutting until I see an adverse effect.  Watching the Tubers is not helping much so far.  I'm convinced that half the tubers haven't a clue and the other half are engineers trying to impress me with their prowess.  Net result so far is I'm wasting a lot of time on YouTube.  One Tuber elaborated on a vector analysis of phase relationships which may be nice to explore down the road but he gave no sense of what is acceptable.  Right now I'm simply interested in SWR, resonant frequency, and loss.  I'm familiar with phase relationships in the audio world but have no idea of the ramifications on a carrier frequency.  

PS....  One big reason I'm "kicking butt" is that I'm retired and only work a couple times a week at a gun range to get out of the house.  It's obviously winter so I have a lot of time to entertain myself with indoor hobbies.  These radios are hitting the spot for that entertainment.  

What you’re doing is certainly the way most of us do it, even with an antenna analyzer.  We locate the frequency of the dip on the SWR sweep screen of the analyzer.  The lower frequencies are to the left and the higher ones are to the right. We cut (or in some cases we fold* over) the wire to make it shorter if the frequency of the dip is too low and we have to lengthen the wire somehow once we cut off too much.

An antenna analyzer allows us to easily test the SWR over a sampling of 200 or so evenly spaced frequencies and then display those samples so we can graphically see the performance of the antenna.  So we can sweep the antenna, record the center frequency of the dip, cut a little bit off the antenna and sweep the antenna again.  This will tell us (more or less) the frequency change per cut length.  When I first started with my EFHW antenna I made a spreadsheet that would calculate the length that I would have to shorten the antenna in order to achieve the frequency I needed. Unfortunately, antennas are less simple than that; my spreadsheet got me into the ballpark but I quickly learned about antenna rule 2, everything affects everything. You can measure the crap out of the antenna on the ground, cut it to a length measured extremely precisely, and have it look perfect until you lift it into the air and the SWR dip suddenly changes frequency. 
Also, you’ll quickly find that just because a piece of wire that has a dip that goes all the way down to 1.0:1 at 459 MHz, when you shorten it to shift the dip to 462.550 MHz the lowest point on the dip might only go down to 1.4:1.  Those are numbers I just made up but what I’m trying to say is that perfect SWR might only be achievable on frequencies that don’t interest us.

*For a bare wire antenna, folding the wire over theoretically has the same effect as cutting, but can be undone if you go too far.  
For insulated wire it’s not that simple.  Folding over ten inches might only have the effect of cutting off three inches. So don’t assume that you can cut off the entire section that you folded over. 

I like the fact that you’re trying all of these different things.  That’s the best way to learn.  Using disks to support the radiator of the antenna is a good idea.  You could also tape it to a piece of Kevlar cord stretched between the endcaps. I’ll be really curious to hear if the pvc pipe and foam has affected the SWR. 

[WSKY567]

29 minutes ago, SteveShannon said:

I’ll be really curious to hear if the pvc pipe and foam has affected the SWR. 

 

That whole experiment was a total bust, lol.  First, you were spot on about the Great Stuff.  I had a little more time than I thought I would this morning so I did some investigating.  The two ends of the PCV were solid with foam.  I did an SWR test and was floored.   17:1!!!!!   I pulled the antenna out of the tube and all of the foam in the center of the tube had degraded to goo along the inner surface of the pipe.  No foam.  Needless to say no more Great Stuff.  Tested the antenna and still 17:1.  Pulled the plexiglass spacer out from between the elements and Voila!  1:1.5.  I don't know if the RF was riding the filaments of the plexiglass or if the plexiglass was acting as a dielectric increasing inter-capacitance, or both, or something else?  I then tried some foam (like you get inside a case) and that was better but still bad, around 1:7.  Next was masking tape only, which yielded 1:3.  You nailed it, anything I did messed with the antenna.  Still don't know the effect of the PVC tube as I had bigger fish to fry.  The foam was just nonexistent so that was a systemic bust.

So......

Enter controlled experimentation.  One change at a time.  Time to get serious with this little enigma.  One thing that came up in Google was the material used in a tie wrap.  I am going to try drilling two holes in a tie wrap and sliding that over the elements, only impacting the elements with the thickness of the tie wrap (capacitance) while providing the rigidity needed.  Kelvar cord just went on the list of things to try as well.  I have found that Google interprets RF transparency only in regard to RF loss passing through a material it does not consider interaction.  I get it as most folks are only interested in getting a signal through a barrier.  I am also not willing to wade through endless white papers to get the answers I need.  Makes my head hurt.  

Can't express how much I appreciate the coaching you are providing.  I'm confident you have cut years off my learning curve.  Not sure when I will get back to the work bench but by Monday if not sooner.  Right now it's time for a mad dash to work.  

[SteveShannon]

4 minutes ago, WSKY567 said:

That whole experiment was a total bust, lol.

I disagree.  In the words of Thomas Edison, you learned what doesn’t work.  That’s a success.

I agree with the plan for controlled experimentation.  I wish you lived next door so I could hand you my antenna analyzer for a day.

[tcp2525]

On 2/12/2026 at 7:57 AM, WSKY567 said:

Thanks!  I like these.  Trying to avoid the expense of the crimp and die set although I'm starting to rack up some expense trying to get a soldering gun/iron that will provide enough heat for the mass I'm trying to heat.  

Invest is a good Weller 100w soldering iron and you will have a versatile tool that will last you a lifetime. I have two of them that I've used regularly for over 20 years. Built many coax collinear antennas made from Heliax and soldered countless connectors. The right tool for practically any job.

https://www.ebay.com/itm/187466008578

[WRYZ926]

I agree that a good soldering iron comes in handy around the house. My suggestion is to make sure you can get different size tips. Sometimes you need the big chisel tip and other times you need a very fine point tip.

Don't get discouraged that the Great Foam didn't work. It doesn't surprise me one bit that it was goo inside the pipe as any spray foam needs exposure to open air to cure.