Whipped up another (no so quick) 2M dipole

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Lawless

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I saw an article about another style dipole that used 1/2" copper pipe for the elements and I sort of copied it and added my own twists. The elements being copper and larger diameter will make a great broad banded antenna. I also ran my coax on the inside of the PVC to protect it.

The connections to the copper elements are made by the brass bolts which are in holes drilled through the threaded part of the PVC.
When the elements are tightened, the brass bolts make good weather proof contact with the threaded copper ends.

I used 1" schedule 40 PVC, 3/4" copper pipe (I already had it, 1/2" would be fine) and 2.5" long X 1/4" brass bolts.

The copper pipe was cut at 18" + the threaded ends and end caps made the elements 19".
I sweated the copper elements together and let them cool before fitting to the coax.
This length plus the tiny amount of coax exposed makes up the elements.

*edited to note*
Once I checked the SWR, the antenna elements were long. The SWR was 2.5:1....
I trimmed incrementally until I got the SWR to 1.3:1. The elements ended up exactly 16" including the threaded ends.
Got a few reports and still full quieting but I won't be stressing my super expensive Baofeng ;)

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I wound a choke, 6 turns of coax, before running the cable inside the PVC.
I wrapped it with 3M rubber tape from DX Engineering topped with 3M Super 33 vinyl tape.
I used some black RTV to very thinly coat the exposed copper from the end of the coax to the terminals.
Remember, this type antenna requires the coax to leave the elements at a 90* angle for a couple of feet.
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A 3/4 pipe floor flange and a street elbow make up the mount.
A "T" at the bottom allows the coax to exit.
This whole mast setup puts the antenna a few feet above my shack's roof.
I did a quick camo job and it's up.
I added a guy rope of 550 cord to the back side to help support it so it won't sag over time.
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Made a few contacts to check performance, reports came back excellent with zero static or noise.

Antennas are fun :) Gonna make a dedicated HF NVIS soon so I can talk with trcubed LOL
 
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Since you're working with copper pipe, consider a copper Slim-Jim.
 
Getting started with radio comms is a goal of mine for this year and these projects you are posting about are making me see it is easier to get started than I thought... Thank you for taking the time @Lawless!

On this antenna, would it be a problem to also sweat on some end caps?

Also, does the added height make a noticable improvement over running the horizontal section right out of the shack, kind of like your first 2M dipole?
 
DurhamDad;n74330 said:
Getting started with radio comms is a goal of mine for this year and these projects you are posting about are making me see it is easier to get started than I thought... Thank you for taking the time @Lawless!

On this antenna, would it be a problem to also sweat on some end caps?

Also, does the added height make a noticable improvement over running the horizontal section right out of the shack, kind of like your first 2M dipole?
Click to expand...

Thanks man, I really like messing with it, even though I mess it up sometimes. Getting your tech license is a piece o cake, do it! Take General too, it is almost as easy.

I did sweat end caps on, it might screw me once I check SWR though if I have to trim it :0 Guy at QRZ told me it is probably a smidge too long. It sounds great though and the Bowwowfang seems happy enough, will see once I check it.

There was nothing wrong at all with the other 2M I made, it was great. I just kept going back to this design and it just looks more solid and hey, who needs an excuse to fool around with making stuff?

I really don't think the little extra height will make a huge difference but with the counterpoise (bottom element) above the roof line it should be a little more uniform in pattern. I want it to be omni-directional as I don't want to be worrying about pointing it in a certain direction and then moving it to point in a different direction later.

I saw some 1/4" hard copper tube not long ago and may make a smaller/lighter portable version of this to hang in the trees when in the woods.
 
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Ah, well I hope the SWR is reasonable... That would suck to have to shave it.

I have started studying the Tech materials (the online doc linked in your sticky) but haven't looked at General yet.

Don't want to derail this thread, but another question comes to mind... There are a bunch of ARRL books. Is it worth investing in any of them at this stage? If so, which one(s) first?
 
DurhamDad;n74414 said:
Ah, well I hope the SWR is reasonable... That would suck to have to shave it.

I have started studying the Tech materials (the online doc linked in your sticky) but haven't looked at General yet.

Don't want to derail this thread, but another question comes to mind... There are a bunch of ARRL books. Is it worth investing in any of them at this stage? If so, which one(s) first?
Click to expand...

I do not own any ham books. There is so much information available online that i have not seen a need.
I think I will eventually buy some stuff that has basics in it in case the time comes when the interwebz is gone.
 
DurhamDad;n74414 said:
Ah, well I hope the SWR is reasonable... That would suck to have to shave it.
Click to expand...

Had to trim. Ended up with each element at 16" including the threaded ends. SWR is at 1.3:1 now.
 
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DurhamDad;n74777 said:
Well that ended up being a good bit more than a shave! Is 1.3:1 about as good as you can expect from this type antenna, or would it have continued to drop if you cut more off?

Edit to add that I found your post on the SWR measurement here:
https://www.carolinafirearmsforum.c...munications/74396-no-vhf-swr-meter-no-problem
Click to expand...

Well, it may have, or it may start to go back up if trimmed any more. Anything under 1.5 is great and there is no real world performance to be gained past that.
 
Looks good! You could raise your transmit frequency a Mhz or so and see if the SWR goes up or down, to determine the value of any further trimming. If it goes DOWN some with the increase in your transmit frequency, you've still got some room to cut.

BUT...as you say, there's virtually zero to gain by more messing with it. The person on the other end will never know the diff between 1.5 :1 and 1.0 : 1 ......
 
What frequency did you tune to / measure against? What is the SWR at the ends and middle of the band?
 
noway2;n75458 said:
What frequency did you tune to / measure against? What is the SWR at the ends and middle of the band?
Click to expand...

I checked @ 146.000
I did not checked at the band edges. Might go out and do that, but I would think it will be acceptable.
I only really use it on JARS 147.270 and Raleigh 145.210 but hope to have a dual band 50W radio soon and may do some simplex



I did get my new mics in the mail, I am high class now!



 
The difference between 1.30 and 1.50 VSWR is only a couple dB of return loss. Using the few watts out of a Baofeng with a passive low-end SWR meter, that's probably within, and may be less than, the expected error of the meter. In other words, I wouldn't sweat it. You're close enough :D
 
RFMan;n76046 said:
The difference between 1.30 and 1.50 VSWR is only a couple dB of return loss. Using the few watts out of a Baofeng with a passive low-end SWR meter, that's probably within, and may be less than, the expected error of the meter. In other words, I wouldn't sweat it. You're close enough :D
Click to expand...

Yeah, real world there isn't much to be had in chasing it down, especially with my "hack" use of the old 11m SWR meter.

I am looking and deciding on a dualband 50w mobile but I still think the antenna would handle it fine.

My HF stuff is where I spend most play time but that antenna is perfect and I won't be doing any experimenting there unless I whip up a low strung NVIS experiment.
 
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Lawless;n75681 said:
I checked @ 146.000
I did not checked at the band edges. Might go out and do that, but I would think it will be acceptable.
Click to expand...


Yep, it'll work fine. The suggestion was (just for grins) to determine where the resonant point of the antenna is. If you go to 147 and the SWR drops more, then the antenna is resonant still higher.

No, it won't make any practical difference, BUT you'll learn something and can use that knowledge with a new antenna, to know whether to trim back or add on.....
 
Lawless;n76055 said:
Yeah, real world there isn't much to be had in chasing it down, especially with my "hack" use of the old 11m SWR meter.

I am looking and deciding on a dualband 50w mobile but I still think the antenna would handle it fine.

My HF stuff is where I spend most play time but that antenna is perfect and I won't be doing any experimenting there unless I whip up a low strung NVIS experiment.
Click to expand...

Sure, that antenna will handle 50W no sweat.
 
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