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J pole FM Antenna

G

guitargrump

Active Member
Hi everyone I am building a FM j-pole antenna to boost the FM radio stations I can receive here in the mountains...

I've heard and read good things about this design and decided that I would make one and see if it was as good as it's reputation...

It seems very simple from the diagrams I've read...

This one plan made sense to me and agrees with several other j-pole plans I've read dimensions wise and that's why I picked it...

I'm about two thirds done with the antenna now... I still have to find the coaxial cable that I intend to use. it's in my materials hoard under something somewhere around here...

The plan I chose to mostly follow was posted here http://uncleikejpole.blogspot.com/2012/?m=1

So far I've used

One 10' long 1/2" piece of copper tubing
2 end caps
1 tee
1 90°

A couple of scrap pieces of PVC and a couple zip ties... And a piece of scrap brass for the cable eyelets...

A picture is worth a thousand words so here's a bunch of pictures...

I'll post more pictures as I finish up the rest of the antenna installation... It might take a couple of days but I'll try to show everything that I do... And I'll report my results...

From what I understand this antenna design can be used for a small FM transmitter antenna too...

but you need a FCC license for more than a couple of transmission watts so...

I think the FCC power limit is 7watts for home and church use but I'm not sure so...

The plan doesn't actually show a earth / ground connection to the bottom of the antenna mast but it definitely needs to be well grounded...IMG_20220124_182540.jpg

J-Plan.jpg IMG_20220125_121622.jpg IMG_20220125_121641.jpg IMG_20220125_124814.jpg IMG_20220125_134711.jpg IMG_20220125_134814.jpg IMG_20220125_135054.jpg
 

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pretty cool design - looks to be a very low-gain omni-directional transmission design.
I have a question. Are you looking mostly for transmission use, or do you have much of an interest in receiving FM broadcasts?
If receiving, have you determined the direction the stations in question you want to receive?
Are they all the same direction, or in multiple directions?
When I was younger I lived midway between Baltimore and Washington,and used a narrow-band, high-gain Yagi design.
An antenna rotor was a big part of DXing stations then, since that design was very directional.
 
hjames said:
pretty cool design - looks to be a very low-gain omni-directional transmission design.
I have a question. Are you looking mostly for transmission use, or do you have much of an interest in receiving FM broadcasts?
If receiving, have you determined the direction the stations in question you want to receive?
Are they all the same direction, or in multiple directions?
When I was younger I lived midway between Baltimore and Washington,and used a narrow-band, high-gain Yagi design.
An antenna rotor was a big part of DXing stations then, since that design was very directional.
Click to expand...

My primary interest is improving reception Radio here is very limited in variety... Radio is free and private nobody is tracking what your listening too...

As far as where the stations are located most of the stations I want to receive well, are either north or east of me... It will be interesting to see if this is a good design for my usage...

I'm pretty sure that just having a outside antenna will solve most of my problems my dipole antenna in the trailer window dose okay...

But I believe that the metal sheathing on the trailer is interfering some with reception... So a antenna just above roof height is my current plan...

I had thought about making a Yagi style antenna too but the j-pole is simpler to make... I honestly prefer the stuff I make or repair...

Although people think it's because I'm cheap often times it costs more... Independence and freedom is my goal and to me that is priceless...

So you're suggesting that a directional antenna might suit my needs better if the stations still are out of range???
 
Yes - I like DIY stuff too - there is a pride in building it yourself - I get that!
Also a good idea to get the antenna above the metal siding (sheathing) that can block signal.

A single bar antenna like the J-pole, is pretty much omni-direction - pretty much the same gain in all directions.
As you add extra bars (elements) in front of and behind the main element, you narrow the beam width and increase the gain of the signal.
I'm sure some of the ham radio folks here can offer more guidance, but thats the general idea.
Think of adding lenses to a telescope - brings more light in but in a narrow view.
 
hjames said:
Yes - I like DIY stuff too - there is a pride in building it yourself - I get that!
Also a good idea to get the antenna above the metal siding (sheathing) that can block signal.

A single bar antenna like the J-pole, is pretty much omni-direction - pretty much the same gain in all directions.
As you add extra bars (elements) in front of and behind the main element, you narrow the beam width and increase the gain of the signal.
I'm sure some of the ham radio folks here can offer more guidance, but thats the general idea.
Think of adding lenses to a telescope - brings more light in but in a narrow view.
Click to expand...

I wish you had been one of my instructors in my service AIT forever ago that's the best plain English explanation of how antenna gain works I've ever read...

Not that I read that much anymore... Ebooks just arnt the same... Neither is my memory...:)
 
@paba

This style of antenna is a very Old Diy design and isn't expected to last forever...

I intend to paint it as well... It should outlast the paint a year or two...

I figure this antenna will last about 7-10 years maybe longer before the stuff that the article was talking about will start to matter...

Most of the commercial aluminum antenna have plastic insulators that the sunlight's ultraviolet destroys too... So the materials used are still a problem...

I'll reuse and recycle whatever is left when it's not useful anymore...

The pipe is a alloy not a entirely pure copper... That may also have some effect dunno...

the weather and oxidation is always a big factor for anything outside...

There are no perfect solutions to these types of issues and probably never will be...

Great Read very good and interesting points, Thank You so much for sharing.

Don
 
I have been using a J-pole I built several years ago using 1/2 inch copper tubing. Works great for me although I do have it inside, out of the weather.

(No idea where the underline came from.)

(No idea where it went.)
 
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I have used J-pole antennas on 2 meter armature stations for about 20 years. I started with a copper tubing design and my latest ( about 10 years ago) was a collinear design made from solid aluminum rod. It consisted of two 1/2wave elements stacked. Hurricane Ida damaged it and I’ll have to repair it soon. Considering it was hit by about a 30foot long tree top on its way to crashing into my house. It faired well. It broke at the area where I joined the two elements- plastic tubing. Metal parts don’t appear to be bent even.
I’ve made portable J-poles from Ladder-Line and kept in a bug out box with 2 meter radio. It performed so well, I made one to use as an emergency antenna for my marine VHF on my boat. I’ve never made one for FM broadcast, opting for a folded dipole hung vertically instead.
 
There is definitely no shortage of antenna designs... It can get confusing... I've forgotten way more than I care to admit, disuse of the Knowledge Age and Time...

AM radio at night was a passion of mine as a kid listening to different radio from all over the world...

But I stopped listening to AM radio at night after my military service ruined enjoying it for me...

A sure way to take enjoyment out of a passion is to do it for a living for the military...

That was a very long time ago now...
 
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