Flagpole as antenna mast

[MarkInTampa]

I wanted a 30ft or so antenna mast/pole but didn't want any guy wires if I could help it. In walking the neighborhood with the doggo I saw a few neighbors that have flag poles and thought to myself that would make a great antenna mast. So I ordered up a 30ft telescoping aluminum flag pole from Home Depot for $160 and it came in yesterday but was kinda bummed that they shipped me a sectional flag pole and not telescoping that I ordered. It's a mixed blessing I suppose. I'd assume the telescoping pole and every section being a smaller diameter tube as it goes up is going to be a bit weaker than a sectional pole that has all the same size of tube but the telescoping would have been much easier to work with. Also with the telescoping pole there is a chance of water intrusion between each section of pole and on the sectional pole there is not.

I used expanding fence post foam for the pole base sleeve, used it before when building a fence and it held up a 6ft tall and 4ft wide wood gate so figured it should work in this case and I'm to lazy to use concrete. I also decided to clamp it to the side of the house even though it could be used free standing. It made it a lot easier to level the pole when pouring in the foam for the base sleeve. Also figured it would make the pole a bit stronger and easier to work with. If I want to lower the pole, just loosen up the clamps and remove sections as needed. Not as easy as a telescoping pole would have been though like I planned.

Overall I think it came out decent, just have to wait for a windy day to see how much it sways in the wind. I can guy it if I have to but time will tell.

 

[WRKC935]

Looks good and it will get the job done.  You need to get some outdoor rated ties and properly fasten the cable to the pole though.  Those little zip ties will harden up in about 6 months and fall apart.  They do make UV rated ties, and that's what needs to be used. 

Also, you need to put a drip loop in the cable.  The way it's run right now, water will get on the cable and ride it down to the point it enters the building and probably run into the building if it's not totally sealed.  This will cause water ingress and the problems that come with it.  Think P-trap for plumbing.  Create a low spot in the cable run and then have the cable come back up a little so the water runs to the lowest point and then falls off the wire before it gets to the entrance of the building.

 

[MarkInTampa]

2 minutes ago, WRKC935 said:

Looks good and it will get the job done.  You need to get some outdoor rated ties and properly fasten the cable to the pole though.  Those little zip ties will harden up in about 6 months and fall apart.  They do make UV rated ties, and that's what needs to be used. 

Also, you need to put a drip loop in the cable.  The way it's run right now, water will get on the cable and ride it down to the point it enters the building and probably run into the building if it's not totally sealed.  This will cause water ingress and the problems that come with it.  Think P-trap for plumbing.  Create a low spot in the cable run and then have the cable come back up a little so the water runs to the lowest point and then falls off the wire before it gets to the entrance of the building.

 

Didn't think about the zip ties being UV rated, I'll take care of that. The cable actually runs low through a doggie door next to the antenna and back up into a window right next to it. I did put a loop per manufactures (Comet) instructions at the antenna mount.

 

[KAF6045]

The upper loop is meant to be an RF choke, blocking RF from travelling down the outside of the coax shield. A drip loop is just a   down below entrance point, U up and then across through entrance point. The goal is for the lowest part of the U to be outside and where you don't mind have rain water dripping off the coax.

[MarkInTampa]

22 minutes ago, KAF6045 said:

The upper loop is meant to be an RF choke, blocking RF from travelling down the outside of the coax shield. A drip loop is just a   down below entrance point, U up and then across through entrance point. The goal is for the lowest part of the U to be outside and where you don't mind have rain water dripping off the coax.

10-4. Right now it's not a problem and the cable feeds way low (through doggy door) and back up into a window so it's not a issue at the moment. However right next to the antenna mast base (see first picture) is a cut and orphaned CATV drop going through the wall. My radio sits directly behind the antenna and that hole. I plan on reusing the hole for the coax, just don't have a masonry bit for a hole large enough to pass a terminated coax through. Hate buying a bit for a one time use, need to bum one from somebody at work. But I will keep the drip loop in mind when I do it.

[wayoverthere]

3 hours ago, markskjerve said:

10-4. Right now it's not a problem and the cable feeds way low (through doggy door) and back up into a window so it's not a issue at the moment. However right next to the antenna mast base (see first picture) is a cut and orphaned CATV drop going through the wall. My radio sits directly behind the antenna and that hole. I plan on reusing the hole for the coax, just don't have a masonry bit for a hole large enough to pass a terminated coax through. Hate buying a bit for a one time use, need to bum one from somebody at work. But I will keep the drip loop in mind when I do it.

Alternately....what about going a little smaller on the hole, and put a so239 bulkhead connector through, with a pigtail between wall and radio?

Then you can change out coax, or radios on the other side of the bulkhead pretty much at will.

[Lscott]

1 hour ago, wayoverthere said:

Alternately....what about going a little smaller on the hole, and put a so239 bulkhead connector through, with a pigtail between wall and radio?

Bad idea. Those bulkhead connectors are not a constant 50 ohm impedance. Those can cause a nasty SWR problem at UHF.

[wayoverthere]

22 minutes ago, Lscott said:

Bad idea. Those bulkhead connectors are not a constant 50 ohm impedance. Those can cause a nasty SWR problem at UHF.

Argh..good to know. Always a hidden trap with the seemingly easy solutions.

[SteveShannon]

3 hours ago, Lscott said:

Bad idea. Those bulkhead connectors are not a constant 50 ohm impedance. Those can cause a nasty SWR problem at UHF.

I’d be interested in seeing what one of the eight inch barrel connectors looks like on an analyzer. 

[Lscott]

On 4/8/2023 at 11:12 PM, Sshannon said:

I’d be interested in seeing what one of the eight inch barrel connectors looks like on an analyzer. 

I did a theoretical analysis some years back just to see what a short one would do.

 

UHF Connectors Rev-3.pdf

RFU-537.pdf

Edited April 11, 2023 by Lscott
Added datasheet for barrel connector.

[SteveShannon]

44 minutes ago, Lscott said:

I did a theoretical analysis some years back just to see what a short one would do.

UHF Connectors Rev-2.pdf 362.76 kB · 1 download

Thanks!  I studied it for a while.  That helps, but I’m even more curious how one would look on an analyzer to see how one tests versus theory.  Theoretically they should be close!

Happy Easter!

[Lscott]

13 minutes ago, Sshannon said:

Thanks!  I studied it for a while.  That helps, but I’m even more curious how one would look on an analyzer to see how one tests versus theory.  Theoretically they should be close!

Happy Easter!

Provided I didn't make any mistakes in the formulas, which is easy to do, you could try using a dummy load on one end with the other connected to the analyzer. That would at least allow you to check the results with a "perfect" load on one end. If there was no effect the match should be exactly 1:1.

I guess the real point is these barrel connectors are likely OK for HF use. Once you get up to the 2M band is where the trouble starts.

Like I mention in the worksheet better quality equipment you will see the center pin on the SO-239 socket is supported by a spoke wheel type of insulator, mostly air. It's done in an attempt to get the connector's impedance back to the ideal 50 ohms. The worse connectors are those using the dark Bakelite material. The white insulator looks like Teflon, but in most cases I think it's something else called Delrin which is similar depending on who you ask.

https://forums.radioreference.com/threads/which-is-the-better-dielectric-teflon-or-delrin.28905/

[SteveShannon]

5 minutes ago, Lscott said:

Provided I didn't make any mistakes in the formulas, which is easy to do, you could try using a dummy load on one end with the other connected to the analyzer. That would at least allow you to check the results with a "perfect" load on one end. If there was no effect the match should be exactly 1:1.

I guess the real point is these barrel connectors are likely OK for HF use. Once you get up to the 2M band is where the trouble starts.

Like I mention in the worksheet better quality equipment you will see the center pin on the SO-239 socket is supported by a spoke wheel type of insulator, mostly air. It's done in an attempt to get the connector's impedance back to the ideal 50 ohms. The worse connectors are those using the dark Bakelite material. The white insulator looks like Teflon, but in most cases I think it's something else called Delrin which is similar depending on who you ask.

https://forums.radioreference.com/threads/which-is-the-better-dielectric-teflon-or-delrin.28905/

Yes, I knew exactly what you meant when you discussed using air as the dielectric.  I could do a two port analysis also from one end to the other.  But probably not today.

Also I would want to look at N barrel connectors.

[SteveShannon]

15 minutes ago, Sshannon said:

Yes, I knew exactly what you meant when you discussed using air as the dielectric.  I could do a two port analysis also from one end to the other.  But probably not today.

Also I would want to look at N barrel connectors.

Specs and drawing of Pasternak N barrel connector.  VSWR maximum of 1.3:1 from DC to 11 GHz.

https://www.pasternack.com/images/ProductPDF/PE9006.pdf

They have others at up to $96 apiece that are 1.2:1 up to 6 GHz.

Unsurprisingly, their UHF bulkhead connectors are rated 1.3:1 but only up to 300 MHz. 

We really should all be using something other than UHF connectors for GMRS or 70 cm.

[Lscott]

1 hour ago, Sshannon said:

We really should all be using something other than UHF connectors for GMRS or 70 cm.

Some radios do. My old FT847 sat radio has an "N" connector for the UHF port.

[WRWE456]

Hello new guy here, first post.

 I am relatively new to radio, became interested and began studying up for almost a year now with an eye towards back up local com's. So still much to learn. Started with interest in ham VHF then HF then settled on GMRS because trying to get non radio folks that I want to talk to interested in a ham license, well I think most here know what I mean.

 Anyway current set up is a copper tube J-pole (GMRS specific) six feet above roof of house with DX Engineering brand RG-8U with UHF connectors, 50 foot run to Wouxun KG-935 Plus. House is on top of a 500 foot hill with good line of sight to most areas I want to reach. It works very well. I have reached a guy in a car 30 miles away.

Lately I have been reading up on best practices for UHF and learned that the RG-8U and UHF connectors are not ideal for UHF. (my original intent was for VHF and a scanner). So now I just ordered some DX Eng. 400-Max (LMR-400 equivalent) with type N connectors and a replacement (same) J-pole with N connector just to try to make life easier on the radio and maybe gain a bit of performance/range.

Lscott your post just reinforces my conclusion.

Also I am wanting a telescopic mast to make adjustments/experimenting easier. I like the flag pole idea. Good price point compared antenna masts.

 

[SteveShannon]

4 minutes ago, WRWE456 said:

Hello new guy here, first post.

 I am relatively new to radio, became interested and began studying up for almost a year now with an eye towards back up local com's. So still much to learn. Started with interest in ham VHF then HF then settled on GMRS because trying to get non radio folks that I want to talk to interested in a ham license, well I think most here know what I mean.

 Anyway current set up is a copper tube J-pole (GMRS specific) six feet above roof of house with DX Engineering brand RG-8U with UHF connectors, 50 foot run to Wouxun KG-935 Plus. House is on top of a 500 foot hill with good line of sight to most areas I want to reach. I works very well. I have reached a guy in a car 30 miles away.

Lately I have been reading up on best practices for UHF and learned that the RG-8U and UHF connectors are not ideal for UHF. (my original intent was for VHF and a scanner). So now I just ordered some DX Eng. 400-Max (LMR-400 equivalent) with type N connectors and a replacement (same) J-pole with N connector just to try to make life easier on the radio and maybe gain a bit of performance/range.

Lscott your post just reinforces my conclusion.

Also I am wanting a telescopic mast to make adjustments/experimenting easier. I like the flag pole idea. Good price point compared antenna masts.

 

Great first post! Welcome to the forum.

[WRWE456]

Thanks Steve. I have been reading here for a month or so, just decided to join in. Been learning a lot here. Hope I can contribute some as I continue to learn. By the way I love Montana!

[SteveShannon]

Just now, WRWE456 said:

Thanks Steve. I have been reading here for a month or so, just decided to join in. Been learning a lot here. Hope I can contribute some as I continue to learn. By the way I love Montana!

I do too!