2M j-pole?

[David Knaack]

Any radio people want to help build/tune a 2M j-pole? Construction is pretty easy, but I don't have the equipment to tune it properly, and I'd like some input from someone with more experience on placement and cabling.

I'd like to set it up on the roof and run coax to the front room at the space.

I'm also thinking that it would be interesting to put together a helical quad and put it up there to see how the SDR dongles like it for receiving NOAA weather satellite images.

Anybody interested?

[Ryan Stille]

David I have an SWR analyzer we can use to tune the antenna. I have built one before. Is this a twin lead j-pole or copper pipe or something else?

-Ryan

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[David Knaack]

I have a twin lead already made that I need to tune, but I was thinking copper pipe would be better for permanent mounting on the roof.

[Ryan Stille]

David I am busy this week but next week I should be able to stop down there some evening and work on this with you.

-Ryan

[Jason Amdor]

I'd like to learn how to use an SWR meter to tune an antenna.  I am planning on running bicycle mobile this summer. 

I was originally planning on building this antenna:
http://www.mikestechblog.com/joomla/ham-radio/ham-radio-antennas-category/63-2-meter-antenna-for-bicycle-mobile-operation.html

But eventually decided I'd be better off buying a ready-made product:
http://www.n9tax.com/Slim%20Jim%20Info.html

Still, it be interesting to see how my mounting solution (ATV mast on a trailer) affects the SWR.

[David Knaack]

I still have to get parts and assemble it, and I don't recall if I have any coax for it (and I should check out the roof to get an idea of how much coax I'll need).

What day would be good for you? I'll be down there Wednesday, and probably either Saturday or Sunday.

[David Knaack]

I want to try using my cheap CB SWR meter and see how closely it agrees with a real meter. I've read that if you run it backwards it can be used to tune an antenna, although it won't give you accurate numbers without calibration.

That bowed PVC mount is a clever idea, I'll have to remember that.

[Ryan Stille]

A CB meter would be designed for 27Mhz. The 2M band is 144Mhz, so it won't work. I do have a VHF/UHF SWR meter that we could use though. Next Wednesday evening should work for me. I may have some extra coax you could use, but it's CATV coax. Which will work, but it's length affects tuning of the antenna.

[David Knaack]

http://www.kb6nu.com/no-vhf-swr-meter-no-problem/

[David Knaack]

I assembled most of the antenna last night. Still waiting on the connector to arrive, but I should have it all ready by next week. Hopefully I got the dimensions close enough.

[Eric Kaplan]

<soapbox>

Since we have a landlord that cares about us as a tenant, and that we at least have some respect for, we should be considerate of this and our lease before we go and mount anything to the roof.  Especially considering that we have roof leak issues at the moment that will require the landlord to address.  Really don't want to give him an excuse to say that we caused the roof leaks, because then the cost/burden would be on us.

Just sayin'....

</soapbox>

On Thu, Mar 21, 2013 at 9:14 AM, David Knaack <david...@gmail.com> wrote:

I assembled most of the antenna last night. Still waiting on the connector to arrive, but I should have it all ready by next week. Hopefully I got the dimensions close enough.

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[Kevin Fusselman]

One of those ballast mounts might be ideal, so as not to put any holes in anything...

[David Knaack]

Yup, I have no intention of making property modifications without permission.

[Eric Kaplan]

Thanks.  

Another option, which is common for satellite dishes, is a base with a flat pan and some cinder blocks or sandbags.

[Steve Sanders]

You could make it look like a palm tree.  Nobody would notice.

[Ryan Stille]

This is a great idea. Might be able to feed the coax through a vent and not need any holes for that either.

David, what connector are you waiting for? What will you terminate the feedline with? PL-259? Do you have coax?

[David Knaack]

The plan is to either put an SO-239 on the base of the antenna, or just wire the feed line directly to it. I still need to go check what I have laying around.  I may have a long half of a cable (RG8X? I don't remember now) with a PL-259 on one end (the other half is connected to my portable twin-lead antenna). If I have to buy more coax I'll put the socket on the antenna.

[Ryan Stille]

Dave you still want to work on this tomorrow night? What time? I can be there a little after 5:00.

-Ryan

[David Knaack]

My connectors haven't arrived yet, so I can't do much in the way of tuning. Might need to put it off a bit longer, depending on whether they arrive before wednesday.

[David Knaack]

Connectors arrived, so I'd like to get going on finishing up the antenna soon.

However, I still need to come up with some cable, looks like I don't have any left. That will take some time to ship, so perhaps it should wait until next weekend or thereabout.

[Patrick Joseph]

How much do you need?  And what type do you want to use? If I have enough I'll donate it to the cause.
Pat Joseph - KØCTU

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[David Knaack]

Brilliant!

As to length, that's a good question. I haven't checked out what it will take to get a cable to the roof. I'm hoping there is an existing hole I can use. If there is not I'll have to include that info with the installation permission request.

I'd like the cable to run to the front room, perhaps running down the back wall where the existing telephone jack is. If there is roof access near there then 30 feet would be plenty. If I need to run back to somewhere near where the laser cutter vents, it's probably going to be closer to 100 feet.

I'll get up there on Wednesday evening and check it out and let you know.

Assuming I could set it up temporarily in the desired location with the right length of cable, can it be tuned that way, and then be installed permanently at a later date? That is, does the routing of the coax have a significant impact on the tuning?

If not we could probably get it tuned sooner rather than later.

DaveK AC0KG

[David Knaack]

I'm going to try to bring the antenna and radio gear tonight, might take a stab at getting it tuned.

[Patrick Joseph]

    If anyone wants to see Amateur Radio in action, come to the Ak-Sar-Ben Amateur Radio Club Field Day site on Saturday. Field Day is when all of the hams in the U.S. try to talk to all of the other hams in the U.S.
   We will be on the air for 24 hours starting at 1:00 PM Saturday. The best time to visit would be between 2PM and 4PM on Saturday (when we are fresh and not grumpy yet), although you are welcome anytime.
   Come out to the stop lights just south of 156th and Maple, next to the Hy-Vee Gas station. Turn east and you will find us at our trailer next to the former Thomas Fitzgerald Veterans home. Visit our web page for more location details.

http://www.aksarbenarc.org/main/