Building a mobile mast for 2M use.

[crawler#976]

I work radio for several races locally, the first being the Prescott Rally, the second the Parker 425.

http://www.prescottrally.com/ (they always need more volunteers by the way, and it's the only way to see the cars on course!)

My location is relatively remote for the rally race, and very, very remote for the Parker 425. For it, we're at the far northern end of the course at mile 76.5 - almost the mid point of the loop from Parker, about 30 miles straight line to the east via simplex. It also has to get over about 600' of elevation between us.

Being cheap, I picked out the MJF-1750 (http://www.mfjenterprises.com/Product.php?productid=MFJ-1750) as an antenna to mount on a three piece PVC pole. It's coming from HRO along with a 30' cable.

With a 6' bed on the truck, I'm limited to 6' chunks of PVC. My thought is to start with 2", step to 1.5", and down to 1" for the top section. The 2" pipe should be sturdy enough to anchor without it being weak. My thought is drive in a concrete form 1" dia stake, slip the bottom over that, guy it via eye bolts thru the pipe to tent stakes.

I know a lot of you participate in field day activities, and use masts, so I wanted to see what you thought about this setup.

Mark

 

[crawler#976]

Hmmm,

1.5" Schd 80 will fit into 2" Schd 80 without a coupler so that will be a strong joint to mount eye bolts thru. I'll plan on sanding it down for an easy match, and use roughly 8" for the joint. The 1.5 to 1" is problematic - there are no slip fit sizes available, so a coupler will be required. That may a bit wobbly, but I guess I'll see how it goes. The antenna isn't heavy, so that may not be an issue. I may go to 1.5" to 1.25" for the top section - a trip to the hardware store will tell the tale.

 

[1leglance]

Funny you brought this up as I was at Home Depot today and looked at the extending painting poles for just this sort of thing.

Looking forward to what you put together.

Gonna be another fun year at the Prescott Rally ....I hope to get Road Block 1 again as I like the shelf roads.

 

[SARguru]

Someone one forum was selling
Camoflage netting mast kit. I have a few friend who use them for mobile mast. You can get them in alum or fiberglass. They come in 4ft lenght and mate together to form a 24ft mast. Some kits have a baseplate about 1 foot square. Some if my friends use a roof sat dish type tripod.

Nic
Ve3rsq

 

[crawler#976]

I also looked at the extendable fiberglass poles, but they are too long to fit in the truck. First thought I had was my tree saw pole, but it's 10' collapsed.

I tried to find schd 80 PVC - no luck yet. Prescott is still a small town in some respects.

Sent via gigawatt laser...

 

[gahi]

 

[DaveInDenver]

I've built 6' PVC sections that fit together, sort of like a poor man's military poles. I cemented couplers on one end and fit as many as I want together for the mast. My experience is more than about two, e.g. 12', needs to be guyed. PVC is just too flexible, even sch 80, and the couplers too loose for them to work like true military poles.

Tapering & nesting them might work better but limits your overall height.

I use an old surveying tripod as the base and it holds up 24'~30' as I guy it, no problem. Also lets me move my truck if I want without upsetting the hasty tower. Beyond that it just leans too much and I usually don't get it erected and guyed before it falls over.

I also have a 50' push up fiberglass pole. It is self supporting for a small dipole but really needs to be guyed most of the time. This I can either tilt up or raise from the middle, so it's never set up without guy lines. Collapsed it's 9' feet, so it's got to go on the roof, not convenient.

 

[bobDog]

View attachment 177737

Okay I know very little about this but that just reeks of genius!

 

[DaveInDenver]

You can make that yourself with lumber and a bulkhead flange.



Another option for a base is to make an 'H' or 'X' with PVC. You guys in AZ could fill it with water but most people use sand where freezing can happen. They end up fairly hefty if you use 1.5" PVC.

 

[crawler#976]

View attachment 177737

I like it! That I can build if need be, and it would work great with:

https://02bc3fb.netsolstores.com/camonetsupportsystem.aspx

Yeah, it cost $50.00 bucks to ship, but I'll sell half of it for half of what I paid, and have a better setup than PVC.

Lance, are you interested in 6 poles and a base for $35.29?

Mark

 

[gahi]

what about PVC conduit? It already had the ends meant to slip fit together. I have a piece of 1-1/4 from a project and it seems fairly rigid.

 

[1911]

The common military surplus fiberglass poles are very stiff and don't need to be guyed for a fair distance, though I would guy them if you're going to put up 30' worth.

Here is my setup for remote 2M; said poles on a home-made receiver hitch mount, with an MFJ-1763 2M beam antenna. http://www.mfjenterprises.com/Product.php?productid=MFJ-1763 The beam is more directional than the 1750, but the mast is easy to rotate by hand and iI get excellent range with this set-up.

 

[1leglance]

yeah Mark I would go for that...
Worse case I can use it to put up shade in the back yard around my son's smithy for when we are both forging.
I can pick it up at the Overland Journal Open House Sept 7th.
If you need money before then I can paypal you.

Good job figuring this out.


Part of me likes the idea of a beam antenna for better directional range...but for these events I like an omni setup so I can get info from people up course & down from me.

 

[crawler#976]

Lance, I'll bring it on the 7th - if you like it, it's yours. If you don't, not to worry, it will get used or sold.

Sent via gigawatt laser...

 

[Jr_Explorer]

DX Engineering has fiberglass tubes meant to telescope into one another. I get it... They are 8' long and you'd be cutting off 25% of them. But they start at a massive 2.75" O.D. and if you wanted to get crazy stiff you could put the 2.5" inside the 2.75" without extending them for a 0.25" wall! Then the first raised section could be a 2.0" inside a 2.25" and the second extended section 1.75". I would think that would be stiff enough to not need guying in a hurricane (maybe a slight exaggeration).

You can look at all the goodies here:
http://www.dxengineering.com/search...dx-engineering-fiberglass-tubing?autoview=SKU