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eHam Forums => Elmers => Topic started by: K8POS on September 24, 2012, 09:03:46 AM



Title: 10 foot non metallic mast
Post by: K8POS on September 24, 2012, 09:03:46 AM
I am looking for a 10 ft non conductive mast to mount two 13b2 antennas on.
One vertical on horizontal.
Have thought about a 1 1/2" schedule 80 PVC , but I don't think that will hold up without a dowel inside.
Any suggestions.

Bob


Title: RE: 10 foot non metallic mast
Post by: AG6WT on September 24, 2012, 09:09:28 AM
You should be able to get wooden curtain rods in that length. I think they are 1-3/8 diameter or so. I've seen them in 12 foot lengths at my local Home Depot for around a $1/foot.

Ray KJ6AMF


Title: RE: 10 foot non metallic mast
Post by: K8AXW on September 24, 2012, 09:34:21 AM
Check eBay.  I've seen telescoping and plug together heavy duty military surplus masts at the one hamfest I attend every year.  It's very possible you might find the same or similar items on eBay.   

Then I could suggest Googling for nonconducting mast sections, etc.


Title: RE: 10 foot non metallic mast
Post by: WN2C on September 24, 2012, 09:55:23 AM
If Iam not mistaken the 13b2 is a Cushcraft antenna and you need the A26B2-VPK for $170 from Cushcraft.  It is the stacking kit for 2 13b2 making it a 26b2.

73 de wn2c Rick


Title: RE: 10 foot non metallic mast
Post by: K8POS on September 24, 2012, 10:32:24 AM
I am not stacking them, I am using them together one horz the other vert or crossed polarized.
Already have them together and tuned.



Title: RE: 10 foot non metallic mast
Post by: N6AJR on September 24, 2012, 12:04:36 PM
I don't know that you need a non conductive mast for them.  I belive all they maks are made to clamp on a metal mast.  I'm just saying..  are these going to be on a switch, for either /or?


Title: RE: 10 foot non metallic mast
Post by: KG4RUL on September 24, 2012, 01:43:56 PM
Put the horizontally polarized antenna on a metallic mast (it will only marginally disturb the pattern).  Then extend the mast from there with a non-metallic material for the vertically polarized antenna.


Title: RE: 10 foot non metallic mast
Post by: WB2WIK on September 24, 2012, 02:02:20 PM
Put the horizontally polarized antenna on a metallic mast (it will only marginally disturb the pattern).  Then extend the mast from there with a non-metallic material for the vertically polarized antenna.

Yep, that would work.

They really only need to be about 6-1/2' apart, so if you used a standard HD steel mast out of the tower to support the horizontal antenna and extended that just 4' or so with a fibreglas mast fitted to the steel one, you should be all set if you put the vertical beam up near the top of the fibreglas extension.



Title: RE: 10 foot non metallic mast
Post by: K8POS on September 24, 2012, 09:40:15 PM
Both antennas will be mounted as a common boom, one boom right on top the other.
The mast must be 100% non metallic.


Title: RE: 10 foot non metallic mast
Post by: K3GM on September 25, 2012, 05:56:43 AM
DX Engineering stocks various sizes of fiberglass tubing diameters up to 2.00".


Title: RE: 10 foot non metallic mast
Post by: W8JI on September 25, 2012, 06:39:06 AM
I have a question.

Why do some people use a non-metallic mast and then just run the coax along the non-metallic mast??? Do they use magical non-metallic coaxial cable?

If the mast is an issue affecting pattern, what causes the coax to NOT be an issue for some of us?

What I do is use an offset boom on a crossover plate with metal masts. My vertically polarized antenna is set out a few feet (at VHF) from the mast, and the coax follows the masts. I have, in some installations, brought the coax cables out the antenna rear away from the reflector and down, behind everything.

If I could buy some of that electrically invisible coax my neighbor has, I would use a non-metallic mast and tape the no-metal-inside coax to it just like he does. :-)   He went through a lot of work to buy fiberglass mast, and then he just taped the coaxial cables along it.

73 Tom


Title: RE: 10 foot non metallic mast
Post by: W9GB on September 25, 2012, 06:49:37 AM
Quote
If I could buy some of that electrically invisible coax my neighbor has ...
Sorry, SOLD OUT .... BUT for those SPECIAL RADIO-PHILES ... a new shipment is expected from Outer Mongolia, Home of those RARE EARTH elements!!

Unfortunately, due to current commodity prices for the Magical Element,
the new prices for the electrically invisible coax will be 50% higher.

Operators standing by to take your orders (and money) for our next shipment !!
CALL NOW, please.


Title: RE: 10 foot non metallic mast
Post by: K8POS on September 25, 2012, 09:02:32 AM
Gee I thought running the coax out the back of the antenna took care of the interference/coupling issue.
Did not know I could use invisible coax.
Can I order a flux capacitor too?
 


Title: RE: 10 foot non metallic mast
Post by: W8JI on September 25, 2012, 06:01:15 PM
Gee I thought running the coax out the back of the antenna took care of the interference/coupling issue.
Did not know I could use invisible coax.
Can I order a flux capacitor too?
 

I'm always surprised how many people bring the coax right down the non-metallic mast. It's more common than you might think.


Title: RE: 10 foot non metallic mast
Post by: WB4SPT on September 27, 2012, 08:55:38 AM
Single, 10' length of FRP, 1/4" wall, 2" square section is just under $100 at McMaster carr.  1/8" wall is also listed.  PVC, wood, is all very second rate.


Title: RE: 10 foot non metallic mast
Post by: WN2C on September 28, 2012, 11:07:54 AM
Bob, take a look at the pic on Cushcraft's web site.  The 2 13b's are mounted side by side (horizontally in pic) but there is no reason you cant mount one horizontal on one side and vertical on the other.  Look at the pic.  Or are you looking to do some thing like the A148-20t?

"I am not stacking them, I am using them together one horz the other vert or crossed polarized."

73 de wn2c Rick


Title: RE: 10 foot non metallic mast
Post by: AA4HA on September 28, 2012, 06:48:57 PM
Single, 10' length of FRP, 1/4" wall, 2" square section is just under $100 at McMaster carr.  1/8" wall is also listed.  PVC, wood, is all very second rate.

Exactly right, thick wall square section fiberglass is very robust. It looks really good and is not going to get that very sad, saggy look like PVC does after one summer or auto-magically shatter into a million pieces on a windy very cold winter night.

PVC is definitely not rated for structural-anything. The fiberglass military mast kits would be a much better choice and come in 4' lengths if you were going to go that route. At least you could use the rest of them for a 20-30' tall field day antenna


Title: RE: 10 foot non metallic mast
Post by: N4CR on September 28, 2012, 07:49:08 PM
You could set one of them at a 45 degree slant, half way between vertical and horizontal and it would work either polarization at -3db.

Considering how much gain those have it might be just fine. Only you will know. It'd be the first thing I'd try.