[TowerTalk] TowerTalk Digest, Vol 153, Issue 42

Tue Sep 15 13:01:53 EDT 2015

Tnx for the various input much apprfciated. This mast is for a friend for the following application. I have sent him all the feedback from u folks: 

"125 MPH version of the M2 log periodic for 10-30 MHZ and a heavy duty 7 element 6 meter yagi from Directive Systems on it (not on the website).  Both antennas have truss supports so I need some vertical space for each.  I am at an elevation of 160' ASL and on the salt water (edit: he is in coastal
Maine ,tough winters).  On the water so there is constant wind and the likelihood of ice loading as well in the winter.  "

73. Steve. K1PEK

Steve Davis
Senior RF Cable Design Engr.
& Founder
DAVIS RF Co. a  division of
Orion Wire Co., Inc.
Tel: 978-369-1738
     ALSO: Davis Rope & Cable Assembly Co., LLC:
      Design Engrs, Distribution

> On Sep 15, 2015, at 12:00 PM, towertalk-request at contesting.com wrote:
> 
> Send TowerTalk mailing list submissions to
>    towertalk at contesting.com
> 
> To subscribe or unsubscribe via the World Wide Web, visit
>    http://lists.contesting.com/mailman/listinfo/towertalk
> or, via email, send a message with subject or body 'help' to
>    towertalk-request at contesting.com
> 
> You can reach the person managing the list at
>    towertalk-owner at contesting.com
> 
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of TowerTalk digest..."
> 
> 
> Today's Topics:
> 
>   1. Looking for good source of 20 ft mast (Jim Thomson)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Tue, 15 Sep 2015 00:37:03 -0700
> From: "Jim Thomson" <jim.thom at telus.net>
> To: <towertalk at contesting.com>
> Subject: [TowerTalk] Looking for good source of 20 ft mast
> Message-ID: <B775B429A6144E73B14E0E76B965B28F at JimPC>
> Content-Type: text/plain;    charset="utf-8"
> 
> Date: Mon, 14 Sep 2015 13:33:37 -0400
> From: Stephen Davis <sdavis at davisrf.com>
> To: "towertalk at contesting.com" <towertalk at contesting.com>
> Subject: [TowerTalk] Looking for good source of 20 ft mast
> 
> Hello all
> 
> Specs :   20 ft. 2" O.D. .50" wall chrome moly
> 
> Yep, .5 "  !
> 
> Tnx a lot.  73. Steve. K1PEK
> 
> Steve Davis
> Senior RF Cable Design Engr.
> & Founder
> DAVIS RF Co. a  division of
> Orion Wire Co., Inc.
> Tel: 978-369-1738
>     ALSO: Davis Rope & Cable             Assembly Co., LLC:
>      Design Engrs, Distribution
> 
> # A  2.875  or 3 inch OD cm mast with just a .25 wall is one helluva lot stronger
> vs a 2 inch mast with a .375 wall......yet they all weigh the same....and cost the same ! 
> You can see all of that on the arrl mast software at a glance.  Huge difference in strength. 
> 
> ##  as soon as u exceed .25 wall, you are essentially wasting your time and $$. At that point, 
> the OD needs to be increased.   A 2 inch mast with a .5 wall  will only be a tiny bit stronger than
> a .375 wall.   A 2 inch solid mast will gain you nothing....but weight + $$. 
> 
> ##  in my case, the HDX-689 was all setup for a 2 inch OD mast so I was screwed.  My only option 
> was to use a 2 inch x .375 wall CM mast.   Another option if u are stuck with a 2? OD mast is to
> insert a 2nd tube inside the 1st one, close fit...then weld the base.   
> 
> ##  for folks that actually have a choice of mast OD, always use a 3 inch OD, 4130 CM  mast...or a 2.875
> inch OD  DOM mast....and both in .25 wall. 
> DX eng sells the 3 x .25  CM masts.   Array solutions sells the 2.875 x .25 DOM masts. 
> 
> ##  Dunno which idiot decided to standardize a 2 inch od mast for ham radio use, but it was fubar. 
> I have been collecting bent and broken mast pix since 1977..think its now up to 36 or 37.   Removing
> mast bent at a 90 deg..with yagis  still on it is beyond extremely  dangerous.    In many cases, a crane
> cant be used, or will not fit the space, to get at them. Then what ?  Ever see one fall and slice the guy wires below it. 
> Then the tower comes crashing down. 
> 
> ##  use the freebie  ARRL mast software to plan your install....and also allow for future expansion. 
> Sure, a 2 inch od x .25 wall CM or  DOM mast sounds wonderful, till u find its maxed out when u go to stack
> your shiny new 40m yagi parked right at the top.   If a single yagi is  mounted within a few feet of the top of the
> tower, anything will work, including plane jane 35 ksi water pipe, in sched 40 or sched 80.   Again the software 
> will tell u at a glance if its even doable for XXX  windspeed.   
> 
> ##  IMO, the mast is the most important thing up there.   It has to be the strongest component in the mix.  A mast
> failure should  not even be a remote possibility.    But if you are stuck with a 2 inch od mast, your only option is DOM, and if that?s
> not up to the task, then  CM.   If CM in .25 isnt up to the task, then  thicker wall CM, like .375 or perhaps .5 thick is an option.
> 
> ##  hams have been cheaping out on masts since day 1...and are still doing it to this day.   Better to pay once, cry once, and buy the 
> real deal..and have it hot dipped galvanized too. Use the dx eng handy cap for the very top, to keep water out of the inside.
> I kicked myself many times for not buying a good mast  35 yrs ago...when they were  a lot cheaper.   A good mast will easily last a lifetime,
> and have good re-sale value.   Section modulus x yield strength =  max bending moment.   Bigger OD + thinner wall results in a bigger section modulus
> vs smaller diam + thicker wall. 
> 
> sri for the riot act. 
> 
> 
> 
> 
> 
> ------------------------------
> 
> Subject: Digest Footer
> 
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
> 
> 
> ------------------------------
> 
> End of TowerTalk Digest, Vol 153, Issue 42
> ******************************************
> 