Hello Steve,
I have been subscribed to Tower Talk for a long time, and enjoy reading the
technical information posted there; especially your professional opinions on
tower/antenna projects. I too thought I could save money by using schedule
80 pipe for my array. Not as large as some, but not small either. I have
an HDBX-48 with the following antennas (top to bottom.)
2 homebrew 22 element 432MHz
CC 32-29 144MHz
Homebrew 4 element 50MHz (12ft. boom)
KT-34A
I moved the rotor plate to the bottom of the top section and installed a
21ft length of 2 in. OD schedule 80 for the mast. That leaves approximately
14 above the tower. I know that is contrary to your advice of following
the manufactures recommendations. However, the tower seems to handle it
quite well. That is, until last August when we had a sever storm with
downdraft winds measured at 98mph. Surprisingly the antennas all survived,
but the mast is slightly bent and will have to replaced.
Now that spring has come to the upper midwest, I am making plans to repair
the damage. My plan is to replace the 12-19 with two 12 element K1FO yagis,
install only one of the 432 antennas and not install the 6 meter antenna.
Of course the KT-34A will also go back on the tower. I do not know what the
wind load will be with this combination,
I I haven't bored you too much after reading all of the above, I would like
to ask a question about the new mast. I purchased a 20ft. length of 2 in.
OD stainless steel tubing from a local welding shop. I was much cheaper
than a commercial alloy mast and I did not have to pay shipping. Printed on
the tube is SCH40S TP304/304L HT-113050. I have been unable to find
specifications for this material. Do you think I should go ahead and use it
for a mast, or am I setting myself up for future problems?
Thanks for your time.
Gary - WY0V
-----Original Message-----
From: towertalk-admin@contesting.com
[mailto:towertalk-admin@contesting.com]On Behalf Of K7LXC@aol.com
Sent: Saturday, March 30, 2002 9:44 AM
To: n9en@voyager.net; towertalk@contesting.com
Subject: Re: [Towertalk] Source for masts?
In a message dated 3/30/02 4:57:52 AM Pacific Standard Time,
n9en@voyager.net
writes:
> I am looking for a source for 10' long by 1/4" wall galvanized
> steel masts. I see that Texas Towers no longer carries this
> size and length of mast. Does anypne know who sells this
> particular size of mast?
US Towers carries some but the freight will be kind of pricey to
anywhere.
Your best bet is to check your local yellow pages for steel suppliers or
do a web search.
>
> I am thinking of visiting my local plumbing distributor and
> buying a 21' length of 1-1/2" schedule 80 galvanized steel
> pipe. I don't need a mast that will be subjected to extreme
> loads; my one application will have a HyGain 105BA
> mounted above a HyGain 155BA, seperated by a distance
> of 8'. The 1-1/2" schedule 80 pipe has a wall thickness of
> .200" and I would think that this would be adequate for my
> application, although a mast with a .250" wall thickness
> would be much better.
>
Okay - first things first. What's your county windspeed rating? If you
don't know, you can go to <A HREF="http://www.championradio.com";>
www.championradio.com</A> and look under Tech Notes. Let me know what the
windspeed rating is and I'll make a quick calculation to get you started.
While schedule 80 and other PIPES are heavy - they're not strong.
They're
used to carry liquids and aren't rated for strength.
For most mast applications, you want steel alloy TUBING; they are rated
for strength. The most common tubing available is the SAE 1026 or 1027 which
has a yield strength of around 65,000 psi which is plenty for most HF
stacking applications.
Cheers,
Steve K7LXC
TOWER TECH -
Professional tower services for amateurs
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