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Thread: Building my first vertical antenna

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  1. #1
    Join Date
    Mar 2008
    Location
    Columbus, OH
    Posts
    110

    Lightbulb Building my first vertical antenna

    I have a couple of days off here next week and wanted to make a new antenna. I live in a town house and they do not allow any outside antennas. I was thinking about building a vertical that I might be able to leave up for a couple of days or until someone yells.

    I was thinking about this one in particular, http://www.hamuniverse.com/kl7jr5bandvertical.html

    My questions for you all:

    I have never used 1/2 and 3/4 inch EMT conduit before. I have sold the hell out of it when I worked at a hardware but never used it. For portability and storage the 10 foot length is a no go. I was thinking about cutting them down to 5 foot lengths and either using the appropriate coupler or some other sort of joining device.

    I'm just not sure if the EMT couplers would be strong enough to with stand a couple days of wind and weather. I wouldn't be leaving it up in bad weather unless something happened to spring up unexpectedly and I wasn't home to take it down.

    Thank you in advance for any help and opinions. I know I could probably buy something and it would be easier but where is the fun in that!
    ~73
    Jeff
    KD8HYU[SIZE=1]
    [/SIZE][SIZE=1][URL="http://www.quotationspage.com/quote/495.html"][/URL][/SIZE]

  2. #2
    Join Date
    Mar 2009
    Location
    Carmel, IN
    Posts
    6,185

    Default

    If you can get aluminum pipe it is so much lighter and easier for antenna construction like this. Most hardware stores carry aluminum pipe also.

    I used 16' pool pole to make vertical on vacation once, along with couple of above ground radials. Above ground radials work better.
    Leroy
    Be sure to listen for my beacon on 28.278.8 MHz

  3. #3
    Join Date
    Dec 2005
    Location
    Sunnyvale, CA
    Posts
    202

    Default

    Do you have room for 16 foot radials? That's 32 feet diameter. Prolly not, in a townhouse. Also, EMT has relatively high resistance which will reduce the efficiency.

    Instead check out c-pole antennas. I made a 20m one and it works great, nearly as good as any vertical, if I can hoist it up 25 feet. It doesn't need radials. The book "Antenna Engineers Notebook" has plans for a multi band c-pole.

    If you have 11 foot diameter, and can get 20 foot up, check out hex-beam antennas.

    Today I used my SuperAntennas. MP-1, got a nice qso with OE3DIA on 20m. MP-1 is really portable and works great.

  4. #4
    Join Date
    Feb 2003
    Location
    SW Missouri
    Posts
    3,738

    Default

    Quote Originally Posted by K6CLS View Post
    ... EMT has relatively high resistance which will reduce the efficiency.
    In theory, yes. But in practice, I doubt that the difference will be noticed.

    Instead check out c-pole antennas. I made a 20m one and it works great, nearly as good as any vertical, if I can hoist it up 25 feet. It doesn't need radials. The book "Antenna Engineers Notebook" has plans for a multi band c-pole.

    If you have 11 foot diameter, and can get 20 foot up, check out hex-beam antennas.

    Today I used my SuperAntennas. MP-1, got a nice qso with OE3DIA on 20m. MP-1 is really portable and works great.
    Anyplace where we can see a C-pole antenna online? I don't have the book you mention, and inquiring minds want to know. :-)
    73, Mike
    http://www.w0btu.com

  5. #5
    Join Date
    Dec 2005
    Location
    Sunnyvale, CA
    Posts
    202

    Default

    ... EMT conduit antenna ... I ought to build one and try it... but what should I compare it to? my R7? which is at 25' and doesn't have radials? for that matter, I don't have room or wire for a good radial system. so what does it mean if my EMT conduit antenna with crummy & few radials doesn't work well? hopefully some one who has tried it will chime in here.

    or maybe KD8HYU will go ahead and try it. You could get sufficient conduit for under $10, add a $35 roll 500' of #14 THHN copper wire for radials... so, do you have room for the radials?


    you can google "c-pole", the second hit

    http://www.qsl.net/hb9mtn/hb9mtn-c-pole.html

    is a great article.

    the hardest part of the C-Pole is finding a non-conductive mast, or a tall enough tree to hang it up.

  6. #6

    Default

    In the August 1959 issue of QST there was an article on building a 2-element 15-meter yagi using E.M.T. This yagi used small loading coils in the middle so that only 10 foot lengths of 1/2 inch E.M.T. were used. I built one as a Novice Class operator and continued to use it after upgrading. Later I built a similar antenna using aluminum tubing. Frankly, I couldn't tell the difference between aluminum and steel except for, of course, the weight.

    If you look at the HyGain HyTower you will see that the main structure is 24 feet of galvanized steel tower. The HyTower is the Rolls Royce of vertical antennas and they work VERY well.

    Also, over the years, I have made quite a number of wire antennas using galvanized steel electric fence wire. Those also worked very well.

    Yes, there is a difference in the conductivity of galvanized steel, copper wire, silver wire, aluminum, and so forth. However, in the "real world", this factor isn't going to make any difference at all in how the antenna performs.

    Also, there have been many vertical antennas made from galvanized "down spout" material. Those antennas also work very well.

    Glen, K9STH

  7. #7
    Join Date
    May 2002
    Location
    Rockport, TX
    Posts
    1,077

    Default Side note---26 foot verticals

    Please excuse my slight hijack here but it's somewhat related:

    Interesting to note that the EMT antenna is the same height as a Butternut HF6V---26 feet.

    I wonder if I took out my old (1984) HF6V whose coils are bent up and doorknob capacitors have come apart---and put it up without them (like the plain-Jane EMT) if it would work OK on 10 meters? (That would be the only band I would be using it for if I did). Perhaps it would still radiate better with the coils and caps as well as plenty of radials, of course.

    So maybe I should refurbish it with new parts before I install it but this EMT vertical intrigued me with its simplicity. Curious...

    Getting back to the point, I also think you would be better off using aluminum tubing instead of EMT---that stuff is heavy and will require a guying system for sure.

    I see that Cycle24.com has good prices on aluminum tubing in a number of different lengths, too.

  8. #8

    Default

    Hi Jeff,

    I'd scrap the idea of using EMT unless there was nothing else readily available. It's heavy and couplers won't take much stress from wind before letting go. EMT isn't meant to slip-fit together (1/2" = 0.706" OD and 3/4" = 0.922" ID). That design uses two 10' sections overlapped 1-1/2'. Apparently, for good electrical connection between them, you sqeeze the 3/4" tube onto the 1/2" tube. But, the zinc plating isn't the best conductor. I'd also not use the (heavy) stainless steel CB whip on the top.

    I recommend "structural aluminum tubing" (not the same as pipe). Sizes with 0.047 or 0.058" wall thickness will slip-fit together nicely. Use 6" to 12" overlap to be able to adjust the length. Tubing can be had in various lengths. When I fabricated my 20m half wavelength vertical, I used a 5' length for the bottom section so I could easily adjust the length. Common 6061 or 6063 alloy has good strength and is easy to machine. Cut two or four slots in the top end of a section of tubing, and you can use a screw-type hose clamp to secure it to the section above it. I prefer all-stainless types (cheaper ones have a steel screw). McMaster-Carr has the good ones.

    You're near Columbus, OH and you have outfits like Central Aluminum nearby. If they can't help you, they should be able to point you in the right direction. Texas Towers also handles aluminum tubing BUT, if you want longer than 6' lengths, it has to ship via truck, and there's a 300# minimum. Buy it locally if you want longer than 6' lengths.

  9. #9
    Join Date
    Apr 2001
    Location
    Shropshire. England.
    Posts
    17,152

    Default

    Readers of your mail seem to have forgotten that you are living in an area where antenna's are not permitted and as you say when someone sees your antenna it may have to come down in a few days. So, why waste money making something which will take your time as well. Buy an extending fibreglass pole 10 metres long to which you can attach some single core plastic wire resonant for the band you which to use, and a radial to go with it. When not in use you can reduce it to about 3 feet long. It will get you all over the US and some DX, and won't cost you much to make and you can lean up against a wall and tell any nosey neighbour that you're "going fishing by a shady wadey pool"

    G0GQK

  10. #10

    Thumbs up

    In the August 1959 issue of QST there was an article on building a 2-element 15-meter yagi using E.M.T. This yagi used small loading coils in the middle so that only 10 foot lengths of 1/2 inch E.M.T. were used. I built one as a Novice Class operator and continued to use it after upgrading. Later I built a similar antenna using aluminum tubing. Frankly, I couldn't tell the difference between aluminum and steel except for, of course, the weight.
    Glen -

    I remember that 15-meter antenna from the early 1970s ARRL Antenna Handbook (Green cover) when I started. It is VERY EASY to build and was a great home DX antenna for the new Novice operator !
    ... using the appropriate coupler or some other sort of joining device.
    I'm just not sure if the EMT couplers would be strong enough to with stand a couple days of wind and weather.
    Jeff -

    Stay away from EMT couplers. You NEED the tubing overlap between sections for vertical strength and to prevent this vertical from toppling over in a stiff breeze.

    IF you worked in a hardware store,
    Don't you have access to Reynolds Aluminum tubing in the aluminum screen door or hobby section?
    These are normally sold is long (6, 8 or 10 foot) sections in 1, 7/8, 3/4, 5/8 and 1/2 inch diameters that can easily telescope into one another

    A band saw or jig saw cut of 1-1/2 to 2" at the end of the larger tube
    will permit a good Stainless Steel hose clamp to be used.

    GO to the DX Engineering (they are based in Akron, Ohio) vertical antenna parts section ---
    Window Shop the Internet catalog -- that will give you many ideas!!
    http://www.dxengineering.com/default.asp?DeptID=32

    You can use PVC pipe or fiberglass rod for your base / feed point insulator.

    UPS shippable aluminum tubing is limited to 6 feet in length.
    I wonder if I took out my old (1984) HF6V whose coils are bent up and doorknob capacitors have come apart---and put it up without them (like the plain-Jane EMT) if it would work OK on 10 meters?
    NH7RO .... SURE -- WHY NOT?

    A Marconi antenna is a QUARTER WAVELENGTH VERTICAL antenna with appropriate radial field.
    QUARTER Wavelength of 10 Meters is 2.5 Meters -- which is 8.20 Feet --
    that is shorter than a standard 10 foot length of EMT conduit.

    A 26 FEET vertical radiator / antenna is equal to 7.92 meters ... times 4 means it is equal to 31.68 meters.

    A QUARTER WAVELENGTH Antenna for 40 Meters is ~ 32.81 feet in Height !

    METRIC to ENGLISH Conversion -- Have this web site do the Math !
    http://www.sciencemadesimple.com/length_conversion.php
    I ought to build one and try it... but what should I compare it to? my R7? which is at 25' and doesn't have radials? for that matter, I don't have room or wire for a good radial system.
    Cliff -

    The Cushcraft R7 (and entire R series) are end-fed Half-wave vertical antennas with balun and choke balun in the Matching box with 48 inch counterpoises at feedpoint/ground connection.
    It works - W8JI has comments about end fed half-wave antennas on his web site.

    IF you want to install a 1/4-wave vertical -- then the radial field is REQUIRED.
    You will NOT be happy trying to use it without the proper radial field.

    Go ahead and build one -- and compare similarities and differences in signals (different patterns) between the 1/4-wave and Cushcraft 1/2-wave -- that is one aspect of amateur radio -- Hands On, Practical Education !

    MANY have tried to use 1/4-wave verticals without radials
    (Convinced that THEORY is WRONG and THEY are RIGHT) --
    PHYSICS is RIGHT. GRAVITY still works --
    jumping out of plane at 10,000 feet without a parachute not recommended.

    w9gb
    Last edited by W9GB; 09-01-2010 at 10:23 PM.

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