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M400 Starduster Repurposed for 6 Meters

Discussion in 'Home Brew' started by tba02, Jul 5, 2015.

  1. tba02

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    Jan 26, 2014
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    I wanted to get on 6 meters, both for SSB and for local FM. I had a few items hanging around, did some quick math and decided to repurpose an M400 Starduster for both options. I call it the CloudDuster.

    Inventory/ Parts List
    (1) Sirio M400 Starduster Antenna - http://www.sirioantenne.it/starduster-m-400/
    (1) MFJ-347 Dipole Mount - http://www.mfjenterprises.com/Product.php?productid=MFJ-347
    (2) 3/8x24 Whip Mount - h**p://www.amazon.com/dp/B00HZ7SPBC/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=201VMU7Q9S093&coliid=I129R8IM4HMEZ0
    (1) Antenna switch
    (x) Various masts, PVC and mounting hardware.

    The Starduster is a 10/11 meter 1/4 wave ground plane antenna . The vertical and radial elements are comprised of 2 sections at ~1400 mm as listed in the manual. I refer to them as Primary and Secondary sections.
    The primary radiator section is 55.875 inches long.
    The secondary radiator section is not used for this project.
    The primary radial section is 55.375 inches long.
    The secondary radial section is 55.125 inches long.

    Self I said - basic theory for 6 meter antennas, with a center frequency of 52MHZ tells me I can use these.
    The vertical needs a 54 inch radiator and a 56.7 inch radial.
    The dipole needs 2 54 inch rods.

    Since I was focusing on two different areas of the band:
    52.5 MHz FM = 53.486 in/56.160 in were my starting points for the radiator/radial pieces.
    50.1 MHz = 56.0625 in per side.

    In Practice
    - The vertical

    I built the 1/4 wave ground plane using the primary vertical at it's given length (I knew it was long but did not want to cut it yet). I used the primary and secondary radial sections to match dimensions commonly used for such antennas.

    Testing confirmed that the antenna was too long, but it was close. and it was however close enough that my tuner could tune it where needed at the higher frequencies.

    I had been reading a few articles that seem to indicate shorter radials also made the radiator appear shorter and not have a significant impact on gain. I was also looking at those secondary radial pieces and wanting to use them for a dipole, so I figured I would give it a shot. Removing the secondary radials did move the SWR curve to a higher frequency. The antenna SWR fell into a curve where my tuner was no longer necessary for the target frequency. I was able to make some local FM simplex contacts with it 10 feet off the ground.

    I considered cutting the the vertical element to bring it closer to the desired frequency but decided to hold off until I had a chance to put it at the final location, which included the dipole below.

    - The dipole
    I took two of the three secondary radials, the MFJ mount and whip studs (ferrels) and made a dipole. It measured out fine. 1:1 at 10 feet from the ground.

    In Position
    I attached the vertical to a vent pipe on the roof providing 25 feet of elevation to the feedpoint. I mounted the dipole a couple of feet below the bottom of the radial at about 18 feet. They are not quite above the roofline so that does have some impact. I check the SWR figures and attached them to an antenna switch and that to the radio. The tuner on the radio switches to pass through over the 50-54 MHz spread. So know I have both vertical and horizontal options for 6 meters. I may eventually cut the radiator and fine tune as I know it is long. I'll post some figures and performance notes in Part 2 and also await feedback.

    In Closing (of Part 1)
    I took the primary elements of an M400 Starduster and made a 6 meter 1/4 wave ground plane. I took two of the secondary elements of the same antenna and made a dipole that mounts below. That is my 6 meter "CloudDuster" project.

    Attached Files:

    #1 tba02, Jul 5, 2015
    Last edited: Jul 5, 2015

  2. tba02

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    Jan 26, 2014
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    Part 2

    The attached image shows the readings from an MFJ-259B antenna analyzer. These are taken with the antennas in place, from the shack, each having 50 feet of RG-8x coax attached. The SWR readings were lower by about 1 (1.4:1 was 1.3:) when mounted in open space attached to a 10 foot pole. I presume proximity to the roof has some negative impact.

    Also of note (as I read elsewhere and can confirm) - the larger diameter of the tubing lowers the resonant frequency even further compared to a 12/14 gauge wire.

    Feedback or review on the numbers would be appreciated as I know the vertical radiator is long.

    Performance reports pending as 6m SSB isn't open right now (though I do hear beacons at S3) and FM simplex in my area is not all that active.

    ETA: I figure I need to cut a little over three inches off the vertical element to improve things for the target frequency.

    Attached Files:

    #2 tba02, Jul 5, 2015
    Last edited: Jul 5, 2015
    Moleculo likes this.
  3. Moleculo

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    Staff Member

    Apr 14, 2002
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    It looks like a fun project and you almost have the setup where you want it. I agree with your conclusion - a little light trimming on the vertical antenna and you're set.
  4. 2RT307

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    Sr. Member

    Nov 22, 2011
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    Very cool, and I like that you made two out of one. Especially nice to have horizontal and vertical on a switch. Should be fun this summer!

  5. Charles Woods

    Charles Woods
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    Apr 10, 2016
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    I am looking for the receive adjustment point for the TRC455, any help
  6. Onelasttime

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    Active Member

    Aug 3, 2011
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    .64 is better than .25 or .50 that is kind of the point of the 5/8 wave antenna.
  7. bob85

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    Supporting Member

    Mar 30, 2005
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    why do you think a 5/8wave is better ? ,

    5/8waves don't have the gain and range advantage often shown in drawings/advertising unless they are mounted over an infinite groundplane,

    in the real world on 27mhz with a few radials that will never happen,

    the main advantage 5/8 have is tip height,
    current maxima is always 1/4wave down from the tip of the antenna without loading.
    so a 5/8 current maxima is higher above ground when mounted on the same pole,

    they also have 1/8wave of out or phase radiation in the lower portion of the radiator so you don't get the full advantage of raising the current maxima,

    1/2waves & stardusters don't have the out of phase radiation,

    when mounted at the same tip height a good 1/2wave puts a little more signal at low angles than a 5/8 groundplane.
    gamegetter, The DB and Marconi like this.
  8. Marconi

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    Usually if I can hear em' I can talk to em'.

    Oct 23, 2005
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    tba02, a very nice project and should work out fine.

    In my real world experience with a SD'r over my horizontal Yagi 4, with the radials right on top of the horizontal elements, I could not detect any performance difference in use, but I did see a little bit of tune-up differences with both antennas vs. them standing alone mounted in the same place.

    My 11 meter models also show, without retuning and a start separation for the SD'r at 100" inches above the beam, down to 24" inches above the beam, both antennas do detune in gain a bit. The maximum angle of radiation for the SD'r does drop as I lowered it down...but I'm not sure you could really tell any of this...just using your radio.

    I compared some models at the same tip height, my Marconi 5x, Sirio Starduster, Imax 4x6' slanted radials, Imax 4x9' slanted radials, SP500, and my trusty old A99.

    IMO, Bob is right on the mark in his comments to our buddy OneLastTime. I will try and post the models in a few days...

    I'm having trouble with Windows 10, scanning consistently with my old Cannon MX870 printer...I think Microsoft hired a bunch of hackers to design the OS. They keep changing my settings and turning my printer off then on...or the default setting changes.

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