1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice
Dismiss Notice
This forum does not allow a single user to have more than one username. If anyone wants to change their username contact an admin and it will be done. Multiple accounts belonging to the same member will be deleted without warning.

Base Sirio 2008 vs 2016

Discussion in 'CB Antennas' started by Greg T, Mar 26, 2021.

  1. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

    Joined:
    Apr 23, 2018
    Messages:
    4,923
    Likes Received:
    6,474
    4 dash 10!


     
    secret squirrel likes this.

  2. freecell

    freecell Well-Known Member

    Joined:
    Apr 6, 2005
    Messages:
    1,818
    Likes Received:
    541
    regarding radial ground systems and loss resistance.
    http://www.w3pga.org/Antenna Books/Reflections III.pdf
    chapter 1, page 6, section (7)-(1) to the end of (7)-(1)

    a collection of the most accurate information regarding
    transmission lines and antennas. (152 MB. download).
     
    #32 freecell, Jul 26, 2021
    Last edited: Jul 27, 2021
    secret squirrel and Greg T like this.
  3. freecell

    freecell Well-Known Member

    Joined:
    Apr 6, 2005
    Messages:
    1,818
    Likes Received:
    541
    (1) A ground system having a hundred properly
    installed radials has negligible loss resistance (Ref
    20). AM broadcast stations operating in the 540- to
    1600-kHz band use either 120 or 240 radials, while
    the FCC requires a minimum of 90. With such a
    ground system the terminal impedance of a thin
    quarter-wave (X/4) vertical is approximately the
    theoretical value of 36.5 + y'22 ohms, and becomes
    approximately 32 ohms resistive when the antenna
    is shortened to resonance. Thus, when fed with a
    50-ohm line, the SWR at resonance will be close to
    1.6, rising predictably on either side of resonance.
    However, a ground system having only 15 radials
    has approximately 16 ohms of ground-loss resistance
    with this antenna. Thus, if we remove a few
    radials at a time from the 100-radial system, the
    increasing ground (loss) resistance adds to the
    fixed radiation resistance, increasing the total
    resistance terminating the feed line. Hence, as each
    radial is removed, the terminating resistance comes
    closer and closer to 50 ohms, reducing the SWR.
    When enough radials have been removed for the
    ground-loss resistance to reach 18 ohms, the terminating
    resistance will be 18 + 32 = 50 ohms, for a
    perfect one-to-one match! While the SWR went
    down, though, so did the radiated power, because
    now the power is dividing between 32 ohms of radiation
    resistance and 18 ohms of ground resistance!
    In cases where losses are very small, it is unnecessary
    to improve an impedance mismatch that produces an
    SWR of only 1.6:1, because only a 0.24 dB
    increase in power will result by reducing the 1.6:1
    mismatch to 1:1. However, in this antenna situation,
    reducing the 1.6:1 mismatch to 1:1 by removing
    radials will cause a 36% decrease in radiated power,
    a loss of 1.93 dB in the ground resistance.
    Ground resistance with 100 to 120 radials is typically
    in the range of 1 to 2 ohms, or less. However,
    ground systems having from two to four radials may
    have a loss resistance as high as 30 to 36 ohms, so
    now the SWR at the resonant frequency will be
    around 1.3 or 1.4. However, when operating at other
    frequencies, instead of rising from this low value of
    SWR, as it should at frequencies away from resonance,
    the ground-loss resistance holds the off-resonant
    SWR to lower values than would result with a
    good ground. The low SWR simply indicates that
    the line is well matched, but it offers no clue that
    approximately half the power is heating the ground.
    Thus, the low SWR in this case is misleading;
    instead of verifying that the antenna system is efficient
    over a wide frequency band, it is actually
    telling us that the efficiency is very poor indeed!

    here's the simple, non-technical explanation. the
    larger the number of radials used, (to collect the
    current radiated by the antenna) the lower the
    loss resistance, the higher the radiation efficiency
    and the better the performance, both in xmit and
    rcve, according to the principle of reciprocity.
     
    #33 freecell, Jul 26, 2021
    Last edited: Jul 26, 2021
    secret squirrel and Greg T like this.
  4. The DB

    The DB Sr. Member

    Joined:
    Aug 14, 2011
    Messages:
    1,918
    Likes Received:
    1,308
    I think it is a stretch to call it "non-technical", given the very low bar that some people consider what is and isn't "technical", and I think this is a tough concept for many to wrap their heads around, but it is correct.

    I would also direct you to chapter 5 of the freely available "Another Look at Reflections" pdf file, a chapter called "to low an SWR for the wrong reasons" or chpater 5 of the same book in freecell's link above, which is broken on my end at the space, which is just an updated version of the same text.

    To get freecell's link to work you have to copy and paste the entire link into the address bar, at least in the firefox browser. Its a good book, and I suggest actually purchasing it rather than using the free download as it is still in print.


    The DB
     
    secret squirrel, freecell and Greg T like this.
  5. freecell

    freecell Well-Known Member

    Joined:
    Apr 6, 2005
    Messages:
    1,818
    Likes Received:
    541
    "try right clicking the link and left click "open in new tab."
     
    secret squirrel likes this.
  6. Greg T

    Greg T 945 (Jazz Singer) Upper Peninsula of Michigan

    Joined:
    Sep 18, 2014
    Messages:
    209
    Likes Received:
    263
    Interesting info, indeed. Kinda makes me wonder now why this antenna is much more wide-banded than the sigma I removed, and IF it's a good thing or not. Regardless of why, I'm not able to do anything about it, anyway. I'm using LMR240 feed with a meter, an amp and a low pass filter in line. Currently, after raising the antenna into position, 26.965 doesn't even move the SWR needle, and 27.705 climbs to 1.1:1. I have not checked how low or high I can go to get 1.5:1. I will have to study that info a bit, tho. Time for this old codger to learn something
     
  7. The Howler

    The Howler Active Member

    Joined:
    Apr 22, 2020
    Messages:
    68
    Likes Received:
    75
    I hear you Greg T,
    I just happen to be moving my radio setup to a different wall, 15 feet from current location. This location is where my detached garages underground electrical panel is mounted to the building. Very good timing for this thread to come up! Very interesting info.
     
    secret squirrel likes this.
  8. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

    Joined:
    Apr 23, 2018
    Messages:
    4,923
    Likes Received:
    6,474
    Then it's harder to cut in paste!

    upload_2021-7-27_7-4-49.png
    Gotta' cut out all those tiny little letters out of the neighbors trashy Playboy
    er, Sport Illustrated's!



    So when someone WANTS to click on that...​
    They get this instead...
    upload_2021-7-27_7-11-2.png
    Come'on @freecell - this is making you look bad!
    BTW - to anyone whom cares - the link in #32 is broken - might want to fix that...
     
    secret squirrel likes this.
  9. The DB

    The DB Sr. Member

    Joined:
    Aug 14, 2011
    Messages:
    1,918
    Likes Received:
    1,308
    In my browser the link is only "http://www.w3pga.org/Antenna" not the full intended link. Opening it in a new tab doesn't change this.

    Yea, you actually have to use scissors and glue...


    The DB
     
    Handy Andy and freecell like this.
  10. snippits75

    snippits75 Well-Known Member

    Joined:
    Nov 11, 2019
    Messages:
    310
    Likes Received:
    456
    Using Google Chrome desktop. Highlight the whole link. Then right click, and then "Go to" the link. Opens right up for me.
     
    secret squirrel and freecell like this.
  11. freecell

    freecell Well-Known Member

    Joined:
    Apr 6, 2005
    Messages:
    1,818
    Likes Received:
    541
    it seems that some browsers don't allow url formatting using spaces.
     
    secret squirrel likes this.
  12. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

    Joined:
    Apr 23, 2018
    Messages:
    4,923
    Likes Received:
    6,474
    You don't know how to cut and paste that?

    Oh Geez...

    HTML - Here...

    http://www.w3pga.org/Antenna Books/Reflections III.pdf

    Keep "%20" it in mind, the Site and or your effort in your browser I'll let you fall flat on your own next time...

    I recommend that you go back to your post regarding this and edit the line and re-paste in PLAIN TEXT - then the site, the HTML the browser works in will process the "%20" as a normal space character.

    Since you knew by others posting the broken link, just go back and fix it.
     
    #42 Handy Andy, Jul 28, 2021
    Last edited: Jul 28, 2021
    secret squirrel likes this.
  13. Greg T

    Greg T 945 (Jazz Singer) Upper Peninsula of Michigan

    Joined:
    Sep 18, 2014
    Messages:
    209
    Likes Received:
    263
    Don't know if this is a coinky dink or not, but immediately after erecting this Sirio 2008 I am receiving skip from directions I was not receiving before. With the old Sigma Silver Rod, I was easily DXing to the south and East. Now, I am also getting strong DX from Canada, Texas, Washington, Cali. etc. Just thought I'd throw this out there.
     
    RT431 and freecell like this.

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!