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.

Marconi comparing New Top One vs. Old Top One

Discussion in 'CB Antennas' started by Marconi, Apr 4, 2011.

  1. RADIOOMAN

    RADIOOMAN Active Member

    Joined:
    Jun 1, 2012
    Messages:
    429
    Likes Received:
    59
    I just visited the website: Gain-Master, the new reference in its class of antennas

    It appears that they are only claiming 25.5 to 30 MHz/2.0:1 SWR bandwidth.
    Not that all of an unreasonable claim.


     

  2. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    3,736
    Likes Received:
    3,115
    Yes, but the impressive figure of 1.2:1 can be found just inside those limits from 25.7 to 29.7 MHz.
     
  3. Marconi

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

    Joined:
    Oct 23, 2005
    Messages:
    6,998
    Likes Received:
    1,972
    Thanks for the comments radiooman, but it sorta sounds like a dodge to bring up skin effect losses without a quantitative example...even if it is true.

    I've said it before, when folks suggest to us there is a difference, "...I ask, how much difference are you talking about?"

    Can you quantify the difference between the examples you site, or is the difference infinitesimal?
     
  4. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    3,736
    Likes Received:
    3,115
    Well, the Trombone and the gamma are not interchangeable matching networks so they can't even be compared. The trombone or any other variation of a tapped inductor matching network is typically used to step up the 50 ohm line impedance to drive a antenna with a higher impedance like an end fed 1/2 wave or 5/8 wave. Gamma's are used in the exact opposite situation where you have to step down the 50 ohms to drive an element that would be under 50 ohms. The gamma does not effectively raise impedance as required with a 5/8 wave.

    You may be thinking of the hair pin versus the gamma match debate. I've argued this one long enough after seeing false claims of "several db gain". If you want to know what's best in terms of loss to drive a yagi element, the last thing you want to do is listen to the sales pitch of the antenna maker.

    Look at what commercial manufacturers of UHF yagi's use on frequencies where loss is a much greater factor. They use neither! The T-Match has the advantage here and it does not even have much at all to do with loss. It's all about symmetrical feeding of the balanced yagi driven element and the T-Match is real hard to beat here.

    The only advantage the trombone style match has that you can see is it's power handling ability. It has virtually no gain advantage because even a 1500 watt open loop inductor has losses reduced to the point where they cannot reduce gain to any measurable extent much less see it on an S-meter.

    With respect to the GM, I know it has low loss for several reasons. First, you can't get gain out of a 5/8 wave antenna if it has significant loss. There is only 1.2 dbd available at best in an end fed 5/8 wave and if the match is very lossy, you'll lose the gain.

    Second, most of the matching takes place in the lower matching stub. It is made from silver plated, Teflon insulated coax. Known for very low loss in use as tuning stubs. Third, the second part of the match, the capacitor is also made of the same material. I've tested it extensively and have been able to detect no RF heating here even when you hit it with enough power to blow up. No heat, just a corona arc from the RF voltage.
     
  5. tuner

    tuner Active Member

    Joined:
    Jul 25, 2010
    Messages:
    229
    Likes Received:
    38
    Thanks for the info Marconi , much appreciated.
     
  6. Staybolt

    Staybolt Well-Known Member

    Joined:
    Mar 20, 2013
    Messages:
    751
    Likes Received:
    302
    You may be thinking of the hair pin versus the gamma match debate. I've argued this one long enough after seeing false claims of "several db gain". If you want to know what's best in terms of loss to drive a yagi element, the last thing you want to do is listen to the sales pitch of the antenna maker.


    Sales pitches are a good thing if you are selling a product so i see nothing wrong with a "sales pitch". I do it all the time selling my products... if i didn't use a sales pitch id be broke and wouldn't make ANY sales!!!:p
     
  7. HomerBB

    HomerBB Sr. Member

    Joined:
    Jan 4, 2009
    Messages:
    3,781
    Likes Received:
    2,168
    Marconi, it has been too long ago for me to properly recall the noise floor comparison between the AP and other antennas. However, if it is any help, the more recent comparison between the homebrew Merlin, a similarly designed antenna, and both an EFHW and 5/8 verticals when the Merlin was in a location usually more noisy showed the Merlin to have a lower noise floor than the others 95% of the time.

    I cannot say why, only that it did.
     
  8. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    3,736
    Likes Received:
    3,115
    True, but no matter how good a sales pitch is I'm confident it would be difficult to sell you the Brooklyn bridge simply because you know it's not for sale. The same is true selling the hair pin as several more db to those who know antenna design fairly well. No real expert required on this one either.
     
  9. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    3,736
    Likes Received:
    3,115
    Homer, could you see any connection between the noise floor and received signal strengths? In other words was there any indication that the Merlin had less noise simply because it was capturing less overall signal? The relative noise floor is less important than the signal to noise ratio and that's where my curiosity is.
     
  10. tuner

    tuner Active Member

    Joined:
    Jul 25, 2010
    Messages:
    229
    Likes Received:
    38
    Although I don't have much experience I do agree with Homer. I have found my Top one has a 2 S unit less noise floor as compared to my IMAX with my local contacts holding the same signal level or maybe a tad better.
     
  11. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    3,736
    Likes Received:
    3,115
    The Imax has a key flaw that makes it hard for me to determine if the 1/4 wave ground plane has any signal to noise ratio advantage or if the Imax was not a good comparison. That is coax radiation. Without a full set of 1/4 wavelength radials at the feedpoint (short GPK doesn't count) we cannot decouple the coax from the antenna properly. It then becomes part of the antenna. That's not just in transmit causing RFI either. It's in receive too. Allowing the path your coax takes to pickup any type of electrical or RF interference before reaching the receiver. The 5/8 wave ground plane would be a more interesting comparison with signal to noise.

    One interesting aspect here is that a good antenna can prevent poor quality coax from radiating and picking up undesired signals in receive but a poor antenna can allow the best coax to radiate and pickup undesired signals.
     
  12. tuner

    tuner Active Member

    Joined:
    Jul 25, 2010
    Messages:
    229
    Likes Received:
    38

    This is true, I did not have my Imax set up with a ground plane at all, only a choke with good rg213.
     
  13. RADIOOMAN

    RADIOOMAN Active Member

    Joined:
    Jun 1, 2012
    Messages:
    429
    Likes Received:
    59
    I thought I was in agreement with what I perceived your sentiments about the exagerated claims made about the I-10k.
    And for that reason I felt the reference I made about the 'TROMBONE' match maybe being a little more efficient only needed to be conceptual rather than trying to speculate about a specific amount or quantity with regard to the lower loss associated with a physically larger tapped inductor as related to 'skin loss'.
    And certainly I thought I was making a statement that was in agreement with your opinion about the I-10k antenna.
    If I have mis-understood your posting, then, my bad.
     
  14. Marconi

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

    Joined:
    Oct 23, 2005
    Messages:
    6,998
    Likes Received:
    1,972
    Radiooman, I may have commented badly, but I don't think we disagree that skin effect has something to do with losses. I was just looking for more information on the subject, whatever that subject was.

    I probably misunderstood what Shockwave said also. I'll have to go back an reread this thread, I've lost track of the subject.
     
    #44 Marconi, Mar 22, 2013
    Last edited: Mar 22, 2013
  15. Marconi

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

    Joined:
    Oct 23, 2005
    Messages:
    6,998
    Likes Received:
    1,972
    Homer, I agree. In my experience the A/P generally shows to be quieter.

    Tuner reports that he is seeing his NTO indicating 2 Sunits less noise than his Imax was. I posted a video above that also clearly shows something similar using my NTO vs. my Gain Master.

    I was reminded that at my mount out back tends to show a bit more noise at times, and that is where my GM is currently mounted. I'm not up to making changes anymore, but I do have videos of my radio while I was doing my last signal reports.

    I've never recorded noise levels on the hard copies of my signal reports, but I did note which mount I used for each antenna. So, I had a thought to compare the hard copies with the videos. So I went through and noted the noise levels when no one was talking. I can say now there is generally a difference to be noted, and the mount out in the back of my yard is a bit noisier than the mount near my shack. Another note is my electric service is about 30' feet from the mount out back, and about 70' feet from the mount by my shack. The service pole also has a transformer. This may help explain my noise...but at times this difference is nil.

    A few weeks ago my Starduster, which is by my shack, was responding with a lot of noise, maybe S7 and my Gain Master was maybe S3. That was odd, and I was concerned that something was wrong with the SD'r. A while latter, the SD was again responding with notably less noise.

    I can not account for what happened, but right now I'm considering that this issue I've raised has no merit. Mother Nature creates variables sometimes that cannot be easily explained.
     
    1 person likes 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!