Good HF No Radial Vertical?

Discussion in 'Amateur Radio Equipment Reviews' started by AA9ZZ, Jun 14, 2008.

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  1. K3DAV

    K3DAV Ham Member QRZ Page

    I was surprised to hear your results with the CHA250B. I only use mine on 160 through 20 meters. I found the performance above 20M to be just OK, but not as good as the lower bands. I use an I-MAX 2000 for 17 through 10 meters.

    I get that same 1.5 SWR all the way down to 3.4MHz. Below 3.4MHz and the SWR starts to climb as you are now out of the antenna's frequency coverage. Most of my best contacts on this antenna were 75, 40, and 20 meters. And with S-9 to 20dB signals.

    Even though the antenna is not supposed to work below 80M, it does. On 160M I have a 3:1 SWR across that band. (Measured with radio SWR meter, and an MFJ-269 Antenna Analyzer). The auto tuner takes it down to flat within seconds. I am near Harrisburg PA. On 160M, I have talked to guys in upstate New York, Ohio, Indiana, Virginia, and North Carolina. These stations were 600 to 700 miles away, and I can do this at most any time. The contacts were not under special conditions. The signals were not the highest, but each side got S-5 to S-9 signals with good audio. And that is from my 746PRO at only 100 watts. The antenna is fed with LMR-400.

    If this antenna is installed correctly, and you do not exceed your expectations of it's capabilities, the CHA250B is a surprisingly efficient little antenna. As I said before. I have worked all continents on 80, 40, and 20 meters. As a nice bonus because of the constant 1.5 SWR across the entire HF spectrum, it works very well on 60M.
     
  2. W8JI

    W8JI Ham Member QRZ Page

    Let's not kid ourselves about antennas. Almost anything, even a wire laid across a floor, is better than no antenna at all.

    How happy an antenna makes people feel really depends on what they are looking for. It often has little to do with how the antenna actually works.

    The Comet antenna is a dummy load connected across the feedline with a 23 foot vertical element hanging off that dummy load.

    There is no such thing as an end-fed antenna without a ground system or counterpoise. The feedline shield is also a big part of the antenna, so if the antenna is installed where the feedline is up in the clear the feedline will contribute to the performance.

    On 80 meters, nearly all of the power is lost as heat. The same is true on some other frequencies. On some bands like 30 meters, if the coaxial feedline is the correct length and layout, most of the power will radiate.

    This doesn't mean the antenna will not "work" or will not make contacts. It does not mean it will not make some people happy, because it will get them on the air. What it does mean is on most bands most of the power is turned to heat, and on lower bands like 80 nearly all of the power is turned to heat.

    A small MFJ magnetic loop antenna will be around 5-10 dB stronger than the Comet on 30-10 meters. A Hustler or Butternut trap vertical, with a mediocre ground system, will be the same all the way down to 80 meters. The Comet will get people on the air, and any antenna is better than no antenna at all.

    73 Tom
     
  3. W8JI

    W8JI Ham Member QRZ Page


    A monopole vertical by definition works against a ground system or counterpoise of some type, even if we don't realize it.

    The Comet vertical is a monopole, and it uses the coax shield as the ground (if no other ground is used).

    The interesting thing that applies is Kirchoff's laws, which dictate an equal amount of current has to leave the feedpoint and flow into a counterpoise as some type as flows at the feedpoint up into the element.

    Even an end-fed half-wave must have the same current flowing toward a ground of some type as flows up into the element. Look at this page and links:

    http://www.w8ji.com/end-fed_vertical.htm

    There is an additional problem with a vertical dipole, and that problem is feedline decoupling. The impedance at the outside ends of a half wave dipole is several thousand ohms. Voltage is very high even at modest power, and that means the electric field is very intense. Somehow we have to get the feedline out of that area without causing current to flow on the shield, and that is a very difficult task.

    [​IMG]

    Even past the skirt there is considerable common mode current!! Enough to make a collinear antenna work. This is why radials are necessary for best performance.

    73 Tom
     
  4. W0BTU

    W0BTU Ham Member QRZ Page

    Neither has anyone else. (Unless, of course, we're talking about a center-fed 1/2λ dipole on its side.)


    Of all the physical laws that there are, none are more well-established than the fact that a bottom-fed vertical needs something to "push against" to be effective. Call that 'something' a counterpoise, radials, or whatever you want to; but to be effective, it's got to be there. Period.


    Case in point: on another forum, someone just shared his experience after he added a bunch of ground radials to his inverted-L. It was a WOW! experience for him. Sure, he made some contacts without the radials. But what a difference it made in the amount of RF that radiated into space and the amount of DX he worked afterward.


    If we make the statement that adding a counterpoise to a λ/4 vertical (for example) is not really necessary, then we might as well say that opening the blinds won't make the room any brighter. Sure, maybe we can see our way around, but when we let the sun in, life is so much better.

    Or someone could say that we don't really need tires on a car. Sure, with enough ground clearance we can drive around on the rims, but isn't the car much more fun to drive with the rubber attached?

    Take the radials off your 1/4λ ground plane and let us know what happens. :)
     
    Last edited: Jan 18, 2011
  5. K7SWS

    K7SWS Ham Member QRZ Page

    I had the same problem with my Cat motor and TS-50 James....I had to build a common ground, ran braid from radio to ground , antenna to the same ground point and boy did the noise go down.
     
  6. AH6OY

    AH6OY Ham Member QRZ Page

    I don't think so and thee are plenty of others around the world just like me who figure advertising a ground plane vertical as not needing radials because it has a snake oil box is nuts. Sure you can get a good swr from the snake oil box because its eating reflected power but not radiating or helping the ground plane.
     
  7. K5TLL

    K5TLL Ham Member QRZ Page

    GOOD HF NO RADIAL VERTICAL

    OK I USE A CUSHCRAFT R-7 VERTICAL ANTENNA. I HAVE BEEN OPERATING FROM AFGHANISTAN AS T6TL 2010 & 2011. NOW FOR THE ANTENNA. I ALSO HAVE COMPAIRED THE R-7 VERTICAL WITH A DIPOLE AND A DELTA LOOP WHICH ARE ABOUT 20 FEET UP. THE BOTTOM OF THE VERTICAL IS 15 FEET. THE SIGNALS ARE BETTER ON THE VERTICAL THAN THE DIPOLE AND LOOP. I HAVE BEEN WORKING THE WORLD WITH 100W AND 50W PSK. CAN NOT PUT UP ANTENNAS ANY HIGHER BECAUSE OF LOW FLYING AIRCRAFT. I MAY TRY A 20M VERTICAL DIPOLE NEXT.
     
  8. K9FV

    K9FV Ham Member QRZ Page

    Congratulations on winning the antenna - you did really good. I've always had to buy everything off ebay - never was able to "win" anything {grinning}

    73 de Ken H>
     
  9. KD0CAC

    KD0CAC Ham Member QRZ Page

    Vertical antennas work with or without radials , but may work better with radials !
    I have a used Cushcraft R5 that I have been using for about 1 yr and my rig is not operating correctly , puts out 3/4 - 3 1/2 watts depending on band and I have made contacts last winter [ bad conditions , low sunspot , urban back yard etc. ] Hawaii , Alaska , Southern Argentina , Eastern Europe etc. form Minnesota .
    I just want to make the point to keep from discouraging others from trying .
    I just got a used Butternut HV9 and put it up , without radials , but plan to add , it is just slightly better receive than the R5 , I have not done enough work with it yet to know how well the transmit is as compared to the R5 , one of the issues is that with them set up on a switch for A / B testing , I need to use my manual tuner , a Palstar ATK2 and tune the antennas , they do not take the same settings , so have to tune separately .
    73
     
  10. K3ROJ

    K3ROJ Ham Member QRZ Page

    When moving into my new home in 1998, I purchased the Cushcraft R8. It has counterpoise rods which seems to make this antenna work well from 40 to and including 6 meters and is 27 feet tall. Only thing I did was drive in 2 ground rods at the base. No guying required and is still performing well using an old Heathkit roller inductor tuner 95 feet away in the shack. Since 1998 I have worked over 20,000 stations, all on CW at 100 watts or less. Now with my Flex 5000A and another vertical (the famous 43 footer) I can use dual diversity listening which made a huge difference in my number of contacts, mostly during contests.
     
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