40 meter sloper question

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by WD8CSL, Aug 13, 2021.

ad: L-HROutlet
ad: l-rl
ad: L-Geochron
ad: L-MFJ
ad: abrind-2
ad: Left-3
ad: Left-2
  1. WD8CSL

    WD8CSL Ham Member QRZ Page

    I have never put up a hf sloper antenna before. Now living in an apartment I find that it is probably going to be necessary due to issues such as space available .. hoa concerns .. etc. I can get it up 32 Ft high, but I'm not sure about the angle. Is there a required angple for the antenna to work properly? Diapole isn't doable .. random or long wire isn't possible. Considered a mono band vertical might work .. thoughts?
     
  2. K6GBW

    K6GBW Ham Member QRZ Page

    45 to 60 degrees is pretty good. Try and point it in the direct you want to transmit most. Although, at 32' on 40 meters it will be low so it will mostly be omni. In an apartment you can expect a lot of wall warts and other electronic noise. Putting a quality common mode choke on the coax right before the radio may help tamp that down and make your receive much better.
     
  3. WD8CSL

    WD8CSL Ham Member QRZ Page

    Thank for the reply, I will use your answer to construct the antenna. TOM
     
  4. WA7ARK

    WA7ARK Ham Member QRZ Page

    A "sloper" is a specific type of antenna where a ~0.25wl wire is fed against a metal tower. I think what you are describing is a sloped, coax-fed, center-fed 1/2wl dipole?
     
  5. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    I'd definitely put up the monoband vertical, especially if you can install elevated radials.

    You haven't answered the question yet, but if this is a typical 1/4 wave sloper, then you need a mass of metal for the antenna to work against, like a tower. In many sloper installations, the tower actually does much of the radiating! If you don't have that, then the antenna will try to work against the outside of the coax shield. This is doable, but not the best solution.

    If, on the other hand, you mean what we used to call a sloper, that is, a regular 1/2 dipole that slopes downward, I would probably go with that, unless your object is DX, in which case, at that height, a 1/4 wave vertical might be the best choice.

    Good luck! Remember, unless you are using a boatanchor, your rig is designed to work into a 50 ohm unbalanced load. The close the antenna is to this load, the easier it is to get good performance out of it.
     
  6. K9XR

    K9XR Ham Member QRZ Page

    I have always thought that a "sloper" was a half wave dipole hung as high as you can on one end and sloped toward the direction you want it to favor. Now a "half sloper can either be a 1/4 wave with a balun or a 1/4 wave fed against the tower. I have used both. I had 3 slopers on 40 and 3 Half wave slopers on 80 actually made out of the insulated guy wires about 64' and fed against the tower. Both worked well, but i felt that my Mosley S401 rotatable dipole blew away the slopers on 40. I would imagine it was because the average height above ground was a lot higher on the Mosley.
     
  7. W3TKB

    W3TKB XML Subscriber QRZ Page

    Not to get off track from the OP, but I have a quick question.

    The first HF antenna I ever used I bought off Ebay (sorry); it was a multi band random length wire with a 9:1 unun at one end.

    The instructions included several different methods of deployment, including what was called a "simple sloper" configuration: the unun at or near ground level and the far end of the wire hoisted up at an angle.

    There was no mention of a metal tower being needed to work properly...only possibly needing a counterpoise wire depending on coax length.

    Was this actually not a "sloper" antenna, based on what's been posted already? How was this different? Thanks
     
  8. WA7ARK

    WA7ARK Ham Member QRZ Page

    What I call a "sloper" (and what others apparently called a "half-sloper") is an inverted-V dipole with a very sharp apex angle (~45 degrees), where one leg of the V is the grounded tower itself. It is fed (no transformer) with the coax center connected to the wire, and the coax shield connected to the tower itself.

    It is a horrible antenna compared to a horizontal or sloped center-fed wire dipole. The apex angle is much too small, so radiation from the wire is partially cancelled by radiation from the tower. Unless the feedpoint is just the right height agl, it is very inefficient compared to a dipole, because current flows down the tower and is dissipated as heat in the earth surrounding the tower base. Its only virtue is that by changing the wire length, you can tune it to resonance. It shows again, that just because an "antenna" has a low SWR, that does not make it a "good" antenna.

    Contrast that to a sloped center-fed dipole, where the two legs are more or less co-linear. As long as the bottom end of the lower leg is at least a few feet agl, then the sloped dipole will work about like if it is placed horizonally, except that the sloped version radiates best in the direction at right-angle to the dipole wires.

    Now the antenna that Brandon deployed is unlike either of the two Hertz antennas described above. It is basically a non-resonant Marconi vertical monopole, fed against earth (capacitive coupling of coax to dirt), but if deployed as Brandon did, the monopole "leans".
     
    Last edited: Aug 14, 2021
  9. KK4OBI

    KK4OBI Ham Member QRZ Page

    If you are thinking about a sloped dipole...
    here is what antenna modeling tells us about its radiation patterns and performance relative to angles, elevation and such. The model is included if you want to adjust it to better match your situation.

    www.qsl.net/kk4obi/Dipole%20Slope.html
     
  10. W9GB

    W9GB Ham Member QRZ Page

    I have a 40-meter half-wavelength dipole (center-fed, coax) in my “travel bag” (for the past 35 years).
    I have used it at Field Days … two decades ago, when I visited my parents’ house,
    I installed it as an E-W Sloped 1/2-wave (~30 feet at high end (W), 7 feet at low end (E))

    One afternoon on 40 meters, 20 years ago, I listened to Bob Heil (St.Louis) talk to Collins Radio amateurs in Cedar Rapids with his “the new” Collins radio acquisition.

    Turning to 15 meters, I had a nice QSO with an amateur in Turkey —
    Thanks to Gray-Line propagation and the Unique Antenna pattern
    of this Slopped 1/2 (40m) Antenna Along it’s Axis at 3/2 Wavelengths (15 meters) !!
     

Share This Page