Which is better G5RV or ZS6BKW?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K4SAV, Jul 4, 2014.

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  1. KC3BZJ

    KC3BZJ Ham Member QRZ Page

    That's my question, I believe that you're supposed to keep the ladder line off the ground and keep it away from anything metal. How do you get it into your shack? Run it taut through the air to your completely wooden structure (log cabin)???
     
  2. AC6LA

    AC6LA Ham Member QRZ Page

    Here's the SWR at the station end of the feedline (combined ladder line plus coax). That is, this is the SWR that a tuner would have to handle.

    K4SAV1.gif

    Or you can use AutoEZ to do the calculations. As Jerry said, the effect of feedline loss is included in the gain. So the feedline loss is the delta in the gain between when the model does or does not include the feedline. Here's a comparison.

    K4SAV2.gif

    And here's an AutoEZ format model. (Save to your computer then use AutoEZ to open it.) Variable "A" lets you choose between ZS6BKW and G5RV dimensions (per Jerry's original post) and variable "B" lets you choose between with and without the feedlines.

    http://ac6la.com/adhoc/ZS6BKWvsG5RV.weq

    To calculate feedline loss first run the model with feedlines included (B=1). On the Calculate sheet, copy the computed gain values (cells J11-J18) down to empty lower rows. Change the model to without feedlines (B=2) and run it again. For any given frequency, the delta between the current computed gain value (without feedlines, B=2) and the previous copied gain value (with feedlines, B=1) is the feedline loss. That delta is what's plotted in the second illustration above.

    For more information on AutoEZ see:

    http://ac6la.com/autoez.html

    If you'd like to use the free demo version of AutoEZ, open the above model and then change the number of segments (cell I11 on the Wires sheet) to "29". In that case you'll see EZNEC segmentation check warnings for the higher frequencies.

    Dan, AC6LA
     
  3. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    BZJ:

    Although I don't use open wire feeders, it is very easy to install an insulated panel in a window, through the wall, etc., and use feed-through conductors, etc., to get the feedline into the building.

    Glen, K9STH
     
  4. W6OGC

    W6OGC Ham Member QRZ Page

    The approach I used was to run twin lead to the AH-4 remote autotuner on the exterior wall of the shack (a separate building here), then coax and control lines into the shack to the transmitter.

    If you already have a manual tuner, or run power, this might be not feasible.
     
  5. KC3BZJ

    KC3BZJ Ham Member QRZ Page

    Appreciate the responses; W6OGC - that makes sense and helps. However my question kind of remains, do you run the twin lead/ladder line on or across the ground? Or do you/should you (or anyone) run the ladder line through the air like a utility line so that it touches nothing but the terminals at each end? Sort of a moot point as I have a ZS6BKW I'm working on getting in the air right now. But I see a lot of interesting antenna designs using ladder line and would like to try one sometime in the future.

    On your comment regarding the manual tuner, I assume that I could use a balun of some sort and mount that on a wall to convert to coax and then run that to the manual tuner/transceiver?

    My apologies for the thread hijack; the G5RV vs. ZS6BKW comparison information is highly appreciated. Very interesting presentation.
     
  6. K8JD

    K8JD Ham Member QRZ Page

    Neither antenna is long enough to be very good on 80M but the 102 ft one is a little closer. My 80M antennas all were 130 ft long and fed with RG8U coax. I have enough room for separate dipoles for 160, 80, 60, 30 and 20M up in my trees.
     
  7. W5DXP

    W5DXP Ham Member QRZ Page

    If one models the antennas with the feedpoint in the middle of the dipole, there is little difference because of length. The problem is not with the length of the dipole but with the losses involving in matching the non-resonant feedpoint impedance. There's not much loss in the 30' parallel matching section of the G5RV and it is a reasonable antenna for 80m operation. Here's how I improved the ZS6BKW match on 80m.

    http://w5dxp.com/ZS6BKW80.HTM
     
    W4KMH likes this.
  8. W6OGC

    W6OGC Ham Member QRZ Page

    I run the twin lead down the center mast to about 10' from the ground, then over to the shack with a Dacron line threaded through it for strength. It stays high enough so you can walk under it. This seems to work ok. The mast is ~70' or so from the shack.

    When I first put up a G5RV to start, the twin lead ended just above the ground and the RG-8 just laid on the ground. Had it worked well enough I would have had to encase it in PVC or something for weather and water protection.
     
  9. KB6HRT

    KB6HRT Ham Member QRZ Page

    Used A G5RV for years it worked very well for my needs at that time, talked on the top end of 75m for 10 years in the mornings did a great job could lissen on other 40-20-15-10m that worked for me, Now I talk local on 75m in the morning 1-250 miles but talk on 40-20-17miles 1-1500miles so put up the zs6bkw An it works very very well. On 75m it has a very good signal to noise ratio and hears fairly well, on transmit its down 2-3S units from a dipole or a Double Bozooka. If the band is in it works ok with a good tuner on 75m, if the band is not in on 75m its just margenal on 75m but works great an no tuner needed on 40-20-17-12-10m.................kb6hrt
     
  10. KV4RH

    KV4RH Ham Member QRZ Page

    I use the ladder-line fed version, 102' wire doublet about 30 feet above the ground (we have short trees here in the sandhills).

    The wire drops down to the top of my back yard fence, and I use 8" electric fence standoffs to run it over to my shack window, use an MFJ window penetration, then into a 941E tuner with 4:1 balun built in.

    In a little over 6 months of operating, have 80 LOTW confirmed DXCC entities, have achieved WAS, and in the DX SSB contest, knocked out over somewhere around 150 DX band entities in only a few hours of operating. All at only 100W on SSB and CW.

    The antenna works great on 10, 15, 20, 40, and 80 for me (all I have on the old Kenwood hybrid I run). And I look forward to it staying up in the air a lot longer.
     
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