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Possible Antenna Solution - Feedback

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KG5NNA, Jul 5, 2016.

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  1. KG5NNA

    KG5NNA Ham Member QRZ Page

    After a few months of contemplating about how to find an antenna solution for my property, I may have stumbled on one. I actually went over to my son's in-laws for July 4th and saw how he had mounted an end fed dipole that ran from his second story balcony down to the corner of his garage.

    Below I have included a picture (albeit a little old, we have a much nicer lawn now!) of the rear of my house. At the apex slightly off center, is a chimney vent you can clearly see. Unfortunately this isn't a brick structure, but it IS the highest point on my house. What my idea involves, is running an end fed dipole from that highest point to the back fence at the lower left of the picture. I'd probably put a 10' piece of PVC pipe on the fence post and anchor the other end there. In essence it would be a pretty long sloper. The end-feed would be at the chimney vent and then I would need to run the coax from that point straight along the roof line to the left side of the house (west). then down that wall and into an MFJ window pane pass-through to my shack.

    Challenge #1: How to get it secured to that chimney vent. It's not flimsy but it's not brick either. We very occasionally use the chimney, only in winter and that's not much (we live in Texas). So I don't think that vent gets that hot. However, I am looking for suggestions on how I would mount the end feed there?

    Challenge #2: The C-Band Antenna. This is an old relic from 33 years ago when the only cable option was C-band. Now it's basically a hunk of metal not hooked to anything at all. However, the direct angle to the back fence post is probably going to be impeded, by the mast/antenna of the C-Band. That's in the ground in concrete, by the way, so it's not going anywhere. An idea I had, was to perhaps run the new antenna to the center post of the deck (support if necessary), then in a direct line to the back post. Will this hurt?

    I'm hoping that I can get 80-6m in some form or another with an antenna tuner (I will have a Yaesu FT DX-1200 by then, and has one built in). I don't know exact measurements here either. I don't know how high that chimney is at it's apex (probably no more than 20-25 feet sloping to perhaps 10-12'.

    upload_2016-7-5_10-29-32.png
     
  2. AK5B

    AK5B Ham Member QRZ Page

    I suggest using that C-band structure for an additional antenna support to raise at least part of your EFHW higher; wood or fiberglass would be appropriate for that.

    Even with additional height your proposed antenna is likely to be a warm-wormer, especially below 20M.

    Built-in tuners in most rigs cannot handle more than a 3>1 mismatch so you may need an outboard manual tuner as well as a good counterpoise or radial system for best results.

    As for the chimney; why not a small roof tripod and mast instead?

    73, Jeff
     
    KC8VWM and K7TRF like this.
  3. K7TRF

    K7TRF Premium Subscriber QRZ Page

    +1 on both suggestions above. If you no longer use the C-band antenna you might as well remove the antenna itself and extend the mast as suggested above. Similarly a small roof tripod supporting something like a fiberglass mast will almost certainly be a stronger support than the roof vent.
     
  4. KD6RF

    KD6RF Premium Subscriber QRZ Page

    Not quite sure how this fits on your supports, but I use 23 foot tall x 22 ft wide Inverted-L's for all band 80 M through 6 M. Naturally, you need a good radial system for efficient operation on the low bands. A 9:1 or 4:1 broadband unun helps with match on the upper bands.

    As said above, a good tuner is also required. If the coax run is short, feedline loss is minimal. Just did the 13 colonies sweep and bonuses on my Inverted-L's (and yes of course, PROPAGATION was a large factor in this blatant anecdotal data :eek: ).
     
    AK5B likes this.
  5. G0JUR

    G0JUR Ham Member QRZ Page

    AK5B likes this.
  6. KC9ZHR

    KC9ZHR Ham Member QRZ Page

    +2 on the G7FEK Its very simple and its what I use at home(see my qrz page for pics). Its also very forgiving, I had to make mine shorter in height but longer horizontally but it didn't complain.

    Believe it or not my TS-480SAT will tune it from the bottom to top of every band 160-6 :D and that is not massaging the swr down either since its only about 85 feet of LMR400 to the radio :eek:
     
  7. W6OGC

    W6OGC Ham Member QRZ Page

    You might benefit from studying the EFHW info at www.AA5TB.com. Steve does pretty well with his modest set up, and, to boot, he isn't that far from you.
     
  8. NW9M

    NW9M Ham Member QRZ Page

    I do not know if this will be allowed by either your wife or your local ordnances, but as mentioned I would also remove your old sat dish and mount a pole there, and from the looks of it put a roof mount TV antenna tripod on the far end of your roof. you should be able to a fit at least a 40M antenna element there, then work out the distance to one of your fenceposts on your fence there and mount another pole there, and end up with a center fed dipole with a V. Then for 80 meters run a separate end fed wire from the satellite pole to another pole on your back fence somewhere. If your wife hates the idea then not much a person can do but that would be a nice setup for your house and backyard. You could also run a trapped dipole but I have not had much luck with trapped wire antennas and prefer to use a fixed length with a tuner.
     
  9. WB1E

    WB1E Ham Member QRZ Page

    Would it be possible to install a PVC mast in each corner of the back fence? Not one, but two total? This will get double the wire in the air to form a Vee Dipole. The one I use employs a manual tuner & a balanced to unbalanced ((coax side)) BALUN that you can wind yourself. See attached file, use the one on the left. Email me for more info.

    As far as the connection at the roof top goes, you want at least 5 feet from any grounded surface. That tripod will be the best for a much more permanent installation. In the Vee Beam install, there is a "T" bar made of solid plastic,
    a piece 12" long by 1 1/4" PVC pipe will work. A screw at each end, a hole in the center to connect to the roof vent/tripod with wire - insulator - wire assembly. Your ferrite doughnut is mounted to the middle & feeds the studs at each end of the PVC "T". I use a flat piece of white glass filled nylon better known as Corian. It's a cutting board I bought at wally world. Works great for guitar nuts as well...1/2 inch thick. This is a bunch of wire in the air, works well on 80m with 105' on one element, & 112' on the other, off center fed. As long as you have the 4:1 BALUM as mentioned, and a manual tuner, it does very well. Lots of gain above 1.5 wavelengths fed vs built. It is beamable where there is gain. A bunch in the high bands with elements of this length.

    Please let us know your thoughts Sir!

    73's
    Doug
     

    Attached Files:

  10. KC8VWM

    KC8VWM Ham Member QRZ Page

    My vote is to forget using wire all together and install a steerable multi-band rotatable dipole on a tripod up on the roof.

    Unless you can get some height, any wire antenna you install and use on 80m is going to be a cloud burner anyways and at least a rotatable dipole will provide you with the idea of using a single support and you can steer it in any direction you want.

    That fact alone is a huge advantage and improvement over any kind of fixed position wire antenna.

    Like this:

    [​IMG]

    Good luck on whatever you choose. :)
     
    AK5B likes this.

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