Tuning a fan dipole in attic

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD0VWH, Nov 12, 2013.

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  1. KD0VWH

    KD0VWH Premium Subscriber QRZ Page

    What is the best way to tune a fan dipole in the attic? I built my first "test" 20m dipole and put it in the front room of my house (I have high vaulted ceilings). For some unknown reason my wife wants me to build a more permanent solution in the attic very soon (HOA rules) so that I can remove the lovely decoration and center piece of her friends discussion. It took some work to tune the dipole using a loaner swr/power meter and that was with great access to both legs. What is the best way to tune in an attic where I will have to walk across my joists and other features (vaulted ceilings)? Will I get close enough if I tune outside where I have space to work prior to putting in my attic? Should I use an antenna analyzer rather than the SWR/power meter? I can get a loaner analyzer if needed.

    Also, I don't have enough space for an 80m inverted V on my home diagonal, but I do if I go with one leg along the back edge and the other leg along the side edge ( think inverted V if looking from the sky). Should I do my 80-40-20-12-10 dipole all this way or just the 80m and the rest as an inverted V on the diagonal?

    Thanks for the help.
  2. N4FBW

    N4FBW Ham Member QRZ Page

    The Google Map view of your QTH shows some nice trees. These would be quite good at hiding some dipoles. There are all sorts of stealth wire antennas.
  3. N4JTE

    N4JTE Ham Member QRZ Page

    Best and only way to tune any antenna is where it's gonna talk from.
  4. G4ALA

    G4ALA Ham Member QRZ Page

    Try sticking a remote antenna tuner in the middle of the dipole and strangling the currents to flow symetrically by installing ferrites on both the power line and the co-ax line. You might find it automatically tunes on many bands.


    John G4ALA
  5. N3HEE

    N3HEE Ham Member QRZ Page

    Install the antenna in your attic before tuning it. Cut each leg of the dipole a little longer than the formula calls for to allow for tuning. Separate the wires as far apart as you can. Mine are 6 inches. Use of antenna analyzer will help tremendously. Start tuning the lowest band first. I have a 20/15/10 meter fan dipole in my attic that works great but was a bear to tune. I had trouble getting 15 meter dipole tuned below 2:1 SWR. The 20 and 10 meter dipole tuned fairly easy.
  6. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    I'm not trying to discourage you from putting a fan dipole in your attic.

    But eventually, you will become frustrated by the limitations of such an antenna. When that time comes, remember that when it comes to simple wire antennas, if it can be easily raised and lowered, and is always lowered when not in use, especially in the daylight, even the most asinine HOA will often look the other way.
  7. AB8RO

    AB8RO Ham Member QRZ Page

    I would have no patience for that and would put up an untuned doublet or loop with a remote tuner like the SGC-239.
  8. KK6DCT

    KK6DCT Ham Member QRZ Page

    Are you going to build other antennas, or add additional bands to your fan dipole? If so then I'd definitely invest in an antenna analyzer (or borrow one). I was trying to tune the length of my dipole just by taking readings on my swr meter, which took some trial and error because I could't work out where my center frequency was. Bought a YouKits analyzer and now I've got and instant picture of the curve showing where the CF is. Makes things considerably easier.
  9. KD0VWH

    KD0VWH Premium Subscriber QRZ Page

    Thanks for the responses. Due to business travel I haven't had much time to respond. As to my yard, the trees you see on the map are not on my property and are also in a small ravine, so they are actually a bit lower in elevation than my house. I potentially could raise an lower dipoles along the back of my house outside but then they would be oriented north/south instead of east/west. I don't know how much this will affect my RX/TX range in the east/west direction, but it is something to consider.

    Is there a good vertical or some other antenna that could be recommended that I could easily raise and lower that would be better than dipoles in the attic? I am looking for multiple bands from 10-80 m. Thanks again for the feedback.
  10. WA0KZL

    WA0KZL Ham Member QRZ Page

    An "End fed Inverted L" base tuned will amaze you.
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