Just a quick question

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD5LPB, Aug 10, 2009.

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  1. KD5LPB

    KD5LPB XML Subscriber QRZ Page

    Living in an apartment complex and trying to operate on the HF bands is difficult. What I've done is taken around #22 or so wire and tie a few fishing weights on the end. I tossed these weights over the apex of the roof of the apartment adjacent to mine and tossed the other end through my window.

    This effectively gives me an antenna length of, I'd say.. 30 feet.

    Now, this wire doesn't come straight to the tuner. In order to prevent pinching it and breaking it, I brought it right up to the window and attached it to the center conductor of some coax, knowing full well that this is a bad idea. I was in a rush to get on the air! So I took the shield of the coax and attached another thin wire to it and hooked it up to a short (ineffective) ground rod about 15 feet below. I used this for about 2 weeks.

    Maintanence, I assume, found the antenna and ripped down the ground wire but obviously couldn't reach the element so let it be. I began experimenting with indoor counterpoises to try and prevent this from happening again. I've since noticed absolutely no difference in SWR when using a counterpoise of any length.

    I took out the coax and just attached an alligator clip to the antenna and brought that through the window to the wire terminal of the antenna tuner, and that hasn't changed anything. I have attached about a 30 foot length of wire (that is tucked underneath the baseboards on my apartment) to the ground terminal of the tuner and after experimenting, found that it has no benefit.

    So, since I'm still a noob at antenna design, could you please guide me to the most efficient technique I could use in my situation?
     
  2. N7IFC

    N7IFC Ham Member QRZ Page

    To be honest, I've never used a counterpoise with an end fed wire, but I did use a base loaded 6ft whip sticking out the window of a dorm room at a 45 degree angle. This whip did use a counterpoise and operated 80 thru 10 meters. The counterpoise was rolled up at the far end for the higher bands and fully extended for 80M.

    I wonder if your tuner is set up for ladder line or end fed wire or both? If you are grounding to the case of the tuner, then a counterpoise (artificial ground) should make a noticable difference. It could be that your rig is grounded through the buildings wiring and it is using that for the other half of your antenna. This can cause undesirable RFI and or increased QRM in your receiver. Back when there was metal plumbing in buildings, decent grounds were easier to come by. These days with plastic plumbing, it is sometimes not an option.

    There are all kinds of hidden antennas for apartment dwellers and each situation is different. Try a bit of reading/google searches and see what you can fit in to the space you have access to. If you are running QRP levels, you have quite a few options including indoor pancake antennas, multiband dipoles made from TV antenna rotor wire, hidden verticals in flag poles... If your apartment is stucco or aluminum sided, then the indoor antennas might not be a good option for you.

    Good luck! Bill
     
  3. KD5LPB

    KD5LPB XML Subscriber QRZ Page

    Wouldn't that whip you used with the counterpoise essentially be the same thing I'm doing? How long was your counterpoise?

    The tuner as of now is set up for end fed wire. Should there be a balun inside of it? There is a spot for it but the manual says to only install one if using ladder line or such
     
  4. KB3RHV

    KB3RHV Ham Member QRZ Page

    Long wire and vertical antennas are unbalanced, so you want to use a unun with them. Aether a 4:1 or a 9:1 unun depending on your tuner.

    Bulan Designs sells them, or you can make your own like I did. I copied EARC's design and it works pretty well.

    http://www.earchi.org/proj_homebrew.html


    Do you have a balcony? If not, dose your windows have sills that stick out from the wall?

    If you have a balcony, you could mount a fiberglass exstion pole to it and use that as a vertical with the unun.

    If you dont, you could make a PVC window mount that holds a vertical antenna like the one I am making. I have an AH-4 mounted on it, but you could just as easly mount a unun on it.
     
  5. KD5LPB

    KD5LPB XML Subscriber QRZ Page

    That's a pretty nice setup, but I'm positive that the managers here would go crazy if they saw it! Haha. I do like it though.

    I do have a balcony but the roof overhangs it so I can't put anything vertical up.

    I've been told that I should just put out as many long counterpoise wires as I can without overlapping them.
     
  6. KB3RHV

    KB3RHV Ham Member QRZ Page

    Ware I am at, we can not put up any antennas out side. I was told this by our property manager. But she also said that if I were to do it at night and then pull it back in when I am done and if no one complains about me doing it, she be OK with it.

    So I am pretty much going stealth mode with it when I am not QRP'ing.

    You know, you could do the same thing with your balcony, and make a PVC hanger that sticks the antenna out past the roof.

    As for the counterpoise, if you run a unun, you will not need a bunch, generally one to two cut 1/4 wave to the lowest band will work.
     
    Last edited: Aug 10, 2009
  7. KD5LPB

    KD5LPB XML Subscriber QRZ Page

    I asked the maintenance guys what they thought about it and they told me that the office wouldn't like the PVC idea but the tiny wire that I have up is probably fine since it's so difficult to see. Don't know if I should have pointed it out but we'll see what happens.

    So my random wire is unbalanced? For some reason I thought it was balanced.
     
  8. W1GUH

    W1GUH Ham Member QRZ Page

    It's for sure unbalanced.

    An alternative to a counterpoise is to work it against ground, and a cold water pipe (if metal) or radiator will do nicely. It'll tune without it, but the ground (or counterpoise) makes the antenna a lot more efficient. Hook the ground to the tuner ground terminal.

    And have fun! You should be able to work lots with a setup like that.
     
  9. KB3RHV

    KB3RHV Ham Member QRZ Page

    Yep, like W1GUH pointed out, its definitely unbalanced. There are not too many antennas that are balanced come to think of it.

    Here is some info from Balun Designs.....
    http://www.balundesigns.com/servlet/the-template/Importance of Baluns/Page

    Book....
    http://www.universal-radio.com/catalog/books/0558.html

    For the coax to wire feed for your long wire, I would use a unun.
    http://www.balundesigns.com/servlet/the-96/QRP-4-cln-1-Unun-1.5/Detail

    With this at the feed point, your radios tuner will be able to tune it better and you will also not have to run a bunch of counterpoise wires.

    When I QRP out at the local parks, I run a random wire of 39' with a counterpoise wire cut to 1/4 wavelength of the lowest band I use, which is 40M. I use this setup with a 9:1 unun and my 703 tuner tunes it just fine.

    Here is an antenna that is based off this design and works quite well.
    http://www.parelectronics.com/end_fedz.htm

    I know a few guys that run these and are quite happy with them.
     
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