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QRP Portable - with a small profile antenna

Discussion in 'QRP Corner' started by N1KTJ, Apr 25, 2016.

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  1. N5JLD

    N5JLD XML Subscriber QRZ Page

    You could wrap this around at ceiling level. I have done that in Hotel room when I can't throw it ow a window.

    Since I made my first one, this has been my goto portable antenna. I have used them at 100w and 5w with good performance.
    I made a QRP one that I take when I travel for business and throw it out the hotel window.
    53' wire seems to give the best performance and about chest high for the UNUN. On me that is 58 ~ 60""
    You do need a tuner.
    This is my "Hotel" portable version. Cost as shown ~$8.00 us

    [​IMG]
     
  2. W0IS

    W0IS Ham Member QRZ Page

    If there's a hole in the screen big enough for coax, I would just run a small wire out that hole and attach it to some convenient object such as a tree. It would probably require a tuner, but it would almost certainly outperform a mobile antenna. If you don't have a tuner, then a quarter wavelength of wire would probably perform well. If no good ground is available, run another piece of quarter wave wire inside.

    Of if two trees are available, then put up a dipole in a (non-inverted) vee formation.

    If you absolutely can't get anything outside, then I would probably use a dipole indoors. Run it as straight as possible, but if a few bends are necessary, they won't cause much of a problem.
     
    KC8VWM likes this.
  3. K8JD

    K8JD Ham Member QRZ Page

    I finally built a "non resonant dipole" as an extended double Zepp to get some gain on 20M, used the 450 Ohm window cut twinlead, random length, and got the MFJ974 balanced line tuner. It works well from 5-18 mHz but it's CERTAINLY NOT something meant to drag around on a camping trip or to a mountain top !!!!

     
  4. K8JD

    K8JD Ham Member QRZ Page

    I finally built a "non resonant dipole" as an extended double Zepp to get some gain on 20M, used the 450 Ohm window cut twinlead, random length, and got the MFJ974 balanced line tuner. It works well from 5-18 mHz but it's CERTAINLY NOT something meant to drag around on a camping trip or to a mountain top !!!! the 974 is a rather large item.

     
  5. K8JD

    K8JD Ham Member QRZ Page

    double posting
     
  6. WB2HLM

    WB2HLM Ham Member QRZ Page

    Most antenna tuners operate with little insertion loss which is not true with baluns and ununs. I use a resonant dipole fed with ladder line, a little tuner and it works everywhere. Sometimes I tie the two feeders together and load up as a "T" antenna. While using it as a dipole, grounding is not as important, when using it as a "T," a good ground is essential. (So I try not to use it as a T very often.) I use a slingshot with a cheap fishing reel to launch the ends up and usually try for 35 feet of center height because my feed line then just reaches the back of the little tuner on a tabletop. I try for a good ground, using the ground connection on the back of the tuner as a central spot, but that doesn't always happen. I have used a length of spare coax stretched over the ground as a "counterpoise" ( I hate to call it a ground) and that sometimes improves the signal. Good luck and have fun.
     
  7. KC8QVO

    KC8QVO Ham Member QRZ Page

    Any time you convert impedance, etc you have "insertion loss". You have "insertion loss" simply putting a PL-259 on a cable (depending on how good of an install - the less loss the better the install). Do a sweep test on a few runs of coax and you'll see. You may get "less" loss with a balun or unun than you will with a "tuner", however - both devices are converting impedance, or in the case of a 1:1 balun - the same impedance but converting between unbalanced to balanced. You will have some loss there, perhaps less than a tuner, but not none at all.
     
  8. W6OGC

    W6OGC Ham Member QRZ Page

    Most tuners are quite lossy, depending on the design, the components, the degree of transformation you are trying to achieve, etc.

    There is a rating of sorts found on the website of DJ0IJ, among lots of other info.
     
  9. N8MRG

    N8MRG Ham Member QRZ Page

    I am not familiar with "DJoIJ", is that the acronym for the URL/site name? I am interested in design and losses as a combination 9:1 UNUN and L-Match is something I've been considering paired with a long wire.
     
  10. KK4NSF

    KK4NSF Ham Member QRZ Page

    [​IMG]

    I use an Icom AH-703, and few ground plane radial wires with my 10W SSB portable rig.... and it works amazingly well. From the Gulf Coast, I've made QSOs all up and down the East Coast and mid-West, and as far away as Califormia, The US Virgin Islands, and Canada. It works best if it's elevated 6-10ft above the ground, but even if it's just on a picnic table it works just fine.

    My rig is built into a metal Ammo Box, and I've made it so that the antenna screws right into a SO-259 connector on the can..... so there's no need for a separate base or coax. I just screw the antenna onto the box, set out the ground wires, and I'm ready to go.
     

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