Need plans for QHA antennas

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KC2USN, Mar 23, 2009.

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  1. KC2USN

    KC2USN Ham Member QRZ Page

    Hi,
    I am looking for plans for a QHA antenna for 145 and 430mhz. I do have the plans from the Arrl satellite book or back issue of QST but that was from 1996 and I know there are some improved versions out there. There are some interesting designs at weather satellite sights but they are for 137mhz.
    Thanks
    Dave
     
  2. AC0GR

    AC0GR Ham Member QRZ Page

    You should be able to take the designs of the 137Mhz versions and simply scale them for 145 and 430Mhz frequencies.

    Another design you might want to look at is the Eggbeater[PDF File]. A bit simpler to make than the QHA
     
  3. KC2USN

    KC2USN Ham Member QRZ Page

    Thanks for the reply.
    I am not sure Scaling down will work for 400+mhz.
    Copper tubing, fittings etc are expensive and I was hoping someone built one of these already in that freq range that could share some lessons learned.
    I already bought 1/4in copper tubing and some pvc pipe but have read that I need to get right angle fittings because radiation pattern will change if I use bent or radius type corners instead of 90s.
    I don't know if I should coat the copper for weathering or will it be fine?
    Any comments are welcomed.
    Dave
     
  4. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    Just be sure you scale the TUBING diameter too! This is especially true on many-element yagis! Trust me, I learned this the HARD way!
     
  5. AC0GR

    AC0GR Ham Member QRZ Page

    Scaling at that freq you will probably want to use 12 AWG wire rather than copper pipe. I am not sure about the corrosion factor of exposed copper, but its never been an issue on my J-pole.
     
  6. KC2USN

    KC2USN Ham Member QRZ Page

    I would rather use #12 but it would require support cross pieces where as the copper tubing is rigid enough to retain it's shape. Copper ground wire #8 is redilly available also. I didn't want to use aluminum fence wire which is very malleable because I want to solder to it.


    Some of the sites I am looking at are but instructions are a bit vague at best.
    http://www.askrlc.co.uk/
    http://n8imo.com/qha.html
     
  7. AC0GR

    AC0GR Ham Member QRZ Page

    Had you by chance, seen this? Javascript QHA Calculator

    With the numbers I got for 430Mhz, you should almost be able to run the smaller loop inside and the larger loop outside a 9 inch length of 4 inch thin wall PVC. :)
     
  8. KC2USN

    KC2USN Ham Member QRZ Page

    Thanks, thats one of the best sites for the QHA so far.
    Dave
     
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