[GreenKeys] OT. Antenna materials

[Ralph Mowery]

If you have the dowel and copper, I would just run a strip down the dowl and not even worry about soldering  it at any point down the line other than maybe at both ends just to hold it together. Years ago TV antenna elements were made out of aluminum that was just wrapped to form a round element.

If you have a SA with the tracking generator, maybe you have a return loss bridge.  That is a great way to check the antenna.  It is just a high dollar swr meter anyway.

Here is a link on how to use one for the antenna.
http://www.sglabs.it/public/Eagle_RLB150.pdf

For ham purposes there are some that are a lot less expensive than the several hundred dollars of that one.

I use one made by Mini-Circuits that I got off ebay for about $ 50.  It is a ZFDC-20-5.  Not lab quality,but plenty good enough for most work.

73

  ----- Original Message ----- 
  From: gil at baudot.net 
  To: Jeffrey D Angus ; greenkeys at mailman.qth.net 
  Sent: Sunday, December 01, 2013 12:59 AM
  Subject: Re: [GreenKeys] OT. Antenna materials


  Hey guys:


  Well, when I mentioned wrapping a dowel with copper tape, I didn't mean some helical thing -- I have a big roll of adhesive copper tape and was thinking of a linear strip of tape along the length of the dowel, that completely wrapped the dowel, with some solder tacks every few inches where it overlaps, forming a pseudo copper tube.  Is that not a good tubular conductor for a dipole if wrapped around a 3/16" wood dowel?  The dowel will not get wet, btw, as we will only launch on a clear day.



  Brass hobby tubing is also a good suggestion, though the dowel will be there and it seems reasonable to exploit it.



  My original plan was to just take some 24-ga or whatever copper enameled magnet wire and epoxy it it along the wood dowel structure.  But it sounds like such thin conductors make the bandwidth narrow, and would make tuning the dipole length all that more critical.


  Regarding tuning:  I can likely measure the antenna impedance with my HP TDR that goes to 20 GHz, but how can I measure the antenna's resonant freq (at x-distance above ground)?  Do I need to buy an swr meter or antenna analyzer, or is there a way to do this with conventional test equipment that I already have (scope, spectrum analyzer...)?  Or is it not that big a deal?  Just cut it to x and call it good?  Am I over-thinking this?  I often do, but rather that than the opposite extreme.


  gil





  gil smith, AF7EZ
  greenkeys moderator
  gil at baudot.net

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