Adjustable metal tape HF antenna

[David Ross]

  Re the unused portion of a tape antenna...

"Stephens, Al" wrote:
>
>      The tapes were marked according to meters or frequencies, as I recall,
> and once pulled out to the requisite length they were tightened down with a
> thumbscrew clamp.  From the design I would say it probably did not add a
> lumped inductance, but the part rolled up acted as a single conductor.

  The ones I've seem were also calibrated in frequency.  Even if the
unused portion did affect the electrical length of the tape, one would
hope that the manufacturer took that into account when they put the
calibration on the tape.
  (Pretty easy to measure that accurately -  is the antenna tape length
1:1 with the wavelength artwork on the antenna tape?)

  The Collins 637T antenna uses uninsulated phosphor-bronze braid, and
the unused wire left on the reels probably just looks like two
conductive lumps right next to the balun -  each reel may see a pF or
so, both to the other reel and also to the incoming coax shield.

73
Dave Ross    N7EPI    ross at hypertools.com.

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