[Milsurplus] AS-251 / AP p/o APT-5
Mike Hanz
AAF-Radio-1 at aafradio.org
Tue Nov 18 08:00:12 EST 2008
This is an exquisitely designed crossed-element phased sleeved dipole
antenna that is capable of receiving and transmitting circularly
polarized signals, and was reflective of the tremendous burst of
technology during the war. It was a wider bandwidth development of the
AS-69 that was targeted against the German Wurzburg radar. There is a
photo on my website - http://aafradio.org/countermeasures/AS-251.html .
You can begin to appreciate its engineering more fully when you begin to
notice the "launch flares" at the transition from the boxed sleeve to
the monopole (helped smooth bumps in the response curve) and the
integral balun feeding the phasing elements at the base. Its bandwidth
was impressive at the time, and the technique allowed a much wider
frequency coverage than the simple verticals and cones of the period.
You can imagine trying to scale this up to an HF version. Luckily, one
can fabricate such crossed element antenna from two loops much more
easily, though the phasing networks aren't trivial to build or adjust.
73,
Mike
Hue Miller wrote:
>That title make sense to you? Good- you qualify
>as a genuine milsurplus nut.
>
>I was looking at my "OUT" box thinking i really
>need to start making some serious progress,
>no excuses. I found this antenna and did some
>Google checking. I found:
>
>Then i looked again and found Frederick Chesson's web
>site. Again - bless Mr. Chesson for all his work!!
>
>and there is listed
>
>AS-251/AP "Fish-Hook" Ant., 440-660 MC P/O APT-5 Jammer
>
>IF you have an APT-5 and would like to have this antenna, it
>is available free - kostenlos - gratis, except for shipping. About
>14" tall, 10" across at top, new condition, FOB Oregon, USA
>
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