[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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