[TowerTalk] Was April Fools, now radiating dummy loads
Roger L. Elowitz
K2JAS@worldnet.att.net
Thu, 07 Aug 1997 23:16:57 -0400
Hi Mark,
Your post was a beautiful response to my serious query. Thanks a
million. Lot's of guys out there have learned something as a result of
your input as well as that of several others who took the time to
comment. We're all obliged to you.
73,
Roger, K2JAS
==================================================
At 11:57 PM 8/7/97 +0000, you wrote:
>Roger asks:
>
>> But WAIT! Didn't some company recently come out with a
>dipole center
>> connector that contained a large fifty ohm load resistor
>across the
>> coax terminals and the entire thing was sealed from
>prying eyes. The
>> claim was that you could use this antenna on ALL BANDS
>with ANY LENGTH
>> OF WIRES and it would load beautifully! I believe the
>claim was
>> accurate. I also believe the military bought loads of
>them. I only
>> wish I were kidding on this one.
>>
>> Please, someone out there.... tell me it wasn't so or
>please confirm
>> what I'm saying is TRUE!
>>
>
>I think it's been a number of years, but I believe that
>statement is true. I would think some government employee
>or military technician would attempt to evaluate a sample
>unit, but in this case, I'm not sure. However, dummy loads
>do radiate! Put your Cantenna on top of your 100 foot
>tower, and attach a coax tee. Plug in a dipole resonant at
>some frequency in the lower third of your coverage range.
>The efficiency is going to be pretty poor, but what the
>heck, you are saving 3 db of loss in not using a tuner in
>trade for about 3 to 20 db less radiated signal across the
>coverage range. No problem, just run 150000 watts output
>and the far end won't tell the difference! Probably
>quieter on receive, too <grin>.
>
>Reminds me of long ago days at W8UM when we worked a fellow
>in one of the dorms about 2 miles line of sight when tuning
>the 32S3 into a dummy load. I think he gave us an S8 or
>so. Asked him to stand by while we tried a new antenna.
>Flipped on the 30L1 and switched to the 40m yagi which was
>pointed in the appropriate direction. "Hows the signal
>now?".. hehehe
>
>Seriously, there have been what I would call reasonable
>attempts to make relatively efficient broadband shortened
>transmitting antennas using resitive loading. The T2FD
>comes to mind as one that has seen more than a little use
>over the years. I believe the B&W folks are still
>manufacturing a dipole and unipole (grounded end) version
>of the T2FD. And then there is my first novice antenna, a
>Hy-Gain base loaded 18V with a three foot ground rod, no
>radials, mounted a foot from a chain link fence. With the
>losses taken into account, that antenna qualifies as a (not
>quite) radiating dummy load. After two weeks of after
>school CQ'ing, I finally worked a fellow in the next suburb
>(15 miles or so) who gave me a 569C report for my first
>QSO. I was quickly instructed as to the advantages of the
>simple inverted V, it's been a blast ever since!
>
>Then there is the terminated V and rhombic class of
>antennas, where you are more or less diverting power that
>would radiate to the "rear" of the antenna into the
>terminations, thereby gaining a unidirectional antenna.
>Ya, not exactly technically correct, but it settled well
>when I gave a two session introductory antenna forum at a
>new novice class back in Chicagoland.
>
>
>
>----------------------------------------
>Mark Shaum K9TR
>mashaum@fcg.net
>Central Illinois Grid EN50
>---------------------------------------
>
>
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