[TowerTalk] t type antenna

[n1bkb at aol.com]

 Different kind of antenna....
Many, many ears ago when I was the signal officer for an army air traffic unit, we operated a low frequency, non-directional beacon.  Our authorization was for 399 kHz at Indiantown Gap Military Reservation, PA.  The antenna we used with the beacon was called a capacitive loaded top-hat antenna.  We erected three 60' tall masts, 200' apart.  The radiating element of the antenna was a 60' vertical piece of wire that went from the transmitter to the top of the center mast.  As a solid "T" connection, 200' of wire was run from that center connection in each direction to the remaining masts ... creating a 400' long top-hat for the 60' radiator.  My most memorable use of that antenna in the military was when I accompanied one of our pilots on a training flight from Indiantown Gap to Annapolis, MD, where we stopped for dinner.  When we lifted off at dusk from Annapolis to return to Indiantown Gap about 150 miles away, the BZZ Morse signal from my beacon was a SOLID (!) 5-9-9 on the ADF receiver in the helicopter.

Fast forward .... Nearly 30-years ago when I was a member of the Fullerton (CA) Radio Club, we set up that same style antenna at a Field Day exercise for use on 160m and 80m.  We were constantly getting 5-9 signal reports up and down the coast running 100W SSB on 160m.  Of course it needs an antenna tuner but it really does work as an omni-directional ham band antenna!

Steve - N1BKB


--Original Message-----
From: john at kk9a.com
To: towertalk at contesting.com
Sent: Mon, Dec 19, 2022 9:01 am
Subject: Re: [TowerTalk] t type antenna

I was also trying to understand the 300 foot top hat. I have never seen that even on top band.  It would be easy to model to see where it's resonant.

John KK9A


Stan Stockton K5GO wrote:

350 feet is about 5 quarter wavelengths at 3.8 MHz.  Quarter wavelength is about 65 feet or so.  If that thing is really 350 feet long you should see resonance at about 700 kHz, in addition to every odd multiple of a quarter wavelength.  Was there a typo or is this really an inverted L that is 350 feet long?

Stan, K5GO

Sent from my iPhone

> On Dec 19, 2022, at 2:57 AM, w5jmw at towerfarm.net wrote:
> 
> Hello all.I have a t antenna.50ft vertical and roughly 300 ft ntip to tip horizontal.I get a nice drop and resonance at abt 3.8 mhz.Is this weird resonant point normal??I would think it would be lower.I have another at abt 2.2 but almost a 3-1 swr..Normal ? I have used an inverted l before and resonant was abt right with a 1/4 wave length..thanks..john

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