Re: Topband: HEBA antenna

[Jim Brown]

On 4/21/2024 9:00 AM, Jeff Blaine wrote:
What I found interesting in the HEBA103 document was that it seemed the 
FS measurements were taken at ground level along two compass points.  If 
I'm not mistaken, the power radiated is spread out over a 3-dimensional 
space and from that standpoint, I don't see how improved FS measurements 
taken on the near field at ground translate directly into "high 
efficiency."


I didn't read the document. Based on my 60+ years old experience in Pete 
Johnson's consulting office as a young EE student, I would expect the 
determination of efficiency to be based on running a couple of radials 
(that is, making FS measurements at increasing distances, and at least 
tens of miles) and comparing them with a lab prediction of FS based on 
FCC ground conductivity data. I'm pretty certain that's what FCC would 
have required to approve the license.


But on this topic, the only think I know **for certain** is that I'm a 
mental micro-midget compared to Maxwell.


Same here.

73, Jim K9YC

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Re: Topband: HEBA antenna

[Jeff Blaine]

What I found interesting in the HEBA103 document was that it seemed the 
FS measurements were taken at ground level along two compass points.  If 
I'm not mistaken, the power radiated is spread out over a 3-dimensional 
space and from that standpoint, I don't see how improved FS measurements 
taken on the near field at ground translate directly into "high 
efficiency."


But on this topic, the only think I know **for certain** is that I'm a 
mental micro-midget compared to Maxwell.


73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com

On 4/20/2024 3:19 PM, Jim Brown wrote:

On 4/20/2024 9:18 AM, Joe Subich, W4TV wrote:

Similarly, to the AM broadcaster, "Broadband" simply means sufficient
bandwidth to keep the transmitter happy and avoid distortion of an
IBOC digital signal.  That is far more narrow than even a "50 KHz
under 1.5:1" for amateurs on 160.


Great points, Joe. I grew up a mile or two from a 5kW DA-N on 930 kHz, 
and as a college student worked at the station. One summer, I helped 
the chief engineer silver-solder new radials to new ground screens for 
the 4-tower array. The bandwidth issue jumped out at me as I drove 
through one of their nulls -- where the carrier cancelled, the 
sidebands didn't.


73, Jim K9YC

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Reflector

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