[TowerTalk] Fwd: Peak Voltage at the Tip of Antennas

[Joe Subich, W4TV]

On 2022-10-20 3:08 PM, Pete Smith N4ZR wrote:
> Not blaming Ed, but is this for real?  I wonder what all the 75 and
> 160M phone guys think of this?

Low Frequency is, by definition, 30-300 KHz.  At the low end of that
spectrum, even SSB with its 3 KHz bandwidth represents 10% of the
operating frequency.   Put in terms of 75 meters, you are asking a
shortened antenna to have an SWR of less than 2:1 (based on 10%
reflected power at the band edges) over a bandwidth of 380 KHz (or
180 KHz on 160 meters)!

It is difficult at times to produce the 10 KHz (2%) bandwidth needed
for AM broadcast at the low end of the MF spectrum (540 KHz in the
US) when dealing with antennas less than 1/4 wave and/or directional
arrays given the limited bandwidth of their phasing networks coupled
with the limited antenna bandwidth.  Note: 2% happens to be the 1.5:1
or 2:1 bandwidth of a typical "short" (inverted L, loaded vertical,
T vertical, etc.) antenna on 160 meters - about 50 KHz.

73,

    ... Joe, W4TV


On 2022-10-20 3:08 PM, Pete Smith N4ZR wrote:
> Not blaming Ed, but is this for real?  I wonder what all the 75 and 160M 
> phone guys think of this?
> 
> 73, Pete N4ZR
> Check out the new Reverse Beacon Network
> web server at<https://reversebeacon.net>.
> For spots, please use your favorite
> "retail" DX cluster.
> 
> On 10/20/2022 1:43 PM, Edward McCann wrote:
>> “In the low-frequency band, bandwidth is quite scarce for any top-loaded
>> antenna type and must be carefully evaluated in order to obtain
>> good-quality speech transmission. In this band, this kind of antenna is
>> practically the only choice, due to the antenna’s size. In the low end of
>> the medium-frequency band, it is quite difficult to obtain a 
>> high-fidelity
>> bandwidth.”
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