[Elecraft] Franklin antennas

[Gmail]

Correction, it was center fed. 

Sent from my iPad

> On Sep 11, 2018, at 19:23, Gmail <anyone1545 at gmail.com> wrote:
> 
> KDKA, Pittsburgh, still has a Franklin, they are not a center fed vertical.  both the bottom and top sections are end fed. The purpose is to lower angle of radiation and reduce skywave and selective fading.  KDKA has a motorized capacitor on the top section.  Both stations have extensive ground systems that would not be needed if they were dipoles. 
> KDs antenna was replaced in 1994. Still a Franklin as changing the antenna would have required a power reduction with the “ratchet rule”.
> Ray
> W8LYJ
> Formerly with Group W Engineering, owner of both stations until recently. 
> 
> http://www.durenberger.com/documents/KDKANEWTOWER.pdf
> Sent from my iPad
> 
> 
>> 
>> Message: 1
>> Date: Sun, 9 Sep 2018 15:48:48 -0700
>> From: Fred Jensen <k6dgw at foothill.net>
>> To: elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] ARRL book on receiving antennas
>> Message-ID: <c130b735-6094-a565-3800-99fc2f9e2174 at foothill.net>
>> Content-Type: text/plain; charset=utf-8; format=flowed
>> 
>> Yes, very straightforward theory.? Just gather all the watts actually 
>> radiated by the antenna and divide it by the watts you put into Rr.? 
>> Unfortunately, I did not really address Bob's question ... "How do you 
>> sweep up all those watts?" :-)? That is a nearly intractable problem at 
>> HF unless you'll tolerate significant inaccuracies and assumptions.? 
>> It's much easier at UHF and uWaves.
>> 
>> An alternative is to measure/compute the losses.? Did something similar 
>> on a 10 KW FM broadcast TX, calculating the power it took to heat the 
>> exhaust air on the premise that the rest went up the coax to the antenna 
>> and I knew what the PA input power was.
>> 
>> KFBK in Sacramento CA [1530 KHz] eliminated a lot of the unmeasurable 
>> variables by employing a Franklin antenna [center-fed half-wave 
>> vertical] over the rice fields of the southern Sacramento Valley [nearly 
>> always standing water, and always wet]. The center-fed vertical exhibits 
>> far less ground losses than bottom-fed monopoles ... at 50 KW, it's 
>> colloquially known as the "Flame Thrower of Sacramento."? It may be the 
>> only Franklin left in NA.? KFBK is also famous as the birthplace of the 
>> RCA Ampliphase transmitters and the radio birthplace of Rush Limbaugh.
>> 
>> NEC models coupled with terrain models can be used to establish upper 
>> and lower bounds on antenna efficiency with pretty good fidelity to 
>> reality.? But Bob still posed a good question.
>> 
>> 73,
>> 
>> Fred ["Skip"] K6DGW
>> Sparks NV DM09dn
>> Washoe County
>> 
>>> On 9/9/2018 2:01 PM, Don Wilhelm wrote:
>>> Skip,
>>> 
>>> That is a great formula for theory - I vaguely remember it from my 
>>> electromagnetic fields course.
>>> But how you measure it?
>>> With practical measurement equipment, it is difficult to isolate to a 
>>> single plane.
>>> 
>>> That may be do-able with fully characterized equipment in a controlled 
>>> antenna field space or in an EMC lab, but it certainly is not 
>>> practical in a typical ham antenna installation - and even the 
>>> radiation resistance is not easily measured.
>>> 
>>> Antenna modeling done properly will provide a much more easily 
>>> produced result.? Comparative results between different antennas can 
>>> be obtained from a reference pickup antenna, but that can only show 
>>> the relative performance, 
>> 
>> 
>> 
>> ------------------------------
>> 
>> Message: 4
>> Date: Sun, 9 Sep 2018 17:20:17 -0700
>> From: Alan <n1al at sonic.net>
>> To: elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] ARRL book on receiving antennas
>> Message-ID: <96b660d3-5a7d-cb60-8d1d-827aaa6d77fb at sonic.net>
>> Content-Type: text/plain; charset=utf-8; format=flowed
>> 
>>> On 09/09/2018 01:01 PM, Jim Brown wrote:
>>>> On 9/9/2018 12:39 PM, Bob McGraw K4TAX wrote:
>>>> How does one measure transmit antenna efficiency?
>>> 
>>> Not easily. :)? B...
>> 
>>> AND -- propagation reporting systems like WSPR and the Reverse Beacon 
>>> Network (RBN) can provide very good comparisons between antennas IF a 
>>> LOT of reports from? a LOT of stations is averaged over a LOT of time.
>> 
>> Back in the late 1970s, when I worked at W1AW, a new 90-foot tower with 
>> stacked monobanders for 20 meters was installed.  We wanted to compare 
>> the new antenna against the big rhombic that had been used for many 
>> years for the 20 meter bulletin and code practice transmissions.
>> 
>> So, for a week or two, we did test transmissions after each scheduled 
>> transmitting session.  We would switch between antenna "A" and antenna 
>> "B", send long dashes, and ask listeners to send in QSL reports.  (Which 
>> antenna was "A" and which was "B" varied randomly for each test.)
>> 
>> I collected the reports and plotted them on a map of the US.  We found 
>> that the rhombic was a little better directly on its boresight to the 
>> west (toward southern California from Connecticut) but the stacked Yagis 
>> had a much wider beamwidth so were better over the country as a whole.
>> 
>> By the way, you don't have to transmit to compare two antennas if your 
>> receiver has an accurate S meter.  Just switch between the antennas and 
>> compare S meter readings.
>> 
>> Alan N1AL
>> 
>> 
>> 
>> ------------------------------
>> 
>> Message: 5
>> Date: Sun, 9 Sep 2018 20:07:16 -0500
>> From: Bob McGraw K4TAX <rmcgraw at blomand.net>
>> To: elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] ARRL book on receiving antennas
>> Message-ID: <ee36342c-268c-4e51-b52a-04a92586ead6 at blomand.net>
>> Content-Type: text/plain; charset=utf-8; format=flowed
>> 
>> Thanks Fred.? I'm familiar with measuring broadcast fields for both 
>> directional and non directional systems.? The variances over the seasons 
>> with varying moisture levels in the ground and the difference with and 
>> without vegetation is clearly measurable and predictable.? But still the 
>> efficiency of the radiator was not clearly defined.
>> 
>> As to hams, I suppose we individually evaluate a given antenna under the 
>> conditions we have available.? From that we can say that given antenna 
>> ZZ is more or less efficient than antenna XX.? What ever that XX antenna 
>> happens to be.? While others may say that their XYZ is the best antenna 
>> they have? ever had,? this may be true, that is until one may find 
>> another antenna to be better. What ever "better" is defined.?? And 
>> again, each of us will have objectives in terms of what our antenna and 
>> station must attain.??? As Rob Sherwood said when asked "what is the 
>> best receiver", his answer; "what ever satisfies your needs and you feel 
>> as comfortable to operate and can afford". ? ? I suppose antennas are 
>> much in the same vein of characterization.
>> 
>> Yes, at VHF and UHF there are means and facilities to accurately measure 
>> antenna efficiency.?? Usually we find those to be in the 60% to 80% 
>> range.? Unfortunately some of the applied power is converted to heat, 
>> the result of IR loss,? and thus is lost in terms of electromagnetic 
>> radiation. ?? Again the means and the equipment required, as Jim K9YC 
>> stated, generally is well above and beyond the means of most hams.???? 
>> Some years ago I was fortunate to have supervised access to the antenna 
>> test range at the Motorola facility in Florida and also at the anechoic 
>> chamber owned by IBM in S. FL.?? These supported my graduate studies.
>> 
>> No further answers required on my part.?? I've launched into a "reading" 
>> project to further educate myself on the topic.
>> 
>> 
>> 73
>> 
>> Bob, K4TAX
>> 
>> 
>> 
>> 
>>> On 9/9/2018 5:48 PM, Fred Jensen wrote:
>>> Yes, very straightforward theory.? Just gather all the watts actually 
>>> radiated by the antenna and divide it by the watts you put into Rr.? 
>>> Unfortunately, I did not really address Bob's question ... "How do you 
>>> sweep up all those watts?" :-)? That is a nearly intractable problem 
>>> at HF unless you'll tolerate significant inaccuracies and 
>>> assumptions.? It's much easier at UHF and uWaves.
>>> 
>>> An alternative is to measure/compute the losses.? Did something 
>>> similar on a 10 KW FM broadcast TX, calculating the power it took to 
>>> heat the exhaust air on the premise that the rest went up the coax to 
>>> the antenna and I knew what the PA input power was.
>>> 
>>> KFBK in Sacramento CA [1530 KHz] eliminated a lot of the unmeasurable 
>>> variables by employing a Franklin antenna [center-fed half-wave 
>>> vertical] over the rice fields of the southern Sacramento Valley 
>>> [nearly always standing water, and always wet]. The center-fed 
>>> vertical exhibits far less ground losses than bottom-fed monopoles ... 
>>> at 50 KW, it's colloquially known as the "Flame Thrower of 
>>> Sacramento."? It may be the only Franklin left in NA.? KFBK is also 
>>> famous as the birthplace of the RCA Ampliphase transmitters and the 
>>> radio birthplace of Rush Limbaugh.
>>> 
>>> NEC models coupled with terrain models can be used to establish upper 
>>> and lower bounds on antenna efficiency with pretty good fidelity to 
>>> reality.? But Bob still posed