[BC] franklin question (was WSM

[PeterH5322]

>Are those still franklins still legal?

Sure, and they are even "blessed" with their own "Sect" code: 3.

Recall that Sect=0 represents a non-sectional radiator, with no top 
loading; Sect=1 represents a non-sectional radiator with top loading; and 
Sect=2 represents a sectional radiator with or without top loading of 
either the top or the bottom sections; while Sect=3 represents a 
Franklin, which is a center-fed sectional, with no top loading of either 
section, where each section is 180 degrees.

There exist other radiators which are almost Franklins, and one of these 
(WHO's) has its own Sect code, too.

For reference, both KFBK's Franklins, and KSTP's almost Franklin perform 
about the same, 510 mV/m/kW at 1 km, which is to say that 50,000 watts 
into one of these radiators gives about the same field as does 100,000 
watts into a minimum conforming Class A radiator.

KFBK's data:

Sect=3
A=180
B=0
C=0
D=0

KSTP's data

Sect=2
A=0
B=0
C=179.40
D=179.40


WOAI had an almost Franklin, 120 over 120 ... WHO's is 180 over 120 ... 
but WOAI's was replaced with a conventional 195 degree radiator. There's 
that 195 number again :-) .

Comparing and contrasting sectionals of the Franklin type, 120 over 120 
gives a good account of itself, with lower vertical field than either 
WHO's 180 over 120 or KFBK's 180 over 180. At the expense of lower 
horizontal field, of course.

One has to wonder, therefore, why WOAI gave up on what was obviously a 
well-performing radiator?

Perhaps a higher than normal perceived maintenance cost.

Or perhaps, as with 570 in Bethesda, MD, now WTNT, the ground under that 
120 over 120 in San Antonio became too valuable, and an asset sale was 
deemed to be in the best interests of the licensee.

Of course, it didn't work in WTNT's case, but it may have in WOAI's case


>I guess one good thing about the Franklin is that there's no radials to
>rip 
>up and run off with.  I've always wondered how the Franklin is fed.  The
>one 
>in Calif. that's the two tower phased DA is fed with unbalanced open
>wire 
>feed.   At the feedpoints, is this feedline terminated so the center is 
>bonded to one side and the outer wires to the other (as if the Franklin
>is a 
>1 w/l vertical center fed zepp) or are both sides of the feedpoint fed
>with 
>the center wire (like two 1/2 w. end fed zepps with one side of the
>feed, 
>the outside, unterminated)?

The interior conductors of the open line go to the bottom of the top 
section, through a network.

The exterior conductors of the open line go to the top of the bottom 
section.

There is no ground system required, although the FCC inspector demanded 
that one be installed, and one was.

If you carefully examine the base of each tower you will notice that the 
"ground strap", if you could ever call it that, is exceptionally small, 
and could hardly be expected to conduct a significant current.

The radials, therefore, are there only to satisfy the inspector, and for 
no other purpose.

Likely, those radials have long since disintegrated, and are 
non-functional.

In the case of KFBK, there is no network at the bottom of the bottom 
section, just an insulator; in the case of WOAI, there was a network 
there, a capacitor across the base insulator.


FWIW ...

McClatchy's engineers built not only this Franklin, but also the first 
practical U.S. implementation of what is now called Ampliphase (or, 
rather, Amplifuzz, for those who have ever had the displeasure of working 
on one).

Two were built: the 50,000 watt one for KFBK, and the 5,000 watt one for 
KOH, which was then owned by McClatchy, in the shops at KFBK's 
transmitter site.

Why one wasn't also built for McClatchy's KBEE (Modesto) and/or KMJ 
(Fresno) is unknown to me.

The KOH transmitter had some unique features, and was radically less 
complex than the Ampliphases which RCA later built based upon the two 
designs which were first implemented at KFBK and KOH.