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K0CQ CSVHF 2010. Back about 1964, I struggled to design a low impedance balanced line to match an array. By 1966, my research showed the common formula was incorrect for low impedance lines. So I wrote the article reproduced in the proceedings as it was published in The VHFer.
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Back about 1964, I struggled to design a low impedance balanced line to match an array. By 1966, my research showed the common formula was incorrect for low impedance lines. So I wrote the article reproduced in the proceedings as it was published in The VHFer. Low impedance parallel transmission lines
Back about 1964, I struggled to design a low impedance balanced line to match an array. By 1966, my research showed the common formula was incorrect for low impedance lines. So I wrote the article reproduced in the proceedings as it was published in The VHFer. Low impedance parallel transmission lines
This was on page 61 of the April 2010 QST by QST's technical editor
I have to admit only about half the professional references mention the restriction on the simple formula and no ARRL resources mention that. The close spaced formula comes from work of Harold Wheeler about 1939 where he found that the charges on close spaced wires concentrated where the gap was smallest and that affect the computation of the distributed capacitance leading to the inverse cosh formula. Low Z TL
The earliest handbook I had with the full formula dates from 1943, an early edition of the Federal Telephone and Telegraph Radio Handbook. It was copied from a Standard T&T handbook probably printed about 1942. ARRL publications have missed the update. Low Z TL
Typo in the fourth line second paragraph. Needs a closing parenthesis after “turn that transistor off.)” FT-8x7 TX-INH line
I've found evidence to indicate there is a similar menu for the FT-817, but I don't know if the values or the menu entries are exactly the same. It is handy to align the transmitter gain to absolutely prevent spikes and to keep the power minimized for transverter service without needing to go to the transverter mode. Because depending on transverter mode allows full IF power to the transverter if that mode switch is missed. Adjusting the FT-857 for transverter service
Typo, third paragraph third line, “loss, So the” Power Amplifier Protection Concepts
We aren't using surplus parts so often. Even Russian tubes are getting more expensive. Exotic SS devices can run a kilobuck each now or can't be bought at all. Voltages and currents rise in picoseconds in UHF and microwave amplifiers. PA Protection
The best protection comes from using devices that can stand a high SWR. The second best protection comes from using an output circulator. PA Protection
What to detect? Excess supply current. Excess SWR. Excess device RF voltage. PA Protection
Tripped off on high plate current. Tripped off on arc detection. Saved many tubes and vacuum variables from destruction. 821A-1
Series switch tube also use for pulse width AM. Saves much energy and power supply damage. Post 821A-1
In these schematics the pass FETs are drawn wrong! Input is to source, load connected to DRAIN. P TYPE FET circuits to follow
PA Protection circuits S D G
Circuits S D G D G S
Circuits S D G D G S
While machining handbooks say if the threads are the length of the screw diameter, a 50% thread cutting depth is plenty, most tap drill charts are for a 75% thread which often leads to binding and a broken tap. For years I have gone to a number drill two or three sizes larger than the standard charts, but a true 50% chart is better and is in this paper. Safe Tapping in Soft Metals
I have been thinking the threads extrude into the clearance space when tapping soft metals. So I bought some alloy 1100, soft and gummy to show that. I've failed. But my experiment has vividly shown the value of lubrication. Safe Tapping
