d23. 2m 200W RF Power amplifier using YL1070/YL1060
The notes apply for QQE06/40 (= 5894) in some degree

The PA was built in 1982 using a discarded FUBA 5W amplifier for BIII TV transponder, it has originally YL1070,
but will also work for YL1060 with somewhat different bias and screen supply voltages.
The brass type box measures 16x14,5x37cm.

Power requirements:
6,3VAC (or 12,6V)
-30...45V variable grid bias
+150....350V variable screen voltage
+950....1000V anode supply voltage

Screen voltage has been variable since it solves some problems (using 6AQ5/EL90 regulator valve), but need
only be variable in steps. It is an advantage to use the highest possible grid bias and as such you can increase
screen voltage. YL1060 needs substantially higher screen voltage than YL1070, when YL1070 need around +200V
YL1060 may need over 300V.

YL1060 and YL1070 are so-called rugged QQE06/40 (QQV06/40, 5894) with 70W anode dissipation instead of 40W.
Believe the RF power output limits are in the region of
200W using YL1060, 190W using YL1070, and 150W using QQE06/40=QQV06/40=5894.
YL1070 is designed for linear mode, while QQE06/40 and YL1060 are designed for class C FM transmissions.

6AQ5/EL90/6005 isn't particularly suitable for voltage shunt regulator since it requires a considerable grid voltage swing
of 30V between 25-30mA anode current and zero, EL84/6BQ5 is far better since it requires less and is easier to
drive from a µA741 or other operational amplifier. This was mentioned in an article in Radcom 15-20 years ago,
but I've been unable to trace the article for reference later.

Today, some FETs might be a better choice. See Amateur Radio Technical Notebook

Screen grid regulator for 5894, QQE06/40, QQV06/40, YL1060, YL1070 and other

Triode-connected 6AQ5.
From the diagram you will learn that still at -30V the triode-connected valve
will draw 3-4mA current with 250V, the figure is somewhat course isn't meant
for operation on this side of the characteristique

Triodeconnected EL84/6BQ5. Not particularly better than 6AQ5 for series- or shunt-
type regulator if screen grid cannot have more voltage than anode, it needs 100V
to draw 50mA anode/screen-current, but may draw 200mA if 250V is available.
It is definitely better as 6AQ5 as screengrid regulator for power amplifier, because
higher screen voltage may be available, and it definitely needs a lot lower negative
bias for cutoff than 6AQ5.

My favourite valve for series- and shunt-type regulators. The valve may draw 50mA @+50V,
120mA @ +100V anode- and screenvoltages.

Updated 2004.01.18 LA8AK