To Bias

Fig, 3- Terminating resistors for A. wait range using 52 ohms, and C«

Exciters under 100 watts using 100 ohms, B. Exciters in the 200 Exciters over 200 watts using 26 ohms.

wired up as choke input. I needed more voltage so a 2 mid 2000 volt filter condenser was placed from B plus to ground ahead of the choke. With condenser input I got 840 volts to get my required 810 volts as per the data sheet. However when 1 tried to get regulators totaling 810 volts (4-VR 150 and 2-VK 105 in series), I found the supply would not keep the regulators fired up under modulation peaks, so 1 had to settle for 5 VR 150 in series for 750 regulated volts; and the output of the rig is not at all impaired. I have adjusted my Zero signal dc plate current to 95 mA per tube, or 190 mA total, because I am running less than 3000 volts on the plates. I merely interpolated the typical data lo fit the voltages available to me.

There are two points I want to make. First, if you use a grid meter an 0-1 mA will do the job. If you are operating properly, it should never read anyhow. My rig had a 50 mA unit in it but by removing R-108, a 2.2 ohm shunt resistor, it now reads 5 in A full scale and serves as a check on overdrive. Second, be sure to use a screen current meter as it will tell you more about how the linear is operating than any other meter you can use. The unit I had in the rig was a 50 in A but I should say anything from 25 to 100 mA would do.

E have found from watching my linear on a scope as I operate, that if it shows over 10 mA screen current, the final is not fully loaded. I load mine to about 2 mA and the data sheet savs 4 mA. 1 also note that if I load to the point where the screen current goes negative I am overloading the linear. Keep the screen current positive and in the area of a very few mA at most and you won't have much trouble with complaints. The meter should not fluctuate greatly under load and the screen voltage must be regulated. Be sure that the VR

tubes keep conducting (stay blue inside) under al! speech conditions, hese precautions will not preclude the use of a scope if you can aiford one. L feel all high powered amplifiers should have the closest control of operating conditions that can be had. After all big power, not properly controlled, can make big trouble for a lot of hams operating on the band many kilohertz away from your frequency. The more power you use, the more responsibility you have to keep your signal clean. This is one good reason for considering building this simple linear.

For a plate meter, used the 750 mA meter that was in the rig. All it is good

This view of the bottom of the linear shows where the coils were located and now contains the four resistors obtained from John Meshna Jr. A pair in parallel for 26 ohms and two sets in series to make 52 ohms at about 200 waits, The blocking condenser is a bigger one than needed but teas handy in the funic box.

This view of the bottom of the linear shows where the coils were located and now contains the four resistors obtained from John Meshna Jr. A pair in parallel for 26 ohms and two sets in series to make 52 ohms at about 200 waits, The blocking condenser is a bigger one than needed but teas handy in the funic box.

for, along with a voltmeter in the plate supply, is to indicate the power input to the final, as required by FCC on 2000 PEP 1 in ears. I never use it to indicate the function of the pi;ite loading on the tubes. J feel the screen meter does a far better job.

The datf? on the tubes shows a two tone average plate current per tube of 215 mA or a total, with a pair of tubes, of 430 mA, This is almost 1200 watts input and over the legal limit. If I swing the tubes from the standing current of 190 mA in my rig up to 350 inA by the meter reading, I am getting 2000 watts P.E.P. from the power

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