Texas star dx 350 hdv staying keyed up after transmission.

[Enterprise312ok]

All I will say is inflation is about to take a bite out of the $1 = 1watt equation. If tx star was still able to make money on those boxes after materials and labor they wouldn't be basically out of business.

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[K9LPK]

Not strange, just lucky.

The difference between a RF amplifier and a RF oscillator is how you control regenerative (positive) feedback. Any amplifier that has a poorly-designed or botched input circuit is a potential oscillator. ALL amplifying devices will feed some of their output back to their own input, INTERNALLY. Add to this the tendency of RF to just magically travel across empty space inside the amplifier, and this just increases the overall unwanted feedback, over and above the transistor's built-in feedback.

The input circuit serves, among other things, to shunt unwanted regenerative feedback to ground, away from the transistor's input terminal. The lower the impedance at this spot the better, up to a point. The lower it is, the more feedback current it carries safely to ground, away from the transistor's inputs.

A coax jumper makes a dandy tuned circuit. Placing a tuned circuit across the input of an unstable amplifier is a good way to construct an oscillator.

Coax length should make no difference whatever to an amplifier with a perfect resistive 50 ohm input. None. Zero, Nada.

The farther an amplifier's input circuit gets above or below that one-to-one SWR impedance, the more difference coax length will make. An amplifier with a five-to-one SWR measured at its input while keyed will almost certainly change behavior as the jumper length is altered.

73

What I found with these amps is the SO-239 insulator moves inward to the inside of the amp and you get a arc connection (WEAK) causes the amp top go into Oscillation. The have junk for SO-239 rear panel connector's Replace them with Amphenol 4 screw connector's. No! Gluing the old ones back does not help!

 

[linearone]

All I will say is inflation is about to take a bite out of the $1 = 1watt equation. If tx star was still able to make money on those boxes after materials and labor they wouldn't be basically out of business.

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I say this all the time. Dc boxes are a race to the bottom.
And tbh, toob boxes are a hard sell when you charge what its worth to build. Everyone is still on the maco 300 and phantom pricing plan. People remember $800 ameritron boxes. Those days are gone people.

 

[Ranch55]

All I will say is inflation is about to take a bite out of the $1 = 1watt equation. If tx star was still able to make money on those boxes after materials and labor they wouldn't be basically out of business.

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Already has....... been gone for quite sometime now.....

 

[nomadradio]

When I first heard the "dollar a Watt" a pack of cigarettes was a quarter. A gallon of regular gas wasn't a lot higher.

Inflation has hit the price of a linear Watt like everything else.

73