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The only thing that should effect VSWR at the transmitter end of the coax is the frequency of operation. The only exception to this rule would be increasing power beyond the rating of a particular antenna. If changing coax length effects your VSWR, you already had standing waves on your transmission line. If adding an amp makes your VSWR a 3:1, don't buy a cheap solid state amp. In fact some of these junkers run even less stable and clean when driven within the transistors specs. Drive them with low power and a self oscillation has a much better chance of becoming the dominant signal. Sometimes keying one on SSB will produce nothing but a full power signal that looks like a carrier on the watt meter but it's far from it.

Poor or missing negative feedback, lack of shielding between stages, poor decoupling from the DC line, use of single sided boards without a full back side ground plane, high inductance emitter connections, and wide band input and output stages with no tuned circuits all combine to make a wonderful free running oscillator. If the situation is bad enough you can even unkey the transmitter and the RF sensing relay in the amp will stay locked on. The amp has become an oscillator and now generates it's own RF that keeps the relay keyed. This RF is the dirtiest stuff you'll ever see on the spectrum analyzer. If the analyzer could talk it would say "are you kidding"?

<blockquote data-quote="Shockwave" data-source="post: 251864" data-attributes="member: 10882">The only thing that should effect VSWR at the transmitter end of the coax is the frequency of operation. The only exception to this rule would be increasing power beyond the rating of a particular antenna. If changing coax length effects your VSWR, you already had standing waves on your transmission line. If adding an amp makes your VSWR a 3:1, don&#039;t buy a cheap solid state amp. In fact some of these junkers run even less stable and clean when driven within the transistors specs. Drive them with low power and a self oscillation has a much better chance of becoming the dominant signal. Sometimes keying one on SSB will produce nothing but a full power signal that looks like a carrier on the watt meter but it&#039;s far from it.Poor or missing negative feedback, lack of shielding between stages, poor decoupling from the DC line, use of single sided boards without a full back side ground plane, high inductance emitter connections, and wide band input and output stages with no tuned circuits all combine to make a wonderful free running oscillator. If the situation is bad enough you can even unkey the transmitter and the RF sensing relay in the amp will stay locked on. The amp has become an oscillator and now generates it&#039;s own RF that keeps the relay keyed. This RF is the dirtiest stuff you&#039;ll ever see on the spectrum analyzer. If the analyzer could talk it would say &quot;are you kidding&quot;?</blockquote>

[QUOTE="Shockwave, post: 251864, member: 10882"] The only thing that should effect VSWR at the transmitter end of the coax is the frequency of operation. The only exception to this rule would be increasing power beyond the rating of a particular antenna. If changing coax length effects your VSWR, you already had standing waves on your transmission line. If adding an amp makes your VSWR a 3:1, don't buy a cheap solid state amp. In fact some of these junkers run even less stable and clean when driven within the transistors specs. Drive them with low power and a self oscillation has a much better chance of becoming the dominant signal. Sometimes keying one on SSB will produce nothing but a full power signal that looks like a carrier on the watt meter but it's far from it. Poor or missing negative feedback, lack of shielding between stages, poor decoupling from the DC line, use of single sided boards without a full back side ground plane, high inductance emitter connections, and wide band input and output stages with no tuned circuits all combine to make a wonderful free running oscillator. If the situation is bad enough you can even unkey the transmitter and the RF sensing relay in the amp will stay locked on. The amp has become an oscillator and now generates it's own RF that keeps the relay keyed. This RF is the dirtiest stuff you'll ever see on the spectrum analyzer. If the analyzer could talk it would say "are you kidding"? [/QUOTE]

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