You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
The Feb 2025 Radioddity Giveaway Results are In! Click Here to see who won!

Reply to thread

Message

You're welcome. My first question would be what are you seeing that makes you think the amp is unstable in high power. Are you seeing significant increase in antenna SWR on high power that might indicate an oscillation? When using high power on SSB do you see signs of a sustained signal between words? If so it's probably not stable. Drive level can effect an oscillation but the problem is within the amp design if see you these symptoms.

What is usually the case is that in lower power modes resistive attenuators are switched in line and this can reduce the likelihood of an oscillation. As you switch to higher power most of the attenuator is removed. Another way to reduce this problem if the amp is able to handle the drive on high power would be to bypass the power level switch and replace it with a tuned input circuit.

One way to improve the ground to the transistors in the event PC board traces were determined to be too inductive would be to place small solder lugs under the two transistor mounting screws and position them so that they can be soldered to both transistor emitter terminals. One on each side of each transistor. Be very careful not to ground out any other terminals in this area. Don't place this amp in a positive ground vehicle after this mod.

<blockquote data-quote="Shockwave" data-source="post: 198509" data-attributes="member: 10882">You&#039;re welcome. My first question would be what are you seeing that makes you think the amp is unstable in high power. Are you seeing significant increase in antenna SWR on high power that might indicate an oscillation? When using high power on SSB do you see signs of a sustained signal between words? If so it&#039;s probably not stable. Drive level can effect an oscillation but the problem is within the amp design if see you these symptoms.What is usually the case is that in lower power modes resistive attenuators are switched in line and this can reduce the likelihood of an oscillation. As you switch to higher power most of the attenuator is removed. Another way to reduce this problem if the amp is able to handle the drive on high power would be to bypass the power level switch and replace it with a tuned input circuit.One way to improve the ground to the transistors in the event PC board traces were determined to be too inductive would be to place small solder lugs under the two transistor mounting screws and position them so that they can be soldered to both transistor emitter terminals. One on each side of each transistor. Be very careful not to ground out any other terminals in this area. Don&#039;t place this amp in a positive ground vehicle after this mod.</blockquote>

[QUOTE="Shockwave, post: 198509, member: 10882"] You're welcome. My first question would be what are you seeing that makes you think the amp is unstable in high power. Are you seeing significant increase in antenna SWR on high power that might indicate an oscillation? When using high power on SSB do you see signs of a sustained signal between words? If so it's probably not stable. Drive level can effect an oscillation but the problem is within the amp design if see you these symptoms. What is usually the case is that in lower power modes resistive attenuators are switched in line and this can reduce the likelihood of an oscillation. As you switch to higher power most of the attenuator is removed. Another way to reduce this problem if the amp is able to handle the drive on high power would be to bypass the power level switch and replace it with a tuned input circuit. One way to improve the ground to the transistors in the event PC board traces were determined to be too inductive would be to place small solder lugs under the two transistor mounting screws and position them so that they can be soldered to both transistor emitter terminals. One on each side of each transistor. Be very careful not to ground out any other terminals in this area. Don't place this amp in a positive ground vehicle after this mod. [/QUOTE]

Top Bottom