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Hey guys, a few things. ALWAYS remember.. a bias source needs to be a low impedance, high current, stable source.

The best, cheapest way to do this is with an AUX relay to turn the bias on and off during TX only. Do not forget to use RF bypassing in your circuit, lots of .01 caps and made sure you use RF chokes capable of carrying the current. About 10-22uh works great here.

As far as the wirewound resistor goes and its value, I think it is a bit too low. About 50-68 ohms would probably provide the current needed.

Also, don't forget a lot of these amps have the input transformer grounded directly effectively killing your bias either through a choke, piece of wire with RF beads on it or some other form. It is important to make sure that this is removed at DC potential but NOT at RF. If it is tied to ground, remove the source of the ground connection and use three .01 ceramic disk caps from the two now disconnected points to keep it at ground for RF.

Next..don't forget negative feedback. This is important to control gain (remember biasing an amp increases small signal gain) and you don't want the amp going into self oscillation or producing strange signals from being unstable. A .01 and 100 ohm non inductive metal film resistor at a couple watts works well here for most purposes.

Happy experimenting.

<blockquote data-quote="JustinDePolis" data-source="post: 368656" data-attributes="member: 9760">Hey guys, a few things. ALWAYS remember.. a bias source needs to be a low impedance, high current, stable source. The best, cheapest way to do this is with an AUX relay to turn the bias on and off during TX only. Do not forget to use RF bypassing in your circuit, lots of .01 caps and made sure you use RF chokes capable of carrying the current. About 10-22uh works great here.As far as the wirewound resistor goes and its value, I think it is a bit too low. About 50-68 ohms would probably provide the current needed.Also, don&#039;t forget a lot of these amps have the input transformer grounded directly effectively killing your bias either through a choke, piece of wire with RF beads on it or some other form. It is important to make sure that this is removed at DC potential but NOT at RF. If it is tied to ground, remove the source of the ground connection and use three .01 ceramic disk caps from the two now disconnected points to keep it at ground for RF.Next..don&#039;t forget negative feedback. This is important to control gain (remember biasing an amp increases small signal gain) and you don&#039;t want the amp going into self oscillation or producing strange signals from being unstable. A .01 and 100 ohm non inductive metal film resistor at a couple watts works well here for most purposes.Happy experimenting.</blockquote>

[QUOTE="JustinDePolis, post: 368656, member: 9760"] Hey guys, a few things. ALWAYS remember.. a bias source needs to be a low impedance, high current, stable source. The best, cheapest way to do this is with an AUX relay to turn the bias on and off during TX only. Do not forget to use RF bypassing in your circuit, lots of .01 caps and made sure you use RF chokes capable of carrying the current. About 10-22uh works great here. As far as the wirewound resistor goes and its value, I think it is a bit too low. About 50-68 ohms would probably provide the current needed. Also, don't forget a lot of these amps have the input transformer grounded directly effectively killing your bias either through a choke, piece of wire with RF beads on it or some other form. It is important to make sure that this is removed at DC potential but NOT at RF. If it is tied to ground, remove the source of the ground connection and use three .01 ceramic disk caps from the two now disconnected points to keep it at ground for RF. Next..don't forget negative feedback. This is important to control gain (remember biasing an amp increases small signal gain) and you don't want the amp going into self oscillation or producing strange signals from being unstable. A .01 and 100 ohm non inductive metal film resistor at a couple watts works well here for most purposes. Happy experimenting. [/QUOTE]

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