There is a way to clean up EBS circuits, I did it a number of years ago and have never once had comment that the improvement isn't short of spectacular. I have a 4CX250B 2 meter amp I built a number
** That there is no reason to switch to not-linear bias during a spoken word. I can spot RF-actuated EBS on the air by the rough sound and increased splatter. - There is no reason to ever switch the
The EBS circuit goes in the cathode/grid path, I.E. cathode to ground (grid). It is installed from the anode of the bias zener to ground (grid) and the B- goes to the junction of the bias zener catho
Ahh - when you mentioned 250s on 2m I jumped to the assumption that it would be the regular grounded cathode, grid driven arrangement and I couldn't figure how the capacitor helped in that situation.
This is the aim. EBS seems to have a poor reputation because of either: 1. Being the only means of keying the amplifier, which is guaranteed to cause hot-switching. Competent EBS works along with th
? Good points, Ian. The solution is to allow the transceiver to control the EBS with its +DC-V on Tx signal. This gives the RF relay contacts in the amplifier at least a 5mS headstart so they can be
It is a grid driven amp. Isn't bias between the cathode and grid? Works the same way, just has grid current flowing through it rather than cathode and grid current. Mark WB8JKR On Mon, 4 Aug 2003 07:
OK - if you're running grid current. You wouldn't normally do so with speech, in which case I figured the capacitor wouldn't do much. If you're keying, does the delayed turn on matter? An alternative
The logic would be to kick the EBS on immediately the PTT line goes low (TX). When the PTT goes high, release the EBS after a short delay (because transceivers typically output RF for a few ms after
** What about those who do not use PTT -- i.e., folks like yours truly who use VOX? In this case, the (+DC-V on Tx) signal switches between +12V or so on Tx and 0V on Rx. This signal is ideal for co
Are EBS circuits worthwhile..? - I would venture to say there is little time where a radio driving an amplifier (combination) has no RF output in the transmit mode. Even quiet station transceivers ha