>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 have a minimal amount of RF output
>result from ambient room noise.
>-
>Add some compression and the story gets
>worse.
>-
>The last Alpha EBS circuit I tested, required less than
>a watt to activate ("trigger").
>-
>(The standby/receive mode of a standard amplifier
>most often cuts off the cathode current, as does
>the EBS type circuit )
>-
>As quiet as I can be, my peak reading watt meter
>and scope often indicate some RF output most
>of the time... even between words on breath and
>room noise. Is the EBS honestly helping much
>in linear mode operation when the input rarely
>falls below the control detector threshold in a
>typical amateur operation?
>-
>I can see the case for CW operation, but
>most SSB operators are going to bias on
>during most any portion of the transmit
>mode where the EBS is supposed to
>pay off..?
>-
>What might I be overlooking...?
>-
** 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 amplifier out of linear-bias
when the transceiver is in Tx mode.
>-
>From: 2 <2@vc.net>
>*** With no input RF, there is always zero RF circulating current, no
>matter what type of bias switch is used.
>-- . When SSB RF drive drops below the EB-switch threshold level
>during soft-syllables, the amplifier switches in and out of non-linear
>bias. This results in more IMD during soft-syllables. Another problem
>with RF-actuated bias switching is that there is no headstart for the
>amplifier's RF relay contacts to close before RF arrives. This results
>in hot-switching the RF input relay and the RF output relay in the
>amplifier. For AM and FM modes, RF-actuated bias switching does not
>switch during soft-syllables, so there is no added IMD, although the
>hot-switching problem still exists.
>>
>>Thanks!
>>
>> ***dan, K6IF
>
>Rich, AG6K, 805-386-3734, www.somis.org / new e-mail adr r@somis.org
>
>
>
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Rich, AG6K, 805-386-3734, www.somis.org / new e-mail adr r@somis.org
|