>
>
>
>On Mon, 28 Dec 1998 10:03:02 -0800 Rich Measures <measures@vc.net>
>writes:
>
>SNIP
>
>>Ä However, some various fault possibilities.
>>1. A gas flashover in the tube due to a leaky seal.
>>2. The anode touches the grid (some 3-500Zs)
>>3. An intermittent vhf parasite generates a large burst in
>>grid-current.
>>
>>- - Each of these faults makes the grid dangerous to an EBS, so
>>rugged protective measures would still be necessary. // Another issue is
>>RF-input actuated transmit/receive bias switching. A friend recently
>>purchased such an amplifier (a 91B), and it generates a pecuilar type of
>>IMD as the amplifier rapidly switches from Tx-bias to Rx-bias between
>>syllables of speech. At the risk of being boring, I believe it is a
mistake to
>>allow the bias to switch to Rx (cut-off) mode at any time when
>>the amplifier relays are in Tx mode.
>
>So what do you think, specifically and not rhetorically, about the EBS in
>the MFJ AL80B?
>Any hard data such as measurements to share with the reflector?
>
>BTW, I agree that EBS systems as implemented in ham amps are inherently
>IMD and splatter producers. Just wondering if anyone has some hard facts.
>
? I have no laboratory measurements, Carl. I listen on the air with a
double filter Rx, measure the signal strengths on the fundamental and on
the adjacent channels 3.5 KHz up and 3.5KHz down. I hear adjacent
channel feculence from RF-actuated bias switching.amplifiers that I do
not hear from amplifiers whose bias switch is synchronized with the RF
relays. However, there is nothing illegal about rotten splatter unless
it goes beyond the edge of the amateur radio service band.
- later, Carl.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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