On Sun, 31 Aug 97 11:31:40 -0800 Rich Measures <measures@vc.net> writes:
>>
>>On Sun, 31 Aug 1997 07:08:12 +0200 lars.harlin@pocab.se (Lars Harlin)
>>writes:
>>>Have followed the discussions abt VHF parasitics on the reflector
>and
>>>other media. Has anyone tried using ferrit in a suppressor?
>>>
>>>Lars / SM3BDZ
>>>
>>
>>The only amps I am aware of were the Heath SB-230 ...
>
>In the SB-230, the ferrite bead is only in series with the HV-RFC. It
>is
>not in series with the anode's VHF-resonant circuit - i.e., the
>circuit
>which supports oscillation.
There were 2 bead placements used by Heath. The QST review mentioned the
Heath change bulletin to the wiring "to eliminate a parasitic problem"
on 10M.
The SB-230 manual I have shows, in the pictorial, a standard arrangement,
not in series. I do not know which version was the later but I always
rewired anyway with a real suppressor. The 8873 costs more now than a
clean SB-220!
73...Carl KM1H
>
>> ... The Heath was a disaster and blew many tubes.
>
>Amen, Carl. With no VHF suppressor in the anode's VHF-resonant
>circuit,
>the life of a high VHF gain tube is often brief. The AL-1500 is
>another
>such amplifier. A number of owners told me that their's went through
>a
>number of 8877s during the first year. One of them discovered the
>seemingly-bizarre technique for making some gold-sputtered 8877s
>useable.
>
>Rich---
>
>R. L. Measures, 805-386-3734, AG6K
>
>
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