Steve Thompson wrote:
>On Sunday 27 October 2002 15:54, Radio WC6W wrote:
>> That sounds like a Microwave Associates part number.
>
>Agreed.
My guess too, though it may have been a special for Bird.
>>
>>
>> You might try substituting a 1N5711 or 1N5712 schottky... or an HP
>> 5082-2800.
>
I'll try that.
>In V/UHF slugs, the diode is a UHF germanium type and I've had good
>success replacing it with a low barrier shottky. In these slugs,
>there's a series resistor for cal, typically 25-30k. Even though it's
>variable, the voltage drop will tend to iron out small differences
>between diodes.
>
Good point. In the 1000H there's a fixed 2.102K resistor in series with
a 20.3K (where do they get these weird values?).
>At a wild guess, the cal might be done with the position of the ferrite
>while the glue is wet?
Doesn't seem to be. The winding on the ferrite makes a fixed-ratio
current transformer which samples the current in the one-turn pickup
loop. The ferrite bobbin has square ends that make a former for the
pickup loop which is bent around it. Really nothing much can move.
Maybe that 20.3K series resistor is selected on test. After the repair
it's probably going to be a trimpot anyhow.
Thanks for all the help, everyone.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
|