From: firstname.lastname@example.org (carltons)
Subject: Re: Improving a Grid Dip Meter
User-Agent: NewsWatcher-X 2.2.3b2
NNTP-Posting-Date: Wed, 25 Dec 2002 12:44:30 GMT
Date: Wed, 25 Dec 2002 12:44:30 GMT
In article ,
email@example.com (N. Thornton) wrote:
> Paul Burridge wrote in message
> > Hi all,
> > I have a fairly oldish (say 1970) GDM which can also function
> > (theoretically at any rate) as a relative field-strength meter.
> > However, it's pretty 'deaf' so the later functionality of it is
> > impaired. The degree of dip when sussing out plain tuned-circuits is
> > also pretty lousy. Taking the back off shows the amplifying section of
> > this unit to consist of two elderly-looking tin-cased 2SB422
> > transistors which for some reason are soldered in circuit with full
> > inch-and-a-half leads. Seems a bit odd given the claimed top-end
> > frequency response of 280Mhz. Anyway, what, in the view of the panel,
> > are the most suitable up-to-date devices to replace 'em with in order
> > to improve sensitivity?
> > thanks
I gather from the info given that the two transistors are part of the post
processing of the "grid dip". Germanium alloy transistors had Ft's way
too low to be usable at 260 MHz. I would guess that your active element
would be a 6CW4 or some other such tube. If my guess is correct, then
replacing the transistors can be done, but would probably not fix your
problem adequately. You would be better off taking the advise given you
already from others and try and salvage what you can from the present grid
dipper, such as the case, meter, supply, etc.
Good luck and happy trails.