Paul,
Once you get to these frequencies, it's often better and easier to use
transmission lines (microstrip) rather than lumped LC components.

What is the application?

Joe
W3JDR

"Paul Burridge" wrote in message
...
Hi guys,

I've just been doing some calculations out of sheer curiosity. It
turns out that to make a tank circuit for 450Mhz (which isn't *that*
high a frequency by today's standards) would take 5pF || 25nF. These
are both *very* low values. 5pF is getting perilously close to being
seriously affected by circuit board stray capacitance and 25nF isn't
much better; little more than a couple of turns of wire, I guess.
What does one do in such circumstances? Should one be thinking in
terms of etching these values out of the PCB by the time one gets of
to these frequencies, or is it still acceptable to make them up out of
discrete components?

p
--

The day Microsoft make a product that doesn't
suck, they'll be making vacuum cleaners.

On Mon, 26 Jan 2004 20:48:17 GMT, "W3JDR" wrote:

Paul,
Once you get to these frequencies, it's often better and easier to use
transmission lines (microstrip) rather than lumped LC components.

What is the application?

I'm just musing with the idea of building a TX for 70cm. Since it's
probably going to end up with a commercial, ready-built 3 stage 40W
module for the PA., I'm just considering what to use for the last
frequency multiplier and buffer stage...
--

The day Microsoft make a product that doesn't
suck, they'll be making vacuum cleaners.

Paul Burridge wrote:
On Mon, 26 Jan 2004 20:48:17 GMT, "W3JDR" wrote:


Paul,
Once you get to these frequencies, it's often better and easier to use
transmission lines (microstrip) rather than lumped LC components.

What is the application?


I'm just musing with the idea of building a TX for 70cm. Since it's
probably going to end up with a commercial, ready-built 3 stage 40W
module for the PA., I'm just considering what to use for the last
frequency multiplier and buffer stage...

Don't construct it like your FSM, please! 8-)

Leon
--
Leon Heller, G1HSM
Email:
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html

On Mon, 26 Jan 2004 23:17:50 +0000, Leon Heller
wrote:



Paul Burridge wrote:
On Mon, 26 Jan 2004 20:48:17 GMT, "W3JDR" wrote:


Paul,
Once you get to these frequencies, it's often better and easier to use
transmission lines (microstrip) rather than lumped LC components.

What is the application?


I'm just musing with the idea of building a TX for 70cm. Since it's
probably going to end up with a commercial, ready-built 3 stage 40W
module for the PA., I'm just considering what to use for the last
frequency multiplier and buffer stage...

Don't construct it like your FSM, please! 8-)

Hehe! No chance. :-)
On the subject of PA modules for the 400-500Mhz range, would anyone
care to recommend a suitable manufacturer?
--

The day Microsoft make a product that doesn't
suck, they'll be making vacuum cleaners.