"Airy R.Bean" wrote -
Picking up a project that has been put down for 6 months - has
anybody got experience of manufacturing their own ATU
switches out of brass, either as knife switches or else as
ginormous banana plugs which then engage axially with
a sliding action?

I have conceived of a design for an experimental ATU that
allows changes of configuration (including the safety earthing
when not in use) using only 8 single-pole single throw switches,
into the most common configurations.

==================================

The trouble with as many as 8 single-throw, high-current, high-voltage
switches in a tuner, is the stray inter-component wiring and inductance and
capacitance they introduce.

Even with a minimum number of, or no switches, it requires TWO independent
tuners, in separate boxes with separate coaxial connectors, to cover the
range 1.8 to 30 Mhz with reasonable power efficiency.

You need practical experience by building one or two to see how they
perform. Try again and then come back!
----
Reg.

"Reg Edwards" wrote in message
...


The trouble with as many as 8 single-throw, high-current, high-voltage
switches in a tuner, is the stray inter-component wiring and inductance
and
capacitance they introduce.

Even with a minimum number of, or no switches, it requires TWO independent
tuners, in separate boxes with separate coaxial connectors, to cover the
range 1.8 to 30 Mhz with reasonable power efficiency.

You need practical experience by building one or two to see how they
perform. Try again and then come back!


Would a solution based on two, contra-rotatinng "roller coasters" not be
better? This would enable a true balanced ATU to be made, offering a wide
matching impedance, and, with motorised capacitor, avoiding switching all
together?

Making a suitable capacitor is straight forward. The rollor coaster former
will turn up on a lathe nicely (I've made a similar former from PTFE in the
past). The rest of the mechanics are easy enough.

--
Brian Reay
www.g8osn.org.uk
www.amateurradiotraining.org.uk
FP#898

Which is why I was considering the use of axially operated
banana-plug-like switches which would then exist in-line with the
wiring, and be operated by fishing line (in a sort of pull-in/pull-out
mode).

Knife switches of sufficient mechanical movement would also serve
to reduce capacitive coupling when open. Now that I mention it, I
do seem to remember discussing this before, especially with regard to
springy brass for knife switch contacts.

"Reg Edwards" wrote in message
...

"Airy R.Bean" wrote -
Picking up a project that has been put down for 6 months - has
anybody got experience of manufacturing their own ATU
switches out of brass, either as knife switches or else as
ginormous banana plugs which then engage axially with
a sliding action?

The trouble with as many as 8 single-throw, high-current, high-voltage
switches in a tuner, is the stray inter-component wiring and inductance
and
capacitance they introduce.

On Tue, 11 Jan 2005 17:32:28 +0000 (UTC), "Reg Edwards"
wrote:



The trouble with as many as 8 single-throw, high-current, high-voltage
switches in a tuner, is the stray inter-component wiring and inductance and
capacitance they introduce.

Even with a minimum number of, or no switches, it requires TWO independent
tuners, in separate boxes with separate coaxial connectors, to cover the
range 1.8 to 30 Mhz with reasonable power efficiency.

You need practical experience by building one or two to see how they
perform. Try again and then come back!
----
Reg.

not posted to uk.radio.amateur cb-group

Don't understand why one should make switches, they are offered in
large quantities at rallies and many other occasions


LA8AK
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm

You don't understand the interest and enthusiasm
that comes from doing things yourself?

Are you really a Radio Ham?

"J M Noeding" wrote in message
...
On Tue, 11 Jan 2005 17:32:28 +0000 (UTC), "Reg Edwards"
wrote:
The trouble with as many as 8 single-throw, high-current, high-voltage
switches in a tuner, is the stray inter-component wiring and inductance
and
capacitance they introduce.
Even with a minimum number of, or no switches, it requires TWO
independent
tuners, in separate boxes with separate coaxial connectors, to cover the
range 1.8 to 30 Mhz with reasonable power efficiency.
You need practical experience by building one or two to see how they
perform. Try again and then come back!
not posted to uk.radio.amateur cb-group
Don't understand why one should make switches, they are offered in
large quantities at rallies and many other occasions

On Wed, 12 Jan 2005 14:54:05 -0000, "Airy R.Bean"
wrote:

You don't understand the interest and enthusiasm
that comes from doing things yourself?

again xposted to the CB newsgroup I deleted in the first place.


Are you really a Radio Ham?


Radio amateurs have official callsigns, did you know? Non of your
postings indicates that you have such callsign to show us

---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm

As the originator of this thread, I retain the two groups to
which it was posted.

"J M Noeding" wrote in message
...
On Wed, 12 Jan 2005 14:54:05 -0000, "Airy R.Bean"
wrote:
You don't understand the interest and enthusiasm
that comes from doing things yourself?
again xposted to the CB newsgroup I deleted in the first place.

Or...I do when I remember to add it!

"Airy R.Bean" wrote in message
...
As the originator of this thread, I retain the two groups to
which it was posted.

"J M Noeding" wrote in message
...
On Wed, 12 Jan 2005 14:54:05 -0000, "Airy R.Bean"
wrote:
You don't understand the interest and enthusiasm
that comes from doing things yourself?
again xposted to the CB newsgroup I deleted in the first place.

"Airy R.Bean" wrote:


Are you really a Radio Ham?


Radio amateurs have official callsigns, didn't you know? Non of your
postings indicates that you belong to such group

LA8AK

---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm