High power tuning caps?
 

As we seem to be winning the battle in part against the ne'er-do-wells
and their attention-seeking gratuitously abusive personal attacks, what
technical
matters can we discuss today to keep the momentum going?

How about is anyone still making their own wide spaced tuning caps for their
ATUs by
lots of shaped aluminium (aluminum to the Yanks) plates, or has the Cheque
Booker's (CBers)
approach of using auto ATUs taken over?

High power tuning caps?
 

In rec.radio.amateur.antenna gareth wrote:
As we seem to be winning the battle in part against the ne'er-do-wells
and their attention-seeking gratuitously abusive personal attacks, what
technical
matters can we discuss today to keep the momentum going?

How about is anyone still making their own wide spaced tuning caps for their
ATUs by
lots of shaped aluminium (aluminum to the Yanks) plates, or has the Cheque
Booker's (CBers)
approach of using auto ATUs taken over?

Fixed components and relay switching with computer control have taken
over.


--
Jim Pennino

High power tuning caps?
 

On 30/11/15 18:39, wrote:

Fixed components and relay switching with computer control have taken
over.



To a large degree but a motorised roller coaster and variable
capacitor(S) can still prove a useful set up. I used to run just such a
setup, with the L&C positioned near the feed point. A couple of motors
with a simple gear chain etc. and some limit switching can be build in a
few hours. I had previously drawn out a simple method for others and had
seen it working. Even without any feedback to the operating desk it was
surprisingly easy to use.

I've used a tapped coil and switch caps as well (also remotely) but the
motorised system gave better control and, once tuned, didn't require power.

I now use an Auto ATU (an SGC) which is marginally quicker to use.

High power tuning caps?
 

On Mon, 30 Nov 2015 16:23:24 -0000, "gareth"
wrote:

"High power tuning caps?"

Wrong questions. Reactive components do NOT dissipate power. Only
the real part of the impedance puzzle, the resistances, dissipate
power. For tuning caps, you're interested in High Voltage, High
Current, and Dissipation Factor, not High Power.

As we seem to be winning the battle in part against the ne'er-do-wells
and their attention-seeking gratuitously abusive personal attacks, what
technical
matters can we discuss today to keep the momentum going?

You can start by eliminated any references to those you allegedly find
offensive. In the midaeval manner, mentioning someones name causes
them to appear.

How about is anyone still making their own wide spaced tuning caps for their
ATUs by
lots of shaped aluminium (aluminum to the Yanks) plates, or has the Cheque
Booker's (CBers)
approach of using auto ATUs taken over?

There are kits available. For example:
http://www.monarchcapacitors.com
Most are used in magnetic loop transmitting antennas, which require
both high voltage and high current features. I haven't been following
the latest in ATU's but as I skim the literature, microprocessor
controlled relays switching capacitors in and out seem to be the
fashion instead of variable capacitors.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

High power tuning caps?
 

On Mon, 30 Nov 2015 21:14:47 +0000, Brian Reay wrote:

I've used a tapped coil and switch caps as well (also remotely) but the
motorised system gave better control and, once tuned, didn't require power.

Not exactly. The relays in most ATU's are magnetically latched and
will maintain their state when power is removed. That's how they get
low power operation.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

High power tuning caps?
 

On Mon, 30 Nov 2015, gareth wrote:

As we seem to be winning the battle in part against the ne'er-do-wells
and their attention-seeking gratuitously abusive personal attacks, what
technical
matters can we discuss today to keep the momentum going?

How about is anyone still making their own wide spaced tuning caps for their
ATUs by
lots of shaped aluminium (aluminum to the Yanks) plates, or has the Cheque
Booker's (CBers)
approach of using auto ATUs taken over?

Nobody has yet come up with a replacement for high voltage variable
capacitors, so they still have to be made. It's low level capacitors that
are getting scarcer.

But I'm not sure that's a reality. I scrapped some old tube two-way radio
strips a few weeks ago, realizing I'd never use them, and got some
variables from that. There is still lots of equipment out there that can
offer up variables, though maybe not high voltage ones. Keep an eye out
for old radios, grab the variables from them if nothing else.

There may be enough high voltage variable capacitors out there for those
who need them. It's just a matter of shaking them out of someone's junk
box.

There have also been some articles in the past (maybe recently but I
haven't seen any ham magazines up close in a long time) about making your
own high voltage variables. And int he early days of radio, there were
aritcles about making variable capacitors (albeit for non-power
applications), so looking for those will likely offer up some useful
details.

Transmitting loops need high voltage caps, so that's where some of the
build it yourself information resides.

Michael

High power tuning caps?
 

In uk.radio.amateur gareth wrote:

How about is anyone still making their own wide spaced tuning caps for
their ATUs by lots of shaped aluminium (aluminum to the Yanks) plates,
or has the Cheque Booker's (CBers) approach of using auto ATUs taken
over?

Stop messing about with ATUs and erect a resonant antenna.


--
Mouse.
Where Morse meets House.

High power tuning caps?
 

On Mon, 30 Nov 2015 17:51:13 -0500, Michael Black
wrote:

Nobody has yet come up with a replacement for high voltage variable
capacitors, so they still have to be made.

I've done fairly well with window glass covered with aluminum foil.
Also HDPE (cutting board) dielectric. These are commonly used in
Tesla coils. Something like this:
http://www.deepfriedneon.com/tesla_f_calccap.html
I don't have any built right now, but they do work. The problem is
mechanical stability. When tuning a magnetic loop with one of these,
the adjustment is rather critical. My last experiment was to build
the tuning capacitor into a plastic box and compress it with a spring.
Adjusting the plates required considerable force, and some of the foil
was torn, but it was fairly mechanically stable. The idea was not so
much to have a variable glass capacitor, but rather adjusting the
capacitance in steps by adding or removing glass plates.

More tinkering is needed, which probably won't happen until summer.

Incidentally, plugging into the above calculator, two 3 x 3 inch
plates, with 0.125" glass dielectric, yields about 120 pF capacitance.
The same dimensions but using an air dielectric yields only 16 pF.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558