Which types of ferrite toroids and capacitors would be recommended
for an antenna tuner that is to be used 1.5 MHz - 30 MHz (possibly
up to 50 MHz)? Max. transmit power is 100 ~ 150 W.

Ideally I would prefer components that are available from either
RS (rswww.com) or Farnell (uk.farnell.com).

Farnell do toroids from N27, N30, 3C85, 3R1, 4C65, 3E5 and 3E25
materials; which ones are suitable for broadband HF power applications?

For the capacitors, would any of the surface mount types be suitable?

Thanks,

John

Exactly what "broadband HF power application" do you have in mind? A
single transformer or balun covering the whole band? Capacitors are
usually avoided in broadband applications. How will you be using them?

Are you a licensed amateur?

Roy Lewallen, W7EL

John Laczik wrote:
Which types of ferrite toroids and capacitors would be recommended
for an antenna tuner that is to be used 1.5 MHz - 30 MHz (possibly
up to 50 MHz)? Max. transmit power is 100 ~ 150 W.

Ideally I would prefer components that are available from either
RS (rswww.com) or Farnell (uk.farnell.com).

Farnell do toroids from N27, N30, 3C85, 3R1, 4C65, 3E5 and 3E25
materials; which ones are suitable for broadband HF power applications?

For the capacitors, would any of the surface mount types be suitable?

Thanks,

John

Roy,

Exactly what "broadband HF power application" do you have in mind?

Sorry, I should have been more precise. What I wrote referred to
an antenna tuner that covers the various ham/marine bands in the
1.5 MHz to 50 MHz range, i.e inductors and capacitors that are
suitable for use in this 'broad' frequency range. Also, the antenna
tuner probably will have a balun in it, which would not be tuned
and hence would be broadband.

Are you a licensed amateur?

Yes.

How will you be using them?

I am trying to set up a rig on a boat, and one of the options is to
make a remote controlled antenna tuner for RX, and up to ~100W TX,
instead of using one of the rather expensive commercial units. The
antenna/tuner will be used to receive marine weather transmissions,
and for CW QSOs on the ham bands.

Thanks,

John, HA5PG/MM

Don't think it is really necessary to use (ferrite) toroids for a
compact 100W capable HF antenna matching unit.
Depending on type of antenna a simple variable capacitor(s) /variable
roller inductor unit will highly likely do the trick, even if remotely
operated.
If the unit needs to have a balun ,you obviously want to use a balanced
feeder, but it is doubtful that an exposed balanced feeder in a 'salt
spraying environment' will be effective.

Frank GM0CSZ / KN6WH

================
Sorry, I should have been more precise. What I wrote referred to
an antenna tuner that covers the various ham/marine bands in the
1.5 MHz to 50 MHz range, i.e inductors and capacitors that are
suitable for use in this 'broad' frequency range. Also, the antenna
tuner probably will have a balun in it, which would not be tuned
and hence would be broadband.

I am trying to set up a rig on a boat, and one of the options is to
make a remote controlled antenna tuner for RX, and up to ~100W TX,
instead of using one of the rather expensive commercial units. The
antenna/tuner will be used to receive marine weather transmissions,
and for CW QSOs on the ham bands.

Thanks,

John, HA5PG/MM

John,

I designed some automatic tuners on the market. It was a very lengthy
process in selecting components and laying out circuit boards. It
really is a much better value to just buy one, unless you want to learn
how to design a tuner.

You probably want powdered iron mixes for low frequencies (larger
inductor values) and air core coils for small values.

The capacitors would have to be silver mica types although you might
find some high current high Q multi-layer ceramics that will work.
There is no reason to go much over the contact voltage breakdown of the
relays when picking capacitor voltage, since the relay would fail
first. Current is another issue. You must obtain capacitors that handle
high current, meaning the capacitor must have low ESR. As a general
rule that would mean a snubber mica capacitor or a multi-layer HV chip
capacitor.

Relay selection is critical. I cut dozens of relays open looking for
good candidates, and then HV tested and RF tested the relays for
breakdown voltage. A DC test will not work.

It's pretty tough to build an automatic tuner that will handle 100
watts or more into a wide range of load impedances. Most of the problem
is parts selection and board layout.

73 Tom