I am looking for the following, in new or in good used condition:

NATIONAL R-175 R-F PLATE CHOKE

Specifications: The R-175 transmitting R-F Choke is suitable for
parallel feed as well as series-feed circuits in transmitters of
up to 3000 volts plate supply. If plate modulation is not
employed, the chokes may be applied to transmitters operating at
voltages up to 4000.

Thanks,

David Goncalves

In article . com,
Dave Goncalves wrote:
I am looking for the following, in new or in good used condition:

NATIONAL R-175 R-F PLATE CHOKE

Specifications: The R-175 transmitting R-F Choke is suitable for
parallel feed as well as series-feed circuits in transmitters of
up to 3000 volts plate supply. If plate modulation is not
employed, the chokes may be applied to transmitters operating at
voltages up to 4000.

Give me a resistance value and an inductance value and I'll tell you
what the current Miller part number is.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Give me a resistance value and an inductance value and I'll tell you
what the current Miller part number is.

Scott,

This is a pretty special job, a custom stepped coil form with seperate
litz windings on each.
I don't think Miller has what I'm looking for. If it came to replacing
the current choke with another model, I've already got several in the
junkbox. What I'm looking for is an exact match to fit in the old
location. The amplifier I'm working with has a very nice period layout
I'm trying to preserve.

But, what the hay, see below:

The characteristics of the R-175 choke a

Voltage breakdown to metal base 12,500 volts.
D.C. Resistance 6 ohms.
D.C. Current Rating 800 ma.
Inductance 225 microhenries
Distributed Capacity 0.6 micromicrofarad.

Thanks for the help,

Dave Goncalves

Dave Goncalves wrote:

This is a pretty special job, a custom stepped coil form with seperate
litz windings on each.
I don't think Miller has what I'm looking for. If it came to replacing
the current choke with another model, I've already got several in the
junkbox. What I'm looking for is an exact match to fit in the old
location. The amplifier I'm working with has a very nice period layout
I'm trying to preserve.

But, what the hay, see below:

The characteristics of the R-175 choke a

Voltage breakdown to metal base 12,500 volts.
D.C. Resistance 6 ohms.
D.C. Current Rating 800 ma.
Inductance 225 microhenries
Distributed Capacity 0.6 micromicrofarad.

Okay, this is all easy to do, EXCEPT for that breakdown voltage rating.
A 2116-H will actually have substantially _less_ DC resistance, and
really only slightly lower Q. But the breakdown voltage is probably
higher. The litz wire design is basically to improve the filter Q,
but these days with modern ferrites you can make coils of the same value
with fewer turns, which reduces the necessity.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Dave Goncalves wrote:
I am looking for the following, in new or in good used condition:

NATIONAL R-175 R-F PLATE CHOKE


Will these do?

http://www.k6mhe.com/n7ws/R175A.jpg

They really aren't bent, that's just distortion in the photo.

Wes, N7WS