Tio Pedro wrote:
"ken scharf" wrote in message
.. .
raypsi wrote:
On Dec 25, 12:46 pm, raypsi wrote:
On Dec 24, 8:58 pm, Bill M wrote:

I'm a little confused again.
Setting up a 1624 tube for cathode biasing and also need to create a
center tap for keying to ground.
The book says 610 ohms at my voltage. So would I use a pair of 1200
ohm
resistors in this case?
My logic is since there is not a separate cathode then the two R in
parallel would raise the filament 'cathode' 600 ohms above B-minus.
TIA and Merry Christmas,
Bill
hey OM:

Exactly and you will need at least 10 watts of resistors to be safe.
Because they also will have to handle plate, grid1, grid2, and the
current they draw across the filament. I suppose if they where wire
wound like 25 watt you could stick a ferrite rod in their hole and
make them your filament chokes also. But if you use carbon comp
resistors then part of your drive will go heating those resistors, so
not much gain going on there.

73 OM
n8zu
Well they ain't filament chokes, but in the drive circuit the drive
signal won't go to heating them up if they are chokes. So they will
only be taking about 1 mil of current from the filament circuit.

73
n8zu
One possible problem. If this is an RF amplifier circuit you probably
want to use NON-INDUCTIVE resistors in the circuit or they WILL act as
chokes!

Would that make a difference? I'd also assume there's two RF cathode
bypass caps in there; otherwise the circuit would be extremely
degenerative.

Pete


So long as the inductance of the resistors doesn't resonate with the
bypass capacitors at some frequency of interest.

ken scharf wrote:

So long as the inductance of the resistors doesn't resonate with the
bypass capacitors at some frequency of interest.

Thanks for all the tips, guys.

-Bill

"ken scharf" wrote in message
. ..
Tio Pedro wrote:
"ken scharf" wrote in message
.. .
raypsi wrote:
On Dec 25, 12:46 pm, raypsi wrote:
On Dec 24, 8:58 pm, Bill M wrote:

I'm a little confused again.
Setting up a 1624 tube for cathode biasing and also need to create a
center tap for keying to ground.
The book says 610 ohms at my voltage. So would I use a pair of 1200
ohm
resistors in this case?
My logic is since there is not a separate cathode then the two R in
parallel would raise the filament 'cathode' 600 ohms above B-minus.
TIA and Merry Christmas,
Bill
hey OM:

Exactly and you will need at least 10 watts of resistors to be safe.
Because they also will have to handle plate, grid1, grid2, and the
current they draw across the filament. I suppose if they where wire
wound like 25 watt you could stick a ferrite rod in their hole and
make them your filament chokes also. But if you use carbon comp
resistors then part of your drive will go heating those resistors, so
not much gain going on there.

73 OM
n8zu
Well they ain't filament chokes, but in the drive circuit the drive
signal won't go to heating them up if they are chokes. So they will
only be taking about 1 mil of current from the filament circuit.

73
n8zu
One possible problem. If this is an RF amplifier circuit you probably
want to use NON-INDUCTIVE resistors in the circuit or they WILL act as
chokes!

Would that make a difference? I'd also assume there's two RF cathode
bypass caps in there; otherwise the circuit would be extremely
degenerative.

Pete
So long as the inductance of the resistors doesn't resonate with the
bypass capacitors at some frequency of interest.

But would the impedance ever be lower than the ohmic resistance
for the resistor?

Tio Pedro wrote:
"ken scharf" wrote in message
. ..
Tio Pedro wrote:
"ken scharf" wrote in message
.. .
raypsi wrote:
On Dec 25, 12:46 pm, raypsi wrote:
On Dec 24, 8:58 pm, Bill M wrote:

I'm a little confused again.
Setting up a 1624 tube for cathode biasing and also need to create a
center tap for keying to ground.
The book says 610 ohms at my voltage. So would I use a pair of 1200
ohm
resistors in this case?
My logic is since there is not a separate cathode then the two R in
parallel would raise the filament 'cathode' 600 ohms above B-minus.
TIA and Merry Christmas,
Bill
hey OM:

Exactly and you will need at least 10 watts of resistors to be safe.
Because they also will have to handle plate, grid1, grid2, and the
current they draw across the filament. I suppose if they where wire
wound like 25 watt you could stick a ferrite rod in their hole and
make them your filament chokes also. But if you use carbon comp
resistors then part of your drive will go heating those resistors, so
not much gain going on there.

73 OM
n8zu
Well they ain't filament chokes, but in the drive circuit the drive
signal won't go to heating them up if they are chokes. So they will
only be taking about 1 mil of current from the filament circuit.

73
n8zu
One possible problem. If this is an RF amplifier circuit you probably
want to use NON-INDUCTIVE resistors in the circuit or they WILL act as
chokes!
Would that make a difference? I'd also assume there's two RF cathode
bypass caps in there; otherwise the circuit would be extremely
degenerative.

Pete
So long as the inductance of the resistors doesn't resonate with the
bypass capacitors at some frequency of interest.

But would the impedance ever be lower than the ohmic resistance
for the resistor?


It would be an inductor with very low Q.

"ken scharf" wrote in message
.. .
Tio Pedro wrote:
"ken scharf" wrote in message
. ..
Tio Pedro wrote:
"ken scharf" wrote in message
.. .
raypsi wrote:
On Dec 25, 12:46 pm, raypsi wrote:
On Dec 24, 8:58 pm, Bill M wrote:

I'm a little confused again.
Setting up a 1624 tube for cathode biasing and also need to create
a
center tap for keying to ground.
The book says 610 ohms at my voltage. So would I use a pair of
1200 ohm
resistors in this case?
My logic is since there is not a separate cathode then the two R in
parallel would raise the filament 'cathode' 600 ohms above B-minus.
TIA and Merry Christmas,
Bill
hey OM:

Exactly and you will need at least 10 watts of resistors to be safe.
Because they also will have to handle plate, grid1, grid2, and the
current they draw across the filament. I suppose if they where wire
wound like 25 watt you could stick a ferrite rod in their hole and
make them your filament chokes also. But if you use carbon comp
resistors then part of your drive will go heating those resistors,
so
not much gain going on there.

73 OM
n8zu
Well they ain't filament chokes, but in the drive circuit the drive
signal won't go to heating them up if they are chokes. So they will
only be taking about 1 mil of current from the filament circuit.

73
n8zu
One possible problem. If this is an RF amplifier circuit you probably
want to use NON-INDUCTIVE resistors in the circuit or they WILL act as
chokes!
Would that make a difference? I'd also assume there's two RF cathode
bypass caps in there; otherwise the circuit would be extremely
degenerative.

Pete
So long as the inductance of the resistors doesn't resonate with the
bypass capacitors at some frequency of interest.

But would the impedance ever be lower than the ohmic resistance
for the resistor?


It would be an inductor with very low Q.

Yes, but it is still Hi Z, the resistive portion
is in series with the inductive reactance.

Pete