Amps
[Top] [All Lists]

Re: [Amps] Choke input filters, design criteria?

To: "Bill Turner" <dezrat1242@yahoo.com>, "Amps" <amps@contesting.com>
Subject: Re: [Amps] Choke input filters, design criteria?
From: "Carl" <km1h@jeremy.mv.com>
Date: Wed, 19 Dec 2012 15:44:01 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>

----- Original Message ----- From: "Bill Turner" <dezrat1242@yahoo.com>
To: "Amps" <amps@contesting.com>
Sent: Monday, December 17, 2012 10:35 PM
Subject: Re: [Amps] Choke input filters, design criteria?


ORIGINAL MESSAGE:
On Mon, 17 Dec 2012 17:36:26 +0000, Chris wrote:

I am
wondering if I should attempt to use it rather than a capacitive input
filter?

REPLY:
Choke input filters are a holdover from the old AM transmitter days
when current draw was relatively constant and HV capacitors were
expensive. Today's amps for SSB and CW need a constant voltage source,
not a constant current one. If you use a choke in a power supply where
the current draw varies a lot, you will see the output voltage
swinging widely, just what you do not want.

Toss the choke. Capacitors only.

73, Bill W6WRT


BCB transmitters often run the Class AB thru B modulators from the same PS as the Class C final so there is certainly a wide current variation. Voltage regulation is helped by the combination of the Class C load and value of the input choke.

Hams can use a choke to limit an otherwise too high B+ and/or to be able to use a high impedance old style transformer. The DC resistance of those transformers is also much higher, often a factor 0f 10-20 or more.

With a sufficient choke value and constant current load to substitute for the Class C final such as a healthy bleeder resistor, they can be used on ham CW/SSB. Not very efficiently tho. In the old days the HV PS was controlled by a toggle switch or PTT activating a relay in the transformers primary. This did away with a big part of the resistive load. Certainly not very practical for VOX, QSK, etc, but fine for PTT or a foot switch.

Carl
KM1H
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps

<Prev in Thread] Current Thread [Next in Thread>