[Amps] 4-1000A in Passive grid-driven use?
R.Measures
r at somis.org
Fri Apr 30 11:01:06 EDT 2004
On Apr 30, 2004, at 6:32 AM, Bill L. Fuqua wrote:
>
> I don't know if anyone has actually made a cathode driven biased
> 4-1000A AB1 amplifier but it should be very low in distortion
> compared to either zero bias grounded grid or common cathode
> operation. That is because of the fact that there would be very
> little grid current
AB1 means there is zero grid-current. AB2 means there is some
grid-current.
> and the plate RF current would be the same as the drive RF current and
> the power gain would come from the ratio of cathode drive impedance
> and plate impedance. If the plate impedance was 5000 ohms and drive
> impedance 200 ohms then the power gain would be 25 or so.
Since there is zero signal potential applied between the grid and
the cathode, the power gain of a Class AB1 / "super cathode
driven"stage is roughly the grid-screen amplification factor -- which
is typically 4 to 6 in most tetrodes.
> It would be interesting to try. I expect that the cahtode impedance
> would be somewhere between 100 and 200 ohms. It should be somewhat
> greater that gg due to the greately reduced grid current.
> And just about all of your drive power would pass thru to the
> output.
Agreed, Bill. cheerz
>
> 73
> Bill wa4lav
>
> 73
> Bill wa4lav
> -----Original Message-----
> From: "R.Measures" <r at somis.org>
> To: n7ioh <n7ioh at cybertrails.com>
> Date: Wed, 28 Apr 2004 20:39:43 -0700
> Subject: Re: [Amps] 4-1000A in Passive grid-driven use?
>
>
> On Apr 28, 2004, at 12:38 PM, n7ioh wrote:
>
>> Are there any problems in using the 4-1000A in a passive
>> grid-driven mode on 160 - 10 meter or on 6 meters?
>
> � Above 30m, it's a good idea to tune out the grid's XC. See:
> http://www.somis.org/D_a_05.GIF
> The XL of L1 tunes out the grid's XC for whatever frequency you choose.
> note -- this is the first step in tuning up such a machine. .
>
>> If not, what kind of output can I expect to get?
>
> � Depends on anode V and screen V. With 7kV and 1kV, you should be
> able to get 2.6 out.
>
>> Second, I have seen amps that use a roller inductor and not a band
>> switch, any thoughts?
>
> � They provide the best match over a wide frequency range.
>
> Richard L. Measures, AG6K, 805.386.3734. www.somis.org
>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
>
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
More information about the Amps
mailing list