[Amps] Ten-Tec Centurion

[R.Measures]

On Nov 11, 2004, at 6:13 AM, Bill Fuqua wrote:

>         I just took a look at some of the emails on this subject. 
> Saying that please pardon any repetition of anything previously 
> mentioned.
>
>         When the amplifier is in idle state what impedances does it 
> see on the input and output. Unloaded amplifiers are prone to 
> oscillate at times at resonance not necessarily at VHF frequencies.

Bill --- At HF, there is unlikely to be enough be enough feedback 
through 0.3pF (20k-ohms at 28MHz) of anode-cathode C to support 
regeneration.

> The parasitic suppressors only eliminate VHF parasitic oscillations.

In my experiences, VHF parasitic suppressors reduce the chances of 
having one, but they do not eliminate them.

>         If the cut off bias is removed before the relays make solid 
> contact for on the input an output the amplifier may momentarily 
> oscillate. Or it may just  amplify the incoming signal and if the 
> output is not loaded  (output contacts not closed quite yet) create a 
> very large voltage across the contacts.
>         Perhaps the problem is that the bias needs simply needs to be 
> removed a bit later.
>
>

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org