Re: [EVGRAY] Re: ? using LNA for front end of PA

Body

Hector,

Can you explain a co-phaser?  Do you mean a feedforward system?

Removing the feedback loop on SS RF causes all sorts of oscillation issues.

Most SS amp circuits are designed improperly requiring loop feedback.
Tubes at least one can remove the loop add a larger grid stopper and not
run into the more serious problems of solid state as a triode has
natural cathode feedback kind of built in. 


On 3/26/2018 4:45 AM, [email protected] [EVGRAY] wrote:
>  
>
> He will also need a phase shifter  in order to mitigate destructive
> feedback if designing an amplifier , that is if you don't want
> destructive feedback on intent to create a ZPE amplification loop ,
> then you need a co-phaser circuit to enhance the condition , RF-RE
> expertise is not gained in a day neither in doctorate degrees , its
> gained at the lab doing heavy R&D ..
>
> (H)
>
>
>
> ---In [email protected], <onielsen@...> wrote :
>
> Hi Mick,
>
> At those frequencies the energy is very radiant. Everything has to be
> made according to RF rules and treated as transmission lines. Else the
> signal doesn't follow the signal path as planned. Any change in
> impedance reflects or splits the signal. Read Ivor Catt on this even
> though he explains it using digital signals. If attaching a current
> buffer everything has to match. I haven't worked on such high
> frequencies. If trying this at least know the theory behind it or have
> the measuring instruments for this frequency range.
>
> This site (http://nov79.com/amr/cont.htm) shows how to make a simple
> current amplifier by using matched bipolar transistors. The upper
> frequency is only limited by the upper frequency of the transistors.
> This can be 40MHz for an audio amplifier. This may cause oscillations
> at the max frequency if not done the correct way.
>
> What about a small 3W broadband power amplifier module:
> https://www.ebay.com/itm/1-1000MHz-3W-RF-Broadband-Power-Amplifier-Module-Radio-Transmission-FM-VHF-/183031453375
> It only goes to 1GHz.
>
> Google search for 'broadband power amplifier module':
> https://www.google.dk/search?source=hp&ei=c8G4Wuv0LIXbwALZxJTQDw&q=broadband+power+amplifier+module&oq=broadband+power+ampli&gs_l=psy-ab.3.2.0l2j0i22i30k1l8.1878.9748.0.22828.21.20.0.1.1.0.104.1822.18j2.20.0....0...1c.1.64.psy-ab..0.21.1820...46j0i46k1j0i10k1.0.jIuIG0_77XA
>
> Or search 'rf power amplifier module'
>
> Regards
> Ole
>
>
> ---In [email protected], <mkjekyll@...> wrote :
>
> Ole,
>
> What would be the negative issues trying to attach a FET current buffer
> to an LNA in order to make a few watt wideband RF amplifier?
>
> As I am an audio guy I am paralleling this to an audio amp seems simple
> a voltage gain stage and then a current gain or buffer stage.
>
> There are plenty of cheap LNA's that are very wideband like this 
> https://www.ebay.com/itm/New-1MHz-2GHz-64dB-Gain-LNA-RF-Broadband-Low-Noise-Amplifier-Module-HF-VHF-UHF/232103825103?hash=item360a774ecf:g:iCQAAOSwgu9ZZEBg
>