🚀 go-pugleaf

This is sounding a little tricky for me...I don't suppose someone has some 
simple circuits I can work with. Like I said I am using a rf modulator on 
channel 0, Australian channel 46 MHz and want to feed a short antenna...any 
help is really appreciated...Rigg



"bin" <bin@bin.com> wrote in message 
news:4193858c$1_1@news.iprimus.com.au...
> such questions are good questions and large signal RF amplifier design is 
> an
> involved subject. I've never met many (any?) people locally with these
> skills and I have only limited ability in this area however, I suggest the
> following;
>
> 1. Perform a class A dc bias design.. .ie... probably no collector
> resistor... only an emitter resistor setting max collector current.
> 2. Choke the collector supply line with a RF choke (10uH probably will 
> do).
> ( you could also use a tank here... but dampen it with a resistor for a
> wideband signal)
> 3. Bypass any emitter resistor you have with a suitably high capacitor 
> (1nF
> will probably do)
> 4. determine from the spec sheets the equivalent input/output impedance of
> the transistor at the supply current levels set in the bias design at the
> frequency of interest.
> 5. design an output matching circuit to match the input impedance of the
> antenna under test (eg. if using a 50ohm whip) to the transistor output
> impedance via a dc blocking cap (1nF again). For a short wire, impedance 
> may
> be high and you could probably dispense with the output matching circuit 
> by
> feeding directly to the collector.
> 6. design an input matching circuit to match the 50 ohm driver to the
> transistor input impedance via a dc blocking cap (1nF again).
>
> (no 4 is the trickiest as not all manufacturers include that info)
>
> bindy
>
> "rigg" <riggdm@hotmail.com> wrote in message
> news:4192c4ff$1@news.alphalink.com.au...
>> I have a tv modulator, ch0 46MHz, and I want to boost its output with a
>> simple one transistor amp connected to a short antenna so it will 
>> transmit
>> up to about 20 metres. I was thinking of using a 2N3866 in a class C
>> configuration with a 12v supply. Can someome give me advice on how to
> select
>> values or provide a simple circuit so I can do this? I am not sure how to
>> pick values when using a short antenna of 30 cm. I assume matching
>> impedances must come into this somehow... I have seen lots of circuits on
>> the web but they are for much lower frequencies. Thanks Rigg
>>
>>
>
>