27 MHz amplifier . Please help

[bkd]

Does anyone have low power 27MHz amplifier (working below 9V Vdd) ( for transmit signal up to 100m). I found MIC919. IS this okie for this application
THank for reading

 

[vfone]

MIC919 is an operational amplifier with 27MHz bandwidth. It will not work as a power amplifier for 27MHz band.

 

[bkd]

I found BC546 547. Is this Okie

 

[glias]

what is the gain of your amplifier ?

 

[bkd]

The gian is about 50 to more than 100

 

[vfone]

BC546 should be fine, but I think will give output power to the limit for a stable wireless communication at 100m in 27MHz band.
I would recommend higher power transistor as 2SC5551, which is very often used as a PA driver for HF.

http://www.datasheetcatalog.org/datasheet/sanyo/ds_pdf_e/2SC5551.pdf

 

[bkd]

Thank you for the answer.
My question is that how to calculate the amplifier before antenna. I used to design amplifier for 50 ohm impedance matching for the antenna withh 50 ohm input impedance at 11 Ghz. But this kind of low frequency I do know how to calculate it. Do ou have material for this kind of amplifier.
Normaly the load of this kind is very hight about 10kOhm or something like that. But I wonder if the impedance of the antenna is 50 ohm or not at this low frequency

 

[vfone]

Definitively the impedance of a small antenna is not 50 ohms at 27MHz.
Impedance matching at 27MHz is not complicated (anyway much simpler than 11GHz). At this frequency you can do the experiment using trim caps before designing the final impedance matching network (as in the application below).
**broken link removed**

 

[bkd]

Do you guy have step by step design instruction for ADS or AWR

---------- Post added at 07:59 ---------- Previous post was at 07:13 ----------

In designing this amplifier , did we use S parameter method to design. Or we use what kind of design method

 

[Borber]

At 27MHz CB Band you need 50-100mW of power to reach 100m distance using simple 1.2m telescopic antenna. For that purpouse you can use BF199 as oscillator which will itself give you abt 50mW. It works on 9V battery. Are you building CB Band walkie-talkie?

 

[FvM]

The first point is to decide about the antenna. The impedance of electrical short monopole antennas (e.g. the said 1.2 m telecopic) can be found in literature, e.g. general RF or antenna handbooks. The matching circuit design can be designed with a Smith chart.

 

[Borber]

Do you guy have step by step design instruction for ADS or AWR

---------- Post added at 07:59 ---------- Previous post was at 07:13 ----------

In designing this amplifier , did we use S parameter method to design. Or we use what kind of design method

S parameters of a transistor are given for frequencies above 50MHz or more often above 500MHz. Try to use y parameters (although they are valid for linear operation).

 

[bkd]

Thank you for answering.
DO you have y parameter design guide.Please support me. I am trying to find using google

 

[Borber]

You can use dual op amp OPA2674 instead. Push-pull configuration will give you up to 1W output power.

 

[starchern]

Definitively the impedance of a small antenna is not 50 ohms at 27MHz.
Impedance matching at 27MHz is not complicated (anyway much simpler than 11GHz). At this frequency you can do the experiment using trim caps before designing the final impedance matching network (as in the application below).
**broken link removed**

Anyone know Why the circuit don't need the base bias?

 

[vfone]

The above circuit don't need bias because is a Class C amplifier (where bias point is set well below cut-off, and there is no collector current without RF signal at the input).

 

[bkd]

I want to caculate feebback capacitor which connect to Emitter of 2N3904. How to calculate please advice me

 

[vfone]

I don't know which feedback capacitor is about. Post the schematic.