40 Mhz amplifier for RC Long Range - advise needed

Hello everyone!

I am new here and I need an advice about this RF amplifier:

https://www.ebay.com/itm/182196835491

I purchased it with the idea to boost the signal of my RC controll which is 40 MHz.
The signal from the RC transmitter is only about 1-5 mW and the range is about 20 m.

The problem is that after looking my RF Explorer the amplifier does not work well in the 40 MHz band. It almoast does not boost the signal. I decided that the input capacitor which is about 15pF is blocking the lower frequencies so I shorted it and BOOM I get 10dB more on my RF Explorer. So it is obvious for me that the schematic can be optimised for 40 MHz.

I will be very grateful if you give me some help in my quest. What could I change to improve the performance in the 40 mhz band.

Thanks in advance guys!

They are lying...
No amplifier can supply 35dBm Output Power over this band ( 9 octaves ) under the sun.
All you want is to send 40MHz signal with 1-5mW to 20m distance ?? Is that right ?

Hello friends. My current RC transmitter is capable of 20 m range and it is providing about 2-5 mW which is pathetic. The statament it that the booster is capable of 1.5 W power so tihis is my goal. I just want to know how I can optimise the transmitter to work better on 40 mhz as it is designed to work up to 700mhz

SunnySkyguy thanks but I can't see anything in your post.

And finaly friends my goal is stable link about 2 km in urban enviroment.

- - - Updated - - -

By the way the used MOS FET in the output is probably 2SK2973

By the way the used MOS FET in the output is probably 2SK2973

lkrustev said:

Hello friends. My current RC transmitter is capable of 20 m range and it is providing about 2-5 mW which is pathetic. The statament it that the booster is capable of 1.5 W power so tihis is my goal. I just want to know how I can optimise the transmitter to work better on 40 mhz as it is designed to work up to 700mhz

SunnySkyguy thanks but I can't see anything in your post.

And finaly friends my goal is stable link about 2 km in urban enviroment.

- - - Updated - - -

By the way the used MOS FET in the output is probably 2SK2973

Click to expand...

I see a pdf file posted as an Image in my iPad of an 3W chip that does 5-1000MHz from minicircuits. HELA-10+

This unit will work well for you but the 2SK2973 chip only has a gain of >15dB, so you can increase range 2x to 3x.
It uses a high quality Mitsubishi chip.
But perhaps gain can be achieved with better antenna.

Thanks man, but I am just looking for an advice how to improve the filtering of that device so it cold work better on 40 mhz.

HELA-10+ is way far to be a 3W amplifier in 5 MHz - 1000 MHz frequency range (see the datasheet picture).
Perhaps is possible to make this multi octave PA using a complex multistage amplifier, but with huge compromise on efficiency.
For a narrow-band 40MHz medium power amplifier I recommend to use a cheap 2SC1971 transistor. Check the net for tons of schematics using this transistor.

Just a word of caution: the 40MHz band (in this country at least and probably everywhere) is one of the 'Low Interference Potential Device" (LIPD) frequencies. According to my local regulatory authority, the 40MHZ range has a maximum power output of 1W EIRP.
I strongly suggest that you check with your local authority for the maximum power output that you can transmit on this frequency range and also the other limitations (such as the exact frequency range, the transmission bandwidth and how close you can come to the band edges).
If you cause interference with other devices and you are outside the permitted power and frequency limits then you could face prosecution and confiscation of your equipment depending on your local authorities legislated powers.
By the sound of it you are looking for point-to-point communications in which chase you could use dipoles that will channel the power you already have into a narrow beam width. This may well let you communicate over the distance you require without the need for an amplifier at all.
Susan