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Budget RF audio generator options for tuning radio receivers

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RiRaRi:
At least as possible. But amount that is neccesary. I have the budget but just want to get cheap but okay option.

geggi1:
If you want to build there are plenty of options.
For AM at low frequencies you can build a small amplifier from a PN2222 or similar low power transistor or an intigrated circuit.
Eksamples can be found here. https://sound-au.com/articles/am-modulation.htm
Then you can make the carrier by using a DDS module like the AD9850 or AD9851 and an arduino.
Build plans, schematics and INO files can be found on the internet.

If you need to run AM in the air band the DDS frequency can be multiplied a few times.
For the 9850 a 5 time multipllier will get you in the air band. http://techlib.com/electronics/2diomult.html

For FM generation you can find soem eksamples here: http://electronbunker.ca/eb/DDS_Controller1.html
You will probably have to use a multiplier to get to the FM broadcast band or VHF two-way bands.

Finaly you will need some kind of attenuator to bring the levels down to something that can be inserted in to the antenna of a radio.
You will probably need somet in gin the range of 120dB attenuation in total split on a few attenuators.
I would suggest 50dB, 40dB, 30dB, 10dB that would give you the posibility of 130dB in steps of 10dB.
Build the attenuators with SMD components (0,25W type)  and match the traces to 50 or 70 ohm depending on system impedanse.
Use connectors beteen the input and outputs of the attenuators with male and female on oposite ends to simplify connecting the units.
The attenuators should have some kind of shielding to prevent RF leakage.

colorado.rob:

--- Quote from: RiRaRi on September 18, 2023, 08:36:30 pm ---At least as possible. But amount that is neccesary. I have the budget but just want to get cheap but okay option.

--- End quote ---
A Siglent SDG2000X arbitrary waveform generator will do what you want. It's a decent lab instrument that has the ability to do AM and FM modulation from the low end of the AM broadcast band to the upper end of the broadcast FM band. You can buy the 40MHz version and hack it to 120MHz.

RiRaRi:
Thank you. It is expensive but it is good tool. As i was thinking to get cheaper scope with built-in sig gen i was thinking that this could be cheaper. Around 50-100 €/$. This does not work?

xrunner:

--- Quote from: RiRaRi on September 18, 2023, 10:21:05 pm ---Thank you. It is expensive but it is good tool. As i was thinking to get cheaper scope with built-in sig gen i was thinking that this could be cheaper. Around 50-100 €/$. This does not work?

--- End quote ---

The specs for this unit are shown below. It is for FM transceiver testing (or it could put out unmodulated RF (CW) ) . This is stated even more clearly in other product descriptions for it. So it doesn't do AM modulation. It also only has 800 Hz modulation for FM, and doesn't state the deviation the FM output is set to. You said earlier you wanted AM modulation too. So you tell us - is that what you really want?  :-//


Features:
Suitable for FM walkie-talkie debugging.
Built-in 800Hz audio modulation, with the analog digital CTCSS function.
The unit is DBM. General hand sensitivity is -120DBM to -130DBM.
The greater the sensitivity to a negative number, the higher the sensitivity.
The signal source cannot input power.
It is absolutely forbidden to press the intercom button to transmit when testing. (self-matching power supply 8V-12V power supply polarity is positive and negative)

Specifications:
Material: ABS
Color: blue
Frequency: 0.5MHz-470MHz
Signal strength: -70-132dBm
Built-in 800Hz audio modulation
Add the analog digital CTCSS function
Use 8-12V DC power supply, frequency 7 digits
For example: 439.6000MHz shows 4396000KHz
Signal strength -70-132dBm valid, other values are invalid.
Audio modulation is only about 800Hz, other values are invalid.
Item size: 155 * 120 * 63mm / 6.1 * 4.7 * 2.5in
Item weight: 271g / 9.6ounce
Package size: 210 * 160 * 70mm / 8.3 * 6.3 * 2.8in
Package weight: 303g / 10.7ounce

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