Can You Identify This Mod To My Radio

[Raccoon]

Hi everyone,
I bought this Icom IC290a 2 meter all mode radio a little while ago . The radio has sideband in it , but it doesn't have tones for accessing the repeaters that use tones . So I bought a tone board to install in it . When I opened it up, I found this little board in the picture on the bottom side , at the back left corner near the coax connector . It doesn't seem to have any apparent effect on how the radio operates , and I've been searching through all the mods that I could find online trying to find out what it's suppose to do . But I haven't been able to find anything yet . So I decided to take a picture of it and see if anyone here might know .

 

[AudioShockwav]

RX Pre Amp is my guess.
Where does it hook up in the radio?

73
Jeff

 

[sp5it]

Yeah, rx preamp

 

[Raccoon]

That's cool, I'm going to be using it in the mobile so that would definitely be a help.

Thanks for replying guys.

 

[BC Coyote]

Those rx pre-amps don't really help much. Yes, they boost received signal strength, but at the same time they boost received noise so the signal to noise ratio stays the same.
You can achieve the same effect much more easily but simply turning up the volume........

 

[SuperLid]

That is an ARR P144VDG GaAsFet RX preamp. It has about 24 dB gain with .5 dB NF. High gain, low noise.

 

[BC Coyote]

High gain, low noise.

Yes the noise generated by the circuit may be low, but it still amplifies outside noise just as much as signal, so the SNR stays the same.......
As I said above, you may as well just turn up the volume.

 

[sunbulls]

I have an old 2 meter Regency with a weak front end. A pre-amp brought it back to life. Stations down in the mud wouldn’t be heard without it. A particular receiver’s sensitivity is a huge factor in determining whether a pre-amp is needed or not. Without knowing how sensitive that particular radio is without that pre-amp, I’d leave it alone. A service generator may indicate its necessity. I love a hot receiver, especially on the VHF and above frequencies. Repeaters commonly apply them, sometimes in their receiver, and on their antenna. Volume doesn’t exist when the squelch isn’t broken.

 

[SuperLid]

Yes the noise generated by the circuit may be low, but it still amplifies outside noise just as much as signal, so the SNR stays the same.......
As I said above, you may as well just turn up the volume.

You have obviously, never used one of these yourself.

 

[BC Coyote]

You have obviously, never used one of these yourself.

You would be wrong. I've used many pre-amps, always on older radios that were expanded but suffered from poor sensitivity at the upper and lower edges of the band. They are indeed a valuable tool for situations like that or as Sunbulls said, on any radio with a deaf front end. On several of my old 858 PLL based radios I built by own pre-amp to get around this problem.......

However, if you are running a radio that already has fine receive, you won't gain anything by using a pre-amp other than raising the noise level along with the signal.

 

[SuperLid]

You would be wrong. I've used many pre-amps, always on older radios that were expanded but suffered from poor sensitivity at the upper and lower edges of the band. They are indeed a valuable tool for situations like that or as Sunbulls said, on any radio with a deaf front end. On several of my old 858 PLL based radios I built by own pre-amp to get around this problem.......

However, if you are running a radio that already has fine receive, you won't gain anything by using a pre-amp other than raising the noise level along with the signal.

Again, you have not used one of *these* yourself.

 

[BC Coyote]

Whatever. Believe what makes you happy. Over and out.

 

[nomadradio]

The higher the frequency, the less noise the antenna brings in. The preamp's internal noise usually becomes the limiting factor on 2 meters or 440 and above. The GaAsFET preamp is probably as good as it's going to get for this purpose. Using the radio for satellite QSOs will probably call for a preamp more than just using local repeaters.

Might be what prompted installing it.

73

 

[SuperLid]

Whatever. Believe what makes you happy. Over and out.

This is not a CB preamp as you are implying. It is most likely making the RX better than .2uV SINAD. This is not a matter of making me happy, it is a matter of you don't know what TF you are talking about.

 

[BC Coyote]

you don't know what TF you are talking about.