Using Audio Amplifier

I have the Home Patrol 2 scanner. I use it in my truck and the audio just wasn't loud enough. So I purchased a Pyle 15 W audio amplifier on eBay. It's so much louder now, but at the start of each conversation, there is an objectionable pop through the speaker. It does this as soon as the squelch breaks. It's tolerable until I get a very weak signal, in and out of squelch. Pop talk pop talk pop talk,

I used the headphone output (1/8" jack) and tied that to the amp input. I have tried adjusting both the scanner volume, as well as the amp volume. Thinking would be better with higher scanner volume and lower amp volume, but little difference to the popping sound.

Any thoughts on what I can do to remove that initial popping sound?

Thanks,
Paul

My first thought is that there might be a DC voltage that is on the scanner audio output your using. I would try to install a capacitor in series with the hot center wire of your connection. This would eliminate the DC on the cable going to the audio amp.

Using a capacitor of say between 1.0 uf and 3.3 uf or what ever you can find in that range. The larger the cap value, the more bass sounding it will be and the highs will roll off some. The voltage rating of the cap should be at least the 15 volt range or even a 25 volt range. Put the positive of the cap towards the scanner.

Uh, the pop is a sudden change in the DC level of the scanner's audio output relative to the amp's input, and any quick voltage change like that will pass right through a series cap. He'd be better off with an isolation transformer.

So, do you guys think that electrolytic capacitor might help, or no ?

Would something like this work?
NEW Innogear SNI-1 3.5 mm Headphone Jack Audio Ground Loop Isolator Noise Filter

I just tried a 1uf electrolytic and didn't seem to make any difference. I also tried a .1uf disc, which was slightly better. Right now I'm using the 3.5mm jack which is supposed to be a headphone output. I have a 2.5mm plug adapter on order so that I can use the Line audio output instead. Not sure if that will help?

The smaller the capacitor the better until you start to lose normal audio. SlicerWizard has it right, the DC shift as the squelch lifts will pass right through a large electrolytic cap and make the pop in the speaker.

I have a little Yaesu VR2 that sounds great on it's internal speaker, but on headphones or earbuds it's very annoying to hear the pop at the start of every transmission. The phones have a better low frequency response I guess.

Thanks folks. Btw, I have to say that the sensitivity with this scanner is not as good as a Uniden BC780. With its included antenna, I cannot even pickup a single NOAA Weather channel. On other scanners, I can at least get 2. I have an antenna on order - as my stab at using the truck AM/FM antenna was a bust.

As with most scanners the stock antenna isn't very good as it is designed to work over the entire frequency range of the scanner. My HP-2 picks up great. I use 760-870 MHz. antennas as this is 99 % of what I listen to but I still receive VHF/UHF from a county away.

Tinkertek said:

Would something like this work?
NEW Innogear SNI-1 3.5 mm Headphone Jack Audio Ground Loop Isolator Noise Filter

Click to expand...

It may help. The real problem is the way Uniden designed their headphone circuit. But for $12, I'd give it a try.

I have a HomePatrol 1 and noticed the same problem when trying to use the headphone out as an input to my computer soundcard for my scanner feed on Broadcastify. It pops when squelch opens or closes. Very annoying!

My solution was to use the line output connection on the HomePatrol. It provides clean audio with no pops. Note that it's a fixed level and not affected by the volume control. If your outboard amp has a volume control, you'd be all set.

The line out uses a 2.5mm stereo connector.. not something I had in my parts. I purchases this adaptor to convert it to the more standard 3.5mm stereo.

http://www.amazon.com/gp/product/B005E2XYYI/ref=oh_aui_search_detailpage?ie=UTF8&psc=1


Dave
k1xd

My 2.5mm adapter is on order. K1XD, it's encouraging to hear that using the Line Out jack solved the popping problem for you. I'll hold out and try it. If not, I'll give that isolation transformer a try. Thanks everyone !