Just got my BCD536HP must be old stock?

[RFI-EMI-GUY]

Remember that the 536 use a "floating" output so you have to set the oscilloscopes probe ground to the scanners chassi and then measure on "tip" and then on "sleeve" of the connector. If you ground the oscilloscope to the "ground" of the speaker you will get false readings if you don't use a transformer ground loop isolator.

But the important thing are what you hear, so an exact measurement isn't neccesary.

Most scanners have noise on both earphone and loudspeaker outputs as they don't put enough attention to the audio amp design. There's several things that could be made to improve a scanner. Tone control, loudness, good audio electronics, speaker, RF front end filters, quality buttons and dials. If the audio sounds distorted, bassy, thinny or rattles at moderate volume levels it doesn't matter how sensitive a scanner are if your listening are compomised by a poorly designed audio solution.

/Ubbe

The 536 uses a BTL, Bridge Tied Load amplifier similar to this schematic:

http://www.learningelectronics.net/circuits/images/1-watt_btl_audio_amplifier_circuit_diagram-2.png

The manual doesn't emphasize enough the importance that whatever you connect to the speaker jack cannot return to ground (or A+). This means only a speaker coil or transformer coil can connect directly to the speaker jack. You cannot drive an unbalanced amplifier or sound card directly. You need DC transformer isolation. If you damage the amplifier, you could get distortion, noise or low output.

Now on to a true story. In the 80's I was involved with the Motorola Smartnet system in City of Miami. There were complaints from the users about distorted audio from the STX radios (They used MX300's previously). The COM was self maintained and the technicians were given a Motorola engineering log book page (By a product group engineer) containing a simple fix for crossover distortion adding a diode and resistor to the simple two transistor BTL amp driving the radio speaker. It worked splendidly. I was not involved directly with this fix.

Fast forward two years and the City's Project Manager "Eddie" takes a new job at Miami Beach and oversees the implementation of that new system. Eddie is considered a "Champion" of Motorola having secured this second no-bid contract. He is also a smart no-nonsense kind of guy.

I am now in the position of being the account executive for this project taking on the new installation and its many problems (I received no sales commission, that fellow conveniently retired taking with him the commission!). So on the day I am to obtain the final payout milestone for the system, Eddie informs me that he is withholding $750K because of the squeaky speaker audio. Eddie hands me the Motorola Logbook page and says, "these radios sound crap compared to my old system (City of Miami), they sound like a 50 Cent speaker". Eddie was right on both counts, Motorola did not fix the crossover distortion on the new version radios and actually installed a different very tinny speaker (actual cost about 50 cents). That tinny speaker was to make the radio SPL appear higher to meet a requirement of an automotive factory.

I had an uphill battle getting the plant to authorize the rework and even falsely accused of disclosing confidential information (the log book page) when the client had been given that info previously. In the end all the radios were reworked by Motorola, and I collected the $750K receivable.

 

[Ubbe]

...... a simple fix for crossover distortion adding a diode and resistor to the simple two transistor BTL amp driving the radio speaker....

The amp where designed to run in class B to preserve battery life. The modification made it run in class A and drained the battery. Probably didn't ment much to the customer if he had a high transmit/receive ratio or change batteries after half a day. The most important thing are that the customer are satisfied long enough to clear the final milestone.

https://www.audioholics.com/audio-amplifier/amplifier-classes

/Ubbe

 

[saboken]

I'm looking at the AOR AR-DV1 as a alternative to Uniden! It cost a little more but seems to be loaded and dmr and NXDN are included the new Uniden handheld cost almost $1000 with all the upgrades this is about $200 more and looks promising!

 

[pro92b]

Remember that the 536 use a "floating" output so you have to set the oscilloscopes probe ground to the scanners chassi and then measure on "tip" and then on "sleeve" of the connector. If you ground the oscilloscope to the "ground" of the speaker you will get false readings if you don't use a transformer ground loop isolator./Ubbe

The scanner was powered by a 12V battery so it is floating with respect to the scope. In that case the scope ground can be connected to the speaker return with no issue. I confirmed that the noise reproduced by the speaker was not affected at all when the scope was connected. The scope display was accurate and the measurements correlated with the listening test.

 

[RFI-EMI-GUY]

The amp where designed to run in class B to preserve battery life. The modification made it run in class A and drained the battery. Probably didn't ment much to the customer if he had a high transmit/receive ratio or change batteries after half a day. The most important thing are that the customer are satisfied long enough to clear the final milestone.

https://www.audioholics.com/audio-amplifier/amplifier-classes

/Ubbe

That was one argument that the product group used to attempt to dissuade the customer from persuing the fix. However the increased current drain when measured, was rather low and only was in effect when the radio is actually receiving so it did not factor into the standby current. The increased fidelity was important to the customer.

Sent from my SM-T350 using Tapatalk

 

[Dewey]

I'm looking at the AOR AR-DV1 as a alternative to Uniden! It cost a little more but seems to be loaded and dmr and NXDN are included the new Uniden handheld cost almost $1000 with all the upgrades this is about $200 more and looks promising!

Just remember that the AOR is not a trunking receiver. Being able to demodulate every mode under the sun is not any good if the receiver is not going to track the signal across a trunked system... that is unless trunking is not an important part of your reception desires. Some receivers can be driven by an external application (think cheap dongle SDR coupled with Unitrunker) to follow trunked systems, but that is not necessarily a mobile friendly solution.

 

[saboken]

True I have several USB sdr dongles and a Ham it up I haven't played with them as much as I planned maybe it's time to experiment with them? I also have several Raspberry pi 3 +'s Don't know if there a way to use them with the SDR dongles? The Pi is very low power and can run off the RV batteries for quite some time! I think my Solar charging system can keep.up with it since I changed all the 12v lighting In the RV to LED there still 2 Florescent 12v lights I have to swap with something but that's not a priority right now. Any ideas on Using a RPi with SDR dongles?

 

[Dewey]

True I have several USB sdr dongles and a Ham it up I haven't played with them as much as I planned maybe it's time to experiment with them? I also have several Raspberry pi 3 +'s Don't know if there a way to use them with the SDR dongles? The Pi is very low power and can run off the RV batteries for quite some time! I think my Solar charging system can keep.up with it since I changed all the 12v lighting In the RV to LED there still 2 Florescent 12v lights I have to swap with something but that's not a priority right now. Any ideas on Using a RPi with SDR dongles?

PM sent to avoid hijacking original thread.

 

[CanesFan95]

Ouch. I would seriously re think about a radio that has been known to have issues and hardware related problems in the past. Uniden is right on the brink of releasing a base unit soon.

When / where was that announced?

 

[mule1075]

When / where was that announced?

Never happened.

 

[CanesFan95]

Then how do they know Uniden is on the "brink" of anything?

 

[mule1075]

Then how do they know Uniden is on the "brink" of anything?

They don't just a figment of the imagination.