Ground Loop Isolators

[nickwilson159]

For those using Motorola radios for Broadcastify feeds, what are you using for a ground loop isolator? I have tried various reputable ones from Amazon (such as Besign), and they always end up severely muffling the audio and cutting the volume in half when looked up to 'RX FILT AUDIO' (or equivalent line-level audio out). This has occurred now on two different XTL5000s and an MCS2000 with multiple ground loop isolators.

These same ground loop isolator will work fine on a Kenwood TK-7180 using pin 17 (AFO - RX Filtered Audio Out) on the DB25 connector, but causes problems on at least the XTL5000 and MCS2000 - have not tested any additional Motorola mobile radios yet. I have read recommendations on both these forums and Batlabs recommending to use a ground loop isolator when using these radios for a feed, so surely something has to work.

I've attached the electrical specs of the associated pins from their respective service manuals.

 

[RFI-EMI-GUY]

Frankly, I would avoid anything on Amazon that claims to be a ground loop isolator or Hum blocker. Here is why. They are designed around low power gadgets like iPods and iPhones. If they really have a transformer (Galvanic isolation) they likely have very tiny transformers that get magnetically saturated by any DC bias on the speaker terminals, if not the high audio levels of 5 watts or so. If they are really cheap, they have simply series capacitors to block common mode currents below 120 Hz.

I would buy an isolator like the ones radio shack used to sell that had two transformers packed into a metal can or the ones sold by auto sound companies like Crutchfield for coupling a car stereo to an audio amplifier.

This subject really should be a sticky here on RR because it comes up a lot and so many feeds sound like distorted crap.

 

[RFI-EMI-GUY]

For those using Motorola radios for Broadcastify feeds, what are you using for a ground loop isolator? I have tried various reputable ones from Amazon (such as Besign), and they always end up severely muffling the audio and cutting the volume in half when looked up to 'RX FILT AUDIO' (or equivalent line-level audio out). This has occurred now on two different XTL5000s and an MCS2000 with multiple ground loop isolators.

These same ground loop isolator will work fine on a Kenwood TK-7180 using pin 17 (AFO - RX Filtered Audio Out) on the DB25 connector, but causes problems on at least the XTL5000 and MCS2000 - have not tested any additional Motorola mobile radios yet. I have read recommendations on both these forums and Batlabs recommending to use a ground loop isolator when using these radios for a feed, so surely something has to work.

I've attached the electrical specs of the associated pins from their respective service manuals.

Look at the last column on the XTL the 1.42 DC bias on TP0204. You will need a DC block capacitor if you use that point while driving a transformer.

 

[K4EET]

Hi everyone. I think this video shows the guts of the ground loop isolator that @nickwilson159 has.

 

[W3AXL]

I would recommend solving the ground loop issue instead of throwing isolators at the problem. You shouldn't be getting any kind of ground loop if all your devices are properly sharing the same ground reference and you're using shielded cables. I have 8 XTLs in my basement rack and the RX audio from all of them into my audio interface is perfectly fine on its own.