Power Microphone - Radio Key Up, Audio Delay Issue

[Lil'Yeshua]

LM-7809 hooked up to the RD's black wire which is hooked up to 13.8 volts at pin 6 on the CRE-8900

 

[Lil'Yeshua]

Okay. I wired the Astatic Road Devil mic for the CRE-8900. Substituted the mic's battery for the LM7809 volt reg and run 13.8 volts from the 8900's #6 pin through the Astatic black RX mic cord wire to power it. Disconnected the black wire inside the mic case and fed it to the lm7809's volt in terminal. Run the 7809's ground leg to the battery ground and the 7809's volt out to the battery red wire. Soldered a 1K ohm resistor between the audio and were the black wire was connected to the circuit board. The CRE-8900's mic gain at 45 and the RD gain halfway. Anything over 3/4 gain on the RD results in squealing. But it works.

 

[Lil'Yeshua]

P.S. I used a 1/4 watt 1K ohm resistor
You'll notice in the pic above that my radio's key down display shows the SWR.

 

[Mudfoot]

I had my RD maxed out and my 8900's mic gain maxed as well. Actually, I had both set throughout a wide range with no squeals at all.

Must have something to do with the factory TB fix my rig just had. It's supposed to completely disconnect the speaker during transmit. At least that's what I was told.

Before I had the fix, I had only used the stock mic.

Anyways, the CRE is going in the car as soon as I get motivated.

 

[Lil'Yeshua]

That's where I think I'm getting the squeal because the speaker isn't shut off
I got the talkback at 1,mic gain at 3/4. With talkback turned off and external speaker unplugged and the radio laying flat on it's belly and mic gain at full,it will squeal. I'm wondering if I need to add a couple of stiiffening capacitors where the battery used to be.

 

[camaro1]

whats your voltage now at the 2 wires that used to go to the mic battery with the radio on??,, i think you need another ground,, the voltage reg needs a b+ input, ground(-), and output,, you have the ground going to the ground for the battery, i think you need to also run this to a radio ground(-) so you are actually getting a (-) to the regulator maybe??

 

[Lil'Yeshua]

whats your voltage now at the 2 wires that used to go to the mic battery with the radio on??,, i think you need another ground,, the voltage reg needs a b+ input, ground(-), and output,, you have the ground going to the ground for the battery, i think you need to also run this to a radio ground(-) so you are actually getting a (-) to the regulator maybe??

I ran out of time last night so I'll check voltages and yes,I thought about adding a ground jumper from the mic wire shield attachment point on the RD's circuit board over to the volt reg's ground leg. Before I did this battery less modification I could run the mic's gain wide open with the talkback off. Now I can only run it 3/4's. I would need my 8900 fixed like M42Duster's radio.
Also,the modulation is doing some slap back kind of thing and isn't able to hold 100% modulation. Whistle backwards and it will sustain a 60 over modulation reading.

 

[Lil'Yeshua]

whats your voltage now at the 2 wires that used to go to the mic battery with the radio on??,, i think you need another ground,, the voltage reg needs a b+ input, ground(-), and output,, you have the ground going to the ground for the battery, i think you need to also run this to a radio ground(-) so you are actually getting a (-) to the regulator maybe??

Alright. I attached a wire from the volt reg's ground leg to RD mic ground. It acts stable. The volt reg's volt out is 8.85 volts and that's with my 8900 hooked up to a Pyramid PS14KX 12 amp cont./14 amp surge new power supply. I got the talkback set to off. It only has feedback when I place the mic next to the radio. On my 8900,I can still hear the talkback even with it turned off. So,thanks guys for the great tips. The extra ground wire defiantly fixed the problem. Now if I can figure out how to turn the talkback all the way off. A cheap alternative might to add a certain value resistor to the speaker/ext. speaker.

 

[Lil'Yeshua]

My TRC-428 on the bottom. It's my first radio and I bought it new in 82'

 

[mdavis735]

I was in frys electronics today in Austin. I bought the stuff to direct inject the tx on my 148 and also the caps to mod the rx for hifi. I was able to find all the parts to do the scottky receive upgrade. All were NPE(the brand they carry). I wish I could find the 12v to 9v step down part number in their brand.

 

[Lil'Yeshua]

http://www.parts-express.com/pe/showdetl.cfm?partnumber=7809

 

[Lil'Yeshua]

This morning I hooked up the radio in the car and imediately had feedback. I'll check everything this afternoon. The PL-259 might not be seated. The big honkin lock washer on the radio's so-239 connector makes it a loose fit for the PL-259.

 

[Lil'Yeshua]

I might have to undo the radio powered road devil mic an put the battery back in. I can't run the mic's gain anymore than halfway before it squeals and the stock mic is louder. Wiring that extra ground to shield obviously degraded it's performance. Before,I could run the RD up to 3/4 and not feedback and was much louder.

 

[Mavrik]

Delay was gone but now its back.

For some reason my delay is back with my Road Devil. I replaced the resistor and it is still has the delay. I tried adding the resistor to my new 636l and it is still delaying too. Tried both mics on both of my CRE 8900's both with a 1k ohm 1/4 watt resistor. What could be going on here?

 

[Mudfoot]

Try resetting the rig.