Trouble with Cobra 148

[Eastside]

I am trying to connect my mixer/studio mic/rack gear to my 148 but my ptt 4 pin works on keying the radio.....but no receive......it has been converted by previous owner to 4 pin from 5 pin...the radio receive comes on with some 4 pin mics but does not with others.....any idea how to make it work?

 

[mechanic]

I am trying to connect my mixer/studio mic/rack gear to my 148 but my ptt 4 pin works on keying the radio.....but no receive......it has been converted by previous owner to 4 pin from 5 pin...the radio receive comes on with some 4 pin mics but does not with others.....any idea how to make it work?

On some mics the shield is common with the ground. Sadelta and some Astatic mics have this done from the factory. The PTT switch or contacts disconnect the receive lines and connect the TX lines. Since the shield was no longer needed the previous owner may have converted the chassis connector to a four pin, eliminating the shield by soldering it to the ground. Some low impedance mic elements need a shield to prevent a feed back loop on transmit.
There is an adapter available for this that is common now but not before....

73 mechanic

 

[Tripple Nickel]

Most converts from 5pin to 4 pin is merely done with a mic adapter, such as I just did on my Washington. Astatic has a chart on line that gives you the correct pin wiring, that's what happened to your receive.
JMHO/Good luck.

 

[Eastside]

Why does the receive stop on a cobra 148 when you unplug the mic?

 

[Sideways]

Why does the receive stop on a cobra 148 when you unplug the mic?

Its because of the type of tx/rx switching inside the radio.
Most cb radios like your 148, use electronic/diode switching while going from tx-rx, the cicuit is broke when you unplug the mic.. Some radios like exports, use relay switching, and leves the circuit energized, even though the mic is unplugged.
Does that make sense?

 

[Eastside]

Its because of the type of tx/rx switching inside the radio.
Most cb radios like your 148, use electronic/diode switching while going from tx-rx, the cicuit is broke when you unplug the mic.. Some radios like exports, use relay switching, and leves the circuit energized, even though the mic is unplugged.
Does that make sense?

Yes

Is there a way to make the receive stay on like the export radios?
I am trying to connect my mixer and rack gear to the 148....but when I connect my 4 pin ptt mic cable the receive will not come on....but it will still key the radio?

 

[tecnicoloco]

Yes

Is there a way to make the receive stay on like the export radios?
I am trying to connect my mixer and rack gear to the 148....but when I connect my 4 pin ptt mic cable the receive will not come on....but it will still key the radio?

Contact Chris " Nomad Radio " he sells an internal adapter to convert 5 pin to 4 pin for the Cobra 2000/148 GTL
==============================================================================

Converting the radio from 5 pins to 4 pins is nothing more than a convenience issue.

If doing this makes life easier, it's worth doing.

For folks who own more than one base radio, life is just easier if you can exchange mikes between them.

If you have just one five-pin radio and only one mike for it, you probably won't care.

If you have more than one radio, there's a good chance most of them have a four-pin mike and socket.

Converting a Cobra 2000GTL to a 4-pin mike socket allows you to interchange mikes with newer or more-popular types of base and mobile radio.

It fits other models on the list, but no pics of those, yet.

This thing is still at an early stage.

It's not being marketed as a DIY kit. Yet.

Once I have installed more of them, and have the confidence that no hidden problems arise, they'll be offered for sale.

But this is the first Cobra 2000GTL to get the 'new' version of the 4-pin conversion.

With any luck, the instructions to install it will be a bit more refined by then, too.

I'm gonna skip the technical reason for converting the radio this way.

If you think you have an easier way, then by all means try it.

But remember that the five-pin socket has two ground circuits.

The four-pin mike has only ONE.

This board serves to keep these two circuits separate so that the risk of weird feedback noises is kept to a minimum.

As a bonus, it permits you to use "Roger K", five-tone and double-beep type boards with this radio.

Those beeps are all designed for radios that do NOT require the mike to get receiver audio.

The five-pin radios will blast your ears with a loud "BEEEP" from the receiver speaker if you install one of those WITHOUT adding a relay to the radio.

This board provides the relay NOT found on those boards.

 

[Sideways]

Is there a way to make the receive stay on like the export radios?

Not that I am aware of eastside. I could be wrong, but i would think it would require quite a bit of circuit surgery to keep the radio from squealing while it was switching from rx to tx.

I don't know much about rack gear. Do you know for sure it it wired for cobra 4-pin? Possibly could be wired for relay switching, and would not require an rx wire? Do you have another radio to try it on to see if the rx will work?

 

[Sideways]

Contact Chris " Nomad Radio " he sells an internal adapter to convert 5 pin to 4 pin for the Cobra 2000/148 GTL
==============================================================================

Converting the radio from 5 pins to 4 pins is nothing more than a convenience issue.

If doing this makes life easier, it's worth doing.

For folks who own more than one base radio, life is just easier if you can exchange mikes between them.

If you have just one five-pin radio and only one mike for it, you probably won't care.

If you have more than one radio, there's a good chance most of them have a four-pin mike and socket.

Converting a Cobra 2000GTL to a 4-pin mike socket allows you to interchange mikes with newer or more-popular types of base and mobile radio.

It fits other models on the list, but no pics of those, yet.

This thing is still at an early stage.

It's not being marketed as a DIY kit. Yet.

Once I have installed more of them, and have the confidence that no hidden problems arise, they'll be offered for sale.

But this is the first Cobra 2000GTL to get the 'new' version of the 4-pin conversion.

With any luck, the instructions to install it will be a bit more refined by then, too.

I'm gonna skip the technical reason for converting the radio this way.

If you think you have an easier way, then by all means try it.

But remember that the five-pin socket has two ground circuits.

The four-pin mike has only ONE.

This board serves to keep these two circuits separate so that the risk of weird feedback noises is kept to a minimum.

As a bonus, it permits you to use "Roger K", five-tone and double-beep type boards with this radio.

Those beeps are all designed for radios that do NOT require the mike to get receiver audio.

The five-pin radios will blast your ears with a loud "BEEEP" from the receiver speaker if you install one of those WITHOUT adding a relay to the radio.

This board provides the relay NOT found on those boards.

So this board will convert an electronic switching radio, to relay switching?

 

[Eastside]

Not that I am aware of eastside. I could be wrong, but i would think it would require quite a bit of circuit surgery to keep the radio from squealing while it was switching from rx to tx.

I don't know much about rack gear. Do you know for sure it it wired for cobra 4-pin? Possibly could be wired for relay switching, and would not require an rx wire? Do you have another radio to try it on to see if the rx will work?

The cable is a heil ptt pigtail jack with a 4 pin yaesu female jack......it will key up a connex and other 4 pin radios and.....and will key up my 148...but will not make the receive come on.