Adding Frequency Counter to Cobra 148 GTL with front panel mic.

[walterjn]

I missed that bit of info in my reading of this thread, teach me to try to read quickly & not take notes.... I went off the pic Sonoma posted page 1 post #11. That was a pic I could follow along with. Looking back @ that pic I noticed that it says Grant lt... Just my luck.
What TP do I want to use?

 

[walterjn]

Ok, quick update... After reading this thread again, I noticed that TP3 was mentioned a lot. So, I unsoldered the center lead from where it was, turned the radio on & touched the center lead to TP3. Lo & behold, I got the frequency counter to give a reading. I soldered the center lead to TP3. I went & got a radio check and now when I key up my radio transmits a hum or buzz without any modulation, just a hum or buzz.

 

[nomadradio]

First question that comes to mind is to unhook the wire from TP3 and see if the radio's transmit side comes back.

If it doesn't, the counter hookup is not the cause of the transmit trouble.

73

 

[walterjn]

I've already in hooked that wire. I just need to get one of the few guys in my area to give me a radio check again.

 

[walterjn]

Ok. My one reliable local just had his base start acting up, so he is unavailable for radio checks. That said, I did get a dx contact with 648 in the Idaho Rockies. This is after I have disconnected the center lead for the frequency counter, which means that the hum/ buzz is gone & my audio is back. The hum/ buzz that I had was so prominent that there was NO audio, I had a buddy passing through call me & ask for a radio check. I was on the phone with him when I keyed up & I heard the hum over the phone, there was no feedback, just a loud hum. I'll see about getting a few pics this coming week of where I had the wire soldered when I got that hum. Right now I currently have it disconnected & heat shrink tubing over it so it won't short stuff out on me.

 

[walterjn]

Ok, now looking at the component side of the board, it looks as though TP3 & r107 are joined together. Am I correct in that view? Or have I missed something there?

 

[Handy Andy]

In your hookups...

Are you using "direct connect" or are you putting in a capacitor in series with the lead?

When you lose audio - it's telling me you have signal - you wouldn't be transmitting there on the frequency if you didn't.

So RF is present, we just need to find you a tap point that isn't pulling down the radios efforts to transmit audio.

So the cap has to be in-line (series) with the main center lead. The shield side goes to any can case / shield - close by.

Just hope the coax used for this probe/tap - point connection.

In my experience with the 148GTL-F - the "tap point" used two headers. I think you have the one that has those many pin header is set ok - it is for toggling and changing the display while you switch modes.

Do you have a "J22" outline on your Radio? The 148 Front panel mic one is these newer radios from Ranger which took over the Cobra 148 from Dynascan. It would be close to the PLL. It (Board) may be similar to the SS158.

You might not have a connector there, but look for the two traces - one trace will go to a junction of two parts a Resistor of 1K R137 and a Capacitor marked 102 or 103 - labeled C118 by a Q29 transistor. The other floats using a capacitor - to connect itself to board ground - so it's left floating but capacitively sent to ground.

This Q29 is one of the secondary oscillators - 10.6X ~ 10.7MHz

Else the only other one I can think of, is to use the 100 ohm resistor IN-SERIES (in-line - not across) at TP1 - but then your GROUND (shield) of that line is the side panel - not a shield can - needs to lifted/insulated from DC ground but not the RF ground possible with the Case. You can tie it off with a cap (in-line) to a shield can case but no guarantees.

The FC-390 series of counters should not have any shorts in their coax "lead" to the IF sense to the main PCB - but in the unlikely event of bad shrink wrapping - accidental shorting of the coax shield or kinks in it's cable causing shorts - is not out of the question - so DVM the lead going into the CB for this test and make sure they are not shorted together.

 

[walterjn]

In your hookups...

Are you using "direct connect" or are you putting in a capacitor in series with the lead?

When you lose audio - it's telling me you have signal - you wouldn't be transmitting there on the frequency if you didn't.

So RF is present, we just need to find you a tap point that isn't pulling down the radios efforts to transmit audio.

So the cap has to be in-line (series) with the main center lead. The shield side goes to any can case / shield - close by.

Just hope the coax used for this probe/tap - point connection.

In my experience with the 148GTL-F - the "tap point" used two headers. I think you have the one that has those many pin header is set ok - it is for toggling and changing the display while you switch modes.

Do you have a "J22" outline on your Radio? The 148 Front panel mic one is these newer radios from Ranger which took over the Cobra 148 from Dynascan. It would be close to the PLL. It (Board) may be similar to the SS158.

You might not have a connector there, but look for the two traces - one trace will go to a junction of two parts a Resistor of 1K R137 and a Capacitor marked 102 or 103 - labeled C118 by a Q29 transistor. The other floats using a capacitor - to connect itself to board ground - so it's left floating but capacitively sent to ground.

This Q29 is one of the secondary oscillators - 10.6X ~ 10.7MHz

Else the only other one I can think of, is to use the 100 ohm resistor IN-SERIES (in-line - not across) at TP1 - but then your GROUND (shield) of that line is the side panel - not a shield can - needs to lifted/insulated from DC ground but not the RF ground possible with the Case. You can tie it off with a cap (in-line) to a shield can case but no guarantees.

The FC-390 series of counters should not have any shorts in their coax "lead" to the IF sense to the main PCB - but in the unlikely event of bad shrink wrapping - accidental shorting of the coax shield or kinks in it's cable causing shorts - is not out of the question - so DVM the lead going into the CB for this test and make sure they are not shorted together.

I did have a 100pf disc capacitor in line when I lost audio.
Is J22 a plain metal jumper? I have a jv22 that is there. As far as a front panel mic, no this is a Uniden Grant XL I'm not sure that they are the same. I'm kinda thinking about powering up my spare radio, rigging the mic plug to just receive, then take the one I'm installing the fc on & touch that center lead to spots find a readout on the fc then see if I have audio when I key up...

 

[walterjn]

Ok, I finally got it hooked up and working. I really don't know what I did different this time over last time. I have taken pics to show where I routed everything, & where I've soldered everything to. Before I started soldering the plug in, I did take a piece of shrink tubing to make sure that nothing will short out. I did not shrink it down though. I just wanted extra insulation on those wires.

 

[walterjn]

Handy Andy, you sir are brilliant. I however, am no where near the level of understanding of most of what you have said. Thank you for your responses, input & information. I do apologise for not being able to understand most of what you posted. Thank you for your help.

 

[Handy Andy]

I had two different boards going thru my head in this thread...

Super-Star 158DX a monster enigma in itself - but that used a similar layout board of the Front Panel types they switched to when Ranger moved their processes in to manufacture their newly taken over lines...

The 148FGTL which I owned years ago, I wish I still had to help all you folks

• - but I just didn't care for how Ranger made the board...
• Jumpering the power feeds?
• 100 ohm resistor on a Ferrite Bead lead for PLL power line? (Pin 9 carp)
• - as a poorly copied clone of the original - I felt - back then - that I was violating a trust I had in Dynascans' abilities - only later to find out that they pretty much sold out to Ranger Lock, Stock and Barrel - their CB line ...

And to see how you dressed those leads, you did excellent work.

Kudos and a couple of ATTA'-BOY's!!! for you as well.

I do apologise for not being able to understand most of what you posted. Thank you for your help.

This seems to happen when I get hired in to a job, sign several NDA's and then have access to lots of different boards and their schematics, then have to leave the job to handle family issues and I'm left with a jumbled mess of memories as if they're broken links...and have to keep my mouth shut...

Much like CB Tricks - back then...

At least something good came out of this thread - congratulations!

IT WORKS!

​

 

[walterjn]

Thank you again for your time and insight. You pointed me in the direction I needed to go. Without your guidance, I'd still be beating my head against a wall.
Thank you for the compliments on my work, it wasn't my best work, & far from the worst I've ever done. I've been trying to keep the inside as clean as possible, both the soldering and the routing. I don't spend a lot of time soldering anymore, electronics are now relegated to small hobby status.