Cobra 148gtl, Unident Grant mods

im surprised that those mods couldnt be found around here through searching, but then again, i have had many troubles with the way the search feature works on this forum.

i just have a couple of things i believe should be changed on the list.
these are just my findings, and should not be taken as gospel.
(unless you pray to the almighty loosecannon. then, go ahead LOL)


i will address #4 last.


5. the purpose in jumpering this resistor is to keep the bias from going negative.
(these are justin depolis's words, not mine)

6. this is the mod that increases the gain of the transmit mixer.
also, you might want to include the older chip that is used here: the S042P.

7. might want to mention the part number here. its TR41.


8. probably some different wire colors used in different chassis. maybe add that the negative lead of the cap goes in the negative hole left open by the removal of C174, and that the positive lead of the cap goes to the base of TR41. (lead closest to the rear of the radio)

9. dont know why this would only apply to the 148F.
this cap is in the mic circuit. the stock cap wasnt rated for enough voltage and would fail. increasing the value of this cap will help keep the mic from squealing when audio gain in the radio is increased.


now, for #4.

C163 can be increased to 4 or 5 pF, but increasing the value of C41 actually makes the tuning of L6 too narrow.
the effect will be that L6 will peak over a very narrow range causing the gain to fall off quicker towards the band edges than it did with the stock 2pF cap there.

a better mod is to leave C41 as a 2pF cap and solder a 1pF cap from the emitter of TR14 to the lead of C41 that connects to L5.

now, i must say here that these are my own findings, and i have never heard anyone else's opinion on this mod. i do know that this is what i observed personally.

just trying to help clarify things,
LC

 

LC, glad I came across your old post. I was going to follow along and change both c163 & c41 to 5pf. I'll do c163 for now and do the 1pf later when I get it. I'll let you know how it turns out.

PS: the document I'm referencing mentions removing c161. Your thoughts?

 

The thief DePushdin really knew his stuff.

His technical expertise was only second to his dishonesty, what a shame.

Right click, save, lol.

 

I think it applies to the 148gtl, not the gtlf.

I had a GTLF (frequency counter model), and it was not up to snuff compared to the GTL (my Grant XL).

Sent it to DTB, got it back and was dissatisfied, until he explained that it was a completely different rig.

 

CORRECTION!!!

just wanted to correct some info i was just reminded of.

in speaking about how to broadband L5, i stated to connect to the emitter of TR14.

it should be the COLLECTOR (middle leg) of TR14.

so the mod should read: connect a 1pF cap from the COLLECTOR of TR14 to the leg of C41 that connects to L5.

sorry about the bad info.
LC

 

So this will lower my DK below 1.5 watts right?

1. Carrier Adjustment: VR10. If lower carrier is desired, change R196 near VR-10. Try about 270 ohms.

 

It should, I got mine down to 2/3w but it sounded like double sideband so I brought it up to 1.25w DK.