Broad banding the 148st ?

[loosecannon]

changing D35 is for the clarifier range, and won't have any effect on the broadbanding of the radio.

Its a combination of factors at play here, and it has to do with both the alignment and changing out one part.

to broadband the TX, change C163 to a 5pf cap. do not go any higher than that.
then, tune the TX on channel 20 like normal.

tune L48, L47, L46, and L45 first, using only a deadkey.
now tune L38 using a modulated carrier. (1khz tone)
now go to your top freq. and re-peak L46 for max deadkey.
go to your lowest freq and re-peak L45 for max deadkey.

now bounce back and forth between the upper and lower channels in order to get an even balance.
you will find that power starts to drop off right around 80-100 channels depending on the particular radio.

you can do the same thing for your receive by bouncing back and forth between L5 and L6.
LC

 

[Harley3315]

I was kinda thinking the same thing but the info he shared was also useful. Excellent explanation lc

 

[sonoma]

LC do you not have all the broadbanding info for this radio. if not I just found all the info KlondikeMike did up plus looks like you put a foot note on it,

 

[loosecannon]

yeah i have all that info, but i don't like most of those mods.
removing R95 does have side effects from what smarter people than me have said.
I don't like messing with the gain in the TX section either.

I have found over the years that the gains just aren't worth it.
I've played with the gain in the receiver front end and found that it just didn't make much difference in the broadbanding.

I do still do that receive mod that was footnoted, but he was only asking about TX power so that's how i formed my response.
LC

 

[Robalo]

I STILL HAVE THIS NOTE FROM ? Add a 100 ohm resistor from pin 12 to pin 14 of the SO42P / TDA6310 transmit mixer.
The 100 ohm resistor from pin 12 to 14 (ground) is there to increase the gain of the TX mixer. I have seen several times where people send pin 12 right to ground. This is 100% incorrect. They often do this in attempt to increase the gain, but they don't understand a TX mixer in general or what is going on, obviously. In this particular chassis, 100 ohms I have found is the best value to bring up the gain without any adverse effects.
This does nothing to "broadband" the TX but rather brings up the gain, and offers uniform performance across a wide range of frequencies, as the "Q" of the TX bandpass filter is high compared to exports, and therefore tend to be more narrow banded.
If you have expanded the radio for more frequencies, you can easily broadband the RX and TX bandpass filters. In the bandpass filters, change the 2pf capacitors to 3pf, and it will widen it right up, but still it's job very well.

 

[sonoma]

Sue from Australia had posted a update a few years ago on Cbtricks for a broadbanding method for the 148 etc radios. I am trying to locate it in all my saved files to post it. she is one of the best techs I have ever known. Loosecannon and Nomad know who I am talking about. she is very smart about radios. she is the one that told me about the diode to help when my old 148st 4 pin mic connector was dropping out on the fartherest channels from the cb bands was dropping out. it worked on my radio for the problem I was having.
she showed jumping some of the Lcan pins like the 858 chassis radios had been done to broadband them.

 

[hpssb]

Two of them were my radios, one was a Hornet which is an aussie rebadge of the cobra 142 or 146, cant remember which one, the same method also works for the uniden washington and the side mike cobra 148 and other uniden made ssb radios with the 16 pin transmit mixer chip.

It involves seven varicap diodes controlled from the PLL tuning voltage connected to the mixers, four for transmit and three for receive. Mine covered NZ channel 1 (26.330) to the phone section of 10 meters (28.650) with minimal variation in power.

I'm taking this text from an old T1 post, it's way beyond my level of understanding, if you want the technical details PM us and I'll pass on a contact address, or ask nicely on T1.

Unfortunately the pics on T1 got wiped when tinypic closed down a few months back.

There were 2 versions, both smt. The first one was a perfboard prototype, the second one used a proper green board. The first one is shown on the pic below.

She probably was the original pictures, heres the only one I saved of the mod:

 

[sonoma]

I was over there looking this morning and did not find what I was looking for. may be gone since a site stop working as you stated.. Tinypic could have let a lot get lost.

 

[Robalo]

SONOMA I maybe tomorrow