DTB "IF Filter Mod" for RCI 29xx radios?

[buickid]

It was aligned, the bottom lid was removed, but the filter mod required access from the solder side of the board, the top lid, which still had the sticker intact. I'm planning to send the radio out at some point to have the filter mod done, but theres not a lot of motivation since most say it won't do anything, and since its no longer my primary radio. And you are correct, shipping is quite killer indeed, also reason for low motivation.

 

[Mudduckmobile]

Bells CB needs to offer this mod, at least he'd post a video.

Bells does almost anything you want but if it is not a good move he (screwdriver) the boss will tell you, and why, I trust him, he is navy, and a sparky, with the paper work to prove it too.

 

[Shadetree Mechanic]

this is an interesting thread.
not sure how i missed it the first time around.

Mad Scientist has it right.
this IF mod is not about the noise floor, and wont make any difference in the sound of the receive with no signals present.

bascially, its like having two small antennas hanging off the bottom of the IF filter, causing some of the trash that "may" be present to be coupled through.

if you had someone close by, or with a really strong DX signal on a harmonically related freq. you might get some additional noise from them.

maybe a ham close by on 30 meters?

as for the noise floor issue, after discussing it with a couple of people who know way more about it than i ever will; the conclusion is that its because of a crappily designed local oscillator in the PLL section, and the only fix would be redesign the whole thing.
IE: not going to happen.

there is a way to make it less noticeable, and anyone who tunes up a galaxy/rci/ whatever style radio should know this.

its called the "antenna coil" and in the 2970DX its L8.
in other radios it may be a different number.

if this coil is tuned for max like you would any other coil during a receive alignment, you will have a high noise floor.

the fix is to do the RX alignment, peak L8 like normal, then remove the sig gen, and anything attached to the antenna jack on the radio.

now give L8 a bit of a turn clockwise and the noise should drop right off.
turn it just enough to drop the noise a bit, and you will notice that you have only lost a tiny bit of sensitivity. (not enough to make a difference IMO)

thats how i do it, and it was shown to me by a Galaxy service tech.
LC

Thanks for the explanation on this L8 adjustment. I have tried this and have gotten great results on my Galaxy radios.

 

[Handy Andy]

Here is the "new Link" the old one has since been 404'd...

CBWI September 2001 RCI 2950DX Image Rejection Modification

As noted in the review, an anomaly, not found in other radios, was found in two of the RCI 2950DX tested.

cbworldinformer.org