Question about tuning the Noise Blanker coils on a 148GTL

[loosecannon]

im hoping one of the techs here has a "cheap and dirty" method for getting the noise blanker coils (L1 and L2) into close to perfect alignment.

i dont expect to get it perfect without the right test equipment, but since i cant see myself affording that stuff anytime soon; im hoping there is another, slightly less accurate way.

so, does anyone have any ideas?
im hoping for something just a bit more technical than "hold a hair dryer up to it". LOL (but if thats the way, i will do it!)

thanks for any ideas,
LC

 

[loosecannon]

im surprised NO ONE has any techniques or ideas for this.

one bump please!
LC

 

[AudioShockwav]

For poor noise supression, the whole NB circuit must be checked for proper alignment.
With a properly working circuit you`ll notice a slightly lower volume with the NB turned on.
A simple alignment procedure is to use a noise source like an electric drill or hair blowdryer at the antenna socket. Tune the NB coil (s) for minimun noise. A second way is to view the NB detector output with a `scope, tuning for max noise reduction. The factory method uses either a noise generator, or a RF signal Generator modulated with a 60 Hz square wave, tuning for min noise. When a Diode detector is used in the NB loop, you can probe the diode (s) with a DC voltmeter, tuning for Maximun detected DC voltage.

Is this of some help?

73
Jeff

 

[GRTS]

The NB alignment on the older 148GTL is very close to the Galaxy radios.
All you need for test equipment is a signal generator and a voltmeter.
Set the generator up for 1000uv at 27.205mhz (ch. 20)
Set radio to channel 21 (10kc from generator frequency).
Make sure RF Gain on radio is set to fully clockwise.
Make sure NB is on.
Connect voltmeter to TP6 and adjust L1 & L2 for max voltage.
Never tell anyone I helped you with a Cobra.


Post results.

 

[chec0]

Never tell anyone I helped you with a Cobra.

LOL

 

[loosecannon]

jeff and ray, thank you guys so much! (and ray, mumms the word!)

just got done building a custom 148gtl, and want to get the NB aligned the best i can.

if you guys are members of "the mod" group, there are pics there.

thanks again!!!
LC

 

[loosecannon]

GRTS (ray),

it worked like a champ!

this was very helpful, as i had them quite a bit off.

one thing though, the TP on the dual conversion mb8719 chassis (148gtl) is TP17, which is the cathode of D2.

couldnt find a TP6, and figured it was a typo.

thanks so much!
LC

 

[DIRTYWHITEBOY]

Ray is the man,very good information.