northstar radio question

[timberwolf]

i have 3 northstar radios.one ns9500,one ns4000,and one 440v.all three radios have some kind of carrier on channel 13.no other radios of mine have this carrier.the ns 4000 is in my mobile and does it no matter where i am.is this a common problem with these radio and does anyone know the cure?

[2600]

Yep.

The cure is to change the 13.56 MHz crystal in each radio to another one.

The choices are 14.01 MHz.

14.46 MHz.

14.91 MHz

or 15.36 MHz.

The problem is being caused by the 13.56 MHz crystal. The second-harmonic frequency of this crystal leaks into the receiver circuits at 27.12 MHz, halfway between channels 13 and 14.

When you change modes from AM to SSB, this crystal frequency changes by about 2.5 kHz, and causes the frequency of the "birdie" carrier to move by twice that much, 5 kHz.

This is the crystal frequency used in most "8-band" radios like these, and a great many Galaxy "DX" models. The cure is to move the birdie's frequency to some other channel that you don't use.

Using a crystal with a higher frequency will cause you to lose the very lowest-frquency bands, and will move the coverage of the highest band UP higher into the 10-meter ham band.

Odds are that you never use the lowest 3 bands, so that would be little or no loss.

RF Parts at www.rfparts.com/serviceparts_galaxy.html has the 14.010 crystal listed. This will "lose" only the lowest band, and move the 10-meter coverage up another 45 channels. The receiver "birdie" won't go away, but will move to twice the crystal's frequency, or 28.020 MHz.

You don't use that frequency, so this solves the problem.

Trouble is, you have to do this to every radio that you want to use on channels 13 and 14.

Or you could persuade your friends to choose another home channel.

Might be cheaper.

One last thought. Some North Star radios would cover the PLL section of the main pc board with a glob of potting resin. If this crystal is under that glob, you are probably better off to just leave it alone and kiss off channels 13 and 14. Too much risk of collateral damage from grinding away the potting resin.

73

[timberwolf]

thanx 2600,i was gonna take them to your shop .the mod would be handy for the base but not the mobiles.i use my tram you went through for me the majority of the time anyways.but curiosity was getting the best of me on the northstars because all three acted similar.thanx again for your help.oh,and while i'm thinkin about it,you actually worked on the northstar base for a previous owner,has the variable ping,bump bump and talkback mod,great radio other than that damn carrier.