Re: 3560 Crystals from eBay


Lee
 

Looking at the circuit – the oscillator is not loaded too heavily by the PA (it ‘sees’ a high impedance at the input of the PA), so no changes there. One simple thing to try is to pull the 2N3904 and replace with a 2N2218, 2N5179, or something NPN and metal-canned with a higher alpha….use a transistor tester to pick a suitable one. Another option is to replace R1 with a slightly lower value; this pulls up the voltage at the base of the 2N3904 and may help it kick on…………this is a non-engineers look, but an oscillator is simply an amplifier with at least unity gain and feedback into the input…..

 

Lee KX4TT

 

From: Bob Groh bob.groh@... [4sqrp]
Sent: Thursday, May 4, 2017 20:43
To: 4sqrp@...; Jim Sheldon
Subject: Re: [4sqrp] 3560 Crystals from eBay

 

 

Ouch.  Not good news but hopefully someone will find a cure.  Ah, well.  Switching to 3560 is a good idea - we just have some implementation problems.  Thanks for your work.

 

Bob, WA2CKY

 

On Thu, May 4, 2017 at 3:34 PM, 'Jim Sheldon' w0eb@... [4sqrp] <4sqrp@...> wrote:

 

I ordered a 10 pack of 3560 crystals (HC/49 style) from 3rd Planet Solar
on eBay. Got them yesterday and finally had a chance to check them out.
NONE will oscillate in the Cricket. The crystals aren't bad (they
oscillate & check good in my crystal checker) they just won't run in the
Cricket. I don't know if it's a feedback problem that needs a component
change or if it's just that there's not enough drive. They will
sometimes try to start and once in a while one of them would run in RX
mode but as soon as you hit the key to transmit (good 50 ohm dummy load
attached). The crystal would stop oscillating and it would be necessary
to cycle power to shock it back into oscillation. Maybe Dave, NM0S
would chime in on this since I'm not an engineer and don't know for sure
which component values to change in an attempt to make these crystals
work.

Jim - W0EB

 

 


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