The AM Forum

I've successfully used "dead bug" and similar techniques with ICs and other solid state devices for years - along with
clip leads CLIP LEADS and *more* clip leads  ;)  So, there HAD to be a way to apply
this technique to surface mount devices - and here it is!

This circuit is a VFO using a Linear Technologies resistor set oscillator. Worked perfectly the first time.  I did end up "loosing"
one device - I dropped it on the workbench, and was (and still am) unable to find it.  The
IC is about the same size as a smaller sized tick, and it was absorbed by the other stuff
around it when it slipped from the needle nose pliars I was using to hold it.

(http://www.classeradio.com/smd_cliplead.jpg)

Click here for larger image (http://www.classeradio.com/smd_cliplead.jpg)

By the way, the oscillator IC generates too much phase noise (hiss) and has too much bit jitter
to be an effective VFO, but it was interesting to fool around with the device, and SMD in general.

Regards,

Steve WA1QIX

Yep, any R/C oscillator is unsuitable for RF use.  Particularly if the oscillator will be driving a high power amp, good citizenship in keeping the wideband noise at a low level is mandatory.

It's kind of an interesting device.  Essentially, the resistor sets a voltage that then is used to control an internal
master oscillator, voltage controlled.  There is a programmable divide by (1, 10 or 100) to range the output.  The result
is 1khz to 33mHz operation.

I was really surprised by the immunity of the device to outside forces, such as load resistance/capacitance changes,
power supply variations and even physically touching the IC while operating.  Stability is good in that respect.  Of course,
the issue is the phase noise caused by the dividers, etc.  There's quite a bit going on in that IC !  You can readily hear
the frequency compensating and locking circuitry working - step-changing the frequency slightly, when listening to the
output in a local receiver with the BFO turned on.

I didn't make lots of quantitative measurements, but I did do a simulation by mixing the oscillator output with the antenna input
to a receiver, listening around.  Tuned dead-on, it's beautiful - tune off frequency, and you're slope-detecting the phase
noise and this shows up as low level hiss.  I set the oscillator 10kHz away from an existing AM QSO.  The hiss generated by the
60 over S-9 oscillator 10Khz away was noticable in the background of the 20 over S-9 QSO. 

The hiss reminded me of some of the very early synth VFOs that I heard on the air during the '70s. I believe Roger, K1CZH had one, and he
had a very noticable hiss on his signal.

This little oscillator is too hissy for a VFO except maybe for a PW rig, but for 2 bucks, I am reasonably impressed by the performance and stability.

And, it was a good test for working with surface mount  8)

Talk later and Regards,

Steve (clip lead alley!)

Wondering out loud here... would running the output through a clean PLL have some benefit here??

            _-_-WBear2GCR

It might improve it somewhat, but a PLL won't be too much quieter than its reference.

Yes, indeed, cervix mount components are just a microcosmic variation on the same old solid state theme.  But they're not all that small.  No problems with Quantum phenomena such as the observer effect, no trouble with time running backwards, no red shift...  y'just need a Luxo magnifier lamp, tweezers, and a small soldering tip.

Jeff
KA1OGM

Hmm...and here I was looking into this as the LO for an NE602/612-based receiver converter...  :-\

Why would you need that?  The NE-602 has an internal oscillator.  Just add a decent L/C tank and you're done.