• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

How do I get the crystal section to work on my Rf gen

Status
Not open for further replies.

dr pepper

Well-Known Member
Most Helpful Member
I have a generic cheap rf gen, it has a function where at least I think you can use the gen to o/p a frequency set by an xtal that you plug into the front.
I tried this and put the function switch to xtal but the machine just works as normal with the o/p frequency being set by the control knob.
Thinking maybe you had to set the o/p freq close to the xtals freq for it to work I tried this but still zip.
I odnt have the instructions for this, anyone know how to use the xtal function, or is the switch dirty or something.
 

JimB

Super Moderator
Most Helpful Member
A few details about the generator would be useful.

Depending on the design of the circuit, it could be that the crystal is just switched into circuit instead of the coil and tuning capacitor.

Also be aware that not all crystals are the same.
Not all crystals will work in the same oscillator circuit.

Try some switch cleaner.
Try a different crystal.

JimB
 

kubeek

Well-Known Member
Most Helpful Member
Jeez dr pepper, 8 years on this site and still you don´t say in the first post what is the type of the rf gen that you are talking about?
 

dr pepper

Well-Known Member
Most Helpful Member
Oops soz I meant to add a pic sorry its a bit naff.

I dotn know if the xtal is series cut or parallel, I tried a rc 27.125mc xtal, and a 4.43 colourburst, the socket is not a hc49, its one of those great big old doofers (the socket centre right, you can just see the 4.43 xtal on top of the machine), neither the 27mc or the 4.43 change anything on the 'scope or counter.
The 27mc xtal is a third overtone, and the 4.43 is a fundamental, if the 27mc one gave me 9mc fundamental at least the thing would be working.
I'll try squirting the sw with some servisol, its never been on the xtal psoition since I've had the thing.

IMG_20160912_121204.jpg
 

JimB

Super Moderator
Most Helpful Member
the socket is not a hc49, its one of those great big old doofers
Big and old are relative terms!
That looks like an HC6 type.
A FT243 or 10XJ socket or even an octal socket would be a big old doofer!

JimB
 

dr pepper

Well-Known Member
Most Helpful Member
Yes its a Hc6.
Cleaning the sw didnt do owt.
I have an xtal that came with it somewhere I'll try that when I find it, maybe the loading capacitance is something weird.
 

k7elp60

Active Member
Oops soz I meant to add a pic sorry its a bit naff.

I dotn know if the xtal is series cut or parallel, I tried a rc 27.125mc xtal, and a 4.43 colourburst, the socket is not a hc49, its one of those great big old doofers (the socket centre right, you can just see the 4.43 xtal on top of the machine), neither the 27mc or the 4.43 change anything on the 'scope or counter.
The 27mc xtal is a third overtone, and the 4.43 is a fundamental, if the 27mc one gave me 9mc fundamental at least the thing would be working.
I'll try squirting the sw with some servisol, its never been on the xtal psoition since I've had the thing.

View attachment 101182
I have a generator that looks just like that, mine is a BK Precision model 2005B.
I just tried it with a 3.5Mhz crystal and connected the output to my frequency counter, which indicated 3.5Mhz.
Here are the instructions:
Set the mode switch to XTAL
Set the RF output to LOW
Set the FREQ. RANGE switch to "F", and the frequency dial to 100KHz
Set the FINE control to minimum.
The output signal is treated in the same manner for the unmodulated carrier with the exception the the output level cannot be adjusted.
 

Tony Stewart

Well-Known Member
Most Helpful Member
Beware that *IF* the crystal is an overtone series mode and the "gennie" is a parallel mode 15-30 pF , the parallel mode loss might exceed loop gain and it won't oscillate.

overtone harmonics are usually >20MHz and series is preferred types in higher f types.
 
Last edited:

dr pepper

Well-Known Member
Most Helpful Member
OK it works like that.
I can adjust the o/p level on mine.
The xtal oscillates at fundamental, but with the wick turned up there is enough third harmonics to do what I need.
Cheers.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top