Oscillator without a crystal?

[W8HDU]

What frequencies did you have in mind?

K5UOS

The one I need to build before winter needs to have at least 10-40 mw output (50-ohm load), and able to lock to .1 hz between 5700 to 7500 kilohertz. It's part of an rf analyzer I use in antenna measurements.

What I would love to be able to do is get something that could replace the whole RF deck which covers 3240 to 10200 kilohertz, and could be set on a frequency, and then varied 10 kc either way for the measurements. I imagine if I searched enough places I could find one from years past that was designed with thumbswitches.

Ideally, something simple would be nice so I can CAD it and build some boards up. The one I need the most is something to operate on 6900, or have something variable to be adjusted between 6840 and 6960 kilohertz. I have some measurements coming up and all I have is some WW-II signal generators which are not stable at all.

[VK2TIL]

The link works for me. Perhaps you have to be a member of the Group; if so, join. It's a good Group and I learn a lot.

I agree with UOS; I was going to make a similar comment earlier but let it go.

For a frequency standard, a simple oscillator does fine.

If you go here;

http://www.hparchive.com/hp_equipment.htm

you will find a downloadable manual, with schematics, for the HP10811 reference oscillator; not a lot in it, really.

The secret is in the construction and in the quality of the crystal.

(Incidentally, I find it very instructive to look at how the greats such as HP designed their wonderful instruments in the "electro-mechanical" era. Whilst commercial practice has changed to a "digital" approach, many of the things we homebrewers do are still of the "electro-mechanical" kind).

The crystal marker generator is somewhat forgotten today but is still a very good instrument. 100kHz or 1MHz crystals were usual and it's a reasonable bet that the 100kHz crystals seen at hamfests & on ebay are of frequency-standard quality.

UOS discussed the "mixer" approach; I agree (if, that is, you require that approach rather than the simple cal oscillator approach).

One place you will find something like this is in older Handbooks (up to about the '80s I think) where it was used as a 'scope "bandwidth extender".

And, if you get hold of a copy of EMRFD before they become scarce (am I glad that I bought SSD and the W1FB books years ago ), you will find a wealth of information about diode mixers (and many other things).

Going back to the PTOs; consider something like this;

http://cgi.ebay.com/Collins-Radio-70...d=p3286.c0.m14

with a crystal and a diode mixer to create a lovely wide-range VFO.

[VK2TIL]

Apropos the EMRFD Group; there is a post today regarding wide-range VXOs and, in particular, the "Super VXO".

The discussion to come should be interesting.