A trifilar transformer with two diodes is the simplest. You could also use a mini-circuits doubler, same thing more expensive.

Alternatively take an SBL-1 and feed 2 inputs with the same 10Mhz and get a doubled out. You will need to filter it a bit.

At 25-05-2011, you wrote:

--
Raj, VU2ZAP
Bangalore, India.

On 05/25/11 07:39 PM, Chuck Forsberg WA7KGX N2469R wrote:

It can not be trimmed via a voltage. Also, I'm not keen to require an external
reference.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

Hi

You also may want to avoid an oscillator with much 10 MHz content in it. All sorts of odd things can happen with spurs when you have unplanned stuff on the main reference. Another thing to look closely at is - how much of the radio tracks the reference? On some radios, they don't really lock everything up. You get better performance, but not quite what you would expect.

Bob

On May 27, 2011, at 3:55 AM, Dr. David Kirkby wrote:

On 27 May 2011 15:21, Bob Camp lists@rtty.us wrote:

Yes, a band-pass filter would seem sensible here.

To the best of my knowledge, everything is locked to this 20 MHz, so
there should be a significant improvement.

However, I must admit as to wondering whether its worth the bother. I
have a Yaesu FT-ONE, which is a pretty poor design, despite it was the
top of the line Yaesu transceiver in its day (~1982) costing $3000. It
has a synthesizer for 100 Hz steps and then uses a varicap diode to
get the 10 Hz steps! This is not very stable, but in practice is
stable enough. There's nothing much one can do about that - perhaps
keeping the temperature constant in the vicinity of the varicap and
other critical components would help. But it also suffers from the use
of more than one reference, so hard to really stabilise.

The Kenwood TS-940SAT should be a lot more stable anyway. The Kenwood
actually seems a lot better technically to me, despite it costs only
$2000 and was released about the same time as the Yause FT-ONE. The
Kenwood TS-940S has a built in ATU (not even an option on the Yaesu
FT-ONE), FM (optional on the Yaesu FT-ONE), TCXO (not even optional on
the Yaesu).

I might however look at using a TCXO o OCXO in the Kenwood.

Dave

Hi

Looking at this in terms of time nut type stability - you really want to lock the 20 MHz up to something like a TBolt. At that point you have a wire out the back of the radio and all that implies. Keeping the ground loops and RF issues at bay in a transmitter is not trivial. For a timing receiver something like a R1051 or an R6790 might be a better starting point.

If it's an internal oscillator (because of the various issues) - spend the time to dig up a 20 MHz part. You loose the Time Nut / "WWV is off by 0.0001 Hz capability". You gain a spur free radio that doesn't do something odd when you transmit at frequency xxxx using mode yyyy.

A lot of outfits had a hard time with the sub 100 Hz synthesizer steps back before modern PLL and DDS chips came out. Many of the big boys in the military radio business put out radios that had very predictable spurs from the fine tuning synth. They can be a real pain if the idea is to track something like WWV and extract carrier phase or timing from it.

Bob

On May 27, 2011, at 10:51 AM, David Kirkby wrote: