Electronic Goldmine has some Pulse Engineering LAN transformers (same as
those used on many LAN boards) on clearance at $1.00 each.
http://www.goldmine-elec-products.com/prodinfo.asp?number=G17078
Datasheet is at http://www.datasheet4u.com/download_new.php?id=541958

Quite cheap, in my opinion.

Cheers,
Dave M

Perry Sandeen via time-nuts wrote:

I'm not much further along then you but I did find a few things...

1. You can buy/salvage good quality 10.0 MHz transformers form networking
   equipment designed for 10BaseT Ethernet.  These are designed for galvanic
   isolation and are used in old 10baseT routers and switches.  Newer Ethernet
   works are 100 and 1000 Mhz but the older version was 10 MHz.  I have a box
   of salvaged parts I removed from junked routers.  These transformers are in
   wide DIP packages with 0.1" lead spacing.

2. Cheap 10MHz crystals need to be measured, sorted and matched by hand.
   And then you want to keep the temperature from moving around to much.
   Before I owned a GPSDO and a two channel scope I used to think the cheap
   crystals where all exactly "spot-on"

3. it is really easy to build a temperature controller using a $2 8-pin uP
   and a few lines of code.  The 8-pin uP will have a few analog inputs and
   outputs and even pins left over for status LEDs.

On Wed, Nov 26, 2014 at 8:08 PM, Perry Sandeen via time-nuts <
time-nuts@febo.com> wrote:

--

Chris Albertson
Redondo Beach, California

If you want to see how to really do it right, check out this
distribution Amp
on the TAPR site.

https://www.tapr.org/kits_tadd-1.html

73, Dick, W1KSZ

On 11/26/2014 9:08 PM, Perry Sandeen via time-nuts wrote:

Perry,

Just three days ago, I posted about my using transformers from
Ethernet cards. I also summarized the results of some measurements
using the spectrum analyzer. There was only one response, so it seems
that what I posted was widely ignored.

Dave M - good find on Electronic Goldmine.

Joe Gray
W5JG

On Thu, Nov 27, 2014 at 8:50 AM, Dave M dgminala@mediacombb.net wrote:

Any suggestions as to which chips, or links to any documentation?
Thanks,
Jim

On 11/27/2014 11:36 AM, Chris Albertson wrote:

This email has been checked for viruses by Avast antivirus software.
http://www.avast.com

Hi

Just as you can “move” 455 KHz IF transformers down with a little padding, you can do the same thing with 10.7 MHz IF cans. They may or may not tune to 10 MHz. If you get some that don’t tune, it’s just a cap to bump them down.

The gotcha to any filter in a distribution system is Q. High Q implies high phase slope or long delay. In the real world things are temperature sensitive. Delta temp -> delta inductance -> delta phase -> bad ADEV. The trick is to get the job done with as low a Q as practical.

The next layer to the onion is loading. If the filter is on the output of the amp, it’s phase will change with load. Same issue as temperature, high Q -> big changes -> bad performance.

Even with a “class C” multiplier, fixed tuned Q< 10 circuits will do the trick for 5 -> 10 MHz doubling. With more exotic multipliers, even simpler filtering will do the job.

If you don’t need -200 db harmonics, and 30 db is fine — don’t go nuts with the filters.

Bob

Hi

We are talking about many different parts here and calling them all “transformers”.

The parts from an Ethernet line card are broadband devices used primarily for isolation. The 10.7 MHz IF transformers are designed for use in a filter. The first could be used to break a ground loop on a cable. The second could be used to knock out a harmonic or sub-harmonic. Each will do quite poorly trying to do the other one’s job.

Bob

I have 4 or 5 devices that use the 10 MHz from my Trimble Thunderbolt.
All but one have high impedance 10 MHz inputs, so the Thunderbolt
can drive the lot without any amplifier.

When I put together my Thunderbolt, power supply, and filter I assumed I
would
need a distribution amp ans made provisions for it.  Turns out it is not
necessary.

The real trick was locating well shielded patch cables to keep the
Thunderbolt from
jamming WWV on 10 MHz.

On 11/27/2014 08:41 AM, Richard Solomon wrote:

--
Chuck Forsberg WA7KGX  caf@omen.com  www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
Omen Technology Inc      "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231  503-614-0430

For the most part, you don't want transformer isolation unless you plan on using balanced lines.  There are worse things than ground loops out there, and lifting a coax shield away from ground is a great way to find all of them.

You definitely don't want 10.7 MHz IF transformers, unless you are just trying to build a thermometer.

-- john, KE5FX
Miles Design LLC