Fwd: RE: [DSP-10] DSP-10 with external Frequency Control

Fri, 1 Mar 2002 10:24:35 -0600

Doug:

I have received page 7 of the schematic and downloaded the LMX1501A data
sheet.

To be able to insert the external clock automatically the following is
needed:

A small relay( SPDT) to move EXT_REF ( P106-2) from XTAL (P106-1) to
EXTERNAL_10MHZ.
In addition a buffer amplifier and if automatic switching IS WANTED a couple
gates to do the job.

All this circuit I am talking about is just a CMOS device like a QUAD NAND
GATE and possibly a transistor to drive the relay.

Reason why you are having a 1.5 KHZ shift is that the coax cable is adding
additional capacitance to the XTAL line, causing the 10 MHZ frequency shift
and with a small relay nearby the local 10 MHZ can be compensated in an
stable manner and when the external signal is inserted the local 10 MHZ is
disable and replaced by the external 10 MHZ.

The circuit can be assembled in a small perforated board, so if you guys are
interested let me know to proceed.

 I will need to know the minimum voltage level for the EXTERNAL_10 MHZ, also
if sine wave or square wave

Regards

Nando KC5FDW

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Doug Bade
Sent: Friday, March 01, 2002 9:55 AM
To: [email protected]
Subject: Fwd: Re: Fwd: RE: [DSP-10] DSP-10 with external Frequency
Control

Correction below...
re-sent due to mail send problem...

>I guess I should have said more specifically, automatic preferred, and
>switched somehow if necessary. The current scheme requires moving a shunt
>on the header or replacing shunt with external connection... We wish to
>simplify this design. Just running a coax loop out and back in causes freq
>change to the lo of about 1.5 kHz.. way too much to compensate.. That is
>the agenda.. Thanks, Doug
>

>At 10:45 AM 3/1/02 -0500, you wrote:
>
>>>         Here is page 7 of the schematic. The 10 mhz oscillator is where
>>> we are talking about. It has an internal and external connection across
>>> the header...
>>>We want to be able to run on board when it can, and the inject external
>>>for higher stab when available.. Let us know, Doug
>>>
>>>
>>>
>>>At 09:30 AM 3/1/02 -0600, you wrote:
>>>>If one of you guys can send to me the schematic and what you desire to
>>>>do, I
>>>>will be happy to design the circuit you need.
>>>>
>>>>I am an Electronic Design Engineer in areas of R.F. ( from low to Ghz ),
as
>>>>well as DC Circuits and power supplies.
>>>>
>>>>Regards
>>>>
>>>>Nando KC5FDW
>>>>
>>>>-----Original Message-----
>>>>From: [email protected]
>>>>[mailto:[email protected]]On Behalf Of Doug Bade
>>>>Sent: Friday, March 01, 2002 9:20 AM
>>>>To: [email protected]
>>>>Subject: RE: [DSP-10] DSP-10 with external Frequency Control
>>>>
>>>>
>>>>          A company I worked  for (20 years ago)  had a 60 hz oscillator
on
>>>>a board and would sync it with line freq when it was available. As I
recall
>>>>it was a NAND gate with a pullup on the line side inserted in the loop.
I
>>>>am trying to rationalize if this approach would work. What I am
envisioning
>>>>is coupling the lo on the board a little looser, and if you feed an
>>>>external 10 mhz in, it would tickle the oscillator and drag it on freq.
I
>>>>tried the direct approach by connecting both at once at the header and I
>>>>got harmonics and 2 oscillations instead of 1 steady... I was
considering
>>>>too a series resistor in the header loop which may allow the xtal
>>>>oscillator to bend a little easier...
>>>>
>>>>          Any engineering thoughts would be appreciated..
>>>>
>>>>          At last case, we could use a 4053 cmos switch and just switch
>>>> with
>>>>a toggle switch. to manual for my likes...but it should work..Doug
KB8GVQ
>>>>
>>>>
>>>>At 06:26 PM 2/28/02 -0500, you wrote:
>>>> >Hi, Doug!
>>>> >
>>>> >Excellent question; I had wondered about doing the same thing.  It is
>>>> >inconvenient here to make the change from the GPS-controlled external
>>>> >oscillator (or the Rb oscillator) to internal frequency control, as
>>>> with my
>>>> >box I need to not only open the large outer Hammond box, but also
open,
>>>> >unscrew, and remove the copper circuit board homemade box housing the
>>>>EZ-Kit
>>>> >Lite to make this change.  And in the course of experimenting, I
fairly
>>>> >frequently want to make the switch.  So if you come up with a workable
>>>> >'front panel switch' solution, please post the details to the list so
we
>>>>can
>>>> >all implement it!
>>>> >
>>>> >Thanks in advance, and
>>>> >
>>>> >73,
>>>> >
>>>> >Roger Rehr
>>>> >W3SZ   FN20ah
>>>> >2 Merrymount Road
>>>> >Reading, PA  19609-1718
>>>> >http://www.qsl.net/w3sz
>>>> >
>>>> >
>>>> > > -----Original Message-----
>>>> > > From: [email protected]
>>>> > > [mailto:[email protected]]On Behalf Of Doug Bade
>>>> > > Sent: Thursday, February 28, 2002 9:02 AM
>>>> > > To: [email protected]
>>>> > > Subject: Re: [DSP-10] DSP-10 with external Frequency Control
>>>> > >
>>>> > >
>>>> > >          This brings up a question I have been meaning to ask.. I
>>>> > > externalized the 3 connections through rg174 for the 10mhz
>>>> > > osc switching.
>>>> > > When I jumper loopback external to send 10 mhz back in, the
>>>> > > oscillator
>>>> > > jumps 1.24 khz off freq due to loading changes of the
>>>> > > oscillator with a 14"
>>>> > > loop of coax more or less...External input works great, but
>>>> > > cannot warp
>>>> > > oscillator that far to get on freq.
>>>> > >          Has anyone figured out a switch scheme to allow
>>>> > > internal/external
>>>> > > 10 mhz from the panel? I am considering a mosfet shunted
>>>> > > across internal
>>>> > > pair on board or similar schemes.. Anyone have a working plan???
>>>> > > Doug KB8GVQ
>>>> > >
>>>> > >
>>>> > > At 04:21 PM 2/27/02 -0800, you wrote:
>>>> > > >Jimmy W7CQ and I made are first LHL7 Qs with 1 mw or less.
>>>> > > >
>>>> > > >We have both of our DSP-10s controlled by our external 10mhz - GPS
>>>> > > >frequency standards. These standards use the Brooks Shera
>>>> > > controller with
>>>> > > >an HP 10544A crystal oven.
>>>> > > >
>>>> > > >If WX holds and I can get the antenna damage repaired this
>>>> > > week end, after
>>>> > > >our major wind storm here 3 weeks back, will be looking to
>>>> > > try other weak
>>>> > > >signal modes.
>>>> > > >
>>>> > > >73
>>>> > > >
>>>> > > >de KO7N   CN84ia
>>>> > > >
>>>> > > >Richard Ewing
>>>> > > >PNW VHF Society C-075
>>>> > > >http://home.teleport.com/~rewing
>>>> > > >
>>>> > > >
>>>> > > >_______________________________________________
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>>>> >
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