[Elecraft] Transverter XV144 way off frequency

Sat May 18 11:00:37 EDT 2019

Bob
My observation is that the K3 reference oscillator is much more stable (moves just a few Hz max) than any of the XV transverters even if equipped with ovens. I would instead use the LeoBodnar Mini to replace the local oscillator in the XV144. The process is identical for the XV222.
Comments below assume an otherwise properly adjusted and operating XV144, and that you are handy with a soldering iron or a hot air rework station.

First, before you start, measure the DC voltage at TP1 on the XV144 with a voltmeter. Write it down.

Be gentle unsoldering parts from the PCB. The traces and pads are fragile. 

Remove U2 - the regulator for the crystal oscillator. Remove the oven if one is installed (no need to create more heat). Remove C15. Repurpose the back panel "Aux" BNC connector and run RG174 (or similar cable) from the connector to the vicinity of C15. Connect the coax center conductor to one end of a small 1000 pF disc ceramic capacitor (value not critical) - short leads! The other end of the 1000 pF capacitor goes into the now empty hole previously occupied by C15 that is closest to Q2 with minimum lead length. Ground the coax at both ends. Done. The other oscillator components can remain in place. 

Set the LB Mini to 116000000 Hz and the output drive to "8 mA". Connect the LB Mini output to the "Aux" connector. Check the DC voltage level at TP1. If the voltage is the same or higher than the original reading, you are done.  If it is less than before, increase the LB Mini output to the "16 mA" setting. Measure the DC voltage level at TP1 again. Repeat if necessary. This step makes sure you have sufficient drive level to the mixer.
My XV transverters are in close proximity to a computer and router, plus several (now shielded) ethernet cables, USB cables and a couple of serial cables. There were many weak birdies observed when tuning across the band. Lots of ferrites helped a little. There are internet articles by Jim, K9YC who discusses why the birdies appear (see his comments and drawings about the "Pin 1" problem), and Bruce, NT4RT, who shows what he did to (among other things) improve the grounding on his XV432. Many of his comments are applicable to the XV144. 

Adding in the LB Mini may increase the number of birdies present in the receiver output unless additional steps are taken. It may also help reduce birdies to run the LB Mini off of a linear lab power supply at 4.5 volts (cut off the computer side connector of a USB cable, use the +5 and ground wires in the cable to connect to the supply). 

YMMV
73, Mike, W3IP

      From: Don Wilhelm <donwilh at embarqmail.com>
 To: Bob KD7YZ <kd7yz at denstarfarm.us>; K3 List <elecraft at mailman.qth.net> 
 Sent: Friday, May 17, 2019 3:24 PM
 Subject: Re: [Elecraft] Transverter XV144 way off frequency

Bob,

I skipped Dayton this year.
It is true that there is no stock means of syncing the XV144 to an 
external standard.
A few owners have said they were successful with replacing the crystal 
with a circuit that is synced to an external standard, but I now nothing 
of that implementation.  Perhaps someone who has done it will speak up.

How is JP9 jumpered in your XV144.  For maximum stability, the jumper 
should be between pins 4 and 5 (no other jumpers).  With that setting, 
the crystal oven will be powered as long as 12 volts is applied to your 
XV144 - don't turn the power supply off!  Let the oven warm things up 
for at least a half hour (longer if possible) and then calibrate.  It 
should stay close on frequency.

73,
Don W3FPR

On 5/17/2019 3:06 PM, Bob KD7YZ wrote:
> My K3 has an external "Leo Bodnar" reference [REF * CAL]  . Thus the K3
> is accurate for my EME and MSK144/FT8 adventures on 2m.
> 
> Except: I discovered that the XV144 is not synced with anything.
> The K3 Menu/Config DOES allow for "XV1 OFS", and knob turning, to set in
> a "Calibration" value.
> 
> As I do not have the luxury of a bench of accurate test and calibration
> equipment, I am unable to get the XV1 to get and remain near to accracy.
> 
> Some friends told me they "Thought" that the XV144, external
> Transverter, does have the option for an external GPS REFLOCK as the K3 has.
> 
> Calls to Elecraft revealed, other than friendly people, that there is no
> way they know to REFLOCK the XV144 ..
> 
> So List people, figuring I do not want to calibrate every day, how are
> you users of XV144 keeping your other friends from naggin you every day
> and every time you call CQ on MSK144 ??
> 
> 
> Hoping Don, W3FPR,  will have some time after hectic daily Dayton
> HamFest schedule to answer too.
> 
> 
> --
> 73
> Bob KD7YZ
> AMSAT LM #901
> 
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