Kuhne G3 10 MHz Ext Ref ?

[VK4GHZ]

Hi all

Any Kuhne MKU xx G3 transverter module owners out there?

I'm interested in knowing how fussy these G3 modules are with the input level of the Ext 10 MHz reference.
Kuhne specifies 10dBm in.

What level of 10 MHz will they reliably work down to please?
9dBm, 8dBm, 7dBm .... 3dBm... 0dBm?

I had considered emailing Kuhne, but manufacturers usually just echo their own specs back anyway.
Looking for some real world observations.

[VK5LA]

Hi Adam,
I can't give you figures, but my bare 10Mhz OCXO with a passive LP filter on the end drives it no problems, as does a FE 5680 Rubidium unit followed by a DEM 10-4 filter/amp
Andy - VK5LA

[VK5RC]

HI Adam
It will be very difficult to even measure as I think the units will revert to their internal TCXO, so picking when they have lost track of the ext reference will be very hard to pick up. One of the 10Ghz units I have works well with about 5dBm in from an attenuated Thunderbolt. I think it may be one of the G2 units though.
If I get a bit of time on the weekend I will try to see if I can pick loss of lock from the external reference from change in transmit frequency accuracy, if that will be of help.
Regards Rob
VK5RC

[VK5ZD]

Hi

I have a Kuhne MKU XO 1 PLL replacing the crystal on my G2 10GHz transverter.
The specs say is requires +10dbm (10mW). In practice it will lock with a +4dbm input.

73
Iain

[VK4GHZ]

There's a few G2's out there!
I believe the LO arrangement is quite different with the G3, hence having to be specific.

Have got two G3's arriving (one for 5.7 and one for 10G) soon --- --- and both of these will go inside the same enclosure.
So planning & ordering all the other bits n pieces needed for the integration, to be ready in time for the MAD!

I am going to use a MiniKits EME144 coax relay to switch the 70cm IF to the active transverter, and was also going to use another EME144 to switch the 10 MHz reference to the active module.

Out of the DEM 10-4 splitter here, I measure +11.3dBm out, which falls to +8.3dBm when connected to two 50 ohm loads.
By the sounds of it, +8dBm is enough, and I wouldn't require a coax switch... so just hook them up in parallel via an SMA T adapter.

I did find this:

DB6NT_transverter_modifications.pdf

Khune mods by F5DQK

(1.13 MiB) Downloaded 372 times

On page 28 of this, it suggests the G3 works happily with +6.8dBm out of a Trimble OCXO.

So +8dBm should be ok for a G3?

[VK5RC]

A small point but may be important , if I recall the documentation for the 10-4 splitter recommends 50 Ohm loads on all unused ports, was a bit surprised re comment re different output levels, my G3 5GHz Transverter definitely locks with the output from a 10-4 attached to a HP z3805 GPSDO (the shack reference)
Rob
VK5RC

[ZL1TPH]

A short off the cuff reply, my MK2 10 GHz TRV (one with a crystal and no heater oddly enough around the crystal) was recently modified, cut a track in the oscillator chain, switched the crystal oscillator power off, and fed a VK3XDK PLL into the chain at the correct point.
No need to return the oscillator chain as the same injection was used at that point
It was 432 IF MK2 10 GHz TRV ..
This work was done by Kevin ZL1UJG, with many thanks to help me out.
Cheers, Steve ZL1TPH

[VK4GHZ]

Ok, some serious testing done this evening...

The Kuhne MKU xx G3 432 transverter modules have inbuilt OCXOs LOs, and whilst very good, they can be locked to an external 10 MHz reference.
So what is the minimum level of 10 MHz signal required?

To determine this minimum level, I used the following;

• 10 MHz @ +12dBm from a Trimble Thunderbolt GPSDO, fed via a DEMI 10-4 Splitter/amp
• Windfreak SynthNV signal generator, locked with the GPSDO
• a number of small value DC-GHZ rated SMA attenuators

It's easy to determine when the G3's internal OCXO locks to the external reference, by listening to a known (ie; locked) signal source.
If we tune to carrier frequency - 1 kHz on USB, we expect to hear a 1000 Hz beat note.
When the OCXO is free running (ie; not locked), the 1 kHz beat note can be found some kHz away instead.

So, the Windfreak SynthNV was locked with the ThunderBolt and tuned to 1920 MHz (3rd harmonic is 5760 MHz)


Above: Windfreak SynthNV set to 1920 MHz, in low output power mode (ideal for front end testing)



Above: SynthNV locked to GPSDO, pipe cap filter on output allows us to pick off the 3rd harmonic, and remove the 1920 fundamental



Above: IF rig (432 MHz IF) tuned to receive a 1 kHz beat note



Above: 10 MHz into the 5.7 GHz G3 module, via the attenuator ladder

The various attenuators (values available: 2dB, 3dB, 4dB, 5dB) could be arranged to provide attenuation of 2dB - 14dB in 1 dB steps.

Once the minimum value of 10 MHz was found for the MKU 57 G3 432, the exercise was repeated for the MKU 10 G3 432 module.


Above: SynthNV running on 3456 through a 10 GHz pipe-cap filter, so that a clean 10368 signal is presented to the front end



Above: 10 MHz into the 10 GHz G3 module, via the attenuator ladder


And what was the end result?



Both of these 5.7 and 10G G3 modules required a minimum of +0.5dBm each.
So based on the results and to allow for headroom, I would suggest a minimum 10 MHz level of +3dBm for a Kuhne G3 transverter module.

As Iain also found (+4dBm), the Kuhne specification of +10dBm appears to build in a substantial safety margin!

Posted in the interests of having some fun experimenting, and sharing the results.