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Flex 6700 Preamp Setting with Transverters

John K4SQC
John K4SQC Member
edited September 2019 in SmartSDR for Windows
I am connecting a DEMI 1296 Transverter to my 6700 using the 144 MHz IF.  Every things works great and I am wondering about the sweet spot between transverter Rx gain setting and the Rx Preamp gain setting on the Flex.  Right now I have the transverter adjusted so there is a just perceptible increase in noise with 20dB of Flex preamp gain.  I don't own a signal generator that goes to 1296 so I can't do MDS testing  What have others found?  The setup worked well in the Jane VHF contest from EM85.  But you all know how it is - can I make it even better?

Answers

  • David-N5PSM
    David-N5PSM Member ✭✭
    edited September 2018
    There is an article/setup guide for the best setting for full duplex.  It was in the downloads section last I looked,,,,,,
  • WA6HTP - Juan Rivera
    WA6HTP - Juan Rivera Member ✭✭
    edited June 2019
    I'm gearing up for 1296 EME and have a Kuhne transverter with a 28 MHz IF.  I have a 2 GHz signal generator, but found that leakage is a big factor when trying to inject very weak signals into a system.    I ended up sticking 50 dB of attenuation right on the RF input connector of the transverter.  Once I got the leakage from the generator under control I found that cranking the gain of the Flex 6700 all the way to +40 dB gave the best results.  That was with a signal right into the transverter and not into the 1296 MHz preamp.  I received the following explanation from Flex:

    The answer is enabling the RF preamp will make the noise floor drop if the antenna is not noise limited.  Refer to this HD article for more details
    https://helpdesk.flexradio.com/hc/en-us/articles/204923669-How-to-determine-the-amount-of-RF-Preamp-gain-to-apply-for-band-conditions
  • John K4SQC
    John K4SQC Member
    edited September 2018
    Juan,

    Understood an very useful.  My question is a little different but maybe you have answered it.  when setting up a DEMI tansverter part of the instruction require that the Rx Gian be adjusted so there is a just perceptible increase in noise when the transverter is turned on,  At least that is the instruction I need to follow as I do not the needed test equipment to do it with a signal generator.  There is an interaction between the Rx gain in the transverter and the Preamp setting in the Flex.  My question was more related to the setting for the preamp during the inital setup of the DEMI transverter.

    John
  • WA6HTP - Juan Rivera
    WA6HTP - Juan Rivera Member ✭✭
    edited June 2019
    The Kuhne transverter has no gain adjustment, so I can't comment on the interaction between the transverter and the flex.  The good news is that you can see the results in your waveform display.  I'd just adjust for the best S/N ratio once you have a signal to look at.  I'll have to do the same once I get a preamp installed and connected to an antenna.

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