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Thursday, 22 March 2018

13cm Complete

Well,

I've received the PA for the 13cm masthead project and added it to the box with a heatsync and suitable input attenuation:


I haven't stuck it down in the photo hence its a bit wonky.

The documentation with the PA suggests that about 5.1V on the monitor pin is close to PA saturation so I have adjusted my input attenuator to give just over 5V from the PA monitor port with CW key down.

With the output connected via these two attenuators:


to my XL Microwave power meter I am reading -2 dbM so that's about 38 dBm or 6.3 watts - it should be closer to 10 Watts.

To check the value of the attenuator at 2320 MHz, I used the spectrum analyser and tracking generator I made back here in zero span at 2320 MHz, and compared the signal with and without the attenuators, I measure a signal of +10.4 dBm without the attenuator and -29.2 dBm with. So that makes the attenuator 39.7 dB - so pretty much on the money.

Local conditions.

**UPDATE** 

I kept finding my TX/RX switching was going into some kind of oscillation on RX. The unit would rapidly switch between TX and RX until I pulled the power. Oddly (and still somewhat a mystery) this only happened when the +ve voltage to the VLNA was connected to the sequencer. No VLNA power, all fine, attach VLNA power, TX/RX oscillation.

There is a VOX feature in the transverter that switches to TRX on detection of RF on the input; changing that to have a long detection time (a jumper on the transverter board) has cured the problem.

I have no idea either.

As SG labs don't seem to link the transverter datasheet on their site anymore, it's included here for reference.




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