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Transverter receive artifacts

KD0RC
KD0RC Member, Super Elmer Moderator
in Peripherals & Station Integration

I have a Flex 6400 and a UT5JCW 2-meter transverter. The transverter works great, especially for such an inexpensive piece of equipment.

I do notice that across the 2-meter band, there is a 10 dB bump centered near145.600. I get this regardless of antenna (or even no antenna) and wonder if this is an artifact of the transverter (which I suspect), or if an expensive transverter like the Q5 would exhibit the same behavior. I am sure that it is not the 6400, as 28 - 32 MHz is quite flat with no antenna connected.

The picture below was captured with an RF Gain setting of 16 dB. At -8 dB, the display goes flat, but weaker signals disappear. At 0 dB, I get a 2 - 3 dB bump, and at 8 dB I get a 5 - 7 dB bump (just eyeballing the display, not a precise measurement). 16 dB gives me the sweet spot of an 8 - 10 dB drop when setting the rig to no RX antenna compared to the XVTR.

image.png

I also get receiver dropouts when strong signals stop transmitting (see circled items, above). I have to believe that this is an artifact within the transverter but want to know for sure. I get no such dropouts on any other band, regardless of signal strength.

If anyone can confirm what is causing these artifacts, I would appreciate it.

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Best Answer

  • reed
    reed Member ✭✭
    Answer ✓
    I have a 144MHz<->28MHz transverter from transverters-store.com (RIP?) which I'm guessing is close enough to which ever version you have. I noticed the same the spectrum shape when I first hooked it up. Hooking up the transverter to my tinySA confirmed that it was the transverter's shape, not the FlexRadio. I grabbed a screenshot from my tinySA just now, and you can see a similarly shaped profile on the instrument.

    Mike's video on transverters (https://www.youtube.com/watch?v=xJ5fIe0bWDE?t=1m15s) does NOT show such a shape, and he says (at timestamp 4:57) he's using Q5 transverters. Since they're 5x the price, it's not too surprising that they perform better.

    I haven't seen dropouts like you showed. I just tried blasting my transverter by keying up my 5W HT right next to the transverter's antenna, and no dropout. Maybe that's not harsh enough?

Answers

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Thanks Reed, that helps confirm what I was thinking. I suspect that the strong sigs are very close, and fairly high power. They show up bright red on the waterfall.

  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    Do you see the same signals on 28.200 Mhz? That is the actual frequency that the radio is operating on.

    73

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Mike. No, 28 - 32 MHz is very flat with no antenna connected. I am pretty sure that it is the Ukrainian transverter. Is your Q5 transverter flat across its operating range?

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