TVRX / pigtail impedance

GNU Radio
1

Hi,

I recently acquired a USRP with a TVRX. In the package there was also a
F -> SMA pigtail to put in the front.

But that kinda surprised me from an impedance point of view because:

  • The TVRX input is 75ohm according
  • F connector is 75 ohm afaik.
  • The RG316 cable used for the pigtail is 50ohm
  • SMA is 50 ohm afaik.

So that looks like a weird mix.

Will that have much influence ? How should I connect the classic 75ohm
antennas & cable feed I have ?

I wanted to try and make a F -> F pigtail with 75 ohm coax but I can’t
find any right angle F connector here at a reasonnable price (ie,
without 30$ of shipping cost for a 2$ connector …)

Sylvain
2

Yes, it is a weird mix. But it doesn’t really make any difference for
that short piece of coax at these frequencies. If you really want, you
could get a 50 ohm to 75 ohm transformer and then just use SMAs.

Ok, and should I consider the SMA input to be 50 or 75 ohm ?
(so If I make an antenna, is it better to make a 50 or 75 ohm to input
it in the SMA ? or maybe it doesn’t matter either ?)

Sylvain

3

Sylvain M. wrote:

So that looks like a weird mix.

Yes, it is a weird mix. But it doesn’t really make any difference for
that short piece of coax at these frequencies. If you really want, you
could get a 50 ohm to 75 ohm transformer and then just use SMAs.

Matt