What kind of effects does a relay have on signals?
FETs pass signal clean too, as their source&lt;>drain path is like a resistor. 
Especially if you are just at 10Mhz.
So don't bother and take discrete FETs. If you need resistance &lt;0.1Ohm you can take power FET's which have 12V Gs and Rdson somewhere at 0.01 Ohm, very comparable to relay and reliable.

Another problem with relays is that their resistance is not consistent, it will change over time and this will cripple your calibration. Anf finally, if you have any mechanical vibration - it will also make things worse.

SSR is usually also based on FET's but with additional input&lt;>output insulation (including optocouples for example).