41 when inserted in housing 44 is soldered to the inside surface of probe tip 32 when probe contact housing 44 is inserted in the probe housing 28 as shown the inner end of resistor 41 contacts and may be soldered to the outer termination of resistor 42 at this terminal 49 resistor 42 is connected from ground as formed by the probe housing 28 to the microstrip line 30 in order to make a measurement probe assembly 20 is placed adjacent a length of microstrip circuitry such as the microstrip 22 and placed so that ground contacts 34 engage ground pads 24 further manual pressure on the probe assembly 20 allows probe contact 32 to engage with the microstrip line 22 so that electrical measurements can be made when probe tip 32 is in contact with microstrip line to carry out a measurement an excellent impedance match occurs as shown in fig6 across the frequency band of interest 0 to 18 ghz there is less than 20 db return loss fig5 shows the insertion and coupling loss with the probe contacting the microstrip line insertion loss is less than 1 db over the frequency range of interest and coupling loss is substantially only 20 db while not shown herein in some applications it may be necessary to place a capacitor in series with probe tip 32 to act as a dc block isolating the probe from any dc bias applied to the circuit under test this capacitor might be a part of the ceramic substrate containing resistor 41 the addition of this blocking capacitor will limit the low frequency response of the probe but operation.