Length to make magnetic loop antenna/probe for 1.6GHz?
Suppose your GNSS receiver has an input filter (perhaps PI matching) with Q of 100.

Suppose your PCB has various fast-edge signals, with 100 picosecond (or 90pS, or 200pS) edges, occurring every 0.5MHz. 

Thus 500,000 times a second, the GNSS receiver gets disrupted by a fast edge that caused the input filter to ring and ring and ring, as the induced ringing dies out. 

If the initial ringing is 1 millivolt, then with 100 cycles of the 1.6GHz RF signal, the residual ringing energy will have decayed to 1/( 2 * PI) of the original energy. [URL to "Q_factor at end of answer]

Using Power = V^2 / R, we find the new ringing voltage is 0.001 / sqrt(2  * PI) or about 400 microVolts. After 100 cycles.

To decay to 1 microvolt requires about 8 more of these 100-cycle delays.

To decay to 1 nanoVolt requires about 9 more of these 100-cycle delays.

Given narrow_band RF signals, perhaps 100Hz bandwidth, need about -140dBm power level for useful data_recovery, and -120dBm across 50 ohms is 0.623 microVolts PeakPeak, we have 0.0632 uV or 63 nanoVolt signal levels. 
[as you work thru the details that follow, you should notice the accuracy of these numbers is not crucial to the overall concept of "induced ringing" as the problem.]

As you can see, even slowly_repeating but FAST EDGE interferers are a problem.

In this case, the 500,000Hz interferer, or 498,322.84 Hertz interferer, or 505,111.11 Hertz interferer, will overload the GNSS receiver for about 15 of these 100_cycle delays. I chose "15" because the ringing amplitude will have decayed to about 30 nanoVolts, which may be low enough to allow a useful SignalNoiseRatio(SNR) for the GNSS receiver.

(Notice the exact repetition_rate is NOT the cause of GNSS receiver overload and loss of data. The fast edge is the problem.)

How long is 15 of these 100 cycle? That is, what is 1,500 / 1,6000,000,000? about 0.9 microSeconds.

Thus the FAST EDGE, tho occurring slowly (and not a sub-harmonic of the GNSS carrier), has overloaded the GNSS receiver for 0.9 microSeconds

Thus harmonics are not the problem; the induced ringing, caused by the fast transient edge, is the problem.

Notice in this example of induced ringing, the repetition rate of the interferer is not a sub-harmonic of the GNSS RF carrier.

[link to Wikipedia "quality factor"]
https://en.wikipedia.org/wiki/Q_factor