Question E2D02:
What information replaces signal-to-noise ratio when using the FT8 or FT4 modes in a VHF contest?  

Choices:  
A: RST report  
B: State abbreviation  
C: Serial number  
D: Grid square    

Correct Answer is  D: Grid square  

Correct answer: D — Grid square

Why D is correct:
- In VHF contests, the standard exchange is callsign and Maidenhead grid locator (at least the 4-character grid, e.g., FN31).
- FT8/FT4 “VHF Contest” mode (e.g., WSJT-X NA VHF) replaces the usual FT8/FT4 SNR report with the grid square as the contest exchange.

Why the others are incorrect:
- A: RST report — RST is common in CW/SSB QSOs and many HF contests, but VHF contests standardize on grid squares. FT8/FT4 normally reports SNR (in dB), not RST.
- B: State abbreviation — Used in some HF contests (e.g., QSO parties), not the standard exchange for VHF contests.
- C: Serial number — Common in many HF contests, but not in ARRL-style VHF contests or FT8/FT4 VHF contest mode.

Useful notes, formulas, and rules of thumb:
- FT8/FT4 standard (non-contest) report is SNR in dB:
  $$\text{SNR}_{\text{dB}} = 10 \log_{10}\!\left(\frac{S}{N}\right)$$
  In VHF contest mode, this is replaced by the grid square exchange.
- Maidenhead grid basics:
  - 4-character grid (e.g., FN31) corresponds to about $1^\circ$ latitude by $2^\circ$ longitude.
  - At the equator, that’s roughly $111\ \text{km} \times 222\ \text{km}$ per 4-character square.
  - Some operators may use 6-character grids (adds subsquare), but 4-character is the contest minimum.