From 497dd86db101e17a4451e5d551bdfc3ecbe90986 Mon Sep 17 00:00:00 2001
From: erikkaashoek <erik@kaashoek.com>
Date: Sat, 2 Apr 2022 13:49:16 +0200
Subject: [PATCH] Eliminate 10MHz spurs with low RBW

---
 sa_core.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/sa_core.c b/sa_core.c
index d0488d9..2a1aab0 100644
--- a/sa_core.c
+++ b/sa_core.c
@@ -3579,9 +3579,15 @@ again:                                                              // Spur redu
                   ADF4351_R_counter(3);
               } else
 #endif
-                if (get_sweep_frequency(ST_SPAN)<500000)
-                  ADF4351_R_counter(3);     // To avoid PLL Loop shoulders
-                else
+                if (get_sweep_frequency(ST_SPAN)<500000) {
+                  if (actual_rbw_x10 < 1000) {
+                    freq_t tf = ((lf + actual_rbw_x10*1000) / TXCO_DIV3) * TXCO_DIV3;
+                    if (tf + actual_rbw_x10*100 >= lf  && tf < lf + actual_rbw_x10*100) // 10MHz
+                      ADF4351_R_counter(4);    // To avoid PLL Loop shoulders at multiple of 10MHz
+                    else
+                      ADF4351_R_counter(3);     // To avoid PLL Loop shoulders
+                  }
+                } else
                   ADF4351_R_counter(1);
             }
           } else {