diff --git a/src/hm/Communication.h b/src/hm/Communication.h
index 38925059..924356e0 100644
--- a/src/hm/Communication.h
+++ b/src/hm/Communication.h
@@ -186,8 +186,8 @@ class Communication : public CommQueue<> {
                             if (p->packet[0] == (TX_REQ_INFO + ALL_FRAMES)) {  // response from get information command
                                 if(parseFrame(p)) {
                                     q->iv->curFrmCnt++;
-                                    if(!mIsRetransmit && (p->packet[9] == 0x02 || p->packet[9] == 0x82) && p->millis < 85)
-                                        mHeu.setIvRetriesGood(q->iv,p->millis < 70);
+                                    if(!mIsRetransmit && (p->packet[9] == 0x02 || p->packet[9] == 0x82) && p->millis < LIMIT_FAST_IV)
+                                        mHeu.setIvRetriesGood(q->iv,p->millis < LIMIT_VERYFAST_IV);
                                 }
                             } else if (p->packet[0] == (TX_REQ_DEVCONTROL + ALL_FRAMES)) { // response from dev control command
                                 if(parseDevCtrl(p, q))
@@ -259,7 +259,7 @@ class Communication : public CommQueue<> {
                     if(framnr) {
                         if(0 == q->attempts) {
                             DPRINT_IVID(DBG_INFO, q->iv->id);
-                            DBGPRINTLN(F("no attempts left"));
+                            DBGPRINTLN(F("timeout, no attempts left"));
                             closeRequest(q, false);
                             return;
                         }
@@ -424,8 +424,8 @@ class Communication : public CommQueue<> {
         }
 
         inline bool parseMiFrame(packet_t *p, const queue_s *q) {
-            if(!mIsRetransmit && p->packet[9] == 0x00 && p->millis < 35) //first frame is fast?
-                mHeu.setIvRetriesGood(q->iv,p->millis < 22);
+            if(!mIsRetransmit && p->packet[9] == 0x00 && p->millis < LIMIT_FAST_IV_MI) //first frame is fast?
+                mHeu.setIvRetriesGood(q->iv,p->millis < LIMIT_VERYFAST_IV_MI);
             if ((p->packet[0] == MI_REQ_CH1 + ALL_FRAMES)
                 || (p->packet[0] == MI_REQ_CH2 + ALL_FRAMES)
                 || ((p->packet[0] >= (MI_REQ_4CH + ALL_FRAMES))
diff --git a/src/hm/Heuristic.h b/src/hm/Heuristic.h
index 642eca13..3fb86614 100644
--- a/src/hm/Heuristic.h
+++ b/src/hm/Heuristic.h
@@ -159,9 +159,9 @@ class Heuristic {
 
         uint8_t getIvRetries(Inverter<> *iv) {
             if(iv->heuristics.rxSpeeds[0])
-                return 5;
+                return RETRIES_VERYFAST_IV;
             if(iv->heuristics.rxSpeeds[1])
-                return 10;
+                return RETRIES_FAST_IV;
             return 15;
         }
 
diff --git a/src/hm/hmDefines.h b/src/hm/hmDefines.h
index 969e4e1b..9235b3f9 100644
--- a/src/hm/hmDefines.h
+++ b/src/hm/hmDefines.h
@@ -94,6 +94,14 @@ enum {INV_RADIO_TYPE_NRF = 0, INV_RADIO_TYPE_CMT};
 #define DURATION_PAUSE_LASTFR   45 // how long to pause after last frame (ms)
 const uint8_t duration_reserve[2] = {115,115};
 
+#define LIMIT_FAST_IV           85 // time limit to qualify an inverter as very fast answering inverter
+#define LIMIT_VERYFAST_IV       70 // time limit to qualify an inverter as very fast answering inverter
+#define LIMIT_FAST_IV_MI        35 // time limit to qualify a MI type inverter as fast answering inverter
+#define LIMIT_VERYFAST_IV_MI    22 // time limit to qualify a MI type inverter as very fast answering inverter
+#define RETRIES_FAST_IV         11 // how often shall a message be automatically retransmitted by the nRF (fast answering inverter)
+#define RETRIES_VERYFAST_IV      7 // how often shall a message be automatically retransmitted by the nRF (very fast answering inverter)
+
+
 typedef struct {
     uint8_t    fieldId; // field id
     uint8_t    unitId;  // uint id
diff --git a/src/hm/hmRadio.h b/src/hm/hmRadio.h
index 0df22f5a..81b27c57 100644
--- a/src/hm/hmRadio.h
+++ b/src/hm/hmRadio.h
@@ -124,7 +124,7 @@ class HmRadio : public Radio {
 
                 rxPendular = !rxPendular;
                 //innerLoopTimeout = (rxPendular ? 1 : 2)*DURATION_LISTEN_MIN;
-                innerLoopTimeout = DURATION_LISTEN_MIN;
+                //innerLoopTimeout = DURATION_LISTEN_MIN;
 
                 if(mNRFloopChannels)
                     tempRxChIdx = (tempRxChIdx + 4) % RF_CHANNELS;
@@ -154,7 +154,8 @@ class HmRadio : public Radio {
                     if(tx_ok)
                         mLastIv->mAckCount++;
 
-                    mRxChIdx = (mTxChIdx + 2) % RF_CHANNELS;
+                    //mRxChIdx = (mTxChIdx + 2) % RF_CHANNELS;
+                    mRxChIdx = (mTxChIdx + 3) % RF_CHANNELS;
                     mNrf24->setChannel(mRfChLst[mRxChIdx]);
                     mNrf24->startListening();
                     mTimeslotStart = millis();
@@ -162,7 +163,8 @@ class HmRadio : public Radio {
                     rxPendular  = false;
                     mNRFloopChannels = (mLastIv->ivGen == IV_MI);
 
-                    innerLoopTimeout = mLastIv->ivGen != IV_MI ? DURATION_TXFRAME : DURATION_ONEFRAME;
+                    //innerLoopTimeout = mLastIv->ivGen != IV_MI ? DURATION_TXFRAME : DURATION_ONEFRAME;
+                    innerLoopTimeout = DURATION_LISTEN_MIN;
                 }
 
                 if(rx_ready) {
@@ -186,10 +188,7 @@ class HmRadio : public Radio {
                     }
                     rx_ready = false; // reset
                     return mNRFisInRX;
-                } /*else if(tx_fail) {
-                    mNRFisInRX = false;
-                    return false;
-                }*/
+                }
             }
 
             return false;