This could be caused by interference from another device (e.g. mobile phone, set-top box etc.). Move any such suspected device further away from the DVR+(CM-7500) or the coaxial cable from your antenna. The interference received will become weaker because of the increased distance. If poor quality coaxial cable or connectors have been used for your antenna, replace them with higher quality ones, ensuring that they have the correct impedance (75 Ohm). Should you suspect a problem with your antenna installation, we recommend that you contact your installer.
Receiving ATSC HD TV signals can sometimes be tricky. Many conditions can influence the ATSC HD TV signal while being broadcast. Anything that is between the TV Transmitting tower and your location can affect your ability to receive that TV signal transmission. (Physical obstructions, flat/reflective surfaces, and other signals. e.g. LTE/Cellular, Microwave signals, etc) You may be able to move your antenna 5 feet from where it is now and you could get different results. Please read on to learn more about the signal that you want to receive.
1. Before checking your signal on a certain channel, make certain that you are not recording anything or it may actually be showing a different channel/signal.
2. Tune your DVR+ to any channel that is important to you and you'd want to check the signal strength and quality.
3. Press the exit button on the remote so you are viewing live TV and no on screen menu's. are present.
4. Now press the "Channel Up" button until you reach the next higher "primary channel". (If on CH13.1, do not change to the next "sub channel", (CH13.2). Change to CH14 or higher.)
5. Now press the "Channel Down" button to return to the channel that you want to view/check the Signal Strength & Quality.
6. Now, using your DVR+ remote; Press, Menu>Select Settings>Technical Info>Signals & Network info>
7. You can now observe the two signal meters. If either are fluctuating, then you could expect some reception issues.
8. The "Network ID" will indicate the Real/RF channel that is being received/transmitted. Not necessarily the same channel number as what is in the guide. (Virtual number)
a. You can now confirm your RF Channel/Transmit Channel number. (Network ID), compared with your Virtual Channel Number. Document that Network ID number in case you need to communicate with us about that channel.
10. The meters will be showing the signal Strength and Quality for whichever TV channel you are presently tuned to/watching.
11. To make this a dependable signal, you should monitor the signal meters for optimum signal strength and especially “Signal Quality”, while you re-orient the antenna direction.
12. Pay special attention to the Signal Quality. If it is fluctuating, then that can be the issue. Keep in mind, if quality is fluctuating, the meter readings are not instantaneous. It may momentarily go down to ~35 on the meter screen, but may actually be dropping to 0. The meter is just not fast enough to register that.
The links below have great information about receiving ATSC HD TV signals. Three are written by an RF Engineer who explains it in terms that most anyone can understand. (Channel Master is not responsible for the content)
The links below go to some very interesting and educational web pages, about ATSC HD TV Signals;
These are not affiliated with Channel Master and we are not responsible for their content.
Another great source for technical info about possible causes for reception issues;