TFT monitor attenuating receive?


Wayne Crawford
 

Greetings!

Mobile set up. Pics can be seen on my QRZ page. Radio is mounted underneath the driver side back seat. My issue is that whenever I have the TFT monitor turned on it attenuates the VHF/UHF receive. I originally thought the poor receive was due to a change that was made to the antenna of our local repeater. I had confirmed this with another local operator who said he was experiencing the same thing. However, today I was away a good distance from home and discovered the issue when I turned the monitor on after turning on the rig. I usually turn the monitor on first, then the rig, but for whatever reason I did it differently this time. When I did a QSO was in progress on the freq. Iif I turned the monitor off I could hear the QSO. Turn it back on, QSO went into the squelched level and was lost. If I turned the squelch back the QSO was there but no longer full quieting. I haven't tried to trouble shoot this just yet but thought I would seek some guidance from the group before proceeding to do so. I really like using the monitor because it provides a larger display for me to see while driving and I don't have to look down when making changes.

Your help is appreciated.

Wayne C.
WV4L



Steve W3AHL
 

Your monitor and its cables are probably radiating RFI, increasing the noise floor, not attenuating the incoming signal.  You may need to use a better quality video cable between the monitor and radio (better shielding, routed away from antenna and remote cable), add ferrite chokes to one or both ends of the video and power cables for the monitor, or improve the bonding of the radio chassis to the vehicle chassis at VHF/UHF frequencies (short, fat braid from radio to well-bonded body panels)

What type of cable are you using to route the video from the radio to the monitor?  It should be a double-shielded copper braid 75 ohm coax, not a cheap video cable with a spiral twist shield.

I can't tell where your dual band antenna is mounted relative to the monitor from the qrz pictures, but you might try moving it farther away to see if the monitor is radiating to the antenna directly.  If you have a mag mount, try it on the roof temporarily.

Bonding the monitor chassis to the truck chassis would probably be difficult (especially at VHF/UHF frequencies) since the monitor probably has minimal shielding inside.  If it is the monitor radiating and not the cables (as determine by the suggestions in first paragraph), there is a spray on nickel coating designed for shielding plastic enclosures that might help, but of course you can't shield the actual display in front.

Steve, W3AHL
---In ic7000@..., <resopkr@...> wrote :

Greetings!

Mobile set up. Pics can be seen on my QRZ page. Radio is mounted underneath the driver side back seat. My issue is that whenever I have the TFT monitor turned on it attenuates the VHF/UHF receive. I originally thought the poor receive was due to a change that was made to the antenna of our local repeater. I had confirmed this with another local operator who said he was experiencing the same thing. However, today I was away a good distance from home and discovered the issue when I turned the monitor on after turning on the rig. I usually turn the monitor on first, then the rig, but for whatever reason I did it differently this time. When I did a QSO was in progress on the freq. Iif I turned the monitor off I could hear the QSO. Turn it back on, QSO went into the squelched level and was lost. If I turned the squelch back the QSO was there but no longer full quieting. I haven't tried to trouble shoot this just yet but thought I would seek some guidance from the group before proceeding to do so. I really like using the monitor because it provides a larger display for me to see while driving and I don't have to look down when making changes.

Your help is appreciated.

Wayne C.
WV4L



Bill Storey
 

The monitor is likely generating in band local RF, causing your AGC to reduce input gain.

Does this happen on all of the bands?  If so, perhaps it is affecting the IF stage?

Bill (AB1LZ)


John Rupprecht K3NOQ
 

Does the monitor have a separate power supply Module?  I have found numerous aux. power supply modules to be very dirty RF-wisè, especially on uhf-vhf freqs.  You may try relocating the p/s module away from the 7ķ (and antenna), and/or physically shielding it in a grounded metal enclosure or use other RF suppression methods. 

If the monitor is 12vdc,  try running it off battery without the p/s module. I use this method to power my ft60 portable here at home as the yaesu drop-in charger was very dirty and masked the receiver on anything less than a extremely strong signal.  Hope this helps.  73// John K3NOQ/K5 Republic of Texas



Sent from my Galaxy Tab® A