K4EET
Chaplain
I need some Radio Frequency Interference (RFI) advice...
My XYL (wife) has a "home office" in the Master Bedroom (MBR). My hamshack is located directly underneath the MBR. She is experiencing RFI to her Dell Monitor with a symptom of wavy lines and to her Plantronics Headset used during telephone conferences that has the symptom of garbled audio when I transmit on a very specific repeater; namely the W3CU repeater on 146.205 MHz (input) and 146.805 (output). When I do test transmissions on repeater frequencies that are below and above the 146.205/146.805 MHz repeater pair (see table below), she does not experience any interference.
My mobile radio used as a base station is an Icom IC-208H (see attached brochure below) that has selectable power for transmit of 5/15/55 Watts on VHF. The temporary location for the antenna, similar to MFJ's MFJ-1724B, is on top of a 4 drawer steel filing cabinet directly underneath her desk that has the affected equipment on it. At this time, the location of the antenna is fixed and cannot be moved to another location which would probably mitigate the RFI. Once I get an outdoor antenna, a Cushcraft AR-270B, that antenna will be much further away from the XYL's "home office" in both the horizontal and vertical directions. If I get the same RFI from the outdoor antenna, well, let's just say I'll cross that bridge when we get there.
The RFI occurs on all three transmit power levels (5/15/55 Watts on VHF) on the 146.205/146.805 MHz repeater pair.
So here are my questions:
Thanks for any assistance and/or ideas that you might have which will be greatly appreciated.
73, Dave K4EET
My XYL (wife) has a "home office" in the Master Bedroom (MBR). My hamshack is located directly underneath the MBR. She is experiencing RFI to her Dell Monitor with a symptom of wavy lines and to her Plantronics Headset used during telephone conferences that has the symptom of garbled audio when I transmit on a very specific repeater; namely the W3CU repeater on 146.205 MHz (input) and 146.805 (output). When I do test transmissions on repeater frequencies that are below and above the 146.205/146.805 MHz repeater pair (see table below), she does not experience any interference.
My mobile radio used as a base station is an Icom IC-208H (see attached brochure below) that has selectable power for transmit of 5/15/55 Watts on VHF. The temporary location for the antenna, similar to MFJ's MFJ-1724B, is on top of a 4 drawer steel filing cabinet directly underneath her desk that has the affected equipment on it. At this time, the location of the antenna is fixed and cannot be moved to another location which would probably mitigate the RFI. Once I get an outdoor antenna, a Cushcraft AR-270B, that antenna will be much further away from the XYL's "home office" in both the horizontal and vertical directions. If I get the same RFI from the outdoor antenna, well, let's just say I'll cross that bridge when we get there.
The RFI occurs on all three transmit power levels (5/15/55 Watts on VHF) on the 146.205/146.805 MHz repeater pair.
So here are my questions:
- Why is the RFI caused by a single frequency of 146.205 MHz and not any adjacent frequencies separated by 0.015 MHz?
- In my current inventory, I have two (2) Model 916, 2X43-151 Ferrite Clamps with a permeability of 850 for general RFI blocking (according to the package's label). The frequency range for this RG-8 sized clamp is 25 MHz to 300 MHz. I will not be able to test this clamp on the affected equipment for a week or so. Being disabled and in a wheelchair, I cannot install these clamps because I cannot get to that floor. I have to wait until our son comes over one day in the future. So the question is this: Is the ferrite clamp that I have in inventory a decent choice to try on the power lead, video/audio leads, etc. or would a ferrite clamp of a different size (I know it will be a loose fit since it is made for RG-8 cable) and/or permeability be better? I know the 917-Ferrite Clamp for RG8X/RG58 coax is better for smaller cable diameters.
- Is there anything that I can do in my shack to mitigate the RFI on my XYL's computer accessories (monitor and headset)? To not transmit on 146.205 MHz is a non-starter. The W3CU repeater is my primary repeater to use.
- Is there anything else (thinking outside the box without changing the location of the mag-mount dual-band antenna) that I may be overlooking?
Thanks for any assistance and/or ideas that you might have which will be greatly appreciated.
73, Dave K4EET
Repeater Input Frequency (MHz) |
| |
146.010 | 146.610 | |
146.025 | 146.625 | |
146.040 | 146.640 | |
146.055 | 146.655 | |
146.070 | 146.670 | |
146.085 | 146.685 | |
146.100 | 146.700 | |
146.115 | 146.715 | |
146.130 | 146.730 | |
146.145 | 146.745 | |
146.160 | 146.760 | |
146.175 | 146.775 | |
146.190 | 146.790 | |
146.205 | 146.805 | |
146.220 | 146.820 | |
146.235 | 146.835 | |
146.250 | 146.850 | |
146.265 | 146.865 | |
146.280 | 146.880 | |
146.295 | 146.895 | |
146.310 | 146.910 |