Q Tim, WD8OQX, asks, “I live in an apartment and I need to run a length of coax from my radio through a window to an outdoor antenna. The trick is that I need to do it without modifying or damaging the window. Do you have any ideas?”
A The Doctor was once faced with a similar problem while living in a condominium. My solution was the old open the window slightly and place a board there scheme.
See Figure 1. Cut a piece of 2 × 4 lumber so that it fits snugly into the lower sash. Drill a hole large enough to pass your coaxial cable. Pass the cable through the board and through the window.
Close the window onto the board and use another length of board between the top of the window and the upper frame to prevent the window from being opened from the outside. Connect the coax to your antenna, but leave enough slack in the cable to form a drip loop just outside the window. Finally, buy some packing foam material and use it to block any drafty gaps created by your new installation. When it’s time to move, the entire assembly can be torn down in minutes without damage to the window.
Figure 1—A narrow 2x4 with a properly drilled hole will pass a coaxial cable through a window without damaging or modifying the window itself.
From QST June 2000
Q Rick, K8SV, asks, “I have seen advertisements for in-line coaxial cable filters. How effective are these devices at reducing or eliminating RFI?”
A If an RFI problem is caused by RF getting onto the outside of a transmitter’s feed line, a filter of this type will help suppress it. This RFI scenario arises only when susceptible equipment is much closer to the feed line than it is to the transmitting antenna. This could happen in an apartment location, or in a ham’s own home (such as when the radiating coax passes near your computer).
If your neighbors are located a distance away from the ham station, radiation from the feed line is not generally a problem. In that case, a low-pass or band-pass filter would be more appropriate, if the interference is to an over-the-air service, such as antenna-connected TV or FM broadcast reception. Even so, in most of those cases, fundamental overload also plays a role.
See http://www.arrl.org/tis on the Web for some good information packages on various aspects of RFI. Of course, The ARRL RFI Book (http://www.arrl.org/catalog/6834/) is another good source of help for all types of RFI problems.
From QST August 1999
