A recent discussion thread on the qrp-l reflector discussed various options for practical methods of bringing an antenna feedline into a house. In particular, the question was "how do you bring an open-wire feedline into a house?"
This article will summarize a number of those solutions to put as much info as possible into one place. Each description will be brief but there *will* be illustrations to assist in visualizing them. The original message text will be paraphrased so this piece will not be boringly long.
However topics will include a number in parenthesis to link to the original e-mails. A corresponding numbered list at the end of the gives the original author, date and time. You can read the messages on the qrp-l archives at http://listserv.lehigh.edu/lists/archives/qrp-l/other.html. Any errors in interpreting those messages are my own so you may want to read the originals to get the "straight scoop!"
Actually the beginning message by NR3E (1) asked how to get a balanced Radio Shack speaker wire lead into a house. But the same methods can be used with any balanced feeder.
First let me set out some points that I think are significant in properly bringing the feedline inside. Not all of these will be addressed for each method, but you should consider them in your installation!
- The method used should have a minimum effect on the antenna system. This means that we don't want to unduly degrade:
SWR (not too bad for open wire feeder if you use a tuner) Radiation pattern (mainly no feeder radiation)
Attenuation Received noise
- While we are at it we have to keep in mind:
No damage to building
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No effect on home security systems Maintaining a good weather seal
Minimzing the possibility of critter ingress (bugs, rodents, etc.) Preventing a fire or safety hazard
Lighning protection
- Aesthetics are important. *All* antennas and feedlines look good to a ham but family members and neighbors usually have different standards for attractiveness. Whichever scheme you use should be unobtrusive, hidden from view, or disguised to look like something
"normal", not sloppy or outrageous like a Dr. Frankenstein or Rube Goldberg creation.
Now here's a listing that I have separated into three categories:
Wall or window frame penetrations
- Radio Shack (RS 15-1200) TV feeder tubes (1). These are 13 inch long plastic tubes that can be run in a hole drilled through a house wall or window frame - see Figure 1. Their inner diameter is only big enough to hold a 300 ohm ribbon feeder or coaxial cable. Something larger is needed for open wire or ladder line. The tube should slope downward to the outside and be sealed with duct seal or (ugh!) tape to keep weather and critters outside.
- PVC pipe with an i.d. suitable for the feedline in use can be used the same way as the TV feeder tubes (7,8,13). The tube can be stuffed with some RF-inert material although I have used a pipe cap on the inside end with a slot cut in it to pass the feeder that is then sealed with airplane model cement - see Figure 2.
- Clothes dryer vents are another solution (5,18). For open wire, ladder line or ribbon feeders it's best to use a plastic type and like the thru-wall tubes it must be properly sealed. This method can be a kind of "stealth" entry since those looking at it may not realize that it is more than a dryer vent.
- A very thin, insulated parallel feeder can be fabricated by using a good quality plastic sheet and copper foil tape (3,6) - see Figure 3. With non-metallic window frames the impedance
"bump" of such a feeder no longer than a foot should be negligible if a tuner is used. The feeder is thin and flexible enough to fit *under* a closed window sash.
- Suitable holes can be drilled into a wall or window frame for threaded rod or ceramic chassis feedthrough insulators (4,14) - see Figure 4. The feedthrough method is probably best since an air gap around the threaded rod gives insulation - ordinary building materials are not very good RF insulators.
- Holes large enough to pass two parallel runs of coax cable can be used. boxes inside and outside use SO-239's connected to the coax cable (18) - see Figure 5. Loss for this short coax run will probably be ok, at least for QRP.
Window pane penetrations
- The window pane itself can be drilled wth a carbide bit and the feedline can be passed directly through these holes (9). The glass provides a very good insulator. With a metal window frame it is best to keep the feedline away from the metal. A rule of thumb might be a separation of twice the feeder conductor separation - see Figure 6.
A variation on the above that I have used is to replace the glass in the window with plexiglas or polycarbonate suitable for windows. Plastic is much easier to drill than glass.
- You can also use a 5 or 6 inch high piece of plastic that the width of the window (12). Drill holes in it or use banana jacks or feedthroughs. To put it in place, open the bottom of the window and place the plastic strip under the bottom sash. I use this method with a metal storm window.
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Other means:
There are lots of other ways though most are probably best suited to coax cable entry.
- Sometimes there is clearance under the house eaves that can be used, particularly if there are vent louvers or access holes.
- Gable end or attic vent louvers or pipes are another potential access location. However take care that a ventilation fan doesn't shred your feeder!
- You may find room in access holes for plumbing or air conditioner lines. Be sure to seal the holes well. Access holes for phone lines, cable TV and AC power feeds may be poor choices because of the potential for interference.
Lighning safety
This can be a big subject however it *is* important. You can check the ARRL Radio Amateur's Handbook and Antenna Handbook for ideas. Methods mentioned in the qrp-l thread include:
- Use a knife switch to disconnect the feedline and ground it when not in use (9, 16,20).
- Use large-value resistors to bleed static charges off the feedline (11,17).
- Use spark gaps or spark plugs (12,15,17).
- Disconnect and ground the feedline when not in use. W4RNL summaries protection methods quite well (17) and stresses one point I feel important - whatever protection method you use, keep the lightning *outside* your house!
Email message list.
Here is a listing of the qrp-l messages related to the feeder-into-the house thread. Not all of these are referenced above, but you may care to read them since they discuss topics not covered above.
(1) Date: Wed, 8 Dec 1999 10:23:47 -0600
From: "David Kreinberg"[email protected] Subject: Getting feedline into house
(2) Date: Wed, 8 Dec 1999 11:48:35 -0500 From: "Mike Yetsko"[email protected] Subject: Re: Getting feedline into house (3) Date: Wed, 8 Dec 1999 12:29:11 +0000 From: "Steven Weber"[email protected] Subject: Re: Getting feedline into house (4) Date: Wed, 8 Dec 1999 11:21:30 -0600 From: Karl [email protected] Subject: RE: Getting feedline into house
(5) Date: Wed, 8 Dec 1999 09:23:17 -0800 (PST) From: Monte Stark [email protected]
Subject: Re: Getting feedline into house
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(6) Date: Wed, 08 Dec 1999 19:31:28 +0200 From: Arjen Raateland [email protected] Subject: Re: Getting feedline into house
(7) Date: Wed, 08 Dec 1999 11:05:36 -0700 From: Jerry Haigwood [email protected] Subject: Re: Getting feedline into house (8) Date: Wed, 08 Dec 1999 16:03:57 -0500 From: Pete Burbank [email protected] Subject: Re: Getting feedline into house (9) Date: Wed, 8 Dec 1999 21:52:27 -0000 From: "Walt Amos"[email protected]
Subject: ANT: regarding getting open wire inside...
(10) Date: Wed, 08 Dec 1999 23:17:53 -0500 From: "T.J. \"SKIP\" Arey N2EI"[email protected] Subject: Re: Getting feedline into house
(11) Date: Wed, 8 Dec 1999 20:31:54 -0800 (PST) From: Monte Stark [email protected]
Subject: Re: Getting feedline into house (12) Date: Thu, 9 Dec 1999 00:12:31 EST From: [email protected]
Subject: Ladder Line Static Bleed
(13) Date: Thu, 9 Dec 1999 03:26:48 -0500 From: Howard D Rubin [email protected] Subject: Re: Grounding shack equipment (14) Date: Thu, 09 Dec 1999 04:36:09 EST From: [email protected]
Subject: Re: Getting feedline into the house (15) Date: Thu, 9 Dec 1999 06:44:59 -0600 From: Karl [email protected] Subject: RE: Getting feedline into house (16) Date: Thu, 9 Dec 1999 09:52:40 -0500 From: "Charlie Fitts"[email protected] Subject: Re: Getting feedline into house
(17) Date: Thu, 9 Dec 1999 10:17:11 -0500 (EST) From: "L. B. Cebik"[email protected] Subject: Parallel feedlines and static discharge
(18) Date: Thu, 9 Dec 1999 12:55:37 -0800 (PST) From: Curt Milton [email protected]
Subject: Re: Getting feedline into house (19) Date: Thu, 09 Dec 1999 14:40:26 -0700 From: [email protected]
Subject: Re: Parallel feedlines and static discharge (20) Date: Thu, 09 Dec 1999 17:16:40 -0500
From: Pete Burbank [email protected] Subject: Feedline etc
All material in HOMEBREWER is copyright 2005 and may not be reprinted in any form without express written permission from the American QRP Club and the individual author. Articles have not been tested and no guarantee of success is implied. Safe constructions practices should always be followed and the builder assumes all risks. HOMEBREWER Magazine is a quarterly journal of the American QRP Club, published on CD-ROM. Each issue typically contains over 200 pages of QRP-related homebrewing construction and technical articles intended for builders, experimenters, ham radio operators and low power enthusiasts all around the world. HOMEBREWER features include construction projects for beginners all the way up to the advanced digital and RF experimenters. Annual subscriptions are $15 (for US & Canada) and $20 (for foreign addresses). For information, contact editor/publisher George Heron, N2APB at[email protected]or visit HOMEBREWER Magazine home page atwww.amqrp.org/homebrewer.
AmQRP Homebrewer, Issue #5 1 Copyright 2005, AmQRP, All rights reserved QRP Miles-per-Watt using Lat/Long or grid squares.
GCGC & DX: DOS executables, notes and sources
GCB: DOS executable, F77 souce
& notes
GCGC: Linux G77 source
Great Circles, Grids & Coordinates (“GCGC”), is a freeware DOS command line program that calculates the ellipsoidal geodesic path for antenna bearings/azimuths (true and magnetic), distances (km, mi, nmi), Maximum Usable Frequencies (MUF), QRP Miles-per-Watt using Latitude/Longitude or Maidenhead/IARU Locators (a.k.a. grid squares).
For the GCGC zip package (link above)
"Read1st.txt" describes how to get started.
"Read2nd.txt" describes the included files.
"Geo-web.htm" has many geographic links.
The DXCC+ amateur radio call prefix, country, city, latitude/longitude, CQ/ITU/Time zone, continent, ... data base is up-to-date. GCGC is Y4K compatible.
Command Line Input Format
Latitude/Longitude input can be in degree (ddd.dddddd), degree-minute (ddd mm.mmmmm) or degree-minute-second (ddd mm ss.ssss) N/S/W/E formats. Degree º, minute ' and second
" symbols are not used for input. Lat/long input is encoded to only as many grid locator characters as needed to use all the data.