Ham Radio Forum

Hello, I have a friend who can not put an outside antenna up But has a 400+ ft. elevation and can talk 15 miles or so using a 4 watt 65-70% modulation walkie talkie. yes it is 11 meters but I am going to loan him a base radio so he can upgrade to sideband. the dipole would be a 1/2 wave 8.5ft. x 2 most of the contacts would be with other vertical bases and mobiles. with 1 vertical element from corner of ceiling towards floor and 1 horizontal element from corner going towards opisite end of ceiling radiating in direction of most communications. the element coupling will be at 90 degrees angles(if I recall 45 degrees for 50 ohm.) so even with the wires being thumbtacked to wall and ceiling I would like to get the s.w.r. around 1.3 to 1 I belive this set up would be low around 30-35 ohms or so? what would be the most efficient way to achieve 50ohms? (surely not a 15-20 ohm resister in series) a trimmer cap or a 1/4 wave stub with a trimmer cap etc.? OR is there another style/shape antenna I can make like a T or modified folded, etc. that would work better and get me closer to 50ohms. this would be a 50 ohm input radio with 50 ohm. coax unless 75 ohm or other coax would work better. for cosmetic reasons 90 & 180 degree shapes only no inverted V tepee in the middle of the room etc. L.O.L. Sorry for the long write up, Mike J.

Hello Mike,

First of all you haven’t taken into consideration what the structure of your friend’s building is.

Is the building constructed of Steel and/or Concrete or Brick or Wood?

Is the building setting on a high hill at 400 feet or perhaps a multi-level apartment / condominium building?

Have you considered how the interior walls are constructed, using steel studs rather than wood?

This would create a worst scenario matching any interior wall mounted antenna. It could create RFI / TVI beyond belief and you could end up jeopardizing your friends contract / lease.

Dan
WA9WVX

Hello Dan, Thanks for your input. I have never actually been to the place but have talked to the person for 3 or 4 years and said I would try to help. It would be a big two story wood house(room on 2nd story) on top of the hills with .25 or so acres between houses. t.v.i. would probably not be a problem it would be a stock 12 Watts p.e.p. ssb and the rich in that area would have satelite or shielded cable t.v. reception and hopefully no plastic unshielded 49$ wallmart d.v.d./v.c.r. equipment. the person owns the house but has to pay a monthly H.O.A. fee to get told what they can and can not do to/with their house. I know there are lots of ham operators out there with court battle$ over getting told by some punk with a clipboard they can not have a tower or antenna it is a violation or disturbs somebodies view etc. sometimes it is nice to have an old house in the flats and be free.

Hello Mike,

Oh, I L-O-V-E property / zoning C, C & Rs like slamming my hand in a car door! That's why I live in a rural unincorporated subdivision 2 miles west of Elgin's "City Limits," IL. My wife and I did our research work with Kane County before ever purchasing a home in this country subdivision. Here's the Key Issue: People that don't do their own C, C & Rs research work with State, County and/or Local Muninipalities have no one to blame but themselves.

Now on to your friend's internal antenna mounted within the wooden home's structure. If this gentlemen's home is a two story house, it most likely has an attic space, perhaps 6~7 feet high unless there's open beam ceilings. Let us think there's an attic space to mount the antenna and the use of an Inverted
"V" is a good choice. The Inverted "V" antenna basicly radiates RF signals in both the Vertical and the Horizontal Axis and has a 360 degree capture area.

Using the 1/2 wavelength formula of 468 divided by Frequency 27.4 MHz Equals 17.08 Feet Long. Then multiply the 17.08' X 71.9% = 12.28' and divide by 2 which equals 6.14' or 6 Feet 1-5/8 Inches High for the antenna's 50-Ohm Apex Feedpoint. Take each wire end and pull outwards 6 Feet 1-5/8 Inches from the center of the Apex. The End to End separation should be 12 Feet 3-1/4 Inches total.

The Inverted "V's" Apex should be mounted on or near the Roof's Interior Peak fastening a plastic (Plexiglass) insulator or a Balun using a Nail or a Long Wood Screw. To insure there's a 90 degree angle use either a plastic drafting angle or a 3" X 5" Post / QSL Card for the Right Angle reference.

The RF Transmission Line can be RG-213/U (98% Shielded 8/U), RG-8X, RG-58A/U or B/U 50-Ohm Coaxial Feedlines.

As far as using a 1:1 50-Ohm Balun, these can be constructed by you by doing an on-line Google search on "Homebrew 50-Ohm 1:1 Baluns" or purchasing a 50-Ohm 1:1 Balun through any Amateur Radio Supplier On-Line

Keep the Inverted "V" antenna wire elements away from adjacent metal objects such as: Electrical Conduit, HVAC Ductwork and/or Vertical Metal Heat Exhaust Tubing/Pipes and internal TV/FM antennas. These objects could cause potential VSWR and coverage problems. Speaking of VSWR, it's totally acceptable in the Commercial Land Mobile 2-Way Radio (Business Band) field to have a VSWR of 1.5:1 or less and have very reliable point-to-point communications.

73,

Dan
WA9WVX

Thanks again Dan for your info. I would have to find out how accessible the attic access is from the room. what are the major lobe take off angles will it have big cloud burning e-plane patterns or low angles like a ground plane. this would prob. be importent since the location is already way above everyone else. Take care, Mike

Hello Mike,

I think you're making a mountain out of a mole hill. Your also lacking the ability to do your own research on this antenna subject. I went back to this website's main page where the subject of "Antenna Designs" field is listed. I clicked my mouse on this Button and it openned the listing for just about every antenna you can imagine. I scrolled down to the "Inverted V" and with my mouse, I clicked on this field and here's the link:

http://www.smeter.net/antennas/inverted-v.php

Now YOU WILL have to read and interpet the information on your own! Down towards the bottom of the page you'll see the following information in Bold words:

Run this Program from the Web or Download and Run it from Your Computer and the Field is Inv Vee and click your mouse over that field to open and use.

73,

Dan
WA9WVX

Hi Dan, Actually I read internet articles on antennas all the time and used to listen to 75/80 mtrs. shortwave several years back just for the technical antenna talk. thats how I knew about the coupling angles of the two dipole elements for near 50 ohm impenence & what the 2 quarter wavelengths should be etc. (mentioned in my first post) although I will never be facing the challenges you guys do especially making efficent antennas on 80 & 160mtrs. I did string up a few dipoles in my high school days and talked dx whith a horizontal dipole in the rafters of the garage. I then went on to put together a 2 element yagi/quad hybrid beam but that does not count as it was a commercial (store bought) antenna HI, HI,. I will prob. go with your inverted v suggestion if the attic is easily accessible, hope they don't have that open fluff fiberglass insulation L.O.L. . Regardless I'll shoot you an E-mail when it gets done and I collect the before and after local reports of the vert. mobile & basestations ragchewing to the new antenna. Thanks again for your input and vast antenna experience. 73's Mike