I'm about finished restoring a Knight Kit Star Roamer and will need an antenna put up. My den/shop is a second story room. I could put a random wire up in the attic and run it through a hole in the ceiling/wall, but right now I'd rather avoid that if possible. My wife isn't keen on wires coming out of the wall, and it's hotter than a firecracker in the attic. I enjoy building radios and electronic projects, so I'm interested in possibly making an active antenna that I can use on my desktop with the Star Roamer. Does anyone have a schematic for a good active antenna? I see MFJ sells one already built but I'm not willing to spend $100 right now if I can make one instead. Of course, it might cost $100 to make a good one anyway!

You could make a shortwave loop antenna. I made one from a quilting hoop. It covers about 5 to 12 MHz.

http://kr1s.kearman.com/html/hooploop.html


http://makearadio.com/loops/index.php

Rich

Nothing beat's an outdoor antenna. They are nowhere near 100$ to make. I might have 30 bucks into some coax, T, pvc pipe and all for a 60 or 70 foot multi element inverted V about 40-50 ft in the air. I used the old TV antenna chimney post as a mount.
Unless you have some sort of neighborhood restriction, or grief from the wife, I'd put it outside.

If you HAVE to keep it indoors, I reckon the next best thing is wire stapled to rafters in the attic. Yeah it's hot and you're gonna sweat. No pain no (RF) gain!
P.S. You can always ditch the wife and move too.

You can maybe try a tiny hole and very small guage wire for a lead in into the room from the attic, that would be very inconspicous. As a desperate move, you could possibly connect to metal eaves at the edge of the roof if the house is not metal sided. With a radio like that, you need all the antenna you can get so try any sort of random length of wire stretched out anywhere. And try to not make any bends at angles under 90 towards the other parts of the wire, no Z configurations if possible. For reception, random wires are not the sin that they might be for trying to use them for transmitting. And if you go with indoors or attic, your greatest enemy will be noise from power line lead ins, or from stuff inside the house.

Thanks for the replies, folks! Well, I guess I'll try the cheapest route first - a random wire in the attic. We have restrictions here that don't allow any type of outdoor antenna, so it will have to be indoors. I have some #24 speaker wire, which I split and soldered together, so that gives me about 70' of wire to work with. I should be able to get 50 - 60' out in a straight line. I'll make a small hole in the wall down low behind the computer desk - I don't think anyone will ever see that.

Not sure what to do about the ground. These old radios used an earth ground, not an RF ground, and are set up for an unbalanced antenna. I have used some older radios before using just an antenna and no ground with OK results, but I suspect on the lower frequencies the lack of ground will hurt the performance. I'm on the second floor with no good way to get a wire up here from a ground rod without running it up the side of the house. I do have a metal gas pipe coming into the house that runs through the attic. I suppose that would serve a similar purpose as the often used cold water pipe back in the day. I'd have about a 35' run to get to it, but it might be worth a try. There is a meter between me and the gas pipe that is in the ground, but I'm guessing there should be continuity across the meter since it is a metal case.

If the random wire doesn't work out, I might be tempted to try the MFJ active indoor antenna. I've read it works well. I see it is set up for a balanced connector such as those used on modern radios. Would I need a balun between it and my Star Roamer?

I had an indoor random wire, about 35 ft.

My homebrew loop was surprisingly better. Did not pick up as much noise from nearby house wiring and fluorescent lamps. Since it has a tuning cap, you can peak it at the exact frequency you want to hear.

The MFJ is just a short whip with an RF amplifier. If you are in a noisy environment, you will get amplified noise.

A loop is directional, so you can try to peak a particular station by orienting the loop, or you can null out noise. It also doesn't need a ground.

For a $15 investment, I got very satisfactory results.

Is it as good as my 100 ft outdoor dipole? No. But it's way better than the indoor random wire. I also take my loop with me in the car. Put it on top of my little SUV and I can demonstrate my homebrew receivers to my friends at our weekly coffee.

Rich

Rich,

I was looking at some loop designs yesterday on the web and they look enticing. What design did you use? One I found used a tuning capacitor from a cheap boom box - looked like the tuner cap from an old transistor radio; not sure I can locate one of those. I checked my attic yesterday also and to get to the room where my radio is, the random wire would have to run several different directions and past heating ducts and quite a bit of house wiring, so doesn't seem like a good idea. A loop is probably the way to go.

Mine was built for shortwave (7 to 12 MHz) and I used a design similar to KR1S. Two turns of wire (anything around 24 AWG) in parallel with a 150 pF cap. I could have used a smaller cap, but this one was convenient. I used a one-turn pick-up winding next to the two turns of the antenna. All on a quilting hoop.... I think it's 23 inches in diameter.

If you use a cap from a regular AM band radio, it will be a bit large for shortwave, depending on what frequencies you want to cover. You can also stick a smaller fixed cap in series with the variable to cut down the range.

You can use coil calculators from the Internet to design your own loop, depending on what frequency you want to cover. Dave Schmarder has lots of BC band designs on his web pages.

Here is my loop next to my homebrew superhet:




Rich

PS: Here is a calculator that is handy. My 23 inch loop with two turns gives me about 4.6 microhenries inductance. Works well with 100 pF variable cap.
http://www.daycounter.com/Calculators/A ... ator.phtml

Neat radio and antenna, Rich! Thanks for the info.

I built a very small 9:1 balun. I put it inside a 3x2x1 RS black box. I ran some RG-174 from the HiZ side, out thru a very small hole I drilled thru the window frame outside to the aluminum downspout near the window. I connected the center conductor to the downspout with a sheet metal screw & the ground or shield down was connected to a short 4' ground rod. I then ran another piece of coax from the LoZ side to my radio ICOM R75. It works very well. Almost as good as my 178' endfed wire antenna and very similar to my 43' vertical. It is very stealthy & surprising quiet.
Good luck - Bob V

I have 52' of aluminum wire that I scrounged from a burned out power transformer taped to the wall near the ceiling in my bedroom. Connected to a Sony ICF 2010 the SW bands come alive all the way up to 13 meters. I'm in Alaska and I receive Australia, New Zealand, BBC, Cuba, of course, and North Korea. There are many others with languages that I don't understand. I've also received Hams in Georgia, Missouri, Illinois, Hawaii and Japan to name a few. However it fails on BCB. KGO in San Fransisco comes in fine on the built in loop but disappears on the makeshift antenna. Last night, I connected the antenna to a National 183D that I just acquired with disappointing results. It either needs an alignment or just plain doesn't like the antenna.

I'm intriqued by Bob V's downspout trick. My house has 46' of continuous steel rain gutter along the back and when it stops raining I'm going to hook it up. I wonder if anyone with aluminum siding has hooked up the whole house.

My house is a combination of Vinyl siding & brick. But the downspout connects to gutters that are in contact with some aluminum trim that goes almost the whole way around the house. I know what I offer is not an "indoor" but it is so simple & effective for me, I thought I'd offer it up as a possible option. The small hole is thru a vinyl window frame, that is easily repaired with a dab of white caulk. But of course before you drill, just try it thru an open window. This antenna also seems to function from 160M to above 10Ms. 73 - Bob V

I've read in a couple different antenna articles that grounding to a gas pipe isn't a good idea. But maybe that only applies if you have an outdoor antenna that could get hit by lightning....

I don't see grounding as that big a deal if it's receive only. I made a good ground once (thick grounding wire from second story bedroom to a grounding rod buried a foot or two into the earth), it didn't make any noticeable difference in the receive for any of my receivers.

Grounding to the gas pipe is useless, as the gas company isolates the system from your piping to avoid electrolysis in the distribution system.

I built a Star Roamer when I was in junior high. It was pretty deaf on all bands from what i remember. I could hear the high powered internationals but never the low powered good stuff like Radio North Sea International (now long defunct.)

Scott Todd

Perhaps this Website gives you some new old ideas:

http://www.aktuellum.com/circuits/antenna-patent/

Best Regards
Jard N.

You can string magnet wire along the roof facias. Put a nail with drip irrigation line over it every 10' or so. String the wire tightly along the nails and secure with a little piece of wire to hold it in place. You could even staple insulated wire along the drip edge of the facia. Either way, It will be invisible. Any outdoor antenna will be much better than an ondoor one. Most modern electronic devices put out a sea of RF hash. You need to get away from that. Make you lead in out of coax. Properly ground the sheath. Make a real ground rod out of copper clad grounding rod. Make your lead in to the radio out of coax. All of this can be done as to be invisible. IMHO you will never get decent SW reception inside a modern house unless you take steps to keep that sea of RF hash at bay. To confirm this turn off your electrical service at the main pannel. Listen on a battery radio. Nottice how all that RF mess disappears!

Hi Al!!

Here's a thought. I don't know if you have cable TV in the house, but if you do, then I know that this will work. Connect your receiver antenna input terminal (hot side) to the cable tv ground block. What you are doing is using the foil side of the coax as the antenna. There are miles of it out there. You would think that this wouldn't work, but the ground at DC is not the same as RF. It will function quite well and it costs almost nothing. IF you don't have cable, then the next cheapest way to get an outside antenna is to use electric fence wire. You can buy a 1/4 mile roll of the stuff (it's steel) for very little. A very small hole in the gable end of the house, just below the eaves will give you access to either get inside with the wire, or make it a little larger (1/4") and run a length of RG-59 CATV wire out and connect the center conductor to the fence wire. The impedance of the coax in this case doesn't matter since the radio is 300 ohm's in. You can use a CATV matching transformer for attaching the cable to the radio for a better match. just be sure to ground the shield of the coax to radio chassis to complete the circuit on the input side. You can wrap the fence wire around the house eaves and it will work good. It usually it ends up being a couple of hundred feet and nobody can see it. It's how I got an antenna on my parents house 45 years ago. I did that when they were gone a couple of times. I did it in stages.

If your upstairs room has a closet, then you're in fat city! You can drop the coax through the ceiling of the closet, hide it in the corner next to the door, and use a CATV wall plate on the other side of the wall for your antenna connection. The plus side here, is that if you decide to add a TV drop later, you can piggy back it with a duplex wall plate or move the radio room and leave it the way it is. No wires or mess. Just be sure to put that wall plate at the same height as the wall outlets so it looks professional. Don't know if any of this helps, but I thought I'd toss it out there

I had success with a rain spout as an antenna
I lived in a three story apt on the ground floor in Maryland. I drilled a hole in the apt downspout, and connected a wire with a self taping screw and a solder lug. Ran the wire into my apartment and connected it to my HW 101 ham radio transceiver by means of a home brew antenna tuner.

It worked pretty good well enough to allow regular schedules to Puerto Rico on 40 meters at night.


The TVI into the apartment master antenna television system was not very pretty but that is another story.

bruce

First Gas pipes are NOT safe or legal to connect to. You will void your insurance if you connect a wire to one.
Also Gas pipes and radiator heating pipes have a DC voltage on them to fight corrosion (I believe the name is cathodic protection, the pipes tend to act as cathodes in the local soil. By applying the reverse voltage the pipes cannot corrode (which is why gas pipes over 100 years old are still good).
Now, Behind the computer is a very noisy location.
You can fold a piece of aluminium foil and put some tape on it to keep it from shorting to the aluminium window. Run it out the window and close down. No holes to drill. Paper clips make good connection for a month or two and are easily and cheaply replaced.
Good luck,
pat