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Author Topic: HF Antenna in an apartment w/o balcony  (Read 1380 times)

KO4VWJ

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HF Antenna in an apartment w/o balcony
« on: January 14, 2022, 11:26:12 AM »

I am fixing to move into an apartment without a balcony, but still would like to work HF bands.. I can get out just fine with my VHF mobile rig so that isn't an issue. I just need to find a way to get out on 20 meters without a massive dipole or vertical. Setting up on the roof is a no go as well, or else that would be my solution, but I cam; t run cable outside of the apartment. any solutions?

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AB5CC

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Re: HF Antenna in an apartment w/o balcony
« Reply #1 on: January 14, 2022, 11:35:16 AM »

You could use a MFJ Loop tuner such as the MFJ-933 or MFJ-935 near a window.  I have one and it is simply amazing for what it is.  You just supply a piece of 1/4" copper tubing or #10 wire.  Look at the eHam reviews for ways people have used them.  It is impressive.
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WX7Q

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Re: HF Antenna in an apartment w/o balcony
« Reply #2 on: January 14, 2022, 12:19:48 PM »

https://www.eham.net/reviews/view-product?id=2035

I used this when I was living in Chicago. I worked Europe using it. ( Maybe living on the 13th floor had something to do with. Mag loops are a good option. ( Alpha Antennas)

https://www.eham.net/reviews/view-product?id=14773

You did not say what floor you are living on. A simple end end wire hung out the window using a 9:1 or 49:1 Balun might work. Kind of depends on your setup and how much stealth is involved. Good Luck and get on the air!

HTH

WX7Q
Jim


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K6AER

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Re: HF Antenna in an apartment w/o balcony
« Reply #3 on: January 14, 2022, 01:11:36 PM »

Unless your the only one in the complex I think your HF experience will be very frustrating. I would suggest you bring a portable SW receiver and see what the noise floor is like before committing to moving in.

Most apartment locations. have a very high noise levels.
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N8TGQ

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Re: HF Antenna in an apartment w/o balcony
« Reply #4 on: January 14, 2022, 02:45:56 PM »

 My situation is about the same as yours. Right now I'm using a 29' end-fed wire running around my ceiling with a 17' counterpoise running opposite under the baseboards. My MFJ 971 tuner will tune it up from 40 to 10 meters.
 A lot depends on what your walls are made of. Wood is best of course. My current apartment has brick on the outside, but I still get pretty good results.

 As mentioned above, having neighbors real close by creates a lot of obstacles.
 The main one is meeting the FCC's RF radiation rules. I'm running QRP, actually only about 2 watts CW and have my wires on the corner away from the neighbors. If the neighbors find out what you're doing, you'll be the first one they blame for any electrical problems they have! The less they know, the better!
 The other problem is the noise you have to put up with. Check with a receiver before putting up anything! It could save you a lot of work.

 I have tried magnetic loops, bigger loops and short verticals clamped to the table. The end-fed has done the best for me. The big thing is not having to constantly retune when I move around the band.

 I only use the indoor antenna during the cold weather months. As soon as it warms up, I head for the parks and play radio there. I'm retired, so my local park is pretty much my private radio site during the day when everyone's at work. Plus no noise at all.

 Try different setups and see what works for you. Start with easy and cheap and see what happens.

Have fun!
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WA3SKN

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Re: HF Antenna in an apartment w/o balcony
« Reply #5 on: January 14, 2022, 03:22:56 PM »

Capacitive coupling.
Duct tape a metal plate on the outside of the glass.  Another plate on the other side of the glass.  Connect a random wire outside and a tuner inside.
You can determine the sizes needed with the ARRL Handbook formulas.
I found some 5x7 inch aluminum at the local hardware that worked OK, but this depends on the frequency and the glass thickness.
Oh, and the newer treated glass has more loss than the old single plate kind.  Sometimes you have to work with what you got!
Good luck with the project!

-Mike.
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W6UXB

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Re: HF Antenna in an apartment w/o balcony
« Reply #6 on: January 14, 2022, 05:02:08 PM »

If you don't want to run power, then I would go with the AlexLoop the latest version in the Ham Pack with the new tuning box works great, it also would deal with a lot of the RFI you are going to get in an apartment building.
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KH6AQ

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Re: HF Antenna in an apartment w/o balcony
« Reply #7 on: January 15, 2022, 08:17:43 AM »

You could use a MFJ Loop tuner such as the MFJ-933 or MFJ-935 near a window.  I have one and it is simply amazing for what it is.  You just supply a piece of 1/4" copper tubing or #10 wire.  Look at the eHam reviews for ways people have used them.  It is impressive.

I agree. I owned an MFJ-933C and the loop tuners offer good performance with possibly the lowest chance of exciting RF in the apartment AC wiring.

HRO currently has the MFJ-935C and MFJ-9232 in stock. 

https://www.hamradio.com/search.cfm
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KH6AQ

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Re: HF Antenna in an apartment w/o balcony
« Reply #8 on: January 24, 2022, 11:09:34 AM »

Another choice in balanced antennas is an MFJ-2220 Mini-Dipole. It is 15' long. A feedline choke can be placed near the feedpoint to reduce RF thru the apartment AC wiring. An example of one is the MFJ-915 RF Isolator. 8 turns of RG-58 or RG-8X coax on an FT240-31 or FT240-43 core also makes a fine choke.

MFJ-2220  https://www.dxengineering.com/parts/mfj-2220?rrec=true

MFJ-915    https://www.dxengineering.com/parts/mfj-915

Chokes     http://www.karinya.net/g3txq/chokes/
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JAHAM2BE

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Re: HF Antenna in an apartment w/o balcony
« Reply #9 on: February 16, 2022, 05:46:27 PM »

You could use a MFJ Loop tuner such as the MFJ-933 or MFJ-935 near a window.  I have one and it is simply amazing for what it is.  You just supply a piece of 1/4" copper tubing or #10 wire.

I think a long piece of wide copper strap -- perhaps 5 cm to 10 cm in width -- would also work well, though you need use gloves and to be careful to avoid cutting yourself on the razor-sharp edges of the copper strap. A copper strap has the beneficial combination of high conductivity and physical flexibility so you can dismantle it and roll it up easily when not in use.

The best loop size is the largest possible, while remaining below self-resonance. This corresponds to a conductor length of about a quarter-wavelength, and the conductor should be stretched out to form a large, single loop. But if your space is limited, you can also try winding the conductor into a two-turn or multi-turn loop.

For 20 meters, a quarter-wavelength is about 5.35 meters, which corresponds to a circular loop of about 1.7 meters diameter or a square loop of 1.3 meters per side, which is a fairly small size and should be quite efficient. I did a quick 4nec2 simulation of a 1.3-meter square loop, 1.45 meters above moderate ground, with round copper conductor of 2 cm diameter (corresponding to about a 10 cm-wide copper strap; see equation 16 at http://web.archive.org/web/20000506045342/http://fermi.la.asu.edu/w9cf/articles/conform/index.html, the accuracy of which I have verified via Finite-Element Method simulations), and an added capacitor loss of 200 milliohms (corresponding to a capacitor Q of about 2400 at 14 MHz when resonated with 24 pF capacitance).



At 15 degrees above the horizon, the gain is only 3.81 dB below that of an isotropic radiator. That's not bad for an antenna of this size, so close to the ground.

As already mentioned, the biggest problem will probably be RFI (both on transmit and receive) inside the apartment building. So you might want to consider portable operation from a park.

N6YWU

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Re: HF Antenna in an apartment w/o balcony
« Reply #10 on: February 21, 2022, 05:10:17 PM »

How big are your glass windows?  And are they coated or not?  (some window coatings are conductive, and turn your apartment into a Faraday cage)

If your windows are very wide and clear glass, then you can try using conductive copper foil tape (1" to 6" in width, available from amazon, etc.), and tape either a loop antenna, or a meander slot antenna to the inside of your window.  Perhaps jumper between multiple glass panes or windows, if needed.  Attach a tuner, and see if it loads up.
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ONAIR

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Re: HF Antenna in an apartment w/o balcony
« Reply #11 on: November 14, 2022, 09:45:54 PM »

I use an ULTIMAX-100 end fed 23 foot antenna inside hotel rooms when I travel, and get surprisingly good results!
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W4FID

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Re: HF Antenna in an apartment w/o balcony
« Reply #12 on: November 15, 2022, 04:23:38 AM »

The advice to bring a SW receiver and check the noise floor is absolutely square 1. If the pace has a high noise floor HF is a no go. Period.

After that a loop by a window is a good option. Keep in mind that there can be high voltage -- even at modest power levels and RF exposure so low power and some distance between your head and the loop is good. Some nice lower power loops have remote tuning -- my LNR and some other manufacturers make them too -- and that way the antenna can be wherever you have the best "view" to the outside but the operating desk is wherever you like and a ways away.

Personally I would not have anything outside. ANY problems any neighbor has will become your problem. Someone's toaster quits working. Someone drops their I-Pad and breaks it. A light bulb in the hallway burns out. All will be blamed on you and your radio. So keep knowledge about it quiet. NO QSL cards or ham call on envelopes in the building mail box. Some postal people are gossips and boxes with large DX Engineering labels in the lobby are red flags.

Portable from your car in the parking lot of from a nice park is an option. I have done super candelestine operation from multi family, and mobile, and picnic table portable over the years. There are ways -- be creative and take what you can get. Work whomever you can work on whatever band and mode you can and enjoy the QSOs you do have. CW and FT8 allow more with less so don't overlook them.
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KD2HCU

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Re: HF Antenna in an apartment w/o balcony
« Reply #13 on: November 15, 2022, 05:51:17 AM »

As was mentioned previously, you can hang a wire antenna.  I have a counter poise wire held up with thumbtacks along my bedroom ceiling (radiator is in attic).  A 20 M dipole can be strung in a room, start at the middle of the wall and go out in both directions, the extra length can either be bent around the corners or let hang down towards the floor.
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AI5BC

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Re: HF Antenna in an apartment w/o balcony
« Reply #14 on: November 15, 2022, 06:24:01 AM »

While you are at it stick your head in a microwave oven. You get to look forward to all kinds of RFI/EMI, RF burns, and shock. There is a good reason why radio sites are required to have barriers and warning signs.
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