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Author Topic: Indoor HF antenna  (Read 6657 times)
KB1WTY
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« on: September 16, 2013, 11:45:35 AM »

Hi everyone,

I've recently gotten into the hobby and would like to expand into HF. Problem is, I live on the third floor of a (brick) apartment building, with no outdoor space, nor roof access. Additionally, the room where I would keep my radio equipment isn't very large, though the ceilings are a normal height (8ft or so). There is a window, though I wouldn't want to have a huge antenna sticking out of it.

Realistically, does it make sense for me to get into HF given the limits I have on antenna placement? I do see indoor HF antennas for sale (i.e., http://www.gigaparts.com/store.php?action=profile&sku=ZMF-1020C&gclid=COvtzI7I0LkCFYWf4AodfUoAwA) but I have no idea if it's going to handicap me so much that I shouldn't bother until I'm living elsewhere. Ideally, I'd love to be able to make international contacts (I live on the east coast, in Boston). What kind of performance can I expect with an all-indoor setup?
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AF6WL
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« Reply #1 on: September 16, 2013, 11:54:43 AM »

I do see indoor HF antennas for sale (i.e., http://www.gigaparts.com/store.php?action=profile&sku=ZMF-1020C&gclid=COvtzI7I0LkCFYWf4AodfUoAwA) but I have no idea if it's going to handicap me so much that I shouldn't bother until I'm living elsewhere. Ideally, I'd love to be able to make international contacts (I live on the east coast, in Boston). What kind of performance can I expect with an all-indoor setup?

That's an active receive ONLY antenna.

The MFJ loops e.g. http://www.gigaparts.com/store.php?action=profile&sku=ZMF-1788 are likely your best option.

They also do a loop tuner, that does not have remote tuning: http://www.dxengineering.com/parts/mfj-935b?seid=dxese1&gclid=CJeewMfM0LkCFSU6QgodBCIAKQ.
This is considerably cheaper - but you need to visit Home Depot and make the loop element yourself out of soft copper tube. Thinner tube so lower efficiency than the 1786/1788.

Local QRM and poor efficiency below 20m will always be your enemies until you can get a larger outside antenna.
« Last Edit: September 16, 2013, 12:02:23 PM by AF6WL » Logged
KB1WTY
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« Reply #2 on: September 16, 2013, 12:03:47 PM »

That's an active receive ONLY antenna.
Oops, thanks catching that!

The MFJ loops e.g. http://www.gigaparts.com/store.php?action=profile&sku=ZMF-1788 are likely your best option.

Local QRM and poor efficiency below 20m will always be your enemies until you can get a larger outside antenna.
Yeah, that's what I was afraid of. I won't be here forever (I'm renting) so I might just wait, or maybe get the radio, upgrade my tech ticket, and go with an indoor antenna for now, and then use an outdoor antenna once I'm living elsewhere in a year or two.

Another thing that bothers me about the indoor antenna is the RF exposure. Not sure if it should, but it's in the back of my mind.

Ouch, also just noticed the price for that antenna.
« Last Edit: September 16, 2013, 12:06:57 PM by KB1WTY » Logged
K5LXP
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« Reply #3 on: September 16, 2013, 12:21:53 PM »

Realistically, does it make sense for me to get into HF given the limits I have on antenna placement?

That depends on your expectations.  It's a given an indoor antenna will not work as well as an outdoor one but if you know that going into it and still achieve some degree of success, that could be considered "better than nothing".

Start with something, anything - a wire thumbtacked to the wall or ceiling - and see how it does.  Then try something different and see if it's any better.  Wire's cheap.  I would avoid commercial compromise antennas, they'll only add inefficiency to the equation.

Consider getting some portable antenna setups together too.  Dipoles and verticals you can set up in a park or other location to operate away from the apartment.  Even mobile is way better than "nothing".


Mark K5LXP
Albuquerque, NM
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KB1WTY
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« Reply #4 on: September 16, 2013, 12:43:17 PM »

Start with something, anything - a wire thumbtacked to the wall or ceiling - and see how it does.
That brings me to a related question: how much wire do I need to create sufficient load not to damage the transmitter?
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WX7G
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« Reply #5 on: September 16, 2013, 01:06:08 PM »

I've used indoor HF antennas in four apartments, all wood frame. I think it's worth giving HF a try from your brick apartment.

I've tried loaded whips, full size dipoles, quarter wavelength loops, and random wires and they all worked well enough to work plenty of DX. The easiest way to get on HF from an apartment is to tune a random length dipole or loop using a tuner such as an MFJ-901B ($99).

Another antenna that works well is a quarter wavelength loop tuned by an MFJ-933 Loop Tuner ($190).

And there's the Budipole which a friend of mine operating from an apartment highly recommends.
« Last Edit: September 16, 2013, 01:08:44 PM by WX7G » Logged
KB1WTY
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« Reply #6 on: September 16, 2013, 01:08:16 PM »

Thank you all very much for your help! I still need to do some thinkin', but in the meantime, I think I'm going to start by preparing for that general ticket.
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AF6WL
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« Reply #7 on: September 16, 2013, 01:10:44 PM »

That brings me to a related question: how much wire do I need to create sufficient load not to damage the transmitter?

Generally you want each arm of an antenna to look like 1/4 wavelength long.
There are tricks that allow you to use shorter than ideal antennas;  such as in line coils ( see buddipole http://lib.store.yahoo.net/lib/buddipole/buddipoleinthefield2.pdf) and tuners.
But these all come at the cost to efficiency and ease of use.

The ARRL handbook would also be a good investment.

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KB1WTY
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« Reply #8 on: September 16, 2013, 01:14:04 PM »

I've used indoor HF antennas in four apartments, all wood frame. I think it's worth giving HF a try from your brick apartment.

I've tried loaded whips, full size dipoles, quarter wavelength loops, and random wires and they all worked well enough to work plenty of DX. The easiest way to get on HF from an apartment is to tune a random length dipole or loop using a tuner such as an MFJ-901B ($99).

Another antenna that works well is a quarter wavelength loop tuned by an MFJ-933 Loop Tuner ($190).

And there's the Budipole which a friend of mine operating from an apartment highly recommends.
I'm sorry, one more (likely stupid) question on my part. What's the difference between the MFJ-901B and the MFJ-933? It seems like the 901 has the better frequency range and supports more power, but costs half as much? Are these different types of devices despite the similar names?
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KB1WTY
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« Reply #9 on: September 16, 2013, 01:16:53 PM »

The ARRL handbook would also be a good investment.
That's excellent advice, thank you! However, I am such a noob, that even this confuses me. Do I want the "The ARRL Handbook for Radio Communications 2013" book, or the "ARRL Antenna Book"?
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AF6WL
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« Reply #10 on: September 16, 2013, 01:24:18 PM »

The ARRL handbook would also be a good investment.
That's excellent advice, thank you! However, I am such a noob, that even this confuses me. Do I want the "The ARRL Handbook for Radio Communications 2013" book, or the "ARRL Antenna Book"?

The new 2014 handbook is just about to go to print:
http://www.arrl.org/shop/2014--Handbook-Softcover-Centennial-Edition/
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KB1WTY
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« Reply #11 on: September 16, 2013, 01:29:27 PM »

That's awesome! You all rock, thanks again for all the help.
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AF5CC
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« Reply #12 on: September 16, 2013, 07:29:47 PM »

What's the difference between the MFJ-901B and the MFJ-933? It seems like the 901 has the better frequency range and supports more power, but costs half as much? Are these different types of devices despite the similar names?

Yes, the MFJ 901B is a manual antenna tuner, whereas the MFJ 933 is an automatic tuner. I would recommend the 910B first, as it is cheaper, and has a wider tuning range for compromise antennas.  Using a manual tuner doesn't take much longer than an autotuner.  I still use a manual tuner, you get the hang of it pretty quickly, and learn where to set the controls for the different bands.

I would try an indoor dipole in your apartment for 20m and above.  Cut it for a half wavelength on 20m, and use the tuner to load it up on the bands above that. I used such a setup for several years while in Graduate school and worked over 100 countries and all 50 states, running 100 watts.  You can also look into running a thin long wire out the window to a tree or other support.  I did that as well, and it worked good for 80, 40 and 30 meters.

At 100 watts I wouldn't worry too much about RF exposure.  I ran that amount with an indoor dipole and I am still here.  Now brain damage on the other hand...... (just kidding).

Good luck with the setup, hope to work you on the air.

73 John AF5CC
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KA4NMA
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« Reply #13 on: September 16, 2013, 08:04:01 PM »

Check out Low Profile Amateur Radio from the ARRL, the publications at sgwworld.com articles, including the stealth kit manual.

Randy ka4nma
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KB1WTY
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« Reply #14 on: September 17, 2013, 06:26:44 AM »

That's GREAT to hear, AF5CC, that really makes me think it's worth going down the HF road even while my antenna's stuck indoors.

And I'll definitely check out that low profile radio article, thanks AF5CC.
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