HF antenna indoors

[SpaceForceCmdr]

I'm pulling the trigger on my first HF radio. My antenna situation will not be ideal, and I'm going to be limited to indoors. I've got about 30' of length in my attic, so I'm thinking I'll get a 20m dipole, and just focus on that band for now. Is there anything else I should consider? Would some sort of loop maybe be better?

Here's my situation: I've been SWL-ing with a wire running the length of my attic, and it works OK. Problem is, part of my attic is finished, so accessing the very peak of the roof's underside is tricky. I could take the easy route and run the wire across the unfinished section (see green line in photo)




But, as you can see, some of the insulation has metallic backing. I'm guessing this would block some of the signal, and I'm also not sure how close the dipole wire could be to it without posing a danger. Could it possibly arc? Most I'd be running is 100W. Also, in this configuration, the antenna would be directly over my shack/room. The ceiling is about 4' above my head, and then however thick the floor is, and then maybe another 5-6' to the antenna, so let's say the antenna would be about 9-10 feet above me. Using an RF calculator, it sounds like I'd be well beyond the min. safe distance.

OK, so now option #2. I could climb up to the "upper" attic and string the antenna from end to end right under the eave of the roof. There is insulation with metal backing up there, too, but the dipole would be over it. The downsides to this are there's also some electrical lines running up there, and there's some old knob and tube wiring which is supposed to be nonfunctional. The other downside is getting up there would be a real pain in the butt. I guess if my tx and rx would be a lot better, it'd be worth the trouble. Here's what it looks like, and the green line is where the antenna would be.





Really appreciate any insight/advice on this situation. Thanks!!

 

[mass-man]

the higher the better...as clear of metal and obstructions, the better! If you have an antenna tuner with a balun, as much wire as you can put up, cut in the middle and fed with 450ohm ladder line works well. You can also drop the ends so you get a bit more total wire length up there.
It's not ideal but it will work somewhat. I have had attic antennas for years with OK success. You might also look into the idea of a portable setup that you can throw into the car and head to a park or hllltop or someplace where you can get wire up and in the clear....
Gud luck....

 

[littona]

You've got the right idea. You just don't know how well it'll work until you try it. There are some folks that have wired up their home gutters, apartment balcony railings, and other odds and ends to throw out some RF. To me, experimenting is one of the more fun parts of amateur radio.
Once you get it on the air, an easy way to see how you're getting out is to run FT8 and look at pskreporter.info. Pskreporter is fed from other folks' reception. It'll show you a graphical representation of who all hears you transmitting. Here's what my last session did, for reference (expires after 24 hours). Display Reception Reports

 

[WRQS621]

Try an EFHW Antenna. They work great. I have QSO's all the way to Russia on 25W, tonight I had a contact in Panama.

 

[SpaceForceCmdr]

Thanks, I was looking at some of those, but from what I've read, the feed line ends up acting like part of the antenna and could introduce RF back into the shack.

 

[mass-man]

any antenna can cause RF in the shack...common mode chokes, either DIY or bought can solve a lot of that. It's gonna be a lot of experimenting and determining what you can put up there and how well it works...

 

[popnokick]

+1 on the End-Fed Halfwave (EFHW) and definitely in the upper attic above the metal foil. The EFHW for 40-10M will be about 60 feet long so you'll have to snake it around. Hopefully your upper attic is longer than the 30 ft in the lower attic. Run the balun end (yes, EFHW's require / come with a balun) in the highest part of the roof as far as you can. Then if you have excess do a 90 degree turn and go as far down the slope of the roof as you can. If you still have excess when reaching the bottom (lowest point) of the slope, do another 90 degree bend and run along the edge of the roofline / floor.

 

[ka3jjz]

And there is this as well...

Mike

 

[sloop]

I have the same problem, HOA. I am getting ready to run a 29 foot length of wire as high as I can get it on the rafters. It will be attached to an Icon AH-4 tuner. Ground wire will be run through the bathroom vent to the outside and then to the ground. I ran something similar to this years ago only outside about 10 feet high on MARS and did not have any problems.

 

[SpaceForceCmdr]

Here's one option I'm looking at.

+1 on the End-Fed Halfwave (EFHW) and definitely in the upper attic above the metal foil. The EFHW for 40-10M will be about 60 feet long so you'll have to snake it around. Hopefully your upper attic is longer than the 30 ft in the lower attic. Run the balun end (yes, EFHW's require / come with a balun) in the highest part of the roof as far as you can. Then if you have excess do a 90 degree turn and go as far down the slope of the roof as you can. If you still have excess when reaching the bottom (lowest point) of the slope, do another 90 degree bend and run along the edge of the roofline / floor.

Would an end-fed wire do better than a dipole? Unfortunately, I don't think 60 ft is going to happen. If the attic weren't partially finished, it'd be no problem, but getting to the edges would be a real challenge.

 

[popnokick]

The advantage the EFHW has over dipole is the EFHW is more effective and usable on multiple bands. But if you can’t put one up, well…

 

[littona]

A dipole is cut for a particular frequency, whereas an EFHW is resonant on multiple frequencies. However.... a fan dipole may work good for you. I started out with a dipole resonant on 10m, made out of scrap wire and stapled on my deck. I added another section to it that was resonant on 20m. Worked pretty good! Yeah, some tweaking is required to get the dipole(s) resonant where you want them, but it's really easy if you have a nanoVNA. Otherwise you do it like the CB guys and cut for the lowest SWR.

 

[FreqNout]

This is a great book with a chapter on attic options and his test results.

You will need to put up wire and see what works in your attic. RFI and noise may be a bigger challenge.

Stealth Antennas e-book on Amazon

Ought to be a good read; not everyone has lots of room for antennas... https://www.amazon.com/Stealth-Antennas-3rd-Steve-Nichols-ebook/dp/B07ZMJGSFG/ref=sr_1_3?dchild=1&keywords=stealth+antennas&qid=1608122635&sr=8-3 Mike

forums.radioreference.com

 

[SpaceForceCmdr]

Thanks for all the input so far. It sounds like I will just have to try it and see what happens. I'll go ahead and try putting the antenna above all the insulation and as close to the eave as I can get it (and try not to fall through the ceiling in the process, lol).

 

[GlobalNorth]

For limited areas and specific bands, have you tried hamsticks? Yes, the bandwidth is rather narrow, but if you like a certain band or want a secondary antenna for specialised work, it is a viable answer.

 

[SpaceForceCmdr]

No, but I'm open to trying anything that would work in confined space.

 

[WA8ZTZ]

Have got a dipole antenna here out in the backyard that has served me well the past several years. It is made by HyPower Antenna Co., their model 2B1040Q.
It works on both 40 and 10 meters and is rated at 150 watts. Overall length is 31'... it will fit in your 30' upper attic space if you let the ends hang down a foot or so (it will not hurt antenna performance). Just be careful up there walking on the joists... if you don't feel comfortable, forget about it. btw... put a switch plate cover on that light switch in the lower attic.

 

[krokus]

Since a 40m antenna would be roughly double the length of the available space, why not a 20m EFHW?

Here is a DIY that I found:

20m End Fed Half Wave (EFHW) Build - GetHamRadio.Com by KC4RCR

Build your own 20m end fed half wave antenna

www.kc4rcr.com

 

[SpaceForceCmdr]

Thanks, the EFHW is something I've been thinking about. I wonder if it'd work better than my 20m dipole I put up there? I am getting decent reception now, but I haven't been able to make any contacts yet. It seems like my signal is not getting out there. I heard someone in Spain yesterday, but when I called back, there was no reply. I opened a web SDR in spain, and it wasn't picking me up at all. Also, late last night, I picked up someone calling CQ here in the US. I tried responding, but got no reply. I don't think he could hear me, either

 

[SpaceForceCmdr]

Thinking more about this.....it was suggested that maybe my dipole is acting as an NVIS antenna since it's close to the ground, and who knows what being indoors does to the radiation pattern. Thinking in this case, the orientation wouldn't matter much. Right now, it's running in and east/west direction.

Would an end-fed wire be much different in an indoor spot like this, or would it also radiate mostly upwards? My main interest is DX, and it sounds like something that would enable be to transmit at a low takeoff angle would be much better. Question is, is that even possible with an indoor setup? What about a loop antenna for transmitting? I've used one for receive, and it works quite well indoors.