HF / Attic antenna questions

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batdude

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Ok, just some odd questions here. First of all, I am in the dreaded HOA restricted community - not that I care about that too much - but I don't really have any trees either. (LOL) - I would really like an antenna that works well on 40m and 20m, 10 and 6m would be a bonus. Running a vertical antenna in the yard is most likely not an option.

I have a Icom 7300 and a G5RV Jr. antenna from MFJ. The antenna is in the attic, probably only about 16-18' above the ground. I have build the recommended Balun using ~10 wraps of the coax feed and a 5inch diameter PVC pipe. It's laid out pretty much as good as I can, but the 450ohm ladder line is most certainly more horizontal than perpendicularly and vertical to the antenna. Rig is grounded to an external ground rod outside.

Biggest problem. The only band the 7300 will tune using the internal tuner is 20m. It does not generate a match on any other band. Second problem - I had a MFJ-915 RF isolator in the line (with the above home brew air-Balun) - but with the MFJ in the circuit the radio would not tune >ANY< band. With the 915 removed, the radio does tune 20m. Needless to say, the 915 is currently removed from the feedline, but my background HF noise is increased.


I am considering some options. Just wanted to hear some thoughts.

First option - get a Icom AH-4 auto antenna tuner - stuff it up in the attic - and just run a random wire in a "L" as the antenna. (again, the question here is the height in the attic - is 16ft above ground high enough?)

Second option - switch to an end-fed design antenna in the hopes that the Icom built-in tuner can tune it.

what will not work >>> I cannot install a vertical in my backyard. I already have a flag pole and it's on the wrong side of the house. running any wire on the roof (a loop) is probably a non-starter, unless it's just laying on the shingles (probably not a good idea in florida)

open to some thoughts/ideas - just be reasonable about it.


doug
 

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<snip> (again, the question here is the height in the attic - is 16ft above ground high enough?)
If 16 feet AGL is all you got, it has to be enough by definition... Definitely not ideal for 40 Meters but it will have to do.

<snip> switch to an end-fed design antenna in the hopes that the Icom built-in tuner can tune it.
You won't know until you try it but built-in tuners are not known for their tuning ability of large mismatches. Did the or does the Icom 7300 come with any add-on optional hardware for the built-in ATU to help it tune end-fed/long-wire antennas? I'll download the full manual and see what it says about the built-in ATU with respect to tuning range, add-on parts like I mentioned, etc. I'll get back to you on that...

what will not work >>> I cannot install a vertical in my backyard. I already have a flag pole and it's on the wrong side of the house. running any wire on the roof (a loop) is probably a non-starter, unless it's just laying on the shingles (probably not a good idea in florida)

open to some thoughts/ideas - just be reasonable about it. <snip>
Thinking cap on. I'll be back...
 

WA8ZTZ

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Check out the Alpha-Delta DX-EE or the Hy-Power 20-40 meter QRP dipole. If the G5RV Jr. fit, they will both easily fit.
The Hy-Power antenna is called QRP but it is rated at 150 watts.
If 16' is all you got then that is what you will have to work with...
Got a 40 meter dipole out in the yard here about that high and recently broke a pile-up on a ZL first call with only 75 watts.
Also, make sure your grounding and bonding are done properly.
 

K4EET

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Here are some noteworthy quotes from the Full Manual for the Icom 7300:

Page 11-2 Full Manual "The internal automatic antenna tuner automatically matches the transceiver to the antenna within the range of 16.7 ~ 150 Ω (SWR of less than 3:1)."
Page 11-3 Full Manual "The optional AH-4 antenna tuner matches the IC-7300 to a long wire antenna more than 7 m/23 ft long (3.5 MHz and above)."
Page 11-3 Full Manual "NEVER operate the AH-4 or AH-740 without an antenna connected. The tuner and transceiver will be damaged."
Page 11-3 Full Manual "NOTE: When the wire antenna cannot be tuned, confirm wire length and connection. Note that the AH-4 cannot tune a wire that is a ½λ long or on a multiple of that frequency."
Page 11-3 Full Manual
"Using an external antenna tuner"
"When you use a non-Icom external antenna tuner, be sure to turn OFF the internal antenna tuner before connecting the external antenna tuner.
"Otherwise, the tuning may fail because both antenna tuners (internal and external) will simultaneously start tuning."
"See the antenna tuner’s instruction manual for details."
 

prcguy

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A full size or original G5RV was designed as a 20m antenna with some gain that would also tune up and work somewhat on other bands 80 through 10m. The Jr version would be basically a 10m antenna that might be usable on 40 through 6m but with varying degrees of mismatch. Your IC-7300 will only tune out a 3:1 mismatch and its done, not enough to handle a regular or Jr G5RV.

How much horizontal space do you have in the attic? Can you go 64 linear feet? If so there are a lot of good options. If not can you run balanced line like 450 ohm or even 600 ohm wire from the radio area to the attic? If so a simple center fed dipole that is the size of a G5RV Jr can easily work 40 through 6m and work them well with a balanced tuner at the radio.

An auto tuner in the attic can work but you need a lot of counterpoise and there can also be a lot of problems to overcome. Going a different direction, how much vertical space do you have in the attic? Can you fit a 6 or 8ft vertical whip? If so imagine covering lots of the attic in chicken wire and planting a good medium size screwdriver antenna up there with a huge ground plane made of chicken wire stapled to the top of the ceiling joists. If the vertical space is limited like 5ft or less you can even replace the screwdriver whip with a short mast or wire that turns into a capacity hat of wire that staple to the rafters. I've played with very short capacity hat loaded screwdriver antennas over lots of ground plane and they can put out an impressive signal for their size.

Some things I would avoid are random length end feds using a 9:1 or 5:1 type balun and an autotuner with end fed wire would need a lot of though to make it play well given the constraints you mention.

Late update....The loop mentioned above my post is a excellent choice that I forgot about and they can also put out a signal that can surprise you.


Ok, just some odd questions here. First of all, I am in the dreaded HOA restricted community - not that I care about that too much - but I don't really have any trees either. (LOL) - I would really like an antenna that works well on 40m and 20m, 10 and 6m would be a bonus. Running a vertical antenna in the yard is most likely not an option.

I have a Icom 7300 and a G5RV Jr. antenna from MFJ. The antenna is in the attic, probably only about 16-18' above the ground. I have build the recommended Balun using ~10 wraps of the coax feed and a 5inch diameter PVC pipe. It's laid out pretty much as good as I can, but the 450ohm ladder line is most certainly more horizontal than perpendicularly and vertical to the antenna. Rig is grounded to an external ground rod outside.

Biggest problem. The only band the 7300 will tune using the internal tuner is 20m. It does not generate a match on any other band. Second problem - I had a MFJ-915 RF isolator in the line (with the above home brew air-Balun) - but with the MFJ in the circuit the radio would not tune >ANY< band. With the 915 removed, the radio does tune 20m. Needless to say, the 915 is currently removed from the feedline, but my background HF noise is increased.


I am considering some options. Just wanted to hear some thoughts.

First option - get a Icom AH-4 auto antenna tuner - stuff it up in the attic - and just run a random wire in a "L" as the antenna. (again, the question here is the height in the attic - is 16ft above ground high enough?)

Second option - switch to an end-fed design antenna in the hopes that the Icom built-in tuner can tune it.

what will not work >>> I cannot install a vertical in my backyard. I already have a flag pole and it's on the wrong side of the house. running any wire on the roof (a loop) is probably a non-starter, unless it's just laying on the shingles (probably not a good idea in florida)

open to some thoughts/ideas - just be reasonable about it.


doug
 

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One option that you do have for a vertical antenna is to replace your existing flagpole with a Commercial Duty Flagpole Antenna from ZeroFive-Antennas. Check out their offerings by clicking HERE. You would bury the coax in the ground. The flagpole/antenna looks like this:

 

mmckenna

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One option that you do have for a vertical antenna is to replace your existing flagpole with a Commercial Duty Flagpole Antenna from ZeroFive-Antennas. Check out their offerings by clicking HERE. You would bury the coax in the ground. The flagpole/antenna looks like this:
I have a retired co-worker that did that. He lived in a mobile home park, so LOTS of HOA restrictions. Mounted a military surplus antenna tuner in a planter box at the base with some fake flowers on top. Snuck some ground radials around his space. No one knew it was there, and he'd run 80 meters AM successfully. Harbor Freight flag pole and flag. Built an insulated base. Worked pretty dang well.
 

AK9R

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First of all, I am in the dreaded HOA restricted community - not that I care about that too much - but I don't really have any trees either. (LOL) - I would really like an antenna that works well on 40m and 20m, 10 and 6m would be a bonus. Running a vertical antenna in the yard is most likely not an option.
I'm in a similar situation. 90 x 140 foot lot in a community with covenants that are antenna unfriendly. I'm curious why you've determined that you can't put up a vertical antenna.

I have a Zero Five 27-foot vertical on a tilt-over base. The tilt-over base is attached to a wooden post on the privacy fence I had installed. I feed the antenna with an Icom AH-4 tuner. Works very well on 40 through 10m and I've made lots of contacts with it, both in the US and DX. It'll tune down to 80m in a pinch.

My other antenna is a fan dipole with the feedpoint mounted about 16 feet of the ground. It has elements for 75m, 40m, and 20m. It works fine though it's not very broad-banded. I'm in central Indiana and I can make 75m contacts into Indiana and the surrounding states. I've used it for making some longer-range contacts, but that's not an everyday thing. On 40m, I can work all over the northeastern US.
 

batdude

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the flag pole antenna is a non-starter for me. it's too far away from my radio room, there is no way I am digging up my driveway to run the coax, i can't have a 30' flag pole, I don't want to dig up my current cemented flagpole, etc.

As for a vertical, I have an extremely narrow "dog run" sized back yard that runs the length of the house. #1 is the RF hazard with my dogs and #2 is a vertical antenna is just not going to work with the HOA - nevermind the fact that I wouldn't want to go out every evening and set it up then drop it. my opinion may change on this over time based on not getting anything to work in the attic.

I do not have enough height in the attic to put in a vertical - i have right at 8 feet at the highest point and the groundplane is just a non-starter due to the layout.

I do have enough linear feet to run a simple dipole - and I think that this is what I am going to try, just as an experiment. I just need to order a Balun today.


thanks for the replies - I appreciate them!

doug
 

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<snip> thanks for the replies - I appreciate them! <snip>
You are certainly welcome. Please do keep us informed on what you experiment with and what the outcome is. The reason I ask for that information is because there may be others following this thread with exactly the same HOA constraints that you have and are seeking an in-attic antenna solution. Your input could be valuable to them.

73, Dave K4EET
 

prcguy

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8 ft in the attic is plenty height for a good mobile screwdriver and if you have room for a dipole you should have room to staple down a decent amount of chicken wire for a counterpoise. You mention a dipole and getting a balun, if this is for a coax fed dipole, unless its got traps or some other way to get multiple bands, you only usually get about two bands out of a coax fed resonant dipole. They don't work well out of their resonant areas and they don't work at all at even multiples of their lowest design frequency like using a 40m dipole on 20m, etc. If you can feed the dipole with balanced line then its a completely different animal and with a tuner at the radio it can tune a very wide range and work well.


the flag pole antenna is a non-starter for me. it's too far away from my radio room, there is no way I am digging up my driveway to run the coax, i can't have a 30' flag pole, I don't want to dig up my current cemented flagpole, etc.

As for a vertical, I have an extremely narrow "dog run" sized back yard that runs the length of the house. #1 is the RF hazard with my dogs and #2 is a vertical antenna is just not going to work with the HOA - nevermind the fact that I wouldn't want to go out every evening and set it up then drop it. my opinion may change on this over time based on not getting anything to work in the attic.

I do not have enough height in the attic to put in a vertical - i have right at 8 feet at the highest point and the groundplane is just a non-starter due to the layout.

I do have enough linear feet to run a simple dipole - and I think that this is what I am going to try, just as an experiment. I just need to order a Balun today.


thanks for the replies - I appreciate them!

doug
 

wa8pyr

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Better option: a loop. There are many designs that will handle 40 meters and up. Check out our loops wiki...

I'm in a similar situation with the HOA. I've got a 40m full-wave loop and a G5RV Jr in the attic, both work reasonably well and my 7300 tunes them nicely; the 40m loop works great on 40, 30 and 15, while the G5RV Jr works nicely for 20, 17 and 12. 10m is kind of a catch as catch can; either antenna works OK (ie the internal tune can match it).

Performance would be better outside, even if the loop was simply draped over the roof. In my old place I had a full-wave loop for 40 draped over the shingles and it worked quite nicely.

Even with the antennas in the attic, I was working out 300-500 miles at night on 40m with an IC-746 Pro at 100 watts before the bands went belly-up.
 

wcsd45

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Hi, I have pretty much same challenges at my QTH. Many excellent thoughts in this thread.

Presently have an Ultimax100 EF dipole mounted NVIS from mast to eave of house. Works nicely 80/40M with shack external tuner, but the propagation is shorter range, certainly non-DX. I've been using Wolf River Coil Silver Bullet (WRCSB) deck rail mount with four ground based 32 ft radials. It is tuned now for 20M FT8 mode and pretty happy with decent number of DX contacts; no tuner, rig or shack external. I'd think you could put one in attic with band-tuned radials; cap hat may reduce whip height needs. The WRCSB is working well enough that do-nothing-more option is making me presently happy, and band can simply be changed from the deck, maybe not so with winter snow-bound deck.

Plans looking forward are attic double bazooka dipoles from Ultimax shaped to fit in attic, apex/feedpoint as high as can be safely achieved, noise vulnerable more attic than outside. These could also be stealth back roof mounted, winter a bit more vulnerable; SOL during winter if fail. At least they could be maintained in attic during winter, i.e cold but you could get to them. Thought is no tuner in shack or at feedpoint on presumed resonance, and maybe tuner internal to rig would handle third harmonic 15M of the 40/20M double bazooka option. Also plan to trial second WRCSB on top of mast using tuned radials for 30M stealth istallation along eaves using electric fence wire stand-offs. The Zero-Five Flagpoles are also options, modest pricey relative to other options here (can't do installation myself - attic or flagpole, need cooler weather for safety) yet it feels and is reviewed robust. Flagpole not subject to approval in my case. *To be clear, these are all options ahead, not yet trialed.* Thanks to Larry WA9TT for help with the overall plan. Of course the plan is bounded by attic size, roughly 70x35 ft. Hope this gives you some things to consider along with other excellent contributions in thread.

On the covenants/developer issues, the mast/vertical and EF dipole were formally approved having made presentation demonstrating towers/yagis were NOT part of plan. The key issue was plan so that antennas not observable from front of house.

A few pix on my QRZ page. Good luck and 73.

Chuck KC9QBY
 

Yagi

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Don't overlook the impact on antenna tuning and performance of the material used in your houses construction. For example an attic antenna will work better with a plywood / asphalt shingled roof compared to a metal roof. Wire backed stucco construction is also not good with signals.

When I moved into a ranch style one story house I started with an attic antenna. That was a down and dirty antenna to quickly let me get on HF. What I discovered was that the antenna's proximity to the house resulted in a very high noise level from all of the appliances and chargers and electronic gizmos in the house. I also found neat things like when I transmitted on some frequencies I could turn a TV off and on and on another band would have garbled audio through stereo speakers. Those are the kinds of issues you may need to deal with.

However any antenna is better then no antenna. As Mike (K4EET) pointed out you work with what you've got.

But before investing very much I would try purchasing a balun and use a roll of wire and make a basic 40 meter dipole. Once you have that tuned go back and add a length on both sides for 20 meters. If your attic access isn't to difficult, tuning them should be fairly doable. With those two bands you have a decent chance of HF activity during both the day and night time. After a few months you will have a better gauge of reasonable expectations for an attic antenna. Also coax feed to the antenna will probably be less of an issue inside an attic then ladder line with your current G5RV jr.

When you decide to invest more in your antenna system then as Doug suggested, something like the AH-4 antenna tuner with a random length wire or a loop antenna might work out really well for you.

WA8ZTZ's suggestion of the Alpha-Delta DX-EE would fit the space you describe and be another good option.
 

n5ims

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There's hope for you if you try. I have a 40 / 20 fan dipole mounted on the side of my fence and with my radio's internal tuner am able to work all bands 10 - 40 without issues. Some work better than others obviously, but was able to get my WAS on FT8 on 40 meters in just under 1 month when I first put it up. LOTW now shows I have 73 confirmed countries (various bands), all since Feb 2020. From outside the back yard you can't see anything and inside it blends into the fence pretty well to boot.
 

prcguy

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That is not a cut to fit antenna, it must be 1/2 wave resonant on 40m, which will then work on the other advertised bands. If you cut that antenna down in size it becomes a random but large coat hanger. In its original size its a good performer.

with the recommendation of a knowledgeable ham - i purchased this antenna today

offset 40m dipole

the offset feed is really "cut to fit" for the space I have available!

will keep the thread updated!

doug
 
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