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Author Topic: Is an Attic Dipole Most Compromised for TX or RCV?  (Read 516 times)

N4OI

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Is an Attic Dipole Most Compromised for TX or RCV?
« on: February 20, 2021, 06:29:08 AM »

Just wondering.... For those of you who have had both, is an attic dipole more compromised for transmitting or receiving, as compared to a conventional outdoor installation? 

I would have expected the transmit to be most impacted, but I can barely hear some DX running KWs that seem to copy me fine...  Perhaps I have such high level of local QRN (S3 to S5) that only the strongest signals are heard? 

Thanks in advance!

73
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K0UA

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #1 on: February 20, 2021, 07:18:14 AM »

Just wondering.... For those of you who have had both, is an attic dipole more compromised for transmitting or receiving, as compared to a conventional outdoor installation? 

I would have expected the transmit to be most impacted, but I can barely hear some DX running KWs that seem to copy me fine...  Perhaps I have such high level of local QRN (S3 to S5) that only the strongest signals are heard? 

Thanks in advance!

73

I think you have pretty much answered your own question. An attic dipole would have worked a lot better 20 or 30 years ago than today. We all fill our houses with small RF emitters, and the effect is cumulative. Of course your roof materials make a difference, obviously metal roofs or foil backed insulation does not help matters, but I think the noise levels from our houses are the worse culprit.
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73  James K0UA

KF5LJW

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #2 on: February 20, 2021, 08:34:36 AM »

Different angle. Not the worse as that title goes to a random wire in an attic. Your dipole in the attic just sucks a little less than a random wire. Can it get worse? Yes by putting the antenna in the same room so you get nuked and burned. Lot of folks like that.
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K6AER

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #3 on: February 20, 2021, 10:08:47 AM »

Different angle. Not the worse as that title goes to a random wire in an attic. Your dipole in the attic just sucks a little less than a random wire. Can it get worse? Yes by putting the antenna in the same room so you get nuked and burned. Lot of folks like that.

Your not going to get "nuked for burned" with a 100 watt radio and an HF antenna in the room any more than running 100 watts HF in the car. The antenna  physics is simple. The higher up the antenna and the farther it is from RF noise sources, the better the performance.

If you are serious about operation from a home or the HF bands, then you seriously should consider where your home purchase is located. Yes you may have just gotten into the hobby and I understand make shift solutions but in the long term everything is location, location and location.

I talk to new hams on HF every day and most of the time they need me to run my amplifier to hear me when they are 57 at my location, running 100 watts. Urban noise levels have just about runned the hobby for new hams. In 1959 I got my novice license and my parents lived in a typical 60's track home. Armed with a ARC-5 and a old BC-348 and a 40 meter vertical I worked the world. The only interference was at dinner time when my mom would use the electric mixer. Today is very much different. Even using an interference cancellation unit such as the MFJ-1025 or ANC-4 does no help null out interference when it is coming in from all directions.

Various remote SDR receivers such as the KFS WEBSDR system will help but propagation can be much different from you home QTH as to these remote receiver locations.

Getting into HAM radio given suburbia interference problems is like taking up surfing in NYC.
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K0UA

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #4 on: February 20, 2021, 01:57:16 PM »

Quote
I talk to new hams on HF every day and most of the time they need me to run my amplifier to hear me when they are 57 at my location, running 100 watts

My findings exactly. I will be running a kilowatt and them with 100 watts, and we are about equally matched in receive levels. If I get on 40 meters SSB in the evenings and call CQ with a Kilowatt, I often get multiple weak callers. And the reason for the pileup is because I may be one of the few strong stations they are hearing. The rest of the 100 watt stations are down in the noise to them. I have some antennas out in the woods, and usually have a better signal to noise ratio than many. I see this on SSB, I see this on CW and I see this on FT8.  I have helped very many hams get on FT8 and in doing screen sharing with them, I get to see their waterfall's. OMG. You cannot believe the "trash" that many of them have to put up with at their station locations. When I compare my waterfall to theirs it is night and day.
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73  James K0UA

N2AYM

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #5 on: February 22, 2021, 07:37:58 AM »

Just wondering.... For those of you who have had both, is an attic dipole more compromised for transmitting or receiving, as compared to a conventional outdoor installation? 

I would have expected the transmit to be most impacted, but I can barely hear some DX running KWs that seem to copy me fine...  Perhaps I have such high level of local QRN (S3 to S5) that only the strongest signals are heard? 

Thanks in advance!

This can depend on what else is in the attic. In my case the heating and ac unit is in the attic
and all the metal from the unit definately compromises the performance to radiate well.

73
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K7JQ

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #6 on: February 23, 2021, 10:06:33 AM »

When I moved to a restricted antenna community 19 years ago, I installed mono-band, remotely switched HF dipoles in the attic over the garage. A typical Arizona concrete tile roof, and no HVAC or other metal in that space. They worked OK, transmit and receive, for what they were. Today, they're basically unusable, receive-wise. Over the years with the proliferation of multiple popular consumer RF hash generating electronics accumulated in my house and my neighbors, the noise level went from about S2 to now over S7+ on all bands. I'm sure the transmit side is still the same, but (here it comes)..."you can't work 'em if you can't hear 'em".

Fortunately, I found ways to put effective stealth antennas outside that let me enjoy the hobby. Try to do the same.

Bob K7JQ
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K0UA

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #7 on: February 23, 2021, 10:41:24 AM »

When I moved to a restricted antenna community 19 years ago, I installed mono-band, remotely switched HF dipoles in the attic over the garage. A typical Arizona concrete tile roof, and no HVAC or other metal in that space. They worked OK, transmit and receive, for what they were. Today, they're basically unusable, receive-wise. Over the years with the proliferation of multiple popular consumer RF hash generating electronics accumulated in my house and my neighbors, the noise level went from about S2 to now over S7+ on all bands. I'm sure the transmit side is still the same, but (here it comes)..."you can't work 'em if you can't hear 'em".

Fortunately, I found ways to put effective stealth antennas outside that let me enjoy the hobby. Try to do the same.

Bob K7JQ

I think that pretty wells sums it up. Attic dipoles that worked 20 years ago don't work today. And we all know why.
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73  James K0UA

KF5LJW

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #8 on: February 23, 2021, 11:15:08 AM »

As a former closet, err attic antenna user many times of 40 years, it does not make any difference if it was yesterday or decades ago, moving the dipole outside, up high without obstructions is always going to outperform any attic dipole.

You gotta do what you gotta do. Attic is better than rolled up in a box.

You knew before you signed the contract no hams allowed. Just remember one thing. Rules do not apply to hams. N2MG the site webmaster clearly states this site is to help hams break the rules with respect to HOA's anddother legal deed restrictions.  If rules are followed, there would be no website. 8)
« Last Edit: February 23, 2021, 11:25:51 AM by KF5LJW »
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K7JQ

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #9 on: February 23, 2021, 12:34:59 PM »

As a former closet, err attic antenna user many times of 40 years, it does not make any difference if it was yesterday or decades ago, moving the dipole outside, up high without obstructions is always going to outperform any attic dipole.

Well....DUH! Everyone knows this. It doesn't answer his question. If ya' gotta put it in the attic, decades ago you could hear stuff. Not so much yesterday.
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KH6AQ

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #10 on: February 24, 2021, 09:51:16 AM »

"Is an Attic Dipole Most Compromised for TX or RCV?"

It is equally compromised for both. If being in the attic reduces the TX signal by 3dB it also reduces the RX signal by 3dB.
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N4OI

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #11 on: February 24, 2021, 04:38:23 PM »

"Is an Attic Dipole Most Compromised for TX or RCV?"

It is equally compromised for both. If being in the attic reduces the TX signal by 3dB it also reduces the RX signal by 3dB.

Got it.  Thanks!

73
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KH6AQ

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #12 on: February 27, 2021, 09:07:32 PM »

I should add that that is for signal amplitude only. For receive on HF even a compromised dipole can produce enough signal to overcome the noise of your transceiver.

If the idea of an attic dipole appeals to you I encourage you to give it a try. Wire antennas aren't forever and you can try them as fast as you can build them. Maybe the attic this month and in the yard next month.
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KM1H

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Re: Is an Attic Dipole Most Compromised for TX or RCV?
« Reply #13 on: March 30, 2021, 07:01:37 PM »

Quote
I think you have pretty much answered your own question. An attic dipole would have worked a lot better 20 or 30 years ago than today. We all fill our houses with small RF emitters, and the effect is cumulative. Of course your roof materials make a difference, obviously metal roofs or foil backed insulation does not help matters, but I think the noise levels from our houses are the worse culprit.

And why dont hams clean up their own home of RFI generators?  One answer is that it can be a lot of work. Another answer is the ferrites needed can get expensive when starting from scratch. Actual work and spending money is not in some hams DNA. Some consumer products are so leaky they need to be wrapped in tin foil such as switching supply wall warts; be sure they dont overheat excessively, a little heat is OK going by the up to 10 years some of mine have been wrapped.

Buying all new linear versions is also $$$ especially when outputting a DC voltage. Used ones may need the electrolytic cap replaced.

RF sniff all cables in and out of your ham radios and also at the main AC panel as one noise source can propagate all the way back to the panel and then all thru the house and drive you crazy trying to locate it.

One good suggestion made by many over the decades is to shut off the AC power and listen on a battery receiver, even a pocket size one for the AM BCB is better than nothing. I use an old Ray Jefferson 630 multi band direction finder that was $20 at a yard sale a few decades ago.  It covers LF, BCB, CB, and VHF from 145-175 MHz, all on AM plus the regular FM band. There were several other models and suppliers as they were popular, even required Ive heard, on small pleasure boats.

An attic antenna can be configured several ways and be useable. Mine is 34' long along the 10' high joists in the attic, it then goes out a small hole at the attic end I drilled and insulated with a small piece or Teflon tubing. Then it slants down and tied off to a low branch on a crab apple tree then a ground rod and a couple random radials complete the package. Some RG-6 and a CM choke at the feed point and into the house. The bedroom rig is a TS-130S I picked up from a CBer who had it posted at the Salem NH HRO, turns out it was from his SK uncle and had the PS-30 PS, the DFC-230 remote VFO, and AT-130 ATU, the 500 Hz CW filter was already installed.

With the house almost noise free it hears very well and loads on all bands with the tuner. I never measured the vertical wire but since the roof peak is at 30' Im guesstimating another 50' of wire for 84' total +/- Just reading up now tonight that 84' appears to be a magic length according to this article:

://udel.edu/~mm/ham/randomWire/
 
Im not using a counterpoise but suspect the radials and ground rod does OK since the actual ground is a laugh here on this rocky granite hilltop as Ive mentioned several times.

Anyway KISS comes thru again.

Carl
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