Typical attenuation of an attic mounted antenna compared to outdoor antenna

[Need2Know]

What is the typical signal propagation loss to be expected from a 2 meter/70cm J-Pole antenna mounted in an attic where the roofing material is the common 5/8" plywood and asphalt shingles, compared to the same antenna mounted outside at the same height?

How much loss can be expected? Is it of the magnitude of reaching only half the distance, or is the loss less significant?

A related question. Since there is signal loss the longer the cable run especially at VHF/UHF, even using decent cable such as Belden 9913 air-dielectric coaxial cable, or its equivalent in other brands---Flexi-4, LMR-400, might I be better off with a 6' cable run to locate the J-pole in a corner of my ham shack, rather than mount it 9 feet higher in my attic that requires a 25' cable run?

This is a cable length versus antenna height tradeoff question.

 

[Mudfoot]

Calculations of loss or attenuation is mute in your shack.

Higher is always going to be better no matter if your VHF/UHF antenna is located indoors or out. Just use the best coax you got.

Of course, you could mount it in both locations and get/make some signal reports. That extra 9' would probably be precious in your shack.

 

[Need2Know]

Calculations of loss or attenuation is mute in your shack.

Higher is always going to be better no matter if your VHF/UHF antenna is located indoors or out. Just use the best coax you got.

Of course, you could mount it in both locations and get/make some signal reports. That extra 9' would probably be precious in your shack.

So, I don't need to worry about the roofing material - any attenuation from that will be insignficant compared to gaining a few feet of height?

 

[Mudfoot]

Your sure to have issues by having your antenna in your house. But, since you can't mount anything outside...what you gonna do?

 

[GnG8d]

Calculations of loss or attenuation is mute in your shack.

mute or moot

 

[Need2Know]

Your sure to have issues by having your antenna in your house. But, since you can't mount anything outside...what you gonna do?

Well, one thing I could do, since I understand that moving the antenna just a few inches one way or the other inside the house or attic can make a big differnece, is to acquire a Field Strength Meter. This would enable me with the assistance of one other guy, to get real time readings of signal strength outside the house from an antenna inside the house. This, in combination with SWR readings, would at least facilitate the best possible location for the indoor antenna compromise.

Here is the post where I inquire about Field Strength Meters.

 

[Mudfoot]

mute or moot

My grammatical error should be obvious.

 

[RatsoW8]

Well, one thing I could do, since I understand that moving the antenna just a few inches one way or the other inside the house or attic can make a big differnece, is to acquire a Field Strength Meter. This would enable me with the assistance of one other guy, to get real time readings of signal strength outside the house from an antenna inside the house. This, in combination with SWR readings, would at least facilitate the best possible location for the indoor antenna compromise.

Here is the post where I inquire about Field Strength Meters.

Sure it will. How will you know the pattern of the antenna and effective range beyond the point where you are standing measuring FS?

 

[Beetle]

GMU -

ALL antenna installations are unique; no two are exactly alike. There will be attenuation of the signal because of the roofing, the number of nails, the amount of ventilation ductwork and/or piping and electrical stuff (along with the length, width and distance from this stuff to the antenna). Just how much attenuation is well-nigh impossible to guess.

You are, essentially, asking us to come up with a number that only YOU can determine from experimentation. And in amateur radio, experimentation is the name of the game.

As far as field strength meters (FSM) are concerned - be aware that the presence of a human being in the vicinity can and will affect the readings. If this human being is actually HOLDING the FSM, you can see large changes in the meter readings simply by squeezing the enclosure a bit more tightly. Some of the more expensive ones might not be as problematic, but I'd take their readings with a large dose of salts.

 

[W5LZ]

I think this whole thing is being 'analyzed'/worked/carried way too far. Which would be better, in a room of the house or the attic? If there isn't any particular reason to NOT put the thing in the attic, which might be a few feet higher, then why not? So how much better would it be? A very definite "little bit" that may or may not be measurable in some way. Would that always be a definite advantage? No, just too many possible differences in attics. So how do you know? How about try it and see? What about the length of the feed line? Use the same length in both places (use the longer of the two feed line lengths needed). If there isn't any significant differences, pick the easiest or most convenient location.
I honestly doubt if there's any 'typical attenuation' for attic antennas.
- 'Doc

 

[Need2Know]

Sure it will. How will you know the pattern of the antenna and effective range beyond the point where you are standing measuring FS?

Since I haven't done this before, I can only guess. And my guess is this:

I would not be standing anywhere near the antenna. I would be outside a couple hundred feet away in the general direction of the repeaters I want to hit. A friend would momentarily transmit while I took the readings. I would take several readings, maybe 10 feet apart and average them. Then I would repeat the process 4 or 5 times with the antenna in a slightly different location each time. I would finally choose the permanant antenna location based on the best of the average readings.

Does this make sense?

 

[Need2Know]

I think this whole thing is being 'analyzed'/worked/carried way too far. Which would be better, in a room of the house or the attic? If there isn't any particular reason to NOT put the thing in the attic, which might be a few feet higher, then why not? So how much better would it be? A very definite "little bit" that may or may not be measurable in some way. Would that always be a definite advantage? No, just too many possible differences in attics. So how do you know? How about try it and see? What about the length of the feed line? Use the same length in both places (use the longer of the two feed line lengths needed). If there isn't any significant differences, pick the easiest or most convenient location.
I honestly doubt if there's any 'typical attenuation' for attic antennas.
- 'Doc

That is what I am learning. And that is exactly why I followed up with a question in another thread asking which field strength meter might be best to measure the differences in signal strength with different antenna after I realized that there is no clear cut answer to the question I originally posed. Yes. This is all about experimentation. I thought the Field Strength Meter would be a helpful tool to assist in being productive in my experimentation.

I am surprised that more hams don't use this sort of meter.