They are frequency specific, with a bit of wiggle room, and can be used on the odd harmonics of the fundamental frequency. (There are variables, which are different for each installation.)
Antenna inside attic vs. outside roof
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I think a good setup for the OP would be a scanner type Discone and an active loop for VLF through HF. They should both fit within a attic and I've found once you map out some stuff with the loop you can usually park it and not have to rotate it. I believe it will also give a lower noise floor than a wire antenna stretched the length of a house inside an attic and you can adjust the loop to null noise out or favor certain directions where you can't with a wire.
You could start with a lower end Discone from Tram or Harvest at around $40 and if this is a test for a hobby that might stick or fade away, you could also go with a cheap Chinese active loop at around $40. Those are getting ok reviews for the price. Otherwise I would highly recommend the W6LVP loop but at a much higher cost around $250. This all depends of course on the layout of the attic and if the roofing material is fairly RF transparent or if its got foil backed insulation or too much AC ducting or wiring running around.
For amateur use the Discone could be used for 2m, 220 and 440 transmitting and receiving. For HF you would have to go with another antenna but there are various transmitting loops that can cover the 40 through 10m range with varying sized and price. An dipole or end fed in the attic is possible but its certainly going to run very close to ducting and wiring which will degrade its performance and increase noise pickup.
Depending on the height of the attic, you could also use an HF screwdriver over a bunch of chicken wire as a ground plane. You could probably set one up in less that 5ft of height by doing some tricks and without loosing any performance.
You could start with a lower end Discone from Tram or Harvest at around $40 and if this is a test for a hobby that might stick or fade away, you could also go with a cheap Chinese active loop at around $40. Those are getting ok reviews for the price. Otherwise I would highly recommend the W6LVP loop but at a much higher cost around $250. This all depends of course on the layout of the attic and if the roofing material is fairly RF transparent or if its got foil backed insulation or too much AC ducting or wiring running around.
For amateur use the Discone could be used for 2m, 220 and 440 transmitting and receiving. For HF you would have to go with another antenna but there are various transmitting loops that can cover the 40 through 10m range with varying sized and price. An dipole or end fed in the attic is possible but its certainly going to run very close to ducting and wiring which will degrade its performance and increase noise pickup.
Depending on the height of the attic, you could also use an HF screwdriver over a bunch of chicken wire as a ground plane. You could probably set one up in less that 5ft of height by doing some tricks and without loosing any performance.
rapidcharger
Member
There's a third option other than mounting the lighting rod- er I mean antenna to your roof of your combustible dwelling or in the attic and that's to use a mast (or tower) out in the yard, preferably as far away from your house (sources of RFI) as possible and easier to ground it. If you're just wanting to monitor, especially HF, personally I think it would make more sense to get that antenna farther away from the house than to go up a measly 30' which, unless you live in a perfectly flat, treeless place, is really small potatoes.
I never understood why people mount antennas and things like satellite dishes to their roofs when they don't have to. It's hard to access to install and inspect, it's still too close to the house and it's somewhat dangerous.
I never understood why people mount antennas and things like satellite dishes to their roofs when they don't have to. It's hard to access to install and inspect, it's still too close to the house and it's somewhat dangerous.
Probably because at frequencies above HF, running coax across the yard generally means the coax loss eats up all the signal gain from getting the antenna up and outside, unless you're running really expensive hardline or something. Getting as much elevation as possible while keeping the coax run as short as possible dictates keeping the antenna near the house.
rapidcharger
Member
Running coax across your yard isn't going to eat up all the signal. And if you use a decent antenna with some gain to help compensate for any signal loss. You also might not need as much power once you get away from the epicenter of RFI.
For UHF and 800MHz, it definitely will, unless you're running LMR600 or better. Or you have a really tiny yard. 250 feet of LMR400 has over 9dB of loss at 800MHz. Also, RFI is less of an issue once you go above 100MHz, so there's a lot less reason to move the tower/mast away from the house.
rapidcharger
Member
My yard is 20 acres and I'm not even running 250' of coax. And while you have over 9db of loss on 800 mhz (Not sure what the need for a base station antenna is for that anyway considering the fortunes spent for in-building body worn portable coverage), it's still over 6 with LMR-600. I'm not sure if I mentioned this in this thread or a different one but the extra cost for lmr-600 is usually not justified.
Grounding for lightning protection may not have any noticeable effect on reception. It won't hurt it, but it isn't likely to improve it, either. You do it because you want to minimize damage from lightning, not because it improves reception.
10ga copper meets code for running from the antenna or grounding block in the coax to the house AC panel main ground for a run up to about 30ft. If its longer then the wire size must be upsized.
Read this: https://www.mikeholt.com/download.php?file=PDF/Radio_and_Television_2014NEC.pdf
Read this: https://www.mikeholt.com/download.php?file=PDF/Radio_and_Television_2014NEC.pdf
Do you own or rent?
I only ask because it sounds like you are not sure what is installed on your residence...
jimbrogers
Member
Wish I could go on roof with mine, my HOA prevents any kind of outside antennas, scanner, ham radio, TV.
So I am moving mine into the attic.
So I am moving mine into the attic.
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