Outdoor Antenna Performace Calcs

It's a metal tower with an open frame fortified by the trusses in the design. I erected one on my bro's roof that held 5 antennas. This was in the pre cable era. I'm guessing the tower I used was 15' or 20'. Look @ any radio or TV antenna that's not erected on a skyscraper. They're all pretty much the same, differing only in size & scale.
 
Heres what I put up at work. Works great for a omni directional. I have one at work 130 or so ft in the air. I have a clue about antennas from other hobbies. You can mount a antenna in you attic with but it won't work as well as outdoor but the added height will make it work better than a indoor. Guys who talk on radios and have a clue will tell you there is no better money spent than antenna and coax. I would rather have a 300 dollar tuner and a good antenna than a 1000 dollar tuner and a crappy antenna. You can find this antenna cheaper its just the first pic I found. For now I'm just using my outdoor tv antenna and it does a very good job even off the sides. I have a great location and this helps a lot also. yagi antennas and quad antennas are directional and work a lot like the beam of a flashlight directing much of your receive in one direction with more elements and boom length making the beam more narrow. There will be small lobes of received signall in other directions but this is kept to a minimum with good antenna design. The second paste up at the bottom of the page shows where the antenna is receiving the most signal direction wise. If wanting alittle wider beam shorter with less elements can be a plus if not using a rotator and wanting channels in one generial direction but not all grouped together. I hope this makes sense. If all the stations you are wanting to receive are basically in one direction a rotator is not really needed. This applies to directional antennas only. Omnis will pick up all around but with less gain.

http://www.staples.com/Winegard-HD-6010-HD-Omni-Directional-Radio-Fm-Antenna/product_209071

yagi beam signal path for fm stereo pics
 
Last edited:
Heres what I put up at work. Works great for a omni directional. I have one at work 130 or so ft in the air. I have a clue about antennas from other hobbies. You can mount a antenna in you attic with but it won't work as well as outdoor but the added height will make it work better than a indoor. Guys who talk on radios and have a clue will tell you there is no better money spent than antenna and coax. I would rather have a 300 dollar tuner and a good antenna than a 1000 dollar tuner and a crappy antenna. You can find this antenna cheaper its just the first pic I found. For now I'm just using my outdoor tv antenna and it does a very good job even off the sides. I have a great location and this helps a lot also. yagi antennas and quad antennas are directional and work a lot like the beam of a flashlight directing much of your receive in one direction with more elements and boom length making the beam more narrow. There will be small lobes of received signall in other directions but this is kept to a minimum with good antenna design. The second paste up at the bottom of the page shows where the antenna is receiving the most signal direction wise. If wanting alittle wider beam shorter with less elements can be a plus if not using a rotator and wanting channels in one generial direction but not all grouped together. I hope this makes sense. If all the stations you are wanting to receive are basically in one direction a rotator is not really needed. This applies to directional antennas only. Omnis will pick up all around but with less gain.

http://www.staples.com/Winegard-HD-6010-HD-Omni-Directional-Radio-Fm-Antenna/product_209071

yagi beam signal path for fm stereo pics
Very well put. Indoor antennas & omnis are a piss poor substitute.
 
Hello friends how can i design a good 11 element fm log periodic antenna to get fm station 100 miles away..I have all dipoles lenght but i dont have the spacing between them..Could you please help me..thanks
 
if you haven't already, it might be worth plugging your location into fmfool.com
to see what ground conditions actually are at your location. I can get 100 mile
reception over 2 edges, but not consistently, regardless the antenna (one
honking big TV/FM combo, or a home-brew 7 element yagi, roof-mounted on
a rotor).

Here are some resources for building your own, though a bit out of date.

This is my home-built 7 element

yagi1.jpg
 
Just put up a chimney mount FM with rotor here
Using a Stellars Labs #30-2460 FM antenna
all can get in Ontario Canada right now thats half decent
works quite well BTW
Total height 41'
 
Hello friends how can i design a good 11 element fm log periodic antenna to get fm station 100 miles away..I have all dipoles lenght but i dont have the spacing between them..Could you please help me..thanks
Antenna gain is secondary to your problem. VHF FM broadcast is line of sight and doesn’t curve over the horizon. Antenna height is the first order. Assume you live where I do where the land is flat. Most stations’ antennas here are 500 feet high or less. Let’s say they’re at 1000’. Google radio horizon or line of sight calculator and you will be able to put in antenna height to get the distance to the horizon. At 1000’, the horizon is 45 miles. If you place your antenna at 1000’ also, the combined line of sight would still only be 90 miles. If you are in a mountainous area, that could work in your favor or if there’s a mountain between you and the transmitter, it could be a deal-breaker. Sometimes there are atmospheric conditions that produce ‘tunnels’ that carry the vhf signals over the horizon, but you really don’t want to rely upon that. There is a trick of sorts that some broadcasters use. They may use horizontal polarization which some say may go over the horizon slightly and perform better than vertical polarization at the horizon. Check the station height and make the calculations it might be workable.
 
LOL, it’s good to know that after two years of waiting with baited breath, he can finally get some answers. Sorry, I didn’t check the date of the post. It’s good info if someone stumbles here.
 
I have a roof mounted FM antenna. Two observations:
  • I had a 10 foot long multi-element antenna. I replaced it with a much smaller 3 element Yagi. Performance seems nearly as good and plenty for my situation. Unless there is a really, really fringe station you are after, any rooftop FM antenna will probably be fine.
  • Although gain in back of the Yagi antenna is less than towards the front, it is still more than an indoor twinlead dipole. Point the antenna toward the faraway station you want and local stations will probably still be fine even if towards the back of the antenna. I have my antenna on a rotator, but never use it.
 
Good FM antennas are becoming more difficult to source, but Innovantennas (innovantennas.com) in England still makes some very good ones.

Their website will convert £’s to $’s and if you’re in the US you don’t pay the tax.

I believe this one is superb, and it’s about $335 plus shipping.

https://www.innovantennas.com/en/our-antennas/241/26/88mhz-108mhz-broadcast/14-element-88-108mhz-op-desInnovAntennas shop.htmlo

It’s specs are:

Typical Gain:11.30dBi

Typical F/B: 26dB

Gain at 10m (33') above ground: 17.62dBi

Power Rating: 3kw

Feed Impedance: 75Ω or 50Ω

Boom Length: 5.6m - 18' 5''

Weight: 4.82Kg / 11LB

Turning Radius: 3.0m / 9' 9''ft

Wind Loading: 0.5 Square Metres / 2 Square feet

Wind Survival: 331KPH / 206MPH

I find the wind survival rating particularly impressive. As always, YMMV :cool:
 
I have a roof mounted FM antenna. Two observations:
  • I had a 10 foot long multi-element antenna. I replaced it with a much smaller 3 element Yagi. Performance seems nearly as good and plenty for my situation. Unless there is a really, really fringe station you are after, any rooftop FM antenna will probably be fine.
  • Although gain in back of the Yagi antenna is less than towards the front, it is still more than an indoor twinlead dipole. Point the antenna toward the faraway station you want and local stations will probably still be fine even if towards the back of the antenna. I have my antenna on a rotator, but never use it.
Increasing height is the best way to improve any antenna’s performance. You’ll increase the distance to the radio horizon. The front to back rejection is important for reducing interference from the opposite direction. The linked 14 element yagi has high fwd gain, excellent front to back and a narrow beamwidth. The beamwidth is the angle between points where the gain typically drops off by 3dB. The linked antenna will have around 25-30degree beamwidth horizontally ( when the antenna is mounted with elements vertically) and around 10-15 degrees vertically. Mounting horizontally can help to really narrow the highest gain area so as not to get unwanted signals.
At VHF, high performance antennas can get pretty large and there’s always a trade-off. The linked yagi is rated for over 200mph winds. Maybe in controlled conditions, but working around RF installations on the gulf coast has taught me that kind of rating is useless. I’ve seen towers rated for 150 mph blow over in a hurricane, coax cable ripped from towers, debris blown into antennas and structures, but it appears to be really well made though.
 
Any user reports on the Innovantennas 14 element yagi? Benn looking at it seriously to replace my APS-13.
 
Hi, Friends, I've got an .... Attic Mounted, Modified Stellar VS Tuned Rhombic ... Q for the group : )

First off, No-thing's going on the roof at least in the near future ... best I can do is an attic mounted antenna. I live around 25 miles west of Boston. The Stellar is doing a great job w/ band packed w/ stations, many of which are fully quieted. Unfortunately the station I really want to conquer is MITs WMBR in Cambridge. I'm hearing it fine out here just not quieted in stereo. If memory serves we're talking less than a kilowatt of power .. it's a really fantastic, eclectic and kinda' wild station. I'm a fool-time musician of many years and have played different shows at the station many times. There's a small college pub just upstairs and I have fond memories of being fetched up there, late for a performance that was due to begin ; ) I've done the calculations and I'm fairly certain I can fit a full wavelength rhombic in my attic and have ordered needed materials. My Q for the group is, if tuned to exactly 88.1, can I expect better performance from rhombic than my five element yagi?!

Thank you and happy spring,
Mike
 
Last edited:
Half the fun is building & tuning so I'd go for it if you have the time. I personally haven't had much success tuning for a specific station with some basic loop designs. Antenna location and orientation seems to pay off better than any tuning I've done.
 
Back
Top Bottom