VHF/UHF radio and antenna questions

[KY_Ham_64]

Hey all, just joined the forum. I got my General license last month and am considering my first home rig setup. I'm still learning about how things work, so forgive my noob questions. I've been looking at the new Yaesu FTM-150RASP, I'm not really wanting to get into digital modes right now, and this radio seems to be a nice transceiver.

Some info, we're in the foothills of NE Kentucky, the local radio club has repeaters on a hill at 1300ft elevation, and we're around 850ft. The distance to these repeaters is 16 miles to the SW, but there are hills in between. We are on a eastern facing hillside in a valley that goes to the SW towards the repeaters. There are others to the east about 30 miles, but with more hills.

My question is this, this Yaesu puts out about 60W/55W on VHF/UHF. If I used say a Diamond X200 or Comet GP-6, the gain on those antennas is about 6.5/9db. I'm guessing with that kind of setup, I could hit those repeaters, but would I be able to hear them in return? Does this antenna gain apply to TX only, and not RX? I'd be putting this antenna on about a 16ft tall pole.

I have a FT65 HT but can't hit or hear anything from these repeaters at the QTH, but I don't really expect to. I can get various FM and NOAA WX transmissions on it tho.

 

[mmckenna]

I'm guessing with that kind of setup, I could hit those repeaters, but would I be able to hear them in return?

If there's no topographical shielding involved (read: lots of dirt between your antenna and theirs), then it should work.

Does this antenna gain apply to TX only, and not RX? I'd be putting this antenna on about a 16ft tall pole.

Gain works in both directions, both transmit and receive.

VHF/UHF tend to be mostly line of sight, so higher is usually better. If your antenna can "see" the repeater, then it'll work.

I have a FT65 HT but can't hit or hear anything from these repeaters at the QTH, but I don't really expect to. I can get various FM and NOAA WX transmissions on it tho.

Hand held radio at face level usually has trouble getting through surrounding buildings, foliage, topographical changes, etc. Plus their antennas are horribly inefficient.

 

[nd5y]

I'm guessing with that kind of setup, I could hit those repeaters, but would I be able to hear them in return?

It's more likely that you can hear a repeater but the repeater can't hear you.
You can't count on ham repeaters being any good. They are not all installed, maintained and operated by technically competent people.

 

[KY_Ham_64]

If there's no topographical shielding involved (read: lots of dirt between your antenna and theirs), then it should work.



Gain works in both directions, both transmit and receive.

VHF/UHF tend to be mostly line of sight, so higher is usually better. If your antenna can "see" the repeater, then it'll work.



Hand held radio at face level usually has trouble getting through surrounding buildings, foliage, topographical changes, etc. Plus their antennas are horribly inefficient.

Thanks. Those repeaters are in the town that I work in. I took my HT with me to work and was able to hit those two repeaters, no problems, but they were only about 2mi away. There's others farther out, I got responses from one about 7mi out and another about 16mi away. Over the weekend we went shopping at an area east of us, and was able to hit a couple more about 15mi away.

I wasn't using the stock antenna, but an Diamond RH77CA. Do HT antennas like these typically have any gain? I'm guessing if I ran a feed line from my HT to like a GP-6 then that would be better, but is it wise or safe for the HT to do so?

 

[AK9R]

Do HT antennas like these typically have any gain?

Yes, though it's typically measured with negative numbers. The antennas that come with handheld radios are generally poor performers. There are 3rd party antennas for handheld radios that claim to have much better performance, but empirical results are mixed at best.

Been meaning to ask approximately where you are. I lived in Winchester 20+ years ago and even though my office was in Lexington, my work took me to Paintsville, Hazard, Cumberland, Berea, Somerset, etc.

 

[KY_Ham_64]

Yes, though it's typically measured with negative numbers. The antennas that come with handheld radios are generally poor performers. There are 3rd party antennas for handheld radios that claim to have much better performance, but empirical results are mixed at best.

Been meaning to ask approximately where you are. I lived in Winchester 20+ years ago and even though my office was in Lexington, my work took me to Paintsville, Hazard, Cumberland, Berea, Somerset, etc.

Thanks. I went outside with my HT and walked around our hillside see if I could reach any of the repeaters and to my surprise I got a response from the club's VHF and UHF repeaters. Very surprised, so I'm thinking if I can pick up those on my little HT antenna, surely I could hear those and others with a X200 or GP6.

We're in Lewis County north of Morehead, where we both work. Been here almost 11 years. I'm from Oklahoma, went to tech school in KC, and worked in the electronics industry for 30 years in north Texas. My wife is from here, we met about 18 years ago, got married a couple years after that. She moved to TX when we were married but wanted to come back here to be closer to her family. So we moved up here to her family farm in 2014, I wanted to get out of the big city and HOA's, and to be more self sufficient. We do gardens every year, I planted out several fruit trees, berry plants so we can a lot of food.

We haven't been down south much in the areas you mentioned, we usually stick around up in the NE parts, like Morehead, Grayson, Ashland etc. We work at Morehead State, I've been there just over a year, she's been there almost 6 years. She also graduated from MSU. My boss actually lives in Winchester, he drives to and from Morehead every work day. My wife goes to lots of conferences, her last one was down at Cumberland Falls state park, said it was really nice. We're on Christmas break, don't have to go back until Jan 2nd. Gotta love university holidays!

 

[AK9R]

Yes, I'm familiar with MSU as I had some work out there, too.

One aspect of amateur radio is contesting where stations try to make as many contacts as they can within a specified time period. Contest rules run the gamut. Contests often have "multipliers" that help you build your score. In HF contests, different ARRL sections around the U.S. or countries around the world might be multipliers. In VHF/UHF contests, Maidenhead grids are often used as multipliers. A friend of mine from southern Indiana used to do VHF/UHF contesting as a "rover" or portable station, so I scouted out some locations in eastern Kentucky for him that were in different grids. I remember taking him to a little town north of Morehead that was on top of a hill, then to another spot south of Morehead or Mt. Sterling that was on top of a hill next to a cemetery, and to a parking lot in Winchester that was on a hill. They were all in different grids, so they counted as multipliers for him. A Winchester police officer stopped by to see what we were doing. They had gotten a report of some guys talking to satellites.

 

[KY_Ham_64]

That sounds cool, never heard of UHF/VHF contests. There's a WMA just a few miles to the east of us. I looked it up on the POTA website, it's had a few activations, mostly from local Hams. If I ever get an HF outfit, I might try an activation there.

I'm curious as to what small town north of Morehead you're talking about. Was it Flemingsburg, Goddard, Bluebank, Vanceburg, or Cranston? Those are the only towns I know of in that area.

 

[AK9R]

I think it was Owingsville, which I see now isn't north of Morehead.

The trick with VHF/UHF antennas, and this ties into your original question, is elevation. Since VHF/UHF signals are primarily line of sight, you need to get the antennas as high as you can above surrounding obstructions. Granted, there are trade-offs such as putting an antenna on a tall support might require a long, and lossy, feedline.

 

[W4AXW]

My question is this, this Yaesu puts out about 60W/55W on VHF/UHF. If I used say a Diamond X200 or Comet GP-6, the gain on those antennas is about 6.5/9db.

6.5/9dBwhat? dBi, as compared to a theoretically perfect antenna in space? Or dBd, as compared to a dipole antenna in space? Beware published gain numbers that do not state what comparison the manufacturer is claiming. Gain is often overstated to sell more units.

By the way, if you fish, you are close to an excellent Musky lake, Cave Run.

7 3

 

[nd5y]

You can't trust gain figures from most antenna manufacturers. The difference between dBi (isotropic) and dBd (dipole) is only 2.15. It's impossible for a vertical omnidirectional antenna that is the same size as a dipole or even twice the size of a dipole to have 9 dBd or dBi gain.

 

[KY_Ham_64]

Sorry the ratings were in dBi. Looking at various dual band antennas, it seems like the longer the antenna, the higher the gain. The GP-9 claims 8.5/11.9 dBi and it's 18.5ft long.

We have an old satellite mount in the roof, I was thinking of removing the dish and mounting the antenna on the metal mount. If not that then I'd use the old 16ft pole which was used for an old TV antenna that was mounted to the back of the house. But that would require a longer run of cable into the office where I'm thinking of making my shack. Either way the antenna would be about 15 ft AGL.

Would LMR-400 be good cable to run? I think I can keep the length about 25ft, so I can minimize losses.

This is the antenna I'm considering.

Diamond Antenna X300A Diamond Antenna X300A Dual-Band Base/Repeater Antennas | DX Engineering

Free Shipping - Diamond Antenna X300A Dual-Band Base/Repeater Antennas with qualifying orders of $99. Shop VHF/UHF Base Vertical Antennas at DX Engineering.

www.dxengineering.com

 

[KY_Ham_64]

I think it was Owingsville, which I see now isn't north of Morehead.

The trick with VHF/UHF antennas, and this ties into your original question, is elevation. Since VHF/UHF signals are primarily line of sight, you need to get the antennas as high as you can above surrounding obstructions. Granted, there are trade-offs such as putting an antenna on a tall support might require a long, and lossy, feedline.

Ok, that's over in Bath county, nice area. Bath County is where you start getting into the big hills coming from Lexington.

There are a couple of repeaters in Owingsville, I can reach the 2m one with my HT from Morehead. I think it's on a tall water tower in town. That is a distance of about 16mi.

Last night I was on my front deck and was able to get a response from the Morehead 70cm repeaters with the HT. Kinda surprised considering I'm 16mi from it.

 

[alcahuete]

Sorry the ratings were in dBi. Looking at various dual band antennas, it seems like the longer the antenna, the higher the gain. The GP-9 claims 8.5/11.9 dBi and it's 18.5ft long.

As has been mentioned, they all lie about their gain. That said, I have had a Diamond X510 (the basic equivalent of the GP-9) up for 30 years, and it is easily the best performing VHF/UHF antenna I have ever owned, outside of yagis.

 

[KY_Ham_64]

As has been mentioned, they all lie about their gain. That said, I have had a Diamond X510 (the basic equivalent of the GP-9) up for 30 years, and it is easily the best performing VHF/UHF antenna I have ever owned, outside of yagis.

Ok thanks. What would you say the gain of your X510 would be? Is there a way to measure/calculate it?

 

[alcahuete]

The advertised gain is 8.3/11.7.

 

[W4AXW]

and dBd (dipole) is only 2.15.

And that number only applies to a dipole in free space. As soon as the dipole is placed over real earth the gain over isotropic can be 5-7 dB. Do the math and those Wonder-Antenna gain numbers don't look quite as impressive.

7 3 and Merry Christmas all

 

[mmckenna]

it seems like the longer the antenna, the higher the gain.

Usually the way it works out.

But, like others have suggested, gain numbers need to be compared equally. dBi to dBi and dBd to dBd.
-Some manufacturers, especially those oriented towards hobby/ham radio, will play fast and loose with the numbers. They know that people look -just- at the numbers, and will claim all kinds of wild things. Buyer beware/if it sounds too good to be true, it probably is.

Also, don't get super hung up on gain numbers. Keep in mind that it gets that gain by smashing the radiation pattern down towards the horizon. That works fine in most cases, but in some really mountainous areas (doesn't sound like your location) that extra gain/compression of the radiation pattern can work against you.

Most repeaters are using pretty good antennas, and generally don't need a huge amount of power to get into them. Like has been mentioned, a lot of VHF/UHF is line of sight, and high gain isn't necessary. High gain antennas are taller/heavier and will require some substantial mounts to properly support.

We have an old satellite mount in the roof, I was thinking of removing the dish and mounting the antenna on the metal mount. If not that then I'd use the old 16ft pole which was used for an old TV antenna that was mounted to the back of the house. But that would require a longer run of cable into the office where I'm thinking of making my shack. Either way the antenna would be about 15 ft AGL.

Couple of things...

I'd not put an antenna that large on a satellite antenna J mount without some serious bracing.
The TV antenna mount might work better if it's guyed with a tall antenna like that. Remember, you don't want this antenna coming down and damaging your home, a neighbors home, hitting power lines, etc.

And do -not- forget grounding. Last time I was in Kentucky, I watched one of the most violent lightning storms I'd ever witnessed (I'm a West Coast guy…). Grounding is important and required by the national electric code. You don't want to stick a big antenna above your home and not properly ground your system. Direct lightning strikes are not the only concern. Even nearby strikes and induce a lot of energy into antennas and feedlines.

Would LMR-400 be good cable to run? I think I can keep the length about 25ft, so I can minimize losses.

For a 25 foot run, that would be fine for 2 meters/70 centimeters. It's a good cable if you get the real Times Microwave stuff. Be wary of "LMR400 equivalent" cables. Some are Chinese knockoff's.
Keep in mind:
You want to have a lightning protection device where the coax enters your home, so you'll want two sections of cable.
LMR-400 is kind of stiff, and you don't want to connect it directly to the back of the radio. It will put some strain on the antenna jack. Industry standard is to use a short jumper of a more flexible cable to make the final connection. A 2-3 foot length of RG-58 or similar size/flexibility cable will work well and not impact performance to any noticeable amount. It'll save you a costly repair down the road.

This is the antenna I'm considering.

Diamond Antenna X300A Diamond Antenna X300A Dual-Band Base/Repeater Antennas | DX Engineering

Free Shipping - Diamond Antenna X300A Dual-Band Base/Repeater Antennas with qualifying orders of $99. Shop VHF/UHF Base Vertical Antennas at DX Engineering.

www.dxengineering.com

 

[nd5y]

Is there a way to measure/calculate it?

The only accurate way to measure antenna gain is on an antenna test range.

You can calculate gain for vertical dipole or collinear arrays if you know how long the active elements of the antenna are and the band or frequency.

The industry standard vertical stacked dipole array is usually 2, 4 or 8 bays of dipoles.
A bay is either one dipole or two dipoles on opposite sides of the mast from eachother at the same level.
The antennas are about 1/2 wavelength long and usually spaced 3/4 wavelength to 1 wavelength apart center to center. 1/2 wavelength at 2 meters is over 3 feet.

The rule of thumb for gain is
2 bay = 3 dBd
4 bay = 6 dBd
8 bay = 9 dBd
unless all the dipoles are on the same side of the mast then the gain is a little higher but the patterns is more directional.

At 2 meters (146 MHz) a 2 bay antenna including the mast is about 10 feet long, 4 bay 20 ft., 8 bay 40 ft.
Anybody that says their antenna has 11 dB gain and is only 8 or 10 feet long is full of $#!T.

Another type of commercial antenna is the coaxial collinear with alternating sections of coaxial elements in a fiberglass tube. You can't usually tell what band they are for because you can't see what is inside the tube. It takes about three or four 1/2 wave coaxial elements (end to end) to make the same gain as 2 stacked dipoles and will be about the same length.

Multi band fiberglass ham antennas have multiple sections of copper or brass elements with hairpins or coils between the sections. They are a design compromize and won't have as much gain as the other types of the same length.

 

[KY_Ham_64]

Usually the way it works out.

But, like others have suggested, gain numbers need to be compared equally. dBi to dBi and dBd to dBd.
-Some manufacturers, especially those oriented towards hobby/ham radio, will play fast and loose with the numbers. They know that people look -just- at the numbers, and will claim all kinds of wild things. Buyer beware/if it sounds too good to be true, it probably is.

Also, don't get super hung up on gain numbers. Keep in mind that it gets that gain by smashing the radiation pattern down towards the horizon. That works fine in most cases, but in some really mountainous areas (doesn't sound like your location) that extra gain/compression of the radiation pattern can work against you.

Most repeaters are using pretty good antennas, and generally don't need a huge amount of power to get into them. Like has been mentioned, a lot of VHF/UHF is line of sight, and high gain isn't necessary. High gain antennas are taller/heavier and will require some substantial mounts to properly support.



Couple of things...

I'd not put an antenna that large on a satellite antenna J mount without some serious bracing.
The TV antenna mount might work better if it's guyed with a tall antenna like that. Remember, you don't want this antenna coming down and damaging your home, a neighbors home, hitting power lines, etc.

And do -not- forget grounding. Last time I was in Kentucky, I watched one of the most violent lightning storms I'd ever witnessed (I'm a West Coast guy…). Grounding is important and required by the national electric code. You don't want to stick a big antenna above your home and not properly ground your system. Direct lightning strikes are not the only concern. Even nearby strikes and induce a lot of energy into antennas and feedlines.



For a 25 foot run, that would be fine for 2 meters/70 centimeters. It's a good cable if you get the real Times Microwave stuff. Be wary of "LMR400 equivalent" cables. Some are Chinese knockoff's.
Keep in mind:
You want to have a lightning protection device where the coax enters your home, so you'll want two sections of cable.
LMR-400 is kind of stiff, and you don't want to connect it directly to the back of the radio. It will put some strain on the antenna jack. Industry standard is to use a short jumper of a more flexible cable to make the final connection. A 2-3 foot length of RG-58 or similar size/flexibility cable will work well and not impact performance to any noticeable amount. It'll save you a costly repair down the road.

Thanks, very good points you're making. Sounds like the old antenna pole would be a safer option, but may require more coax cable as its mounting brackets are on the back of the house. There's no worries about power lines, other buildings, vehicles, etc because of its location.

Being here ten years, lightning isn't as intense as it was in Texas where I used to live, or like Florida, which is probably the worst. But we do get occasional intense storms. We've not had any nearby strikes, it within 100 yards that I can think of. But that doesn't mean it can't never happen.

So I guess I'd need some kind of inline lightning suppressor to keep such strikes from damaging any radio equipment? But also, should the metal pole have some kind of lightning dissipation means? That is, maybe some kind of connection at the bottom of the pole to a grounding rod?

The LMR400 cabling I'm looking at is from DX Engineering. It comes in various lengths, mostly PL-259 connectors. It sounds like I'd need some kind of adapter you're suggesting between the LMR and radio antenna input.

So regarding the antenna's radiation pattern, are you saying that the longer the antenna, the more depressed the radiation pattern? So maybe the longest antenna wouldn't be the best for my location. Perhaps a middle length one would have a more elevated pattern?

Here's the cabling I'm looking at, seems like some good coax.

DX Engineering DXE-400MAXDX025 DX Engineering 400MAX PL-259 Low-Loss 50-ohm Coax Assemblies | DX Engineering

Free Shipping - DX Engineering 400MAX PL-259 Low-Loss 50-ohm Coax Assemblies with qualifying orders of $99. Shop Coaxial Cable Assemblies at DX Engineering.

www.dxengineering.com

Okay it's Christmas Eve, so I'll say good evening and thanks for everyone's help, I appreciate it. Hope y'all have a blessed Christmas.