QRP- Low power max range-- Help

[bcrez]

Hey everyone. Im a new HAM. KB1WNZ. I got certified mainly for backcountry communication- between vehicles and as emergency gear.

I have an iCom 2820H 2m/70cm transceiver. It's an amazing radio, but I havn't been able to reach out that far, even while using repeaters. 40-60 miles max so far.

I have seen videos with guys using handhelds on different bands 10m etc. who are getting incredible distance with low power.

What is this attributed to? besides fluctuating atmospheric conditions what is an effective way to increase your radio's range? On a mobile truck rig like mine I would rather not have a massive whip on the roof. Any antenna suggestions? Do certain bands lend better to range?

Don't feel inclined to do my research for me, if you can point me to a good online resource I can check it out myself.

Much thanks.

-Brad

[DaveInDenver]

The most basic way to put this is that not all electromagnetic (EM) waves interact the same with the rest of the world.

All radio frequency (RF) waves are EM waves, but so are a lot of other things, light, microwaves, etc. Light for example is an EM wave and easier to understand conceptually. RF is the same except lower in frequency. The most obvious parallel to light is the 'direct' wave. Think of your radio like a flashlight and the observer only sees the beam directly (ignoring reflected light for the moment). RF works this way, too, on a point-to-point direct path.

The interesting part, you remember from physics that blue and red are on opposite sides of the light spectrum? The light spectrum has a range of wavelengths. You can see from prisms how colors get separated physically due to various amounts of bending (called refraction). This is the light's wavelength reaction through a particular medium. RF does this too, react within the medium in which it travels. Light is just a relatively narrow range which is why the spectrum seems continuous to our eyes.

The VHF part of the spectrum is something all hams know. These frequencies do not often (they can, just rarely) refract in the earth's atmosphere, so they pass through into outer space. This would be roughly similar to some parts of the EM spectrum going right through the prism and not bending. The medium of glass or plastic might conceptually be invisible so-to-speak to UV, for example. This is true of VHF and basically always true of UHF to the ionosphere, where it is essentially invisible and goes right through. That's why VHF/UHF are substantially line of sight (or direct wave) bands and only work if you can basically 'see' the other station. VHF is affected by reflection, which is why you get multipath interference with it. But RF reflection happens from objects and not an ionospheric charge. You do get some reflection from the atmosphere from dust for example, just not much of it and it's basically not useful for communication.

What happens as you go down in frequency (up in wavelength) is that EM waves begin to 'see' the ionosphere and begin to interact with it rather than passing through it. They seem to reflect off of it (it's actually refraction, just like light in the prism). This begins to happen quite rarely on 6m and more periodically on 10m. It happens reliably when you get down to 20m, etc. It does work down to the longer wavelengths, though other things (like atmospheric absorption) begin to change how well. At some point the wavelength becomes so much longer than the height of the atmosphere over the surface of the earth that it become 'invisible' again and no longer refracts. For example, 160m is only marginally refracting in the ionosphere.

All of this mostly depends on the sun. During the day we have 4 layers (D, E, and two in the F) in the ionosphere and at night some of them collapse, the F1 and F2 become one layer and the D layer disappears. Effectiveness of refraction varies with how many charged particles are available and what layers of the ionosphere are present. What you count on is the majority of energy during refraction going back to earth. This is where a beyond-the-horizon contact is made. Waves travel better during the day with the sun charging ions, although this also creates more noise. At night the atmosphere is quieter but there are fewer ions available for refraction and the layers having collapsed provide a narrower range of potential frequencies. Basically in this you can think of the sun and ionosphere as varying composition of glass in a light prism.

Sometimes it then reflects (actually reflects in this case) back off the ground and refracts in the ionosphere again. When it does the ionosphere-ground boogie several times, called hops, a wave can travel a long distance. The most effective wavelengths for the ionospheric phenomenon move up and down over the day and around the year, but generally the best DX chances lies within 40m to 15m. It's here where QRP has the best chance to go long distances because your signal does not lose much energy along the way. It might only happen efficiently at a very narrow range of wavelengths at any instant in time or it can happen over a large range.

This barely scratches the surface of RF propagation (reflection, polarization, incident angle, wave penetration depth, ionic charge density for example) but maybe will get you going to investigate it some. There are all kinds of good books about RF propagation, whole textbooks about it. I personally like Seybold's book, but the one the ARRL sells by Poole isn't bad either.

And BTW, yes, you have to put on a long antenna if you want to work mobile HF effectively. Just the nature of the beast. There are some laws that you just cannot break no matter how hard you push the throttle pedal.

[Mashurst]

Ya what Dave said...
But to bring it down to a more practical, less theory level. On 2m say you should be able to do better than 60 miles with that radio. I have a good spot up on a hill but I routinely chat with guys on a repeater over 100 miles away with my 5 watt hand held. Some of them are another 50 or 60 beyond that. I have heard people say you can count on about one mile per watt and that may be a good rule of thumb, but it is by no means that max range. In the Denver area I would think there would be a lot of great repeaters that cover huge area of the flatish land to the east from the mountains to the west but I don't know firsthand. While you are traveling in the mountains how well you can hit a repeater is going to depend a great deal on how high you are and where the repeater is compared to you. VHF/UHF (2m/70cm) is more or less line of site for the reasons Dave laid out so you need to have a good shot at the repeaters antenna, but they tend to be is spots that are easy to hit on mountain tops.
So I think you should be able to do better with your setup. Have you checked the SWR on the antenna? Do you have the power set to its highest setting (50w)? Don't leave it there all the time but to reach out you will want everything you have.
To do the long range stuff (DX) you will need a different radio. That's just not what your radio is for. Also when operating HF in the lower bands you need to be a bit versatile because like Dave said there is not one band that will always work. Working HF is very cool but it's kind of its own thing and will take regular participation to keep your skills in good working order. VHF is a great tool for getting communications from wilderness areas that are reasonable close to urban centers. Huge swaths of the west and I would imagine most all of the east fit that description but there are holes and it does have its limits.
There are a lot of smart folks here so ask and you shall receive.

[DaveInDenver]

Just noticed that you're in Denver. Welcome! Having a '1' call, it didn't register.

It's true that we have super coverage repeaters, but something to be aware of is the in town you get significant shadows up against the foothills because the majority of them are sitting up at places like Squaw Mt, Lee Hill, Conifer Mt and Mt Thorodin. If you are right up against the Hogback, along C470 or up in Boulder you probably will have a tough time hitting the repeaters without some power or height, if at all. Go east away from the foothills just a mile or so and you can use most of the machines with a HT.

I use 5W with a 1/4 wave 70cm on the roof of my truck and hit the 449.450 machine up on Squaw Mt from most everywhere. Helps a lot that it sits at 11,440 AMSL and we're at 5,280. With 50W there are guys who hit the machine mobile from Franktown and Ft. Collins, which would be nearly 100 miles.

Some of the machines can be worked (maybe needing a directional antenna using 50W) from Cheyenne or Monument.

Hit me with a PM and we can hook up. Or listen for me on the radio. :-) We'll take a look at your rig and I have an FT-817 and we can mess with QRP.

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[bcrez]

I cant thank you guys enough. This explains a lot... and has left me with lots more questions. The 1 in my call is because I took the test, and am registered in CT (the closest thing to a permanent address I have). Which I should have explained is where I have been transmitting, at about 10ft above sea level. That mixed in with all the tree's and buildings might account for my short range.

What sort of radio would be ideal for DX mobile?

I dont have a SWR meter, nor would I know how to use it if I did. I guess I should look into that. I did get really good range once driving through North Carolina. I was hitting the same repeater with great clarity for about 4 hrs while driving 70mph north to south. In a big rain storm that stretched from north florida to NY. But I would have thought that would inhibit my range.

I can't wait to get back to Denver and see how far out I can transmit. When I do I will send you a PM and see if I can get you on 70cm. Do you know the name of Seybold's book?

Thanks again for your replies.

[Mashurst]

For mobile DX, 'Ideal' would be the Icon IC-7000 or the Yaesu FT-857D... but to be clear mobile is not ideal for DX. Any antenna you run while mobile will be severely compromised. That not to say you shouldn't do it. Also you will need to upgrade your license to use the lower bands of course.

[DaveInDenver]

It's called Introduction to RF Propagation by John Seybold. This is an upper class undergraduate, maybe entry level graduate level engineering textbook that I used in school, so I would warn you that it's not easy to approach. Let me think about it and see I come up with some recommendations from a ham operator perspective.

[bcrez]

Thanks Dave.

Time to start studying for my general...