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Looking to get ~40 mile range out of CB without 102" whip?

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w9cll said:
I never advocate an amp over a good antenna but someone needs to flaunt their knowledge.
Click to expand...

Let's change the way we look at a radio signal from expressing it in sheer watts to expressing it in DB - since any RF engineer you talk to is going to explain it to you in this manner.

The radio as you like to call it will be called the Generator, and the antenna will be called the load. In theory, if the load matches the generator, all of the power applied will be adsorbed by the load and radiated. If dealing with a mobile, we won't worry too much about loss, since there is not a lot of loss in a piece of coax 20' long.

The greatest gains are between 3 watts and 500 watts since 3 watts is enough power to radiate a good signal and can easily be converted into Db.
When referring to Db we either have to use the term DbM or DbW =- dbm being decibel milliwattt, dbw being decibel relative to one watt.

In theory, Mr. Collins devised a way to express gain linearly using a scale of 1 - 9 and then 10/9. Each number increase from 1 to 9 represents a 6 db gain in signal strength. After S9 signal strength increases 10 fold.

To increase signal strength we need to increase power or radiated power or move closer to the source.

A true 1 s unit RST gain requires a increase 4x or 400% in power.
A 10 decibel increase in power requires a power increase of 10 times.

Using 3 watts as a example with two identical dipole antenna's
S-5: 3 watts
S-6: 12 watts
S-7: 48 watts
S-8: 192
S-9: 768 watts.

If we use a more efficient antenna and we can increase our perceived transmit power.

S-7: 3 watts
S-8: 12 watts
S-9: 48 watts
10/9: 480 watts
20/9: 4800 watts

Using a 25 watt Ranger 2950 - we could expect a signal report of about an S-6 with the 4 foot whiles, while we could expect a S-8 to S-9 signal report using the Solorcon A99 antenna @ 30' above ground...

The Solarcon A99 would have at least a 12 Dbd ( decibel over dipole ) gain over the 4' whip.

Again, it is all just using what you have more efficiently.
On 11 meters I would use signal side band, not AM and I would use two Solorcon A99 antenna's and two masts 30' or more long. You could attach them to the side of your truck - since you already referred to 4 foot whips on headache racks.
If both trucks were at the highest points, this would probably get you 20 miles in any one direction..

Once you get above S-8, there is no reason why two people shouldn't be able to hear each other, as long as you pick a clear frequency.... Avoid any channel below 30 and you should be ok...
 
w9cll said:
I never advocate an amp over a good antenna.
Click to expand...
I agree on the antenna part. I run a Icom IC-746 and make contacts all over the place with out a linear. Even though I have Yaesu FT-2100 I have never powered it up. The antenna I'm running is a "QSO-King 80 to 6 meter". 44 feet of wire with a well designed 9:1 UN/UN transformer. I have made good contacts on all bands with it.
 
Won't work at all with hills in the way no matter how much power you use or whether they are base or mobile stations if you are using vertical antennas and even using horizontal antennas in NVIS configuration isn't really going to work.

My home QTH is a perfect example.

Where I live there's a hill between me and the next town 12 miles away, not a particularly tall hill but a hill nonetheless. My house is on a hill as well at the highest point in my town but not high enough to clear the hill in the way. My house is 40metres above sea level, the hill in the way is 50 metres above sea level, just a mere 30ft higher. I can put 400W into an Imax 2000 30ft up in the air and barely make it to the next town. The received signal is so low as to not be able to hold a conversation.

I can jump in my car, drive half a mile down the road which is enough to get out of the way of the hill. Even though I am now mobile, I'm also 60ft lower than at home and the antenna on the car is 80ft lower than the Imax 2000 is and length wise is 1/4 the length, I can talk to someone in the next town perfectly well with perfect clarity with just 4 watts.
 
I still think purchasing a few pre pay cell phones would be the easiest way to do this. Shoot even Bluetooth ear pieces are cheap these days. Find which carrier has the most coverage. There are plenty of coverage maps where you buy the phone. Unless you are in some remote area that just doesn't have cell phone coverage this is going to be the best bet. They even off the push to talk feature on some phones still. And the mobile to mobile minutes are usually free on most of the carriers these days. The 2 best carriers are will be ATT and Verizon. And the cost of a prepaid phone isn't too bad these days either. Place to buy, Walmart. JMO!!
 
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datenschwanz said:
First post, I poked around but did not see this answered elsewhere so apologies in advance if it's been covered before.

I am looking to get a pair of mobile units that can achieve ~40 mile range on SSB. Can this be done with a pair of 4' antennas mounted on a headache rack or the roof of our trucks? Do we need to get one of the other types of units to do this like a 2 meter or 10 meter unit?

We're running cycling events and need to be able to get the truck that goes with the race leaders to communicate with the broom wagon that can be up to 40 miles back over varied terrain like hills and small mountains or across forests.

Thanks for looking!
Click to expand...
Out of the box with two wilson 5k magnet mount antennas 40 miles on ssb means you have low expectations. I would expect that at a minimum.
 
All effective communications is line of sight.
When you put something 3 or more stories high between the transmit and the receive, you will have little or no reception.
Even in my situation, being on a high plateau, when you have signals behind a mountain, you cannot talk to them, because the mountain shadows their signals.
You see if something blocks your signals, if you move back away from the object, you can see beyond the object, but you cannot see what is behind the object.
Even in my case, there is directions where I do have a good horizon, but even in those directions my radio line of sight is only about 15 miles in two directions.
My elevation is 1400' amsl and to the north there is a mountain 5 miles away that is 1850' at its highest point. That negates anything locally to the north.
When you get out towards OHIO, the land levels out and the line of sight increases.
The curvature of the earth on flat ground is still about 8 inches per a mile.
This means that in 40 miles we have about 320 inches of curve - more than 26 feet.
To get 40 miles, your car would need to be 36 feet higher than the other vehicle and nothing in between you and them. An open field or a interstate highway.
Interstate highways in the USA are built with a curve about every 3 miles, due to studies done on the autobahn that showed that when you lay a flat slab of concrete with no curves, eventually the driver gets bored and falls asleep.
So I can't compare what your signal can do in a place like Kansas or even the northern part of Ohio - where the highest elevation in the whole northern part of the state is the garbage dump! 65' amsl....
All I can say is that anyone that claims reliable reception anywhere else with a 5, 50 or 100 watt transceiver into a mobile whip is just a flat out liar.
You can't fix stupid!
M0GVZ said:
You need to learn how to install antennas properly. Using properly installed antennas a friend and I communicated quite well over 30 miles mobile to mobile on FM with just 4W each.

To answer the original poster....

Not going to happen with hills in the way. What you need to do is investigate if there are any commercial VHF repeaters in the area and if the companies operating them do a hire service. It is the only way you're going to guarantee as much coverage as possible. Vehicle to vehicle will work over the distance you want over flat terrain on CB or VHF. As soon as you put a hill between the two vehicles then despite what w9cll says you've got no chance no matter what you use and how much power you put out.
Click to expand...
 
Doesn't even need to be 3 storeys high. A hill between me and the next town 5 miles from me is barely 20-30ft higher than the antenna.
 
Ham Man said:
Let's change the way we look at a radio signal from expressing it in sheer watts to expressing it in DB - since any RF engineer you talk to is going to explain it to you in this manner.

The radio as you like to call it will be called the Generator, and the antenna will be called the load. In theory, if the load matches the generator, all of the power applied will be adsorbed by the load and radiated. If dealing with a mobile, we won't worry too much about loss, since there is not a lot of loss in a piece of coax 20' long.

The greatest gains are between 3 watts and 500 watts since 3 watts is enough power to radiate a good signal and can easily be converted into Db.
When referring to Db we either have to use the term DbM or DbW =- dbm being decibel milliwattt, dbw being decibel relative to one watt.

In theory, Mr. Collins devised a way to express gain linearly using a scale of 1 - 9 and then 10/9. Each number increase from 1 to 9 represents a 6 db gain in signal strength. After S9 signal strength increases 10 fold.

To increase signal strength we need to increase power or radiated power or move closer to the source.

A true 1 s unit RST gain requires a increase 4x or 400% in power.
A 10 decibel increase in power requires a power increase of 10 times.

Using 3 watts as a example with two identical dipole antenna's
S-5: 3 watts
S-6: 12 watts
S-7: 48 watts
S-8: 192
S-9: 768 watts.

If we use a more efficient antenna and we can increase our perceived transmit power.

S-7: 3 watts
S-8: 12 watts
S-9: 48 watts
10/9: 480 watts
20/9: 4800 watts

Using a 25 watt Ranger 2950 - we could expect a signal report of about an S-6 with the 4 foot whiles, while we could expect a S-8 to S-9 signal report using the Solorcon A99 antenna @ 30' above ground...

The Solarcon A99 would have at least a 12 Dbd ( decibel over dipole ) gain over the 4' whip.

Again, it is all just using what you have more efficiently.
On 11 meters I would use signal side band, not AM and I would use two Solorcon A99 antenna's and two masts 30' or more long. You could attach them to the side of your truck - since you already referred to 4 foot whips on headache racks.
If both trucks were at the highest points, this would probably get you 20 miles in any one direction..

Once you get above S-8, there is no reason why two people shouldn't be able to hear each other, as long as you pick a clear frequency.... Avoid any channel below 30 and you should be ok...
Click to expand...
Just for the record it is expressed dB, not DB or Db. It is deciBell, 1/10 of a Bell. Bell in honor of Alexander Graham Bell.
Rich
 
Water is great reflector of RF.

I stuck a 102" stainless steel whip on a 19' open fisherman. The base of the antenna was 5' off the water. At the house, we had a 1/2 wave Radio Shack "Crossbow" - a Shakespeare "Big Stick" made for Radio Shack. These are well built antennas, but not particularly strong talkers. The base on it was barely 10' above the water.

We had a Johnson Viking 4740 with a Turner Super Sidekick at the house. We had a Realistic TRC 222 walkie talkie with an antenna adapter in the boat. With both radios putting out under the standard 4 watts, we were able to communicate 44 miles on AM. Talking to the same base, I am able to talk about 20 miles with my little 3', 20+ year old Radio Shack magnetic mount mobile antenna.

At one point, I swapped out the Viking 4740 and used an old Realistc TRC 431 base with a Johnson desk mic (essentially Turner +2 guts in a Turner +3 shell). As expected, the results were identical for all practical purposes.
 
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