4 watt radio

Matthew D. Sibole

Well-Known Member
5PLS
I was testing a few things this afternoon and decided to look for a local usgs horizontal control monument. I set my base up and radio as normal and drove 1.6 miles to the coordinate location listed on the NGS data sheet. What do you know, I was still receiving corrections. 5 fixed engines at 1.6 miles from my base.
 

Matthew D. Sibole

Well-Known Member
5PLS
It had been torn out by a driveway. I had just set my base up autonomous. I then entered the state plain coords for the monument in the LS and staked to it. I didn't spend a lot of time looking for it. It was pretty cold out here today. 4" of snow on the ground and only 20 deg for the high today. Windchill did not get above 10 today.
 

Jim Frame

Active Member
Is 1.6 miles a long way for a 4-watt radio? Any idea what kind of range I can get with my 1-watt? (I haven't had time to test range yet.)
 

Matt Johnson

Well-Known Member
5PLS
When I tested this I was able to get about 4000' out of the 1 watt radio before the signal started dropping out. This was in fairly flat area but with trees and houses obstruction the line of sight.
 

Jim Frame

Active Member
When I tested this I was able to get about 4000' out of the 1 watt radio before the signal started dropping out.
Ooof, I was hoping for quite a bit more than that. I may go with the 4-watt after all. John Evers told me that if I went all the way up to a 35-watt radio I'd need a full-size car battery to run it reliably all day. I don't mind using an external battery -- though the built-in battery of the 1-watt is definitely appealing -- but I don't want to be lugging a car battery around.
 

Matt Johnson

Well-Known Member
5PLS
Another option is to get a 35 watt radio and broadcast at lower power levels with a smaller battery. When you need the extended range you could set it at 35 watts and use the large battery.
 

Matthew D. Sibole

Well-Known Member
5PLS
Is 1.6 miles a long way for a 4-watt radio? Any idea what kind of range I can get with my 1-watt? (I haven't had time to test range yet.)
I typically only get about 4000' with my 4 watt. However, I have a lot of relief in the area I work in. I would expect a couple of miles in flat open ground.
 

Shawn Billings

Shawn Billings
5PLS
Tonight I did a little test with my 4 watt radio modem to see what kind of range I could expect. Terrain and obstructions play a big part so, as in most things, "it depends" applies. To the West of my base about a quarter mile away is a highway overpass. This earth embankment seems to affect range in that direction. I was able to get reliable radio reception at about 1 mile. To the North and Northeast I was able to get about 9000 feet. To the southeast about 7000. This was done rather hurriedly but I think I can safely say that range in my conditions should generally be 1 to 1 and 3/4 miles. Note that this test was with the internal antenna on the LS. Using the external UHF antenna with the LS will improve range somewhat, but I don't know how much.
 

Doug Carter

Active Member
5PLS
Jim,
I would go for the 35 W radio, it's not worth losing yours signal and having to go back and move your base. you can also use a smaller lawn tractor battery which is smaller, or lower the wattage when not needing 35 watt power. Doug
 
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Matt Johnson

Well-Known Member
5PLS
I just ordered a 35 watt radio today to go along with the 1 watt radio I already have. I will use the 1 watt when I don't need a lot power and I will also use it as a repeater when there is a ridge between the base and rover. I plan to be done with the days of losing a radio signal.
 

Jim Campi

Active Member
I just ordered a 35 watt radio today to go along with the 1 watt radio I already have. I will use the 1 watt when I don't need a lot power and I will also use it as a repeater when there is a ridge between the base and rover. I plan to be done with the days of losing a radio signal.
That's an interesting idea. Does an additional radio operating on the same frequency as a repeater require a modification to the FCC license?
 

Jim Campi

Active Member
Jim,
I would go for the 35 W radio, it's not worth losing yours signal and having to go back and move your base. you can also use a smaller lawn tractor battery which is smaller, or lower the wattage when not needing 35 watt power. Doug
Does anyone know the operating time for the 35 watt radio (full power) using the standard battery pack for the 4 watt?
 

Matthew D. Sibole

Well-Known Member
5PLS
Does anyone know the operating time for the 35 watt radio (full power) using the standard battery pack for the 4 watt?
I am not sure about the size of the battery pack for the 4 watt radio, but was told a 40 amp hour battery was needed for the 35 watt radio.
 

Matt Johnson

Well-Known Member
5PLS
Battery life can be estimated with the following formula:

(amp hour battery rating)* (battery voltage)/(power consumption in watts) = (expected battery life in hours)

From the spec sheet 38 watts are consumed when broadcasting at a 35 watt output with a 30% duty cycle. I think the 30% duty cycle corresponds to a 1 Hz TX rate so for a 35 watt radio with a 12 volt 40 amp hour battery:

40 Ah * 12V / 38W = 12.6 hours is my best estimate
 
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Kelly Bellis

ME PLS 2099
5PLS
Battery life can be estimated with the following formula:

(amp hour battery rating)* (battery voltage)/(power consumption in watts) = (expected battery life in hours)

From the spec sheet 38 watts are consumed when broadcasting at a 35 watt output with a 30% duty cycle. I think the 30% duty cycle corresponds to a 1 Hz TX rate so for a 35 watt radio with a 12 volt 40 amp hour battery:

40 Ah * 12V / 38W = 12.6 hours is my best estimate
Great answer - thanks Matt!
 

Jim Frame

Active Member
I think the 30% duty cycle corresponds to a 1 Hz TX rate
I'm curious where you found this documented. I've always looked at duty cycle as a component heating issue, and assumed 1Hz to effectively be continuous. I never thought that it might have different impact on power consumption, but I suppose it does.
 

Matt Johnson

Well-Known Member
5PLS
When the TX light on the radio is lit up, it is transmitting radio waves. If it was transmitting with a 100% duty cycle the light would be solid and not blink. I have confirmed this my very high tech testing equipment. When I have the radio broadcasting in my office near my computer speakers I can hear interference. The audible interference occurs every second with a duration of about 1/3 a second and corresponds to the TX light being lit.
 

Kelly Bellis

ME PLS 2099
5PLS
Matt, does your very high tech testing equipment also produce the Morse Code signal of your call sign every 15 minutes?
 
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