HPT435BT Radio Range in SE Oklahoma - DQPSK

Hello friends,

I am having a heck of a time getting any range with my setup. Ya'll help me out here.

T2, LS, HPT435BT pushing 35watts w/ 14ft pole,
UHF Whip Antenna 5/8, 5dB, NMO
RTCM 3.0 Min, 0.2 Sec, 464.5 MHz (FCC approved),
D16QAM, 12.5 KHz bandwidth

I notice the quickstart guide states "Field test have found that D16QAM modulation decreases the working range of the radio approximately 20% as compared to DQPSK modulation." I'm guessing my radio don't have DQPSK, since I don't see the option?

I also notice the whip antenna manual shows cutting it? Right now it's already too short between the phasing coil and base per the chart? By about 1/4". Will this be a game changer???

Also, see my attached pic of a recent job where I couldn't get over 1 mile with this setup. Granted, I don't always spend the time to get to the highest point with my base, but not even a mile??? Come on. At my old place of employment, our old topcon hiper-v never required an external radio and worked all day in the same stuff at farther distances. Ironically, we did the south line of this same tract where I couldn't make it half way without losing radio.

This is the only thing I have really not liked about my system. I am going to try the Verizon jetpack, but no signal in a lot of places. What can I do to improve my radio range?

Green I was able to get it, RED was a no go at all. The 2 southeasterly ones were BARELY done. I know I'm not the only JAVAD guy in hilly terrain like this...

Thanks in advance.

- Jason


Matthew D. Sibole

Well-Known Member
First off you should be broadcasting at 1 Hz instead of .2 and you should be using data upsampling. This will increase your battery life and you can switch back to DQpsk which will increase your range.

Change your radio setting to 1sec and your modulation back to DQpsk in base rover setup. Now go to setting/ edit at the top left and hit advanced and hit RTK/dgps and hit .2 seconds there and hit “use data upsampling” check mark box.

Do you have a ground plane? If not you should get one. It will increase your range as well.

Shawn Billings

Shawn Billings
You should run at 1 second rate, DQPSK. In advanced settings (press hardware setup button on the bottom left of the receiver twice). Select RTK/DGPS, set rate to 0.2 and check on use data upsampling.

This will keep you running at 5HZ at the rover with 1HZ transmission at the base.

Matthew D. Sibole

Well-Known Member
FWIW, I have customers in northern Michigan that can barely get 1 mile. It is flat but the canopy is so dense the uhf can not penetrate the foliage. Uhf just has limitations. I have found that if I set my base down low and try to go high it doesn’t work nearly as well as setting it up high and going down low.

Matt Johnson

Well-Known Member
Radio waves do not travel through the ground regardless of the modulation, output power or the height of the radio. The two points where you show no radio reception are 80 feet and 60 below the top of a ridge with your base on the other side. You will not get reception in these areas. For planning purposes you can count on getting reception in the areas within the viewshed of the base radio.

http://www.heywhatsthat.com/ is a good website to calculate the viewshed of a location to help predict where you should have radio coverage from a given location. A repeater is needed to get around terrain obstructions.

Thanks. This is a typical style job for me, so what would you all do to accomplish this job without cell data? There’s a locked gate at W4. I can’t get to the upper elevation with any sky view unless I go up the highway which moves the radio even further away. Thanks again.
I have had problems with my 35 watt radio. It's been to the shop, I think 3 times. I finally bought a 4 watt radio, to use as a repeater, or backup should my 35 watt need service.
Since the 35 watt came back this time, it's been flawless. I have not yet set up the 4 watt, to repeat.
My feeling is that the 35 watt from arWest, Javad are more delicate than the old Pac-crest, units. Trimble has now bought Pac-crest. This effectively cuts out these units, from use. Also, my feeling about the Javad radio products is that when working properly, they give cleaner data than the old Pac crests. They are digital radios. Narrow banding has hurt range too.
To compare the Javad radios, with the Pac crest ones, you'd have to set them to 25 band width, instead of 12.5. (Legal problems there).
In any case, we cannot go back to the 25 band width, due to regulation. So, I suggest a repeater, something like I did.
Also.... We are pushing this equipment DEEPER into the woods, than we ever did the older gear. I had a job, where signal was great, until I walked off into the trees. Er.... Pine Forest, where signal could not penetrate.
So, times... They are a changing... And we cannot go back.
Reminds me of the old adage about 4 wheel drives. Those that can afford them, don't need them. And, those who really need them, cannot afford them. When you are at the edge of your equipment's ability, you may have to spend money. (Repeater)
One more option, is a taller antenna mast, at the base. I have a 20' hixon pole for that. Every foot you go up, you exponentially improve your range. Get it up. You'll be glad you did!
I'm just a user, and I earn my keep, with survey dollars. Those kind are worth twice as much as the dollars bankers, or insurance agents earn! (Grin!)
One more thing. Go to your radio shop, and buy a yagi. Put all the connectors together, to use at the rover end. This can be a cheap fix, for the occasional use, "down in the hole". I did this. I use it about 2-3x a year.
Thanks everyone. I didn’t have my radio broadcasting at 1 sec and it wouldn’t let me use DQPSK. I was confused about the 0.2 setting and had it there. Today I got it all squared away and I left my job site to grab some food and man was I surprised to hop out of my truck at the handy stop and have radio and be able to take a shot... about 5.2 miles from my base. Good feelin. Fingers crossed.