RTK base station Antenna advice needed.

[prcguy]

My guess: nowhere near 100 watts is getting to the antenna.

Who installed the antenna and put the connectors on the LMR400 cable and were they all new at the time? Got pics?

Which amplifier model, exactly? 1.6 / 100 seems like a lot of gain. [I wander off and find the Henry specs] Yes, 5 in / 100 out is the lowest output spec for continuous/base and should be plenty for this application as long as much of it is actually getting to a working antenna. A tech with a wattmeter would first check forward and reflected power at the amp output and then (if necessary) at the antenna.

Got a pic of the mobile install? It may not be needed, but a real antenna on top of the cab for the mobile makes sense if it can be done in a way that's durable. Just a cheap Laird or PCTEL 1/4-wave spike.

Others have covered how crazy it was to put you on 464.500 and 464.550, freqs that have been commonly put in radios by default and used without proper licensing for decades. There's mostly no such thing as unshared channels for your application, but depending on how far out in the country you are, a proper licensing guy should be able to find and co-ordinate something that's not in use anywhere nearby.

The original Henry Radio would make most any of the 5w input amps for lower power, here is a statement from an old ad. "On amps listed as 5 watts input, specify your drive power of 2, 3, 4 or 5 watts to get rated power output".

 

[WB5UOM]

Yes...you have no business on iternant frequencies
ergo then the FBI goes away it should be FB (and that has nothing to do with existing low band voice channel)

 

[kayn1n32008]

With over a decade of expérience utilizing Trimble RTK, the LAST people I would let anywhere near doing a permanent install would be the RTK equipment retailler sales company.

You need a LMR dealer to come and see what's going on.

I have had good success using a portable RTK Base set up for YEARS, fed with RG58, a 5.9dBd NGP NMO mobile antenna on a 'surveyor' thread mount, on a 4m tall range pole. This is using a 35w base radio. I've almost ALWAYS gotten 5+ miles of coverage from that set up. Where I've needed more, I've used a temporary data link repeater.

I missed your antenna elevation, but at a minimum, it should be fed with 1/2" hard line. The antenna needs to be above the top of the support structure, and shouldn't need to be more than 3-6dBd gain. I always favor exposed dipole arrays over fiberglass verticals. The company I use to work for did a permanent install, on a 50' yard light that was modified to beable to have a 4 bay Bluewave dipole mounted and it worked well beyond anything g we expected. It was fed with 1/2" hardline, and a 35w datalink radio. 2 other permanent stations they had were 3dB fiberglass sticks fed with LMR400 because it was 'cheap to deploy', but we ALWAYS had to use repeaters with them. That site we would do layout on one base, then switch to the other to do our check shots on the layout.

High quality components are an about must for RTK permanent reference stations. You really need the data to be recovered intact, or at least intact enough for the forward error correction to be able to send useful data to the RTK receiver.

Not being in the US, I can not speak to what frequencies to use. In Canada, RTK systems and survey comapnies are licensed for blanket use, usually with in the provinces they operate, on a bunch of 'common' channels in the 440.000-440.500MHz and 445.000-445.500MHz portions of the UHF band. This helps the surveyors but having dedicated challenge, that won't be licensed to other users for things like voice. Usually through the station index, you can ignore another one-handed base station, as long as your station index number is different that the other one.

Definitely different here that's forsure. Having said that, maybe call a few different coordinators and ask if they have specifically coordinated frequencies for RTK use. The use is quite different than just some voice, radio to radio.

 

[Shulerfarm]

My guess: nowhere near 100 watts is getting to the antenna.

Who installed the antenna and put the connectors on the LMR400 cable and were they all new at the time? Got pics?

Which amplifier model, exactly? 1.6 / 100 seems like a lot of gain. [I wander off and find the Henry specs] Yes, 5 in / 100 out is the lowest output spec for continuous/base and should be plenty for this application as long as much of it is actually getting to a working antenna. A tech with a wattmeter would first check forward and reflected power at the amp output and then (if necessary) at the antenna.

Got a pic of the mobile install? It may not be needed, but a real antenna on top of the cab for the mobile makes sense if it can be done in a way that's durable. Just a cheap Laird or PCTEL 1/4-wave spike.

Others have covered how crazy it was to put you on 464.500 and 464.550, freqs that have been commonly put in radios by default and used without proper licensing for decades. There's mostly no such thing as unshared channels for your application, but depending on how far out in the country you are, a proper licensing guy should be able to find and co-ordinate something that's not in use anywhere nearby.

[Re-reading the thread for more detail, I see:]

Well, that sounds about right. Maybe there isn't a problem with the feed/antenna. I'm not familiar with their amps any more, but if it's +13 dB gain at 5W in (=100W out) and the input is turned down to 1.6W and the gain is the same there, output would be 32W, which might yield exactly the coverage you're seeing (and, coincidentally, be below the earlier-quoted 35W legal limit). Hmmm.

[and in the Henry specs:]

Some pictures attached. Amp not hooked up right now. Tractor shows 4 antennas: small on radio currently used, at left is Laird antenna (no real improvement), back right is low band mobile radio, am/fm radio antenna.

 

[kayn1n32008]

Yikes. I've seen some crappy installs in my day, but never anything quite that bad.

Might have to add this to my list of possible retirement side-hustles.

You could keep busy between improperly installed BDA and retail RTK installs

 

[Shulerfarm]

Some pictures attached. Amp not hooked up right now. Tractor shows 4 antennas: small on radio currently used, at left is Laird antenna (no real improvement), back right is low band mobile radio, am/fm radio antenna.View attachment 181757View attachment 181758

 

[mmckenna]

Couple of things looking at those photos.

The Polyphaser doesn't have any of the connections waterproofed. Water will get in the connectors and destroy them. Water can wick up the coax and corrode everything. That would be the first/easy thing to check. Waterproofing -all- the outdoor connections is required.

Looking at the antenna, it looks like the coax is hanging loose. The weight of the coax can pull the connectors apart. A good tech with a wattmeter can check to see if that's an issue.

Based off the lack of waterproofing on the Polyphaser, I'm going out on a limb and say that the coax connector at the antenna wasn't waterproofed. Again, water intrusion will corrode everything. A tech with a watt meter could easily check that part of the system.

How many amps is that power supply rated for? And is it enough to drive the amplifier?

Before spending money on anything, hire a competent tech with the right test equipment to come out and check the system.

 

[mmckenna]

You could keep busy between improperly installed BDA and retail RTK installs

And late night/drive by NMO installs.

 

[mrsvensven]

Before spending money on anything, hire a competent tech with the right test equipment to come out and check the sysystem.

Do this. Those photos show multiple red flags (that mmckenna listed) which indicate that this system wasn't installed to good standards and therefore needs a full inspection. Have both the tractor and the base station checked.

If you're in the middle of nowhere enough that you're sure there is nobody with radios within 30 miles, interference might not be your problem. That doesn't make your licensing and frequency choice are legal or good, however.

 

[AM909]

Looks like the arrestor setup is using PL-259/SO-239 connectors, which are an inherently poor choice, especially for something that needs to be waterproof.

I'm still kind of fixated on the power levels involved, too. Did someone calibrate things and give you switchable low/high power on the radio so you could run it as shown with the amp disconnected?

 

[clbsquared]

Looks like the arrestor setup is using PL-259/SO-239 connectors, which are an inherently poor choice, especially for something that needs to be waterproof.

I'm still kind of fixated on the power levels involved, too. Did someone calibrate things and give you switchable low/high power on the radio so you could run it as shown with the amp disconnected?

The wattage on the radio can only be changed if it has the 4600 display connected to it. There is no “on/off” button on the radio. And I doubt anyone would willingly purchase a $8000.00 display just to leave it attached to the StarFire receiver at an RTK site.

 

[Shulerfarm]

Couple of things looking at those photos.

The Polyphaser doesn't have any of the connections waterproofed. Water will get in the connectors and destroy them. Water can wick up the coax and corrode everything. That would be the first/easy thing to check. Waterproofing -all- the outdoor connections is required.

Looking at the antenna, it looks like the coax is hanging loose. The weight of the coax can pull the connectors apart. A good tech with a wattmeter can check to see if that's an issue.

Based off the lack of waterproofing on the Polyphaser, I'm going out on a limb and say that the coax connector at th intrusion will corrode everything. A tech with a watt meter could easily check that part of the system.

How many amps is that power supply rated for? And is it enough to drive the amplifier?

Before spending money on anything, hire a competent tech with the right test equipment to come out and check the

Everything is new. No rain on connectors because it didn't rain for two weeks since install and have keep it taped up and covered since these first two weeks. Coax is support at the top with tight zip ties. I have taken the polyphaser out of the system and attached directly to the radio. The transformer is rated at 40 amps and the amplifier draws 27 amps and the gps/radio draws 1 amp. This is not continuous since the signal from the radio pulses. I have put a DC amp gauge on the wire and it shoots up and down.
Summary of my range:
1) 100' grain elevator, no amp, 2 watt output with Comet 9 dBi antenna get about 4.5 miles
2)100' grain elevator, no amp, 2 watt output with Laird B4505CS 5 dB get about 2 miles
3) same setup as above but 15' high I loose about 1/2 mile.
4) 45' high using Comet antenna, no amp get about 3 or 4 miles.
5) 45' high using Comet antenna with 100 watt amp I get skippy signal at 7 miles.
I also started the planting season with a mobile base while I waited for my amplifier. This was a tripod in the back of a pickup with the radio/receiver attached to a battery and Laird B4505CS antenna at 15'. Work good for 2 miles.

Back to my original question. Better antenna fiberglass or expensive dipole? Suggestions on models. Or just move my setup to grain elevator? Would rather not. Also sounds like I got a common frequency that may be causing problems with interference. Also remember the amount of trees I am trying to penetrate. This is why "Bob" at Henry Amplifiers would not sell me less than 100 watt output.

Looks like the arrestor setup is using PL-259/SO-239 connectors, which are an inherently poor choice, especially for something that needs to be waterproof.

I'm still kind of fixated on the power levels involved, too. Did someone calibrate things and give you switchable low/high power on the radio so you could run it as shown with the amp disconnected?

Yes the arrestor has SO-239 ends. This was the arrestor recommended to me from the store that sold me the antenna. I made it work by putting PL-259 connectors on the LMR400 cable.
It is easy to change the wattage output on the radio. I can attach an older 2600 monitor to the harness going to the receiver and change the output setting from .2 to 2 watts.

 

[clbsquared]

Everything is new. No rain on connectors because it didn't rain for two weeks since install and have keep it taped up and covered since these first two weeks. Coax is support at the top with tight zip ties. I have taken the polyphaser out of the system and attached directly to the radio. The transformer is rated at 40 amps and the amplifier draws 27 amps and the gps/radio draws 1 amp. This is not continuous since the signal from the radio pulses. I have put a DC amp gauge on the wire and it shoots up and down.
Summary of my range:
1) 100' grain elevator, no amp, 2 watt output with Comet 9 dBi antenna get about 4.5 miles
2)100' grain elevator, no amp, 2 watt output with Laird B4505CS 5 dB get about 2 miles
3) same setup as above but 15' high I loose about 1/2 mile.
4) 45' high using Comet antenna, no amp get about 3 or 4 miles.
5) 45' high using Comet antenna with 100 watt amp I get skippy signal at 7 miles.
I also started the planting season with a mobile base while I waited for my amplifier. This was a tripod in the back of a pickup with the radio/receiver attached to a battery and Laird B4505CS antenna at 15'. Work good for 2 miles.

Back to my original question. Better antenna fiberglass or expensive dipole? Suggestions on models. Or just move my setup to grain elevator? Would rather not. Also sounds like I got a common frequency that may be causing problems with interference. Also remember the amount of trees I am trying to penetrate. This is why "Bob" at Henry Amplifiers would not sell me less than 100 watt output.

Yes the arrestor has SO-239 ends. This was the arrestor recommended to me from the store that sold me the antenna. I made it work by putting PL-259 connectors on the LMR400 cable.
It is easy to change the wattage output on the radio. I can attach an older 2600 monitor to the harness going to the receiver and change the output setting from .2 to 2 watts.

I’m fighting the same thing you are with trees. A 100 watt amp isn’t needed to accomplish what you want. I’m running a 50 watt amp on a 120’ tower and have 15 mile coverage. You need height.

 

[Shulerfarm]

I’m fighting the same thing you are with trees. A 100 watt amp isn’t needed to accomplish what you want. I’m running a 50 watt amp on a 120’ tower and have 15 mile coverage. You need height.

Do you know what model antenna you have? I am going to try some different things when I get a chance. I am worried I am getting interference from others using the same frequency nearby. With me at 100 watts I am probably causing havoc for others as well. I was unaware of receiving a general use itinerate frequency.

 

[mmckenna]

Everything is new. No rain on connectors because it didn't rain for two weeks since install and have keep it taped up and covered since these first two weeks. Coax is support at the top with tight zip ties. I have taken the polyphaser out of the system and attached directly to the radio. The transformer is rated at 40 amps and the amplifier draws 27 amps and the gps/radio draws 1 amp. This is not continuous since the signal from the radio pulses. I have put a DC amp gauge on the wire and it shoots up and down.
Summary of my range:
1) 100' grain elevator, no amp, 2 watt output with Comet 9 dBi antenna get about 4.5 miles
2)100' grain elevator, no amp, 2 watt output with Laird B4505CS 5 dB get about 2 miles
3) same setup as above but 15' high I loose about 1/2 mile.
4) 45' high using Comet antenna, no amp get about 3 or 4 miles.
5) 45' high using Comet antenna with 100 watt amp I get skippy signal at 7 miles.
I also started the planting season with a mobile base while I waited for my amplifier. This was a tripod in the back of a pickup with the radio/receiver attached to a battery and Laird B4505CS antenna at 15'. Work good for 2 miles.

OK, that's good info.

If you haven't waterproofed all the connections, make sure you do it. You need more than just electrical tape.

Back to my original question. Better antenna fiberglass or expensive dipole? Suggestions on models. Or just move my setup to grain elevator? Would rather not. Also sounds like I got a common frequency that may be causing problems with interference. Also remember the amount of trees I am trying to penetrate. This is why "Bob" at Henry Amplifiers would not sell me less than 100 watt output.

I usually go for better antennas, but "better" doesn't necessarily mean more gain. Gain is only part of the equation, you need to consider the radiation pattern, down tilt, etc.

Height usually increases range, but longer coax will reduce it. If you are going to go for a 100 foot high installation, and the radio will be at ground level, you need something better than LMR-400. 1/2" Heliax would be the minimum.

But as we keep suggesting, I don't think more gain/more RF power is the answer here.

If the topology is fairly flat, you shouldn't need 100 foot high antenna to get the range you are expecting.

At 100 feet, you will have clear line of sight out to the horizon at 19.7 miles. If the antenna on the tractor is at 10 feet, you can add another 6 miles. So, you should see about 26 miles of range if everything is working well.

At 45 feet, line of sight to the horizon with a 10 foot high antenna on top of the tractor should give you almost 20 miles of range.

Again, all dependent on the topology.
So, no wet coax, good antenna, a bunch of LMR-400, it's still suggesting that you've got at least two issues:
1. Co-channel interference. Try one of the other frequencies you have and see if range improves.
2. Still chance of a faulty component. Again, a tech with proper test equipment could help you confirm your equipment is good.

Don't rule out an issue with the tractor end of all this. Could be a bad antenna, bad antenna mount, bad coax, bad coax connector or an issue with the receiver. Issue with the receiver could be that it's gone deaf, or it's getting interference from the tractor, other radios, noise via the power feed.

I really think that a good tech with about an hour of time could locate the issue quickly and save you a lot of time and money swapping out equipment.

 

[clbsquared]

Do you know what model antenna you have? I am going to try some different things when I get a chance. I am worried I am getting interference from others using the same frequency nearby. With me at 100 watts I am probably causing havoc for others as well. I was unaware of receiving a general use itinerate frequency.

I couldn’t tell you what antenna I’m using on the tower. It’s been so long ago that I just don’t remember. I do know that the tower antenna has never been an issue for us. There are seven other farms that use my RTK network. There could be anywhere from 10-40 tractors a day on the network at the same time. But I can tell you that changing the antenna on the tractor to a Laird Phantom eliminated a lot of reception issues for us.
Laird Technologies - 450-470 Phantom Ant. Blk 3dB
Amazon.com

I’m in Southeast Virginia close to the North Carolina line. Our topography is exactly the same as yours. The frequency was coordinated specifically for an RTK system. Same coordination company that did my VHF LMR repeater. There’s a lot of radio waves in my area from a ton of other organizations. The only time I lose signal with RTK is when I’m up against the woods. Even keying up a 45 watt VHF mobile with the antenna 3 feet away from the RTK antenna on the same tractor doesn’t cause me to lose signal. If you have a couple rainy days coming up that keeps you out of the field, you can take a road trip and come see me. I’ll take you to the tower site and you can see what I have. You’re more than welcome to ride a few rounds with me in the tractor and see how it’s set up and how far from the tower some of the farms are. Might have to help me load a few bags of corn seed in the planter, though.

 

[jeepsandradios]

I would think good quality feedline (1/2" or larger) and a quality LMR antenna would eliminate many of your issues. I run 3 GMRS repeaters and all run the DB408 and 7/8" hardline. As said the receiving end is just as important as the base end. So quality antenna on the tractor will make a world of difference as well.

 

[AM909]

Attenuation spec at 450 MHz of 100 ft of LDF4-50A 1/2" Heliax is 1.45 dB. LMR-400 is 2.71 dB. Difference in the current install is probably 1 dB or less? Is Heliax better for other reasons? Sure. Will it solve this problem? I don't think so. (If you do spring for the Heliax, especially for the grain elevator install, pay up for the 7/8" LDF5-50, which is 0.81 dB per 100 ft.)

Could it be interference on this highly-used freq? Maybe. Listening with a $30 BaoFeng could tell you.

4) 45' high using Comet antenna, no amp get about 3 or 4 miles.
5) 45' high using Comet antenna with 100 watt amp I get skippy signal at 7 miles.

If the transmitter is putting out 1.6 W and the only difference between the two scenarios is a barrel connector vs. the amplifier, it really points to the amp not putting out 100 W. For double the distance, the theoretical additional path loss is about 6 dB, meaning an increase from 1.6 W to only 6.4 W. Put another way, if the amp is putting out 100 W, that's 18 dB more than 1.6W. If you got a certain signal level at 3.5 miles, you should get the same signal level 7.9x the distance, or 27.7 miles. Of course, as mmc pointed out, the pesky horizon starts getting in the way at 20 miles, but it still should get more than 7 miles.

That all assumes that everything between the amp and the air is linear – that the feedline and antenna have the same gain/loss at 1.6 W that they do at 100 W. I do recall seeing situations that work fine at low power or receive, but then break down at high-power. Maybe that's what's happening here? Put a tech with a wattmeter at the amp and then the antenna and you might find out.

Could the amplifier be behaving strangely (non-linearly) at different times during the transmission?

[add] I'm assuming there is a way to key the transmitter continuously for testing. Hard to see anything useful during short pulses (how long are they?)

 

[clbsquared]

add] I'm assuming there is a way to key the transmitter continuously for testing. Hard to see anything useful during short pulses (how long are they?)

The RTK radio sends out a time correction every second. The only way to key the amp continuously would be to put a LMR in place of the RTK radio with the same input power and frequency as the RTK radio.
There are also GPS and GLONASS satellites still in play on both the transmitting radio and receiving radio. If either of those sat signals are weak or not there at all, it will lose the RTK signal as well.

 

[clbsquared]

Do you know what model antenna you have? I am going to try some different things when I get a chance. I am worried I am getting interference from others using the same frequency nearby. With me at 100 watts I am probably causing havoc for others as well. I was unaware of receiving a general use itinerate frequency.

When you go into your setup page and select the tripod (RTK base station) tab, can you see your distance from the tower and the voltage at the base station?