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Old 04-09-2016, 3:00 PM
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Default Problem with FR4000 radiating noise

I bought a used FR4000 and just hooked it up to my antenna. Everything seems to work ok except the repeater keeps opening my HT squelch on the TX channel (when the repeater is not transmitting) if I am within about 20-30ft of the unit even through a wall. The antenna is on top of a 40ft tower and I am using Heliax so I am pretty sure it is the FR4000 box itself and it opens the HT squelch even when the repeater is not transmitting (TX LED off). It is not spurious environment noise because if I turn the FR4000 off the HT goes quiet, if I turn the FR4000 back on the HT squelch opens and I get white noise (but again the repeater does not indicate that it is transmitting). When I key up the repeater everything works as expected (and the TX light comes on). My HTs are ICOM F60's by the way (it is the same on multiple HT units). I do not have this problem with them and my GR1225, just the "new" FR4000.

I can turn the HT squelch WAY up and it will stop, but I need the HT to work in proximity to the repeater and at range so a high squelch is not ideal.

Again, I don't have this issue with the GR1225 when it is on and connected to the same antenna system in the same freq range, so I am uncertain if this is normal for a FR4000 or not. Or is there some issue? Any ideas?

Edit: For what it is worth, I tried some Beofeng HTs and it does the same thing. If I am within a room or so of the repeater the HT squelch intermittently, but frequently, opens on the HT RX channel (repeater TX) and nothing but noise. As far as I can tell the repeater housing is radiating on the TX channel even when it is not officially transmitting.

Thanks

Last edited by LakeMan2; 04-09-2016 at 3:29 PM..
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Old 04-09-2016, 5:07 PM
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"As far as I can tell the repeater housing is radiating on the TX channel even when it is not officially transmitting."

The transmitter VCO runs all the time and does radiate some signal due to poor shielding. Why do 'some' manufactures do this? So the start up and lock time for the TX VCO is eliminated on transmit.
Some repeaters need to have a idle freq set in the transmitter programming section.
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Old 04-09-2016, 6:55 PM
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Interesting...Thanks. I had the seller program it for me as I am waiting on the software to ship to me. I don't know (and can't look at the programming section yet) if the FR4000 needs a different idle freq set or not. I will have to look into that. Hopefully that is it.

If you can't set a different idle freq and it does radiate some signal due to poor shielding that will be a show stopper. I need to be able to operate an HT in near by rooms and right now you can't without the squelch going on and off (and sometimes staying on) very annoyingly.

Thanks

Last edited by LakeMan2; 04-09-2016 at 7:25 PM..
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Old 04-10-2016, 1:33 PM
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They all do that. I've seen it many times. Actually, EVERY FR3000/4000 I ever had anything to do does this.
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Old 04-10-2016, 3:51 PM
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Quote:
Originally Posted by ElroyJetson View Post
They all do that. I've seen it many times. Actually, EVERY FR3000/4000 I ever had anything to do does this.
I guess the question is, if there is anything that can be done about it on the FR4000? I am pretty much stuck with the location of the repeater and I need to be able to use a HT in the rooms around it. Right now the issue with it opening the HT squelch, and sometimes keeping it open, even when no transmission makes it not usable.

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Old 04-10-2016, 4:39 PM
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Did you put a Tone in your handheld radio receiver?
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Old 04-10-2016, 5:21 PM
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Quote:
Originally Posted by cmdrwill View Post
Did you put a Tone in your handheld radio receiver?
No, I do not, and have not, used any tones (PL or DPL). The system is out in the middle of no where and there is no competing traffic so I have always had TX and RX tones blank. That plus the users have a bad habit of talking as soon as they press the button, and I have read that tones slightly delay transmission/reception.

But I guess you are right. If I at least use a tone on the HT RX (repeater TX), that should keep the HT squelch from opening due to the nearby noise generated by the repeater.

I was also thinking maybe putting the repeater is some sort of shielded cage, but a tone would certainty be much easier.


Thanks
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Old 04-12-2016, 10:47 AM
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After continuing to look into this more, I would rather not use a tone if I don't have to. I would rather avoid any possible encode/decode issues etc.

While I am still waiting on the software I have been doing some research online and found some programing documentation with screen shots and have not seen any evidence of a idle freq. I suspect that is a Motorola thing.

What is interesting is that in the service manual I did find reference to a TX VCO reference freq (which can only be adjusted with a freq counter). That might be the ICOM equivalent of an idle freq. But for my unit (FR4000-3), according to the service manual that should be at 450.2750. If that is the same as an idle freq, it should not be radiating noise in the 463 range. Unless people routinely adjust that closer to their TX freq. Maybe the previous owners moved it up, I don't know. More work to do.
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Old 04-12-2016, 4:30 PM
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The "TX VCO reference frequency" usually refers to the master reference oscillator. That is the reference that the phase lock loop uses to 'make' the repeater's transmit frequency. Most Ref oscillators are in the 16 mHz range.So you would not want to mess with that as it will not help the "radiating noise" which IS the repeater's TX VCO's output.

" If I at least use a tone on the HT RX (repeater TX), that should keep the HT squelch from opening due to the nearby noise generated by the repeater." That may be the only answer.
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Old 04-13-2016, 3:15 PM
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Copper tape around the radio might help. I used to to a lot of EMI compliance work and copper tape was the first line of defense. If you can't get your hands on copper tape, you can probably find aluminum tape (almost as good, but not quite) anywhere that heating system supplies are sold (I bought several rolls on ebay a while back).

Even wrapping grocery store aluminum foil may help a little.

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Old 04-16-2016, 7:43 PM
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While I technically could not make the FR4000 stop radiating the TX freq noise. I did stop it from getting past the unit. I got some copper mesh and put it around the unit and made sure it was grounded to the chassis/antenna ground. That seems to keep it from getting out enough. The squelch on my HTs no longer open up in the next room even with no tone, so that is good.
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Old 04-16-2016, 7:51 PM
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I was going to say, either you need to RF shield the repeater or unplug it and put something else in its place. All FR3000/4000s radiate via the local oscillator and are not well enough shielded to stop the described issue from happening.

I actually found it kind of useful because if my radio unsquelched when I got near the repeater that needed a service call, then I immediately knew that at least SOME of it was working.
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Old 04-17-2016, 10:57 AM
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Quote:
Originally Posted by ElroyJetson View Post
...put something else in its place.
I would not mind doing that, but I can't afford to trial and error like this over and over again. I did my research on the ICOM repeaters before I bought it and none of this came up. Now I got the unit fairly cheap so it was worth trying anyway. I bought it to replace a GR1225, that while it did not have the problems the ICOM has , is getting harder and harder to program. The computer I had to program the GR1225 quit and it is getting hard to keep a system old enough to program it. The ICOM at least I can program with my win7/8.1 laptop and will be able to do that for some time now.

This is probably a topic for another thread but I use the repeater for private family use out in the country to cover people as they roam over ~ 14 sq miles of trees and rolling hills. Due to topology I only get ~ 1 mile with HTs alone. With the repeater dead center that means ~ 7 mile radius. Since it is just private family use it is hard to justify paying high dollar for a new system that may or may not have similar issues. I have not seen much on line when it comes to any of the repeater brands and shielding for example.

I have looked at Vertex 7000s, Motorola MTD2000, etc, but they all are more expensive and no guarantee that they don't have their issues. And I need to be able to get the software and program it (which might be an issue with newer Motorola's).

So, having said that, if someone knows of a specific older UHF/50W manufacturer/model system (analog is fine don't need digital) that may sometimes be available on the used market, that software is readily available at a reasonable price, can run on current computer systems, and is "better" than the ICOM FR series with better shielding, sensitivity etc, I am open to suggestions.

Thanks

Last edited by LakeMan2; 04-17-2016 at 11:18 AM..
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Old 04-17-2016, 3:31 PM
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GR1225/R1225 program in Win XP. Check your latest and so called greatest OS for a compatibility mode.

Elroy, it is NOT the 'local oscillator',

So it does look like you need a tone on the receive in your radio...
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Old 12-04-2017, 10:04 PM
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I have a couple FR4000 repeaters that are having a similar type issue. The issue I am experiencing is that the transmitter will randomly key as if it is in a really noise or spurious location. However they are not. They are at separate locations and I have noticed this occurring without any equipment attached to the repeaters. I wanted to continue to observe this so I did put a 150watt dummy load on the transmitter side.

I have the manual squelch dial turned up all the way along with the internal digital squelch turned up all the way (255) and it seems to have stopped.

Is this normal for these repeaters? What is the solution? Is there a combination of squelch dial and digital internal squelch that is recommended?
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Old 12-04-2017, 10:30 PM
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You DO have a CTCSS enabled on RX?
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Old 12-04-2017, 11:35 PM
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Quote:
Originally Posted by cmdrwill View Post
You DO have a CTCSS enabled on RX?
Yeah, actually I do have a MultiTone Table setup. Maybe that is part of my problem?
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Old 12-05-2017, 7:02 PM
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Check your firmware revision. It seems to me in the past we ran across this issue, and flash updated firmware fixed the problem. The earlier units had an issue that was related to what you're experiencing.

Keep in mind, if it's a 1.0 firmware, it cannot be flashed to newer firmware. Has to be 1.1 and above. It requires a special cable (or modified cloning cable) for firmware just FYI.
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Old 12-05-2017, 11:24 PM
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I just checked and one of the FR4000 repeaters that I am having issues with has Firmware 1.5 It appears that the most current Firmware version is 1.6 however I need to find the OPC-1211 flashing cable before I can flash the repeater with the latest firmware.
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Old 12-07-2017, 2:41 PM
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I believe I might be narrowing down the issue. Right now the repeater is set to use a few CTCSS and DCS Tones. I do not have mixed CTCSS and DCS transmit and receive tones however I am running a mixture of CTCSS and DCS in the MultiTone Table.

The FR4000 that I have at the house has a Firmware version of 1.5. The latest Firmware update is 1.6. I am in the process of ordering a Flashing Cable.

I have tried several slightly different programming configurations to see if I can narrow down the issue. When using only CTCSS Tones in the MultiTone table the problem seems to almost or completely resolve. I will post a screen shot of the repeaters randomly transmitting behavior a little later.
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