VXR-7000 poor receiving

[MTS2000des]

I will switch out the LMR400 coax. I am running a 5.26MHz split.

Depending on the model of the duplexer inside, that may be cutting it close. Most flatpacks on VHF require a 6-10MHZ minimum to obtain the rated TX/RX isolation. If it gets 80db I'd be surprised. A good set of duplexers for VHF can cost more than the VXR7000.

Having cut my teeth on VXR7000s on VHF, they are GREAT radios IF you have a good duplexer/filter setup, feedline and decent antenna. As far as your fan running 24/7, the VXR7000U we have as a spare does not do that. It's thermally activated.

People go in debt and spend tens of thousands of dollars to try and obtain an education so they can work in their respective field.

Yep, and sometimes they spend thousands more learning "the hard way", but those lessons usually are not repeated.

I don't want to just burn money but the cost of this education is much more appealing than just paying someone to come out and do it for me.

I get that you want to learn. I just had this very conversation with someone on my ham repeater yesterday who is eager to put a P25 backyard repeater. He, like you, has a thirst for knowledge which is awesome. We need more people such as yourself who actually want to LEARN the why's and how's of RF instead of just writing a check or changing parts.

That being said, there is quite a bit of a black art to making repeaters work, and the ugly truth is that expensive test equipment like a service monitor/tracking generator is really necessary (along with the knowledge to use it!) to do the job RIGHT.

You're on the right path. Hopefully you can find someone in the radio community in your neck of the woods who can come out with his service monitor and show you how and let you drive so you can get the hang of it. It's really not that hard but you do need the car to take round the track!

Good move on dumping the LMR400, it's great cable for base stations, but not repeater (duplex) operation. LDF-50 is a good choice.

 

[BlueDevil]

Thanks for your reply. I will look further into what kind of duplexer I have. I have been looking for a setting in the programming software for the fan. I just can imagine there is a need for it to run continuously. Maybe I have a thermostat that's stuck closed. Do you have any suggestions for a entry level service monitor with tone generator and capable of narrow band?

 

[MTS2000des]

I have been looking for a setting in the programming software for the fan. I just can imagine there is a need for it to run continuously. Maybe I have a thermostat that's stuck closed.

Is your enclosure vented? If it's in a sealed box and the ambient temp is above 90 degrees, that is most likely why the fan runs continuously. It is thermostatically controlled.

Do you have any suggestions for a entry level service monitor with tone generator and capable of narrow band?

an IFR-1600S is a great service monitor w/tracking generator and can be had for $1500-3000 depending on who is selling, condition, calibration, etc. Motorola R2660 is another good choice and plentiful on the surplus market thanks to iDEN being shut down.

Remember a piece of test equipment is only as good as the calibration and the operator.

 

[BlueDevil]

Enclosure is vented and the air temp has been in the mid 70s. I will look into those service monitors.


Cheers,

Brandon

 

[MTS2000des]

Enclosure is vented and the air temp has been in the mid 70s.

Use an IR thermometer and measure the temp through the vents of the heat sink. In mid 70s temps inside a box in the sun can easily get close to 120 degrees.

That's most likely why your fan runs all the time. If it does it on the bench at room temp then it's worth worrying about.

 

[BlueDevil]

Fan runs all the time. I didn't use a IR thermometer but I brought the unit home for more testing and turned it off while it sit in a air conditioned room. As soon as I turned the unit on the fan immediately comes on.

It appears that I must have a significant desense and/or bad receiver problem. When disabling the repeater and disconnecting the duplexer and connecting the antenna straight into the receiver my reception drastically improves...


Cheers,

Brandon

 

[MTS2000des]

It appears that I must have a significant desense and/or bad receiver problem. When disabling the repeater and disconnecting the duplexer and connecting the antenna straight into the receiver my reception drastically improves...

Which indicates the problem is in your feedline, duplexer/filter or combination of both. When the transmitter is off, your receiver is not overloaded. My guess is once you get better feedline and have swept the duplexers and confirmed the tuning, your desense should go away.

 

[BlueDevil]

Replaced the feed line. Don't have equipment to check the tuning of the duplexer or test the sensitivity of the receiver. I will have to send it to the depot or find a shop that can do it for me.


Cheers,

Brandon

 

[MTS2000des]

Replaced the feed line. Don't have equipment to check the tuning of the duplexer or test the sensitivity of the receiver. I will have to send it to the depot or find a shop that can do it for me.

Get rid of the flat pack and get a "real" duplexer, the notch only/reject only designs work poorly especially at the power level your VXR7000 is capable of running at.

Sorry this may not be the answer you want to hear, as good quality BP-BR "cans" for VHF can exceed the cost of your repeater, but if you want a good performing duplex system, they are essential, otherwise you're just headed to nowhere fast.

 

[MTS2000des]

A good article from Tessco about duplexers, how they work, and how to properly care and maintain them.

 

[BlueDevil]

I understand the concept of the duplexer and the different type. Ultimately a set of "cans" would be great. However I built a repeater from scratch using two Icom 5021 VHF radios. I built the interface cable and used a "flat pack" duplexer for filtering. It works extremely well and significant out performs some of the other area repeaters in which techs and engineers installed systems at better/higher elevation locations.


Cheers,

Brandon

 

[BlueDevil]

I think that some or a lot of my problems maybe related to over power noise/RF issues at my repeater site causing my receiver to act deaf.

 

[MTS2000des]

I think that some or a lot of my problems maybe related to over power noise/RF issues at my repeater site causing my receiver to act deaf.

I think you're referring to overhead power lines?
A simple check with a spectrum analyzer will confirm/rule out that theory.

 

[BlueDevil]

How close to power lines (residential or high voltage) does a repeater have to be in order to experience S-8/9 interference?

 

[BlueDevil]

I think that my receiver in the VXR-7000 was being almost completely desensed by RFI produced by my solar panel MPPT charge controller. I have removed the charge controller from the system and there is no more noise. Now I need to find a charge controller with no (or very little) RFI and take the repeater back out there to test the coverage.

See this thread for more info regarding the interference and write up on the solar panel MPPT charge controller equipment.

http://forums.radioreference.com/showthread.php?t=322417


Cheers,

Brandon

 

[jim202]

I think that my receiver in the VXR-7000 was being almost completely desensed by RFI produced by my solar panel MPPT charge controller. I have removed the charge controller from the system and there is no more noise. Now I need to find a charge controller with no (or very little) RFI and take the repeater back out there to test the coverage.

See this thread for more info regarding the interference and write up on the solar panel MPPT charge controller equipment.

Over powering RF at Repeater Site - The RadioReference.com Forums

Cheers, Brandon

I would contact the solar charger vendor and ask then what they are going to do to eliminate the noise to radio systems that their product is causing. This might be a case of the company is not aware of the noise problem. But they have to conform to the FCC rules about generating noise to the radio spectrum with their device.

 

[cmdrwill]

Palomar Engineers