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R2670 RF In/Out Woes

This forum exists for the purposes for discussing service monitors (This includes but is not limited to Motorola, HP, Aeroflex, GD, etc). Additional topics allowed include test procedures, interpretation of test results, where to find information about specific tests, antenna VSWR, return loss testing, duplexer and filter alignment, etc.

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jmfirefighter20
Posts: 171
Joined: Tue Sep 08, 2009 6:47 pm
What radios do you own?: /\/\ AS, APX7000

R2670 RF In/Out Woes

Postby jmfirefighter20 » Sun Jul 16, 2017 9:14 am

Hello All,

I have a "new to me" GD R2670 that I picked up a week ago. Came to me labeled "bad antenna port"....replaced the fuse and good to go.

I've been playing around with a few Quantars and have found that it seems the RF In/Out Port is NOT putting out what it should be, and is not letting RF pass as it should. A Quantar at 20 watts into the RF In/Out port causes the "PA LOW" to come on, if I put a "t" on the port and have a dummy load connected I get "PA FULL". My Bird shows about 20 watts, but the R2670 input numbers don't jive, they are too low, like -10 dBm.

Same thing if I generate out the port, both of the Quantars open up at -60 output....not jiving for sure.

I'm assuming something is wrong with the port. I don't have the service manual...is there a fuse hanging out in there too, or something I should check internally for connection?

Thanks gurus.

Josh
Joshua
W1DPT
Raymond, NH

mac1_131
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Joined: Mon Dec 08, 2008 3:20 pm

Re: R2670 RF In/Out Woes

Postby mac1_131 » Sun Jul 16, 2017 9:53 am

Ohm out the port should read 50 ohms? I'm not really that familiar with the R2600s but most service monitors have a flat substrate 50 ohm attenuator maybe that's blown?

jry
Posts: 315
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Re: R2670 RF In/Out Woes

Postby jry » Sun Jul 16, 2017 11:27 am

the RF I/O input pad is blown in most cases....about 99% sure just based on your issues.

$$$$$$$$

jmfirefighter20
Posts: 171
Joined: Tue Sep 08, 2009 6:47 pm
What radios do you own?: /\/\ AS, APX7000

Re: R2670 RF In/Out Woes

Postby jmfirefighter20 » Sun Jul 16, 2017 11:44 am

I should have gotten ambitious before I posted......

I took the screws off the RF I/O connector and the darn thing fell out. Looks like there is a little "ribbon" of metal that connects the center pin to the I/O unit, and it was broken. Took the bottom of the monitor off, and the cover of the I/O unit. A little solder, heat, and lining the pieces back up, and the RF I/O port is back in business. My Bird and the monitor jive, and the quantar now opens up at -120.

I noticed that the center pin of the RF I/O was sticking out too far, so I pushed it back in. My theory is that someone got a little rough with the unit, breaking that ribbon. Looks like I got lucky.

Thanks for the input...hopefully someone else can use this info!

Josh
Joshua
W1DPT
Raymond, NH

jry
Posts: 315
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Re: R2670 RF In/Out Woes

Postby jry » Mon Jul 17, 2017 5:39 am

you were very lucky ...I have only seen a broken input connection on an R26XX one other time.

Usually the input pad fails due to the duty cycle being exceeded and just the overall thermal stress on the device.

Be very careful on testing high powered devices ...my rule is to NOT connect them directly to any service monitor since it's easy to loose track of how much TX on time and in general these devices have aged and been thermally stressed to start with.

Most service monitor input pads are non standard values , difficult to obtain , expensive and require re-calibration after replacement. The R26XX is no exception and actually the worst when it comes to this situation.

jmfirefighter20
Posts: 171
Joined: Tue Sep 08, 2009 6:47 pm
What radios do you own?: /\/\ AS, APX7000

Re: R2670 RF In/Out Woes

Postby jmfirefighter20 » Mon Jul 17, 2017 9:40 am

I always turn down the power or use a pad into the monitor....no exceptions!
Joshua
W1DPT
Raymond, NH

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d119
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Re: R2670 RF In/Out Woes

Postby d119 » Mon Jul 17, 2017 12:57 pm

jmfirefighter20 wrote:I noticed that the center pin of the RF I/O was sticking out too far, so I pushed it back in. My theory is that someone got a little rough with the unit, breaking that ribbon. Looks like I got lucky.

Josh


I have personally (recently) broken two RF I/O connectors on two separate R2600 monitors. It was due to using LMR400 type coax directly on the monitor with many connect/disconnect cycles in a very short amount of time. Same thing happened - Center conductor pulled out, everything broke. Sent them in for repair.

I'd HIGHLY suggest when using coax of any real thickness on one of these monitors, you throw a 90 degree connector on the RF I/O port and let THAT get broken.

jmfirefighter20
Posts: 171
Joined: Tue Sep 08, 2009 6:47 pm
What radios do you own?: /\/\ AS, APX7000

Re: R2670 RF In/Out Woes

Postby jmfirefighter20 » Tue Jul 18, 2017 7:15 am

d119 wrote:I have personally (recently) broken two RF I/O connectors on two separate R2600 monitors. It was due to using LMR400 type coax directly on the monitor with many connect/disconnect cycles in a very short amount of time. Same thing happened - Center conductor pulled out, everything broke. Sent them in for repair.

I'd HIGHLY suggest when using coax of any real thickness on one of these monitors, you throw a 90 degree connector on the RF I/O port and let THAT get broken.


During my inspection and repair of the RF I/O, it certainly appears to be a pretty "cheap" design. A super thin, fragile piece of metal connecting the center pin to the pad. Almost like it was set up for failure.......
Joshua
W1DPT
Raymond, NH

jry
Posts: 315
Joined: Fri Feb 06, 2004 3:14 pm

Re: R2670 RF In/Out Woes

Postby jry » Tue Jul 18, 2017 10:11 am

the N connector and bracket are actually part of the input attenuator assembly which Motorola OEM'd from a couple of vendors.

The actual pad connections were really intended for a rigid PCB and not intended to tolerate any flex you get from the N connector.

Guess using an inline 20db pad would avoid both the flex issue and exceeding the duty cycle.

Better to blow or break the $40 pad than the RF I/O module

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d119
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Re: R2670 RF In/Out Woes

Postby d119 » Sat Jul 22, 2017 8:32 am

jry wrote:the N connector and bracket are actually part of the input attenuator assembly which Motorola OEM'd from a couple of vendors.

The actual pad connections were really intended for a rigid PCB and not intended to tolerate any flex you get from the N connector.

Guess using an inline 20db pad would avoid both the flex issue and exceeding the duty cycle.

Better to blow or break the $40 pad than the RF I/O module


Hence my suggestion of just using a 90 degree adapter (or two if necessary) to avoid working with the N connector too much.

Thinking about it, an N to BNC would be even more ideal, just deal with the required cable changes. That's what I do on my R2014D/HS.


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