MTR3000 Reference Sync - Generating a clock for annual calibration on IFR 1200s

[leopoldocosta]

Greetings!

I'm maintaining a Motorola MTR3000 Base Station Repeater. I've tested it for with every single troubleshooting available in Motorola detailed and basic service manual. Finally what is left is that i recalibrate it providing a clock reference to its SCM board.


Anyway's, i've two service monitor: a HP 8920b and an IFR 1200s. As far as i know both generate signals, but only the 1200s is able to generate Motorola MTR3000 required signal wich is: 10Mhz with 3v peak-to-peak, sine or square wave.

I'm having some difficulty with this 1200s, trying to generate the signal. A helpful tip would be welcome. Is anyone here used to operate this service monitor?

 

[kf8yk]

I don't think your service monitor has enough drive for this application. The IFR 1200s signal generator tops out at -20 dBm, which equates to only 63 mV peak-peak.

IFR offered option 5 which added a 30 db external amplifier to the service monitor, increasing the generator output to +10 dBm. Here's a link to a modern replacement that's still available for purchase: W6KCS IFR Amplifier

 

[Project25_MASTR]

You need 2 Vpp is what the service manual on the MTR3000 specs (up to 5 Vpp). What has worked for me, 10 Mhz at 5 dBm with an R8000 but one day I'd love a device that was actually geared for alignment via the reference.

 

[leopoldocosta]

kf8yk
Thanks for the reply. Was very clarifying. If i convince my boss about purchasing this IFR Amplifier by Steve, what would be the steps to configure the 1200s? I got very confused when reading its manual.




MCore25
1- I have a Tektronix CFG253 that provides up to 3Mhz. Would it do the job?
2 - What did you mean about the geared device? I failed to understand.

 

[kf8yk]

kf8yk
Thanks for the reply. Was very clarifying. If i convince my boss about purchasing this IFR Amplifier by Steve, what would be the steps to configure the 1200s? I got very confused when reading its manual.

[RF] [0] [1] [0] [.] [0] [0] [0] [0] [ENTER], rotate MODULATION to FM NAR, rotate MODE switch to GEN, turn GEN LEVEL to desired level.

Make sure any modulation sources are off (tone generators, DCS, etc.)

The amplifier just plugs into the T/R port, no other setup is needed, you just mentally add 30 dB to the gen level markings.

 

[Firebuff880]

Aeroflex 8800sx I think has the reference capability as a feature code.

 

[TampaTyron]

I was looking at the inexpensive gpsdo kits on eBay. Maybe it is a reasonable choice for your application? TT

 

[cmdrwill]

I don't think your service monitor has enough drive for this application. The IFR 1200s signal generator tops out at -20 dBm, which equates to only 63 mV peak-peak.

IFR offered option 5 which added a 30 db external amplifier to the service monitor, increasing the generator output to +10 dBm. Here's a link to a modern replacement that's still available for purchase: W6KCS IFR Amplifier

I purchased one of the W8KCS amplifier for our IFR500's last week. I can say this is an excellent amp, well designed, and works better that the old IFR amp. Very fast shipping. Well worth the price.
Altho + 11 dBm may not get enough output to do the MTR3000 Ref Sync. Works great for tuning duplexers and filters.

 

[RFI-EMI-GUY]

Try this;
Connect a cable to the back of your HP8920B to the 10 MHz reference output. It should generate > 0.5VRMS which is about 1.42 V P-P and more than you have tried thus far..

10 MHz REF OUTPUT
This connector furnishes a 10 MHz reference for external instruments.
Operating Considerations
Waveform = sinewave
Output frequency = 10 MHz
Output level >0.5 V rms
Output impedance approximately 50 Ohm.
NOTE: The reference output frequency is always 10 MHz, independent of the selected input reference
frequency.

If you need more signal, you can use a video distribution amplifier like used to connect several video cameras to a monitor. Be careful though as the BNC's on a video amp will be 75 Ohm, there may be some mechanical problems properly mating. You might need to make up some cables.

 

[zz0468]

Doesn't your 8920b have a 10mhz reference output on the rear panel?

Edit: Oops. Shoulda read RFI-EMI-GUY's post first.

I've used that to reference Quantars, MSF5Ks and MTR2Ks. It should work fine.

 

[Project25_MASTR]

Try this;
Connect a cable to the back of your HP8920B to the 10 MHz reference output. It should generate > 0.5VRMS which is about 1.42 V P-P and more than you have tried thus far..

10 MHz REF OUTPUT
This connector furnishes a 10 MHz reference for external instruments.
Operating Considerations
Waveform = sinewave
Output frequency = 10 MHz
Output level >0.5 V rms
Output impedance approximately 50 Ohm.
NOTE: The reference output frequency is always 10 MHz, independent of the selected input reference
frequency.

If you need more signal, you can use a video distribution amplifier like used to connect several video cameras to a monitor. Be careful though as the BNC's on a video amp will be 75 Ohm, there may be some mechanical problems properly mating. You might need to make up some cables.

This is the problem I've always had with using the reference output on the R2600 and R8000 series service monitors. They don't output enough on the reference for the repeaters to recognize. Makes me think about checking prices on amplifiers at Mini-Circuits.

 

[RFI-EMI-GUY]

Don't blame the test equipment. Motorola should have increased the gain of their reference calibrator to match readily available portable sources. Or simply put manual access to the calibrator DAC in the tuner software.

This is the problem I've always had with using the reference output on the R2600 and R8000 series service monitors. They don't output enough on the reference for the repeaters to recognize. Makes me think about checking prices on amplifiers at Mini-Circuits.

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