UHF Saber 11 - Receive Deaf - 20dB down

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g8tzl2004
Posts: 1128
Joined: Wed Sep 08, 2004 10:13 am

UHF Saber 11 - Receive Deaf - 20dB down

Post by g8tzl2004 »

I have recently acquired four UHF Saber 2 radios - all in really nice condition - I think they were only used for "emergency" use.

All work except one Saber is about 20dB down on RX. TX is OK so its not an antenna issue.

Any ideas?

The front end pre-amp provides 10dB of gain so I think its more than just the RF amp module - maybe filter issues?

Thanks
RFguy
Posts: 1357
Joined: Wed Dec 21, 2005 6:17 am

Re: UHF Saber 11 - Receive Deaf - 20dB down

Post by RFguy »

Is the power output OK?
g8tzl2004
Posts: 1128
Joined: Wed Sep 08, 2004 10:13 am

Re: UHF Saber 11 - Receive Deaf - 20dB down

Post by g8tzl2004 »

Yes, TX power output is OK - same as one of the other radios.

I think there is no front end alignment in the UHF Saber 2 so I don't think its an alignment issue?

The radio is also on frequency (or near enough..maybe 500Hz out..so I do need to adjust the ref osc but all the other radios are 500Hz + out..I guess its expected for old radios at UHF...I've seen worse!!
RFI-EMI-GUY
Posts: 51
Joined: Fri Jun 02, 2006 7:23 pm

Re: UHF Saber 11 - Receive Deaf - 20dB down

Post by RFI-EMI-GUY »

Are you testing the radio through the option connector and proper programming and servicing cable or "off the air" using the antenna? If via the antenna, there is a possibility that the antenna connection to the mother board is poor. It is via a spring clip. It can get noisy or intermittent. You will have to carefully tear down the control top from the chassis (screws and cables) to fix.

I would also suggest it may be the filter detector switch module (FDS). Make sure the metal clip is in place and the module seated correctly. You can easily swap the module with one from another radio.

Does the radio have the proper modules for the frequency band that you are programming? What frequency band are you using the radios in and what are the numeric suffixes on the modules inside the radio?

Example:

Synthesizers
NLE9461x = 403-433 MHz "Government" split
NLE9462x = 440-470 MHz

Receivers
NLE9431x = 403-433 MHz. Government. split
NLE9432x = 440-470 MHz.

Filter Detector Switch
NFE6061x = 403-470 MHz. Government. split
NFE6062x = 470-512 MHz

Power Amplifiers
NLE9471x = 403-433 MHz High Power 5W Government. split
NLE9472x = 440-470 MHz High Power 5W

x = revision

Here in the US the 440-470 band is most useful, 403-433 MHz ? I got plenty.
TV DINNER BY THE POOL, IM SO GLAD I FINISHED SCHOOL. FZ
N4KVE
Posts: 1647
Joined: Wed Apr 02, 2003 10:35 am
What radios do you own?: APX XTS XTL TRBO 900MHZ

Re: UHF Saber 11 - Receive Deaf - 20dB down

Post by N4KVE »

RFI-EMI-GUY wrote:
Does the radio have the proper modules for the frequency band that you are programming? What frequency band are you using the radios in and what are the numeric suffixes on the modules inside the radio?
This right here. Many times the wrong module was used to get a radio back on the air right away. I would check this out before proceeding any further. GARY
WB6NVH
Posts: 270
Joined: Tue Apr 19, 2005 5:08 pm

Re: UHF Saber 11 - Receive Deaf - 20dB down

Post by WB6NVH »

As the above say. I think you really need the service extension cable so that you can say what the SINAD sensitivity is. If I remember correctly it's part of the stock original Moto programming cable. Going from there, it gets a bit tricky. I had one Saber receiver that was great on the bench with the cable but on its own was rather deaf. Turned out the antenna to board interconnection path was not making good or any contact, so that it looked good on test but not in the real world. And of course since the radio is new to you, check for the right receiver and FDS board as they are saying above. I have gotten several parts queen Sabers in recent years at flea markets that had a mish-mash of wrong or bad modules stuffed in them. At least they were just a few Dollars...
g8tzl2004
Posts: 1128
Joined: Wed Sep 08, 2004 10:13 am

Re: UHF Saber 11 - Receive Deaf - 20dB down

Post by g8tzl2004 »

Thanks for the feedback.

The radio is currently on around 456 MHz - so I don't think it will be a 403 - 433 MHz RX module - will the RX VCO lock 23 MHz out of band? I guess I can try programming in a 433 MHz freq and testing sensitivity.

I've just been using the antenna to carry out simple tests. I have an external antenna connector but the Saber accessory cover uses a "security" screw as its an FM IS radio - somewhere I have the correct tool but I will need to find it - I guess that will help determine if its an antenna spring clip issue....but the TX works perfect. Identical TX output using a "relative" signal strength meter and an identical radio on the same frequency.

I worked out the RX dB loss using inline 10, 15, 30 dB attenuators and a low level signal source.

As you say, Sabers now cost just a few $ ...mint condition but no batteries although I already had some batteries
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