This may sound very beginner but I have never done any alignments on 12.5KHz, all my work has always been 25KHz. So here it goes:
I'll start by asking if my thoughts are on the right track. The service monitors I will be using are IFR1200SS'. Will these service monitors work with 12.5KHz (do I just have to turn down the deviation to 1.5KHz instead of 3KHz)?
System is a conventioal analogue 12.5KHz VHF repeater system, with a 25KHz UHF Link attached to the repeater.
So basic check of the repeater, I will inject a 1KHz test tone deviated at 1.5KHz into the repeater receiver and make sure that I get the same thing out of the transmitter?
The next step will be to inject the 1KHz test deviated at 1.5KHz into the repeater receiver and then adjust my link to get 1KHz test tone with 3KHz deviation out of the link?
The next step will be to inject 1KHz test tone deviated at 3KHz into the Link receiver and then adjsut my link to get 1KHz test tone with 1.5KHz deviation out of the repeater Tx?
Does any of this sound correct, am I on the right track? Your thoughts and suggestions would be much appreciated!!
Thanks,
Jamie
12.5KHz Alignment Help - Never done it before
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12.5KHz Alignment Help - Never done it before
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Re: 12.5KHz Alignment Help - Never done it before
Sounds pretty reasonable to me, but:
1) Watch out for subaudible tones screwing up your deviation measurement: if you have a PL on output it will add to the deviation measured, so you will need to filter the input to the deviation meter.
2) Also check for compression/deviation limiting: make sure that if you TRY to cram a 3kHz deviation signal into your system it will correctly limit the deviation going out.
3) As a corollary to #2, make sure you aren't going into deviation limiting when you make your measurements: insure that if you decrease the deviation from 1.5kHz to 1kHz that the output tracks.
1) Watch out for subaudible tones screwing up your deviation measurement: if you have a PL on output it will add to the deviation measured, so you will need to filter the input to the deviation meter.
2) Also check for compression/deviation limiting: make sure that if you TRY to cram a 3kHz deviation signal into your system it will correctly limit the deviation going out.
3) As a corollary to #2, make sure you aren't going into deviation limiting when you make your measurements: insure that if you decrease the deviation from 1.5kHz to 1kHz that the output tracks.
This is my opinion, not Aeroflex's.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
Re: 12.5KHz Alignment Help - Never done it before
Yep, you have it right. Wowbanger has some good info. I like to slowly turn up the deviation to make sure that you are not into limiting. Wideband (25 kHz) should not limit until close to 4.5 Khz dev, narrowband (12.5 kHz) should not limit until about 2.2 kHz.
Wideband max deviation is +/- 5 kHz, Narrowband max deviation is +/- 2.5 kHz
Wideband PL (CTCSS) is 500 to 850 Hz deviation (I aim for 700 Hz), Narrowband is 400 Hz deviation.
Also a good idea to check the repeater is contant deviation at sevel frequencies. At a minimum, inject a 500 Hz, 1000 Hz at 2000 Hz tone. Should be close to flat at all 3 freqs.
Wideband max deviation is +/- 5 kHz, Narrowband max deviation is +/- 2.5 kHz
Wideband PL (CTCSS) is 500 to 850 Hz deviation (I aim for 700 Hz), Narrowband is 400 Hz deviation.
Also a good idea to check the repeater is contant deviation at sevel frequencies. At a minimum, inject a 500 Hz, 1000 Hz at 2000 Hz tone. Should be close to flat at all 3 freqs.