I've been tuning a bunch of UHF MSR-2000 exciter boards from scratch, and, I've noticed an anomaly. I'm wondering if others have seen it.
After presetting the boards, it is virtually impossible to figure out where the oscillator and first multiplier start because of extraordinarily low readings on the Moto test sets. Even when I do get them moving, the Moto test set is worthless. I have to use a voltmeter (or very sensitive microammeter) to get any usable readings in meter position 1. Even when all is well with the board, it is barely more than a few needle widths.
All of these boards are right at the edge of the range, but, end up with rated power and are clean.
Any thoughts? Since they seem to work, I don't see much need to go poking around with components, but, what a pain in the butt at a site.
Rob
MSR-2000 UHF Exciter Tune-up Issue
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The MSF5000 receiver injection filter is the same way. If you're moving the unit more than a few MHz, you start from scratch. Tuning any coil gives you at best one uA on a 50uA scale, so you have to really look to find it. Once you get one of the coils to give a slight motion, you can go to another and get a lot more, etc. Eventually you get up to 25-30uA and you are done.
I suspect this is just normal for a lot of equipment. Luckily a complete retune in the field is a rare occurance.
Another way to deal with this is to preset the slugs, then turn each one 1/2 turn, in sequence, until you get something visible on the meter. If everything is working properly, you'll see something eventually and will then be able to properly tune the rest.
Of course, there are the few radios where you have to sneak up on the tuning, one slug at a time, without going too far, and then using just one pass. If you go back and try to peak them again after tuning them all, you end up chasing your own tail and have to start all over again. When they give you a step-by-step procedure and say not to repeat, they mean it.
Bob M.
I suspect this is just normal for a lot of equipment. Luckily a complete retune in the field is a rare occurance.
Another way to deal with this is to preset the slugs, then turn each one 1/2 turn, in sequence, until you get something visible on the meter. If everything is working properly, you'll see something eventually and will then be able to properly tune the rest.
Of course, there are the few radios where you have to sneak up on the tuning, one slug at a time, without going too far, and then using just one pass. If you go back and try to peak them again after tuning them all, you end up chasing your own tail and have to start all over again. When they give you a step-by-step procedure and say not to repeat, they mean it.
Bob M.
Same with several older stations.
I often use the service monitor tuned to the osc freq or the desired multiples thereof, and a coax with the shield cut back about 6 inches to "sniff" for the desired signal. As in the above post, once you get the first couple of coils tuned, you can find it on the meter.
I often use the service monitor tuned to the osc freq or the desired multiples thereof, and a coax with the shield cut back about 6 inches to "sniff" for the desired signal. As in the above post, once you get the first couple of coils tuned, you can find it on the meter.
Re: MSR-2000 UHF Exciter Tune-up Issue
Shouldn’t you be using meter position 3 (M3) for tuning the multiplier and injection filters instead of M1?rodell wrote:I've been tuning a bunch of UHF MSR-2000 exciter boards from scratch,
After presetting the boards, it is virtually impossible to figure out where the oscillator and first multiplier start because of extraordinarily low readings on the Moto test sets. Even when I do get them moving, the Moto test set is worthless. I have to use a voltmeter (or very sensitive microammeter) to get any usable readings in meter position 1. Even when all is well with the board, it is barely more than a few needle widths.
All of these boards are right at the edge of the range, but, end up with rated power and are clean.
Any thoughts? Since they seem to work, I don't see much need to go poking around with components, but, what a pain in the butt at a site.
Rob
Nand.
Re: MSR-2000 UHF Exciter Tune-up Issue
I see now that you are dealing with the exciter and not the receiver. So my comment does not apply here.Nand wrote:Shouldn’t you be using meter position 3 (M3) for tuning the multiplier and injection filters instead of M1?rodell wrote:I've been tuning a bunch of UHF MSR-2000 exciter boards from scratch,
After presetting the boards, it is virtually impossible to figure out where the oscillator and first multiplier start because of extraordinarily low readings on the Moto test sets. Even when I do get them moving, the Moto test set is worthless. I have to use a voltmeter (or very sensitive microammeter) to get any usable readings in meter position 1. Even when all is well with the board, it is barely more than a few needle widths.
All of these boards are right at the edge of the range, but, end up with rated power and are clean.
Any thoughts? Since they seem to work, I don't see much need to go poking around with components, but, what a pain in the butt at a site.
Rob
Nand.
Nand.