I need a little advice from the MSF GURU's you know who you are. All kidding aside I came accross a 110 watt uhf station with several problems most of which have been straightened out with the extra parts I have laying around. The main concern that I now have is the circulator in the P.A. At some point in this stations life it must have burned up the original circulator and someone has added a db products aftermarket. Is this kosher or am I playing with a hand grenade waiting for someone to pull the pin?
Doug
I have to add the station does key at full power
MSF5000 with a strange oddity
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MSF5000 with a strange oddity
May the Schwarz be with you.
The internal one has a thermistor on or near the built-in dummy load, so if it starts getting too hot, the SSCB will cut back the IPA drive power and attempt to save the PA and circulator. I doubt you'll have that with the external unit. Make sure the external dummy load is big enough and that the circulator is mounted to an adequate heat sink.
It should work just fine.
You can run the PA up to its maximum rated power before the circulator. The PA output with its circulator is usually derated by 1-2dB, so the 110w PA would generate about 80 watts out of the circulator. Add their internal duplexer/filter, and you're down to about 55 watts to the antenna. The MSF5000 manuals show you the recommended power levels with single and triple circulators, internal and external, and the duplexer/filter.
Bob M.
It should work just fine.
You can run the PA up to its maximum rated power before the circulator. The PA output with its circulator is usually derated by 1-2dB, so the 110w PA would generate about 80 watts out of the circulator. Add their internal duplexer/filter, and you're down to about 55 watts to the antenna. The MSF5000 manuals show you the recommended power levels with single and triple circulators, internal and external, and the duplexer/filter.
Bob M.
Hello Bob and Al,
Believe it or not there is a thermister attached right at the dummy load and it is wired into the PA whether or not its attached properly inside the PA remains to be seen, I haven't gotten that far yet. I'll do some research on the circulator and see if I can't find out its specs. Currently the station is keying at 94 watts through the low pass harmonic filter (externally duplexed station) I wanted to check and see if this would play out before I do an alignment on the station.
Thanks a bunch
Doug
Believe it or not there is a thermister attached right at the dummy load and it is wired into the PA whether or not its attached properly inside the PA remains to be seen, I haven't gotten that far yet. I'll do some research on the circulator and see if I can't find out its specs. Currently the station is keying at 94 watts through the low pass harmonic filter (externally duplexed station) I wanted to check and see if this would play out before I do an alignment on the station.
Thanks a bunch
Doug
May the Schwarz be with you.
There should be almost no loss through the tubular low-pass filter, so measure the power coming out of that and don't go higher than 110-120 watts at that point. Whatever you get out of the circulator is what you're stuck with.
Sounds like that external circulator was meant for the MSF5000, or someone really knew what they were doing. Nucleus paging transmitters on 900 MHz can have an internal single, or external triple circulator, and I'm sure they run a thermistor in both versions.
By the way, I swept that LPF on my C64 station once - it cuts off around 620 MHz and definitely removes any 2nd or 3rd harmonics.
Bob M.
Sounds like that external circulator was meant for the MSF5000, or someone really knew what they were doing. Nucleus paging transmitters on 900 MHz can have an internal single, or external triple circulator, and I'm sure they run a thermistor in both versions.
By the way, I swept that LPF on my C64 station once - it cuts off around 620 MHz and definitely removes any 2nd or 3rd harmonics.
Bob M.