A=frequency 1 B=frequency 2 Formula for your frequency products is 2A+b, 2A-B, 2B+A, 2B-A. Simple math!
-----Original Message----- From: mch [mailto:[EMAIL PROTECTED] Sent: Sunday, April 18, 2004 16:46 To: [email protected] Subject: Re: [Repeater-Builder] Re: Is there a relationship between 147.225 and 146.925? Michael Singewald N1PLH wrote: > > First...Wow, you guys are FAST! I cannot believe how many responses > in 15 minutes! Thank you all very much. > > The 147.225 has input 147.925 and the 146.925 has input 146.325. Actually, your input should be 147.825 for 147.225 out. To be honest, I didn't follow Ken's math. Must be that west coast version. ;-> Here is how I add it up: 2A-1B: 147.225 + 147.225 - 146.925 = 147.525 146.925 + 146.925 - 147.225 = 146.625 (these are both OK unless you mix the results with the outputs, as each are 600 kHz off the TX of the other repeater) 3A-2B: 147.225 + 147.225 + 147.225 - 146.925 - 146.925 = 147.825 (sound familiar?) 146.925 + 146.925 + 146.925 - 147.225 - 147.225 = 146.325 (again, sound familiar?) Each of these cases results on the two TXs mixing and ending up with products on the inputs of the other. > I don't understand the problem with the small difference in transmit > frequency. The transmit frequency is still about 1 meg away from the > receive frequency of the other repeater. How far apart in frequency > would they ahve to be to co exist while running relatively low power? It's not how far apart they are - it's the math associated between them. The mixing products are killing you, not the signal strength. You can have a 5 MHz TX and a 440 MHz TX mix and end up with a product (3A-2B) on the 440 input, and those are 435 MHz apart! I don't know how the guy in Colorado put on 440 repeaters with WWV so close out there. Similarly, 600 kHz signals are bad for 2M repeaters, 1.6 MHz signals are bad for 220, just about everything is bad for 6M depending on where you live ;->, Etc. > I don't think a different frequency will be possible since all seem > to be taken. Another location is always a drag as well. It may be a drag, but may be the easiest solution. One case in my area had two repeaters that are about 20 miles apart had a very similar problem. I think the frequency outputs were 146.670 and 147.270 MHz. Again, 2B-1A was killing them. The solution on that case, I think, was to change to a BPBR duplexer rather than a notch duplexer. Joe M. Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
