[Repeater-Builder] Cable lengths
Here's an excerpt from a TX RX publication that ties in with this discussion Adverse cable length between Duplexer and transmitter using varactor or broadband hybrid combining type transmitter outputs. Even though the Duplexer VSWR is flat on frequency, the reflected impedance of the Duplexer off resonance, transformed by changing cable lengths, can cause parasitics to be generated. Change the length of cable between the transmitter and duplexer, traversing through a half wave in increments of between 1 and 2 inches until the desensitization ceases or is minimal. A ferrite isolator will also cure this condition when it is installed between the transmitter and duplexer. However, this is a much more expensive remedy. Chuck WB2EDV
[Repeater-Builder] Cable lengths again
Have a Phelps Dodge 526 UHF duplexer that's missing the cables from the tee to the cans. Google came up with one vague reference where someone thought these cables were 12 inches long. Is there a chart or formula somewhere to determine their proper length? Thanks, Al, K9SI
Re: [Repeater-Builder] Cable lengths again
Good timing, I just now have one on the bench tune up. This 526 was originally on 454/459MHz. Both cables from the tee to the cans are 12 inches. This is measured from the far end of the N connector on both ends. In other words, it includes the length of the N connector. The 2 cables are Intercomp RG-214/U, so if you use something else you will have to take Velocity Factor in mind. Interestingly, the 4 inter-cavity cables are PDCC Type RG-8A/U cable. I don't know if this was an economy choice, or if the cables needed to be more flexible to make the sharp bends. Or, someone replaced some or all of the cables on the duplexer I have here. I'll see if I can check a couple of other 526's. 73, Joe, K1ike Al Wolfe wrote: Have a Phelps Dodge 526 UHF duplexer that's missing the cables from the tee to the cans. Google came up with one vague reference where someone thought these cables were 12 inches long. Is there a chart or formula somewhere to determine their proper length? Thanks, Al, K9SI Yahoo! Groups Links
[Repeater-Builder] Cable lengths - critical?
Hi guys. We finally secured a brck type UHF amp for our hamtronics machine. The Hamtronics puts out 7 watts after all the filtering into my Bird Termaline wattmeter. This needs to be knocked down to below 4 watts so as to not over drive the outboard amp. I had 2 options - one is to insert a pass-can into the TX line before the new amp. I have one at home. Tuned it to the correct frequency and it has an insertion loss of about 3db or so. The other suggestion from Hamtronics is to drop the V+ to the internal PA of the repeater to 11 volts or so (I can insert 3 or 4 diodes in series with the V+ to the PA to do this). But , in any case, we will need to make 2 patch cords. Is the length critical (i.e. electrical 1/4 wave or odd multiple thereof) work or will any convenienient short length work? We have some 9913 for this. Also, the way the repeater is configured right now, at the TX port of the repeater (before the filtering) there is a circulator. Should the circulator now be installed after the outboard amp? Or leave it where it is? Thanks. Ian VA2IR VE2RMP Repeater Group
[Repeater-Builder] Cable Lengths and Connectors
I am building notch filters for my 6m repeater project (out of 1 5/8 heliax) The connecting cables between the filters are all 1/4 wavelength, per the design instructions. The cable connecting the notch filters to the radio will need to have connectors in the line (to pass through the cabnet, etc) and be about one wavelength long. Should I put the connectors at the 1/4 wavelength, or should I avoid putting connectors there? Does it matter? To put it another way, where is the place of least loss to put a connector in a cable? Should I use BNC, PL-259, or what? John- KI4AWK 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/
