The jumpers between the repeater and duplexers have been changed. They are now 9913. The coax on before, were small in diameter, but according to their owner/builder they are low loss. This is a club repeater and as sometimes happens, opinions differ. The lenghth issue may very well be the problem.
I'm not familiar with Bird meters. The owner of it has one length of coax he says has to be used between the transmitter and meter for Vhf, and he also has another extremely short piece of coax for UHF. I had a similar discussion with Kendecom way back when about possible critical lengths of jumpers from the repeater to the transmit duplexer. Does the jumper need to be 1/2 or 1/4 wave multiples of the transmit frequency? And that length is multiplied by the velocity factor, correct? I think we may have too many working working on this project. Tnx..73 Mike ----- Original Message ----- From: DCFluX To: [email protected] Sent: Wednesday, January 16, 2008 20:05 Subject: Re: [Repeater-Builder] Low Repeater output at site only Certain duplexer types, like the Wacom BpBr style use a mission cricital length of coax between the duplexer and the transmitter. Putting a watt meter in line with this coax will change the length of coax and effect the impedence that the transmitter sees. If this is the case you may want to invest in a circulator to sit in between the transmitter and duplexer, or experiement with different lengths of coax until you have a decent match. It could also be that your coax is bad and blowing in the wind is shorting it out. Are you using Belden 9913 or a foil braid dirivitive? On 1/16/08, k9mi <[EMAIL PROTECTED]> wrote: > Sorry, this isn't actually a repeater-builder question, but it is a > repeater problem, and this is where I thought I could get the best > info for the problem. > > We have a Mark IV that has worked well for 9 years. It's really still > working well, but here is what is going on. > > With a Bird watt meter, the Mark IV shows 3 watts out. If another > member of the club, using the same meter and a dummy load, shows 32 > watts (usual for the Mark IV). > > We also have a backup repeater, and Icom IC-RP1510 that has always > had an output of 18 watts, and still does. It shows 18 watts out, 1 > reflected, same as it always has. These output readings are before > the duplexers (Wacom 641). > > The mystery is the Mark IV works fine into a dummy load, but not at > the site. The Icom works the same as always. The a/c voltage (this is > at a hospital) is 124 volts. > > It is a multi-transmitter site, and the MFJ analyzer shows our DB 224 > as "pegged" on the swr, then it will drop briefly to a low SWR, and > then go back up for a couple of minutes, and then drop again > . > I "think" the MFJ analyzer is just getting RF'ed from another > transmitter, and that the Bird is much more reliable under these > circumstances. The Icom with 18 watts out, 1 reflected leads me to > believe the system is fine, but why would the Mark IV have an output > of 3 watts into the Bird watt meter (nothing reflected), but into a > dummy load, the Mark IV behaves as it should. > > My only other thoughts on testing would be to take a 50 watt 2m > rig/ps and a different Vswr/wattmeter up and see how it behaves with > the system. > > Any help/ideas would be appreciated. Tnx... > > 73, Mike K9MI [EMAIL PROTECTED] > > > > > > > > > Yahoo! Groups Links > > > >
