Ok, thaks Gary. That must be the length the owner of the Bird refers to. Thanks.. 73 Mike
----- Original Message ----- From: Gary Schafer To: [email protected] Sent: Wednesday, January 16, 2008 21:35 Subject: RE: [Repeater-Builder] Low Repeater output at site only When inserting the bird meter between the duplexer and the radio make sure that you have a jumper that you use with the bird meter that makes the meter and jumper cable a 1/2 wavelength at the frequency of the transmitter. That way inserting the meter will show the transmitter the same impedance that it sees from the duplexer without the meter in the circuit. This is the jumper that you add along with the meter between the regular cable from the duplexer and the transmitter. The bird manual tells you how to calculate the jumper cable length to use. 73 Gary K4FMX > -----Original Message----- > From: [email protected] [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Scott Zimmerman > Sent: Wednesday, January 16, 2008 3:11 PM > To: [email protected] > Subject: Re: [Repeater-Builder] Low Repeater output at site only > > Mike, > > I would strongly suspect the Mark IV is having problems. My experience > with > those repeaters has NOT been good. They seem to be VERY spooky. Especially > when it comes to high RF environments. Most of these units were fine when > they were first produced, but as the components age, they are becoming > increasingly more problematic. Our local club had one since the early > 80's. > They dumped it in favor of a Micor conversion about 7 years ago and > haven't > looked back. Another local club still has theirs on the air. About the > time > our club got rid of ours, they decided to re-build theirs. Many hours and > capacitors later, they had it working OK. Now, it's so deaf you have to > run > 50W 5 miles from the site to make an S5! > > If I were to hazard a guess at what your problem might be, I would guess > it > might be 2 things: > > 1. The PA drive control circuitry is interpreting the high RF at the site > coming back down from the antenna to be reflected power and shutting the > power amp down to keep from blowing it up. > > -- OR-- > > 2. The transmitter is spurring and the drive control is doing what it is > supposed to do and shutting the transmitter back to keep from blowing it > up. > > Do this: > If you connect a dummy load and wattmeter to the duplexers instead of the > antenna. Connect a wattmeter between the Tx and the duplexer . How many > watts are coming from the Tx and how many watts do you have into the dummy > load? Your duplexer loss should be less than 1/3. In other words if you > have > 30W from the PA, you should have more than 20W coming out of the duplexers > into the dummy load. If not, you have duplexer trouble, or a spurious > transmitter. I would then look at the transmitter on a spectrum analyzer > and > see how much 'grass' you are growing. > > Good luck, > Scott > > Scott Zimmerman > Amateur Radio Call N3XCC > 612 Barnett Rd > Boswell, PA 15531 > > ----- Original Message ----- > From: "k9mi" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Wednesday, January 16, 2008 2:29 PM > Subject: [Repeater-Builder] Low Repeater output at site only > > > > 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 > > > > > > > > > > > > -- > > No virus found in this incoming message. > > Checked by AVG Free Edition. > > Version: 7.5.516 / Virus Database: 269.19.5/1228 - Release Date: > 1/16/2008 > > 9:01 AM > > > > > > > > > > > Yahoo! Groups Links > > >
