I checked it into a dummy load (with one of those celwave signal insertion boxes), and didn't see any signs of desense.
A friend of mine who used to work for Mot said that he had a desense problem with a VHF Quantar - Mot sent out some kind of memo that said you had to use some special kind of duplexer. But figured I'd ask around here. Thanks, Tim --- In [email protected], DCFluX <dcf...@...> wrote: > > Yeah, I understand VHF quantars or supseptable to something called > 'quantar howl' which is digitally delayed desense. > > http://www.youtube.com/watch?v=SRfvh0UTFHw > > The hypnotoad also has the ability to make the same sound > > http://www.youtube.com/watch?v=kiVYjRbZMe0 > > > I've never owned one so I cant put too many conclusions together about > what causes it. > > I saw the back of one at a ham fest and noticed the wire ties and > thought that was the dumbest thing I've seen Motorola do. > > My next guess could be that the switch mode power supply runs at > 600kHz. anyone got any schematics? > > Also check if you have desense into a dummy load, could be another > 600kHz noise source close to your antenna. > > On Fri, Aug 7, 2009 at 2:11 PM, tahrens301<tahr...@...> wrote: > > Hi Dcflux, > > > > Yeah, I did that 1st. Actually, they now come out of the > > front of the box & are as far apart as I can get them. > > > > Tim > > > > > > --- In [email protected], DCFluX <dcflux@> wrote: > >> > >> Cut the wire tied together TX and RX cables on the back of the quantar > >> and seperate them as far as possible. > >> > >> On Fri, Aug 7, 2009 at 1:43 PM, tahrens301<tahrens@> wrote: > >> > Hi Folks, > >> > > >> > Guess it's a good thing the antenna party didn't happen yet. > >> > > >> > Put the DB-224 up on a pole here attached to a portable building. > >> > > >> > Ran the 7/8" heliax from the antenna into my garage - about 100'. > >> > > >> > With a signal source from my monitor, the repeater would chop in > >> > and out. Ugh-desense. > >> > > >> > I am using an old DBproducts 8 cavity notch-type duplexer. 4 on the > >> > receive, & 4 on the transmit. The transmit side also has stubs. > >> > (see old thread). > >> > > >> > First, I used my spectrum analyzer & sweep gen, and got what I > >> > thought were pretty good notches in the right places (depending > >> > if I was working on the xmit or rx side. According to the > >> > analyzer, the notch was about 70dB below the high point. However, > >> > I think that it was seeing the floor of the analyzer, not the real > >> > notch. > >> > > >> > Then, I hooked up a signal generator on one side, and a receiver > >> > on the other side, and tweaked a bit more for the least signal. > >> > > >> > All looked pretty good with definite notches, but it's obvious > >> > there's desense. > >> > > >> > All cables are double shielded. > >> > > >> > The system is 147.10/70, running about 60 watts out of the > >> > Quantar. Even running with battery-backup (20 watts), there's > >> > still some desense. > >> > > >> > Could it be that these cans are just not enough, or am I doing > >> > something wrong. > >> > > >> > Thanks! > >> > > >> > Tim > >> > > >> > > >> > > >> > > >> > > >> > ------------------------------------ > >> > > >> > > >> > > >> > Yahoo! Groups Links > >> > > >> > > >> > > >> > > >> > > > > > > > > > > ------------------------------------ > > > > > > > > Yahoo! Groups Links > > > > > > > > >
