Correct, but if I remember you were claiming 3dB loss at the pass frequencies. I was seeing about 1.5dB loss. I claimed respectable results, not perfect results. I think it is still acceptable for ham use. Everything is a compromise when you push the equipment past it's limits, but the typical ham is frugal (aka me) and accepts a little degradation for economy.
73, Joe, K1ike Another parsimonious Yankee ham. 73, Joe, K1ike Eric Lemmon wrote: > Joe, > > Your screen shots actually prove my point. Both of the pass plots reveal > that your duplexer's pass response is far from optimum, which is precisely > the reason for selecting the proper duplexer model to tune. If your > duplexer was originally designed for operation in the 440-450 MHz band, the > peak of the pass plots and the nadir of the notch plots would be exactly 5 > MHz apart. Your TX pass plot shows that the peak is about 900 kHz to the > left of your desired frequency, and your RX pass plot shows that the peak is > off-scale to the right- considerably more than a MHz away from the desired > frequency. > > 73, Eric Lemmon WB6FLY > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Joe > Sent: Friday, February 05, 2010 6:55 PM > To: [email protected] > Subject: Re: [Repeater-Builder] RFS TDE-7780A > > > > Eric, > > I tuned up a 633-6A from a GR-300 recently and got some respectable > results. Pass frequency loss was around -1.5dB and notch loss was > around -85 to -90dB. I've attached the sweeps. > > 73, Joe, K1ike > > Eric Lemmon wrote: > >> Paul, >> >> The Motorola TDE7780A duplexer is simply a relabeled Celwave 633-6A-2N >> > unit, > >> and it is designed for 450-470 MHz. It is the standard duplexer furnished >> in GR300, GR1225, RKR1225, and CDR700 repeaters. The duplexer is okay for >> non-critical use at low-density RF sites, such as at construction sites. >> The compact mobile notch design has very little bandpass action, since its >> operation is based solely upon the notch. >> >> I have tried to tune such duplexers down into the Amateur 70cm band, with >> little success. >> > > <snip> > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > > >
