Sounds more and more like the duplexer is not tuned as well as you were led to believe. Use two 2m ham rigs, one as a rx and one as a tx, into the duplexer, and let us know the results.
I've also seen cans that looked good on a tracking generator but then worked horribly once on the antenna at the site due to a bad jumper to the antenna feedline. Once I even had a bad N-UHF adapter that was causing horrible desense. That adapter now resides some 100m into the woods behind the site! If a bad connection after the duplexer changes the impedance far from 50 ohms, it may affect the operation of the duplexer. Eric KE2D --- In Repeater-Builder@yahoogroups.com, "tomnevue" <[EMAIL PROTECTED]> wrote: > > Thanks for all the input. I have some information now and I hope I'll > have the rest tomorrow. > > Repeater was at 155Mhz with a 700Khz split. It was fully operational > at the time of removal, due to 800Mhz upgrade about 5 years ago. The > Units were stored in an airconditioned/heated environment and were > not touched my anyone until I received it. I confirmed that the > repeater was fully operational before doing any Ham conversion. I did > this by operating into a dummy load and using 2 HT's that were part > of this system. The only thing done to the repeater for Ham > conversion was retuning, moving the configuration jumpers needed and > modifying the Squelch Gate card per Skipps article. All internal > cabling is exactly as supplied by Motorola. The Sinclair Q202 (4 can) > duplexer was aligned in a laboratory by someone who has experience > doing this; notch slightly better than 90dB. This exciter has the > added backplane filter plug assembly. > > The base unit was at approximately 155Mhz also. I moved jumpers as > needed to look like the repeater. I got another SG card and made the > same modification. The Rec / Trans cables are the same cables > supplied by Motorola with TR switch removed and bulkhead connectors > added. So, the Base looks just like the original repeater. > > The jumper cables from the repeater cabinet to the Duplexer is > Milspec RG400 and no adapters are used. > > I tuned both units the same way (for the same frequency). For the > exciter, I pre-adjusted the coils the amount estimated by the graphs > from the starting freq (155 MHz). The final adjustment is > 147.120/147.720MHz. I built a test meter and followed the step by > step instructions to tune the RF circuits. I netted the crystal. I > did not make any adjustment to the modulation at this point. I did > make receiver / repeater audio level comparisons and the 2 are very > close. I did not make any adjustments to the PA except to turn down > the power to 50 watts. The 2M power out was approximately the same as > it was at 155MHz. > > I tuned both receivers by presetting the coils the appropriate amount > from the starting frequency of 155MHz. Then again I followed the tune > up procedures in the manual. The signal source was a well shielded > low power HT into a dummy load. > > The starting points for tuning both the receiver and transmitter were > very close to the final settings. > > I am testing the 2 repeaters by swapping 1 set of receive/transmit > elements. > > When the transmitter power is turned up above 4 watts into either a > separate antenna or the duplexer or combinations of duplexer/separate > antennas the receiver is badly desensed, the repeater randomly hangs > and sometimes makes a loud growl sound when dropped. With the > transmitter turned down to about 4 watts (into the Duplexer) or 50 > watts into a dummy load (at the cabinet) the receiver sensitivity is > about what I expected (receives weak signals). So, it's a fine > operating 4 watt repeater. > > I tested the 2 units with a 3rd unmodified SG card and had the same > problem. > > Tomorrow I'll put a different transmitter and receiver thru the > duplexer and see if the receiver experiences desensing. Of course > these will not be connected as a repeater. I guess after that I'll > have to see if I can get help from someone with a spectrum analyzer > or station monitor. > > Have I missed anything?? > > MODEL NUMBERS: > Repeater - C73GSB3105AT, Transmitter ABZ89FC3632, Receiver > ABZ89FR3633, Receive unit TRD6182APR, Exciter TLD9242C, PA TLD2532A > > Base - C73GSB3105B, Transmitter ABZ89FC3632, Receiver ABZ89FR3633, > Receive unit TRD6182A, Exciter TLD9232B, PA TLD2532A > > > Tom W2MN >
