Ron, My suggestion wasn't really to tee both radios together, but to minimize interference between them if you used separate antennas that were relatively close to each other.
To combine two systems into one antenna poses some significant challenges. Were this a commercial installation with the money to pay for the equipment, a cavity/ferrite or cavity/hybrid combiner would probably be used, along with a cavity multicoupler. A commercial installation usually combines the transmitters into one antenna, with the receivers all fed from a multicoupler. But, that's not the case here, so let's boldly press on... A bandpass cavity has far more selectivity in the "pass" function than does a pass/reject cavity, so you might be able to tee the packet radio into the antenna used by the repeater- if you use two or three sharply-tuned bandpass cavities on the packet. In order to achieve optimum isolation, the loops on each bandpass cavity should be adjusted so that the VSWR and return loss is the same in both directions. Don't go overboard on the loop settings; the performance of two cavities each set at 0.5 dB is better than one cavity set at 1.0 dB. The jumpers between cavities must be cut so that the match is maintained between cavities. Try it and see. You might find that you can couple the APRS without degrading the repeater. 73, Eric Lemmon WB6FLY Ron Stordahl N5IN wrote: > > 1) Yes the intention is to put both 147.09tx/147.69rx and APRS > packet 144.39 on the same antenna. > 2) The WP-641 is spec'd for 500 KHz separation, and works very well > at 600 KHz separation. The repeater is very sensitive, apparently > little desense. It's a high power Micor cranked down to 75 watts. > The packet 144.39 is a lower power Micor cranked down to 30 watts. > We have other sites using the WP-641 successfully as 2 meter voice > repeaters (600 KHz separation). > 3) Eric's suggestion that I try adding to the WP-641 by putting two > additional band pass cavities before the 147.690 receiver and tee'ing > the antenna off to the packet radio with two band pass cavities > (144.39) would be something I am tempted to try. > > In my original posting I said I had 3 DB products bandpass cavities, > but checking further I actually have 4 of them. > > In my earlier posting I noted that they were old DB Products > rectangular bandpass cavitites (4.5" square by 21" high). > > If anyone has any specs on it would be appreciated. > > But since these are only band pass and not band pass/band reject I > would guess the 147.09 tx might severely impace the 144.39 receiver? > > Any suggestion on improving the reject? > > Again if all else fails I have a set of WP-639's which I could split, > 2 cans on the 147.69 receive and two on the 144.39 packet. These are > bpbr cans but I had another use for them...maybe Ill have to use them. > > Does this stuff ever show up on e-bay? > > Ron N5IN > > --- In [email protected], Kevin Custer <[EMAIL PROTECTED]> > wrote: > > I own several sets of Wacom 641's, so I'll correct Eric's figures. > The > > Wacom 641 is a 4 cavity BpBr duplexer using 8 inch cans. > > > > Eric Lemmon wrote: > > > > >A 2m repeater on 147.090/147.690, with a 50 watt transmitter and a > 0.35 uV receiver generally requires about 88 dB of isolation for no > desense. The WP-641 duplexer is rated at 85 dB, > > > > > > > While the WP-641 is rated at 85 dB, that spec is at the highband > > literature standard of 500 kiloHertz separation, not 600 kc as > > referenced above, when used on a 2 meter repeater. > > > > >but most can manage only 80-83 dB. > > > > > > > Incorrect, Wacom specified the WP-641 at 90 dB isolation at 600 > kc, but > > they will actually manage 93 dB with careful tuning. > > 93 dB will allow a 100 watt 2 meter repeater to properly work using > a > > .35 uV (-116 dBm) receiver. A *good* repeater like a Micor or > Mastr II > > (read less than typical transmitter side band noise) will allow a > 100 > > watt repeater operate properly with a factory preamp (-125 dBm) > > receiver. Granted, this is its limit, but that isn't too bad > considering. > > > > A Tube Type amplifier (GE 4EF5A1) or PLL exciter and solid state PA > will > > allow about 250 watts to be duplexed using the Wacom WP-641. > > > > These specifications can be backed up from the factory literature > > available here: > > http://www.repeater-builder.com/pdf/wp641.pdf > > > > Maybe Eric was thinking of the WP-639 duplexer that uses 4, 5 inch > > cans? His figures would be much closer.... > > > > Kevin Custer > > > Yahoo! Groups Links > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
