This forum is for discussions regarding System Infrastructure and Related Equipment. This includes but is not limited to repeaters, base stations, consoles, voters, Voice over IP, system design and implementation, and other related topics.
I have a 110w UHF R2 Quantar on the way, and I am looking to put it into service on the 70cm Ham band. The Quantar is not coming with a duplexer, so I've been on the search for an appropriate unit to do the job. I found a seller with the duplexer pictured below. It is currently set for 450.3XX/455.3XX, but has no identification tags or part numbers besides a PN for one of the cables. Can anyone identify the unit pictured below? I'm guessing if its tuned for 450 it should be tunable to 440? I would also like to know isolation/power handling, and insertion loss. I am planning on running the Quantar at somewhere between 60-90 watts. It looks like a newer version of the T1507A. Its a bit of a long shot, but I know there are super knowledgeable folks here.
IIRC, these are Motorola T1500 UHF series cans, but I've never seen a duplexer configured this way. Typically there are 2 connectors on each can and specific length cables connecting the cans together. I've never seen a 1500 series duplexer with UHF connectors either. All fo them I've worked on have Ns. Maybe some type of combiner/splitter? If its some type of 'SP' configuration you'll play the devil getting ANY documentation on them. The T1500 cans aren't the most stable either....best kept in a temperature/humidity stable location. They can be a bear to tune as well.
OP, you'd be much better off finding a set of pass/reject cans from Phelps Dodge/Celwave, Decibel, Telewave, Wacom, etc..
Look to spend around $150 - 300 for a good 4 or 6 can set that will handle your power level - remember, this stuff don't come cheap.
Those are the same duplexers sitting in my MSF5000 225 W UHF Repeater and are operating fine on 443.750/448.750 with 225 watts into the cans. . . . .
they are a little touchy to tune and take some time to set up properly. . . .
As always this is my $2.25 and YMMV!
That is a MSR2000 UHF duplexer. Pass-notch on each cavity. You only have to tune the screw, pass, to go a small freq change, the notch will tend to follow.
Thanks for all of the great replies. RFGuy, thanks for fixing my broken picture link. Not sure what happened there. Anyways, after doing a bit of reading, my understanding is that the pictured unit is a combination Band Pass/Notch type unit. The screw on the front controls the band pass frequency, and the slider on top of the can controls the notch.
I did find a Decibel Products 4072 Duplexer, but it appears to be of the Notch only variety. As I understand it, this "Notch" only type is not good for stopping interference outside of the set two frequencies. Probably not what I want if this repeater ends up at a busy site, correct?
One question on tuning the pictured unit, it appears as though the cable connections to the can are soldered. I assume this is part of what makes them so hard to tune, as you cannot isolate each can during the tuning process?
I don't mind spending the money, I just want to completely understand what I'm buying first. I'd prefer to only to cry once, which may not be possible with a repeater project :/
What makes these particular duplexers a nightmare to tune (at least for me) is the tight reject notch. . . controlled by loosening a thumbscrew and sliding a slider. . . (Cans in my case were originally set for 3 Meg between TX and RX and needed reset for 5 meg)
Have everything perfect, tighten the screw and a drift comes in play. . . once you figure out the drift you can nail it on the head pretty quick and easy. . . . Once the cans are set, they stay there and are happy. . . .
My site is a high profile site (antennas sitting around 2800' above sea level with an average HAAT at around 1000'. HAAT on eastern side of ridge is around 400-500', HAAT on western side of ridge is around 1800-1900' and the ridge is the highest point in Western PA going west --slightly higher ridge to the east of us but this ridge is the last one before the ground levels out before you get close to the Rockies. . . . .)
We plug a 440 mobile into the repeater antenna and can hit repeaters over 130 miles away. . . . .
Noise floor on UHF is significantly high and only slightly had a problem @ 448.75 RX with a paging transmitter 10' away on the tower @ 454.225/454.100 MHz at around 200 Watts. If in CSQ repeater would key up and chatter when paging TX was running. if in PL, very slight desense) Everything we tried including the paging company putting pass filters on their equipment didn't help much.
These particular cans were better than most when we switched to them at our site.
These run good for 1/4 KW stations and have respectable performance.
These particular units were paired with MSF5000 UHF repeaters among others.
Same design as the T1500 series cans except the cables are fixed to the cans and can't be removed. Harness is same way. . . Book specs from what I remember matched the MSF @ 435-470 so if it was tuned anywhere in 450-470 range you should be good to go at Ham band. . . . ..
talviar: Thanks for the info. I think I'm going to be going that route for the duplexer. On a somewhat unrelated note, what kind of antenna are you running? I'm looking to experiment with the Quantar at a mediocre site. I'll be 200ft ASL (on the coast), and just above the trees. Not looking to cover a huge area. This is my first repeater project and want to get the hang of things and see if its worth figuring out a better site for it. So far the antennas range from lower grade ham stuff (Diamond) to commercial (Telewave) where most higher gain setups are >$800. Trying to find the middle ground with not much luck thus far.
Thanks Will, I sent you a PM. I would love a Telewave 8 bay folded dipole, but the bank account says nay :/ Looks like it performs well in all regards.
I did end up ordering the pictured duplexer. I don't mind spending a little more time setting it up right. I will let y'all know how the tuning process goes...
We got this Motorola unit tuned up today. Band passes were easy. The notches were definitely a lot more challenging. Took some time, but we got it. The insertion loss ended up being a little below 1.5dB. The guy helping me tune them commented on how nice the notches were. The TX and RX ports ended up being opposite of what the manual said, as the TX was the high side in the commercial setup, and the RX on the low. Now the RX is the high side, and TX is the low. As I understand it it doesn't matter which side is used for which. I'm waiting on a few more bits for the repeater, should have in on air in the next few weeks.
