Where could I find a cost efficient UHF duplexor?

[DylanMadigan]

I only have a couple hundred dollars the most right now, and I found a couple used ones on Ebay that didn't seem bad but I'm new to the radio world and don't have experiance with these yet. I'm a little cautious about trying random websites. Anyone have any suggestions where I can look and nit have to worry about the unit not working right? And would a used one be a bad idea?

 

[Project25_MASTR]

If you had access to a tracking generator, there are actually plans online of guys who built UHF dupelxers out of coffee and paint cans. Cost was around $15 a cavity.

 

[N4GIX]

If you need 50watt or less, then there are many sources for new, mobile (small form factor) duplexers available for <$100 including free tuning and shipping.

 

[SteveC0625]

I only have a couple hundred dollars the most right now, and I found a couple used ones on Ebay that didn't seem bad but I'm new to the radio world and don't have experiance with these yet. I'm a little cautious about trying random websites. Anyone have any suggestions where I can look and nit have to worry about the unit not working right? And would a used one be a bad idea?

The Antenna Farm has UHF duplexers from $899 down to $299. Might be a bit above your budget, but you're buying a quality product from a respected vendor.

There's always a lot of them on Ebay. I would not buy from overseas, but instead look for a US or North American vendor. Shop the seller as much as the item. 100% feedback and lots of sales is a good indicator. Get one that includes tuning as part of the sale. If you don't have the equipment to tune a duplexer, you need one ready to go on your specified frequencies. Again, look closely at the seller. There are some who are very open about their ability to tune a duplexer, and they have 100% feedback. It makes sense to buy the service as much as the product.

Think about your connectors. You will need a jumper from each radio to the duplexer and then connect the antenna to the duplexer. You'll probably want to buy ready made jumpers. Again, lots of good sellers on Ebay if you shop smart.

Do some reading over at repeater-builder.com before you buy anything. There's lots of info about all aspects of building a home brew repeater. Much of what is there is not specific to any one brand of radio. Connectors, coax, etc. are what they are, unaffected by what they are connected to. Better coax and better connectors mean less loss between the radio and the antenna. Less adapters matters too.

As for a used one, you still need it tuned to your needs. If you save $20 on a used duplexer and then have to pay $40 to get it tuned, it's not a bargain is it? You might find a deal on Ebay that includes tuning on a used duplexer, but they're few and far between. Most folks who use duplexers (hams and GMRS) don't have the capability to tune them.

 

[RFI-EMI-GUY]

If you had access to a tracking generator, there are actually plans online of guys who built UHF dupelxers out of coffee and paint cans. Cost was around $15 a cavity.

At 15 bucks a can, he paid too much. Was that Jamaican Blue Mountain Coffee?

 

[K5MPH]

FYI their is two different type of Duplexers the Band pass and Band reject,the Band pass will give you better performance but will cost more on the other hand the Band reject (Notch) are cheaper in price and will do alright for most repeater use......

 

[Project25_MASTR]

At 15 bucks a can, he paid too much. Was that Jamaican Blue Mountain Coffee?

That's assuming you don't have the copper scrap laying around.


Sent from my iPhone using Tapatalk

 

[DylanMadigan]

It seems all the $100 to $250 ones are from china but allot of them have good reviews.

And i dont think ill trust the tiny ones that are $12 with no reviews...


Im looking for about 50w. Is it safe to put 50w in a unit that said its made for it? I see allot of things that say not to pass 30, and that it wold work better at like 25 then 50 anyway.

 

[N4KVE]

At the last ham radio free flea, the local 2-way shop was selling GR1225 repeaters for $200, & duplexers for $100. He guaranteed them, & for a few $ more would align, & tune the equipment. Always buy in person. You have no idea what you are buying from the other side of the country.

 

[Project25_MASTR]

At the last ham radio free flea, the local 2-way shop was selling GR1225 repeaters for $200, & duplexers for $100. He guaranteed them, & for a few $ more would align, & tune the equipment. Always buy in person. You have no idea what you are buying from the other side of the country.

Or world if it's a chinese vendor.

Assuming the OP is looking to put up a repeater, what you want really depends on the location. The mobile duplexer (notchplexer) only notches out the transmit frequency from the receiver and receive frequency from the transmitter. I spent about an hour tuning a Celwave model last week and I managed to pull ~70 dB of isolation between the two frequencies. Where the mobile duplexer fails is where it will be co-located with other transmitters. For that you will need something more along the line of a cavity filter.

The duplexer I tuned last week was a quick temporary job at school for their security team (long story short their existing system cooked itself when contractors doing roof repair cut the feedline). That was only running 10W on a duplexer built for 50W. Pushing more power through the duplexer will only increase the chance of desensing the receiver. Plus at 50W those little duplexers start getting a little warm.

 

[N4GIX]

If you shop carefully, there are mobile notch duplexers available that are not Chinese, but are built in Germany, for around the same <$200 price, and are delivered tuned to your requested frequency.

 

[SCPD]

Hey Dylan
I read this as requesting duplex'r information, but not giving anything as to what you want to do with it. Is it for a repeater?.... separating two antennas?....etc. The others responding have given you some good ideas, but these are along the lines of your building a repeater, which may not be the case.
.
Personally I like taking the experimental routes to these issues... I am a 'coffee can' -filter type, and since you are new to all this, it represents a good opportunity to learn. There are plenty of resources on how to construct them- the older ARRL Handbooks, for example, have plenty of good, simple designs for V/UHF notch and band pass filters-- constructed from aluminum minibox's, or my favorite, large diameter copper pipe. Using a handful of air variable capacitors and some N, or BNC connectors you can construct a very respectable unit....Or you may consider helical wound filters-- And while it is nice to have the lab equipment to tune them, you can do a fairly decent job my using your ear and S-meter- just run very low power when you start out, and lower your expectations as to insertion losses and such.
.
While is nice to be able to buy one new, ready, out-of-the box- what is in that box remains a mystery, and if something goes wrong - then you need someone else to handle it.
.
Sorry--was I lecturing??... I didn't mean to. If there is more information it will be easier to help you.

Smiles
.
................................................CF