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Thread: SQ-450N Chinese Duplexer

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    Default SQ-450N Chinese Duplexer

    I ordered and put one of the chinese eBay duplexers through their paces and I've posted my test results. Let me know what you think.

    http://axfp.org/?q=node/18


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    Quote Originally Posted by broadcom View Post
    I ordered and put one of the chinese eBay duplexers through their paces and I've posted my test results. Let me know what you think.

    http://axfp.org/?q=node/18
    I have purchased and used many of these at less than 30 watts and have never had an issue with them, both their UHF & VHF high band ones

    If it was mission critical stuff I would maybe think a little more before plonking one in there but for the everyday casual comms stuff yes put one in.

    Sometimes cheap can be OK :-)

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    Motorola now ships straight off the boat Chineese duplexers and filters with the MTR3000's. The exact name escapes me right now.
    "Don't worry about what I am, cause I'm a state agent so what you need to do is make sure your doing the right thing **** boy" -J. Dewitte

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    "I had to get UHF mini->N connector cables to connect my SM120 radios, as no UHF-mini version is available in higher than 20 watts."

    What? The mini UHF connector is rated beyond 900 MHz and at way more than 20 watts. The adapters will cause you way more problems. What you need is double shielded, NO foil, cable, with N on one end and mini UHF correctly crimped on the other.

    Yes, I have seen some way off brand mini uhf male connectors that are junk.

    Heck never had any fail at 120 watts UHF.

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    Quote Originally Posted by Will View Post
    "I had to get UHF mini->N connector cables to connect my SM120 radios, as no UHF-mini version is available in higher than 20 watts."

    What? The mini UHF connector is rated beyond 900 MHz and at way more than 20 watts. The adapters will cause you way more problems. What you need is double shielded, NO foil, cable, with N on one end and mini UHF correctly crimped on the other.

    Yes, I have seen some way off brand mini uhf male connectors that are junk.

    Heck never had any fail at 120 watts UHF.
    I should have specified. They don't make duplexers with UHF-Mini connectors at more than 20 watts power rating. Most of their duplexers are manufactured with N connectors. I was referring to the duplexer specifically, not the connector.

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    I have been looking at these on eBay and have been curious about the quality.
    Thanks for the info on them.
    I want to get one of these for a QRP solar powered repeater.
    Would you care to share the seller name?
    How long did it take to receive after ordering?
    Common sense is Uncommon.
    You can't fix stupid, but eventually it takes care of itself.

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    Quote Originally Posted by broadcom View Post
    I ordered and put one of the chinese eBay duplexers through their paces and I've posted my test results. Let me know what you think.

    http://axfp.org/?q=node/18
    78db is decent, the repeater association I am involved with has used these filters with decent results in low noise sites only. If we are going into a site with any other equipment we will use 4 cavity BpBr Resloc's.

    Quote Originally Posted by Will View Post
    ... What you need is double shielded, NO foil, cable, with N on one end and mini UHF correctly crimped on the other.
    well said. Double shielded coax and no adapters is the way to go. Anything else will, at some point, cause you no end in grief.

    Quote Originally Posted by BobbyBoucher View Post
    I have been looking at these on eBay and have been curious about the quality.
    Thanks for the info on them.
    I want to get one of these for a QRP solar powered repeater.
    Would you care to share the seller name?
    How long did it take to receive after ordering?
    Myself and a friend have tested the Chinese duplexes side by side Sinclair Radio Labs mobile duplexer, that they appear to be a direct copy of, and the Chinese ones are just as good as the Sinclair ones in every aspect.

    Do keep in mind that these are notch only cans. If they are going in a high RF environment then you will have to get proper BpBr cans.

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    A quick search on Ebay found this: http://www.ebay.com/sch/i.html?_saca...uplexer&_frs=1

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    Quote Originally Posted by BobbyBoucher View Post
    I have been looking at these on eBay and have been curious about the quality.
    Thanks for the info on them.
    I want to get one of these for a QRP solar powered repeater.
    Would you care to share the seller name?
    How long did it take to receive after ordering?
    I purchased from jaco3378.

    Paid January 12th and received the 29th of the same month. Bear in mind that I had mine tuned so it wasn't actually shipped until the 18th.

    They make a smaller version which would appear to be of the same quality as this, from a visual photo inspection.

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    Thanks, I am going to order a unit.
    Common sense is Uncommon.
    You can't fix stupid, but eventually it takes care of itself.

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    Fingu, Motorola is now shipping MTR's and GTR with the RFS/Celwave 526 look alike duplexer.

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    Default Tuning is not Perfect, but sufficient.

    An update:

    I finally figured out how to actually use the HP 8924C. If you change the tracking generator to "invert" it displays a large notch regardless of the frequency. By re-adjusting the sensitivity parameters, I was able to get a good reading on regular mode and the results are a little different.

    The page has been updated to reflect the new information. Basically, the tuning was measurably off (approx 1 mHz, see picture on article). Not enough to cause de-sense of any measurability, but it was off. With proper tuning it exceeds the specified attenuation by almost 10 dB. Quite good.

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    Having sampled two of the UHF units recently, they're very decent. We're using them in a project for two local aviation companies. They work great so far. Put them on the Network analyzer (HP 8505A) & everything looked fine. Our application is 15W TX power & using CDM750 radios. (typical flatpacks handle up to 50W) Zero desense or other problems. Always verify tuning before installation, though. In low RF environments these work great. Higher RF environments will require additional band-pass filtering. BpBr duplexers are often sufficient, however a pure pass cavity on RX & TX is suggested. Most BpBr filters have poor 'out of band' rejection, the PD 526 being a great example. Useless out of band. Inband response is OK, but at VHF or 600, 700, 800, 900 it's virtually nonexistent. Pure pass filters typically are better in their out of band characteristics.

    The Chinese duplexers are great pricewise. Better still, if they do this properly, the matching network of rigid between cavities will be designed around where you order it. If you order it within the ham band for example, 420-430Mc, it'll work properly without excessive insertion losses, tuning anomalies or poor rejection, assuming they make-to-order. Often a downbanded 460 will tune down that far but be very picky or exhibit poor performance because of this difference. Needless to say ordering new from a domestic manufacturer will set you back more $ than these "eBay specials".

    (adding to the above, these are newly made with your frequency range in mind versus the typical second-hand Celwave/Sinclair/etc. units on eBay or at swapmeets that we commonly stretch from 450/460 down to ham frequencies with varying results)
    Last edited by grandnational; Feb 22, 2013 at 10:57 AM.