SW2012N                                                 Amtronix Instruments, Inc.
  0.5 - 1500 MHz  Return Loss Bridge    
Amtronix Instruments, Inc. 
Ph 716-763-9104
Amtronix is no longer making the SW2012N, however,  Masters Communications  is now making them.

SW2012N Return Loss Bridge
    Turn your service monitor or signal generator / signal receiver into an accurate antenna analyzer. This will provide the same accuracy as antenna analyzers costing thousands more. The SW2012N is a commercial duty 0.5 - 1500 MHz return loss bridge (RLB) for your antenna/feed line testing. Bridges are individually tested and include a performance graph. This unit has a 0.5 - 1500 MHz range and minimum 35 db directivity (40 dB typical).  The unit has high quality type N connectors for all ports and a new configuration with the input and output ports conveniently on one side. The new design will withstand 4 watts of accidental power input to the DUT port. Use your existing rf generator and receiver/power meter/spectrum analyzer to make accurate measurements.
    Please note: This product is being discontinued. We have just a few units left in stock. The SW2012N continues to be an excellent working rugged and dependable product. We originally manufactured this bridge to provide a lower cost alternative that had compairable or superior performance to more expensive units. The profit margin has been slim and for that reason, this product will soon be discontinued. We will continue support should it be necessary. Another company will soon continue the manufacturing of this bridge with some design changes. Their contact information will be posted here as soon as they have the product to sell.
The Basics of a Return Loss Bridge
      In simple terms, the return loss bridge is a device used to measure RF power reflected from a load or device under test (DUT) when power is sourced to the device through the RLB. The return loss bridge has 3 ports. An RF signal generator is applied to the input port. The output port provides an RF signal to go to a measuring device such as a spectrum analyzer, power meter or other device used to measure this signal. The DUT port connects to the device that you are testing (antenna, coax, etc.). A signal is generated into the input port. The RLB applies this signal to the DUT.  The DUT will reflect a portion of the signal that it receives (due to impedance mismatch).  This RF signal appears at the output port. The closer your DUT impedance is to 50 ohms, the lesser the signal will be at the output port. A perfect 50-Ohm DUT will have no reflected power so a perfect RLB will have no output signal at its output port (infinite return loss). If a non-50-Ohm load is at the DUT port, there will be an RF signal at the output port. The extreme cases are for the DUT to be a short or an open connection. This will cause maximum reflected power and, therefore, maximum signal at the RLB output port. Return loss is measured from the worse case (short or open) with 100% power reflected. It's the difference amount in dB of the reflected signal of your DUT compared to the worst case reflected signal. The further you go from "worse case" the better. The higher the return loss number, the closer the DUT is to 50 ohms. This is somewhat the opposite when compared to SWR ( high SWR means high reflected power or poor match) For example: with an open or short connected to the DUT port and an RF signal source generating into the RLB input port, let's say we measure the RF power at the RLB output port to be -22 dBm. If the open or short were replaced with your load at the DUT port, the amount of power at the RLB's output port would then change. If the output signal is now measured to be -42 dBm, this would be a return loss of 20 dB. The amount of reflected power is 20 dB less than the worst case. This is equal to an SWR of 1.22:1. If this were an antenna, it would be considered an excellent match with about 1% of the power to the antenna reflected. A return loss of 10 dB would correspond to an SWR of 1.91:1 with 10% of your power reflected. This is generally considered a poor match. Most commercial systems want to see a return loss of 18 dB or better.

    Directivity is the measure of how well the RLB isolates 2 opposite traveling (foreward and reflected) signals. As the reflected signal becomes smaller and approaches the specified value of the RLB directivity, the measurement uncertainty becomes larger. To get accurate return loss (SWR) measurements, it's important to have a bridge with directivity of 10 to 20 dB higher than what you want to measure. The higher the directivity, the greater the accuracy the RLB can measure small signal levels of reflected power. A perfect 50-Ohm load should have infinite return loss, which translates to no output signal from an RLB. If we could build a perfect RLB, the output port would show no signal with a perfect 50-Ohm load. In the real world, the highest quality RLB would show a return loss of up to 50 dB.  50 dB would be pushing the physical limits because the N connector itself has a tiny amount of return loss. This is great, but most techs really don't care about directivity above 20 dB. A higher quality bridge will have higher directivity than needed to provide better accuracy at all levels. The SW2012N has guaranteed directivity of 35 dB with typical directivity being  40 dB or better over the 0.4 - 1500 MHz range. A 20 dB directivity means that you'll see as little as 1% of reflected power. A directivity of 30 dB is 0.1% and 40 dB is 0.01% ( 1/10000 of worse case reflected power level). The SW2012N Return Loss Bridges are individually tested and include a performance evaluation graph.

SW2012N Return Loss Bridge

SW2012N Return Loss Bridge

Using your RLB
Many service monitors have "swept return loss or SWR programs" built in. When used with a return loss bridge, these programs provide a frequency vs. return loss graph on your screen. You need 2 cables. One is from your service monitor output port (RF Source) to the RLB input port, the other is from the RLB output to your service monitor's antenna port (RF Measurement). Your service monitor will poll you to "begin test" with an open or short connected to the DUT port. It will then have you connect your DUT (antenna or coax) to the DUT port. It will then give you a  graph of your DUT performance. There are many ways to capture and save this graph for later viewing or comparison. Try not to move your cables or RLB from the time you start the cal with the open or short until after the sweep of your DUT. At higher frequencies, this may cause errors in the results.
    If your service monitor does not have a Swept Return Loss Program, you can still use the bridge in a manual method. Similar to above, you need to connect a signal source to the RLB input, and some device to the RLB output port to measure the RLB output. This can be a spectrum analyzer or power meter. Generate a 0-dBm signal with your source. Set your signal source to the desired frequency and measure the RLB output with an open or short connected to the DUT port. The RLB output is viewed with your spectrum analyzer or power meter. You can check one frequency, several, or sweep up and down and note the signal level(s). Now connect your DUT to the DUT port. Observe your power reading on your spectrum or power meter. Subtract your original reading from this reading (or vice versa with negative numbers) and this is your return loss.
    To test your RLB, it's necessary to have a precision 50 ohm termination. This will allow you to sweep your RLB from 1-1500 MHz to make sure its working properly. If your service monitor has a RLB program, you should see return loss vs. frequency similar to the graph on the left below. We offer the Narda 370 BNM, 50 ohm N male termination for testing this RLB.  
    Using your RLB with HP's RF Tools Software

Typical Performance
SW2012N Performance  graph of 28-30 sweep
    Here is a typical return loss graph printed from an HP E6380A Service Monitor. The left graph shows the typical response when sweeping the Narda 50 ohm precision load.  Sweeping to 1000 MHz shows this return loss bridge is working properly with a better than 35 dB directivity over this range. On the right is a sweep of a 10-meter yagi antenna. At the top, the maximum return loss was 15 dB at 28.6 MHz. Generally, you want to sweep just 1-2 MHz to get the resolution needed to see the exact resonant frequency as well as the usable frequency range. The SW2012N can be a valuable tool for duplexer tuning. See Duplexer Tuning with the Amtronix SW2012N  for details.
    The SW2012N was compared to several higher priced units and provided similar results for return losses below 40 dB.

Return Loss
Power Refl%
Power Trans%

    To place an order, call 716-763-9104 or  email Amtronix Instruments  
                           Summer Sale !!
SW2012N  0.5-1500MHz RLB  (includes performance chart) Specifications............................................$279.00
Narda N male 50 ohm precision test load with chart (35 db).....(these are used / tested)................$ 40.00
24" N male to BNC male RG400 (double shield) cable set.(for input and output connections)...$ 40.00
24" N male to N male RG400 (double shield) cable set..(for input and output connections).........$ 40.00
6 dB BNC to BNC fixed Attenuators (includes 2) for cable end to your equip...........................................$ 35.00
6 dB N male to N female Fixed Attenuators (includes 2) for cable end to your equipment............$ 49.00
SW2012N Kit with cable set, Narda precision load and carry case..................................................................$419.00
SW2012N Kit as above with (2) 6 dB BNC to BNC attenuators...........................................................................$439.00
Huber Suhner 4901.17.A  50 ohm power divider (used for distance to fault measurements)....$165.00
SW2012N Super Kit Includes all above and the Huber Suhner Power Divider.......................................$539.00
UPS Ground Shipping...........................................................................................................................................................................$ FREE

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