Testing of 409Shop UHF Diplexer

Hello OMs,

I’m going to share some measurements made on my UHF Diplexer that will be installed on my MMDVM equipment for the upgrade from simple hotspot to a repeater, using a Diamond X-510 antenna.

I bought this very cheap Diplexer from the Chinese e-shop “409Shop”, at only 97$: http://www.409shop.com/409shop_product.php?id=104460

SGQ-450D-N

caratteristiche

It’s a 6 cavity Diplexer (2 notch + 1 bandpass for each path), so I expected a very good out-of-band attenuation, which is a very interesting feature in installation sites with strong RF signals coming from other transmitters.

I choose the 50W version, because the price difference between the 35W and 50W was only 14$.

For the payment, I used paypal, without any problem. As suggested on the site, I specified the Low and High Frequency of my repeater in the order notes.

The Diplexer arrived very quickly. The order dates are the following:

  • Order and Payment: 14 November 2017
  • Order Confirmation: 15 Novemver 2017
  • Shipment confirmation and Tracking Number: 18 November 2017
  • Arrival: 01 December 2017

Before the installation, I took some measurement with a Vector Network Analyzer, at ambient temperature and at cold and hot temperatures, in a climatic chamber, in order to verify the tuning made by the seller, and the temperature drifts, which affects the low-cost Diplexers.

I choose +55°C and -25°C as worst case temperature, although my region has a very mild climate.

Note: during every measurement, the third port (not connected to the VNA) is connected to a 50ohm dummy load.

The frequency of my repeater are:

  • Low (TX): 430.325 MHz
  • High (RX): 435.325 MHz

The more interesting measurements are:

  • Attenuation from Antenna port to RX port;
  • Attenuation from TX port to Antenna port;
  • Matching at RX, TX, and Antenna ports;
  • Isolation between TX and RX ports;

Here below, the ambient temperature measurements are reported:

P1antP2high_3

P1lowP2ant_3

MATCHING_TX

MATCHING_RX

MATCHING ANTENNA

P1lowP2high_3

Considerations about performances at ambient temperature

  • The isolation between RX and TX ports is >70db, as declared on the datasheet
  • The loss from ANT to RX port and from TX port to ANT is <1dB
  • The resonance at RX and TX ports are slightly different from the desired frequencies, but the matching is very good anyway (>20dB)
  • The matching at antenna port is good (>20dB)

 

Here below, the temperature drifts of the main measurements are reported:

P1antP2high_hot_cold_1

Note: the attenuation @435.325MHz is 1.2dB at +55°C and 1.1dB at -25°C

P1lowP2ant_hot_cold_1

Note: the attenuation @435.325MHz is 1.1dB at both +55°C and -25°C

P1lowP2high_2_HOT_COLD

Considerations about performances at cold and hot temperatures

  • In all the cases, the responses moves up in frequency when the temperature increases.
  • The isolation is still >=70dB also at hot and cold temperatures.
  • The attenuation from ANT to RX port and from TX to ANT increases slightly (1.2dB),but is still very good, even if the curves move in frequency.

Conclusions

Here below, I judged and assigned a score for every aspect of Diplexer, from 0 (min) to 5 (max):valutazioni

Considering the cost, this Diplexer is a good compromise between cost and performances, and I suggest this product for hamradio applications.

The out-of-band rejection is good as well as the temperature stability, so it can be used also in mountain sites or in RF polluted sites.

 

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