March 17, 2016

Expanding your RF test bench to UHF

In a previous blog posting, I talked about setting up a test bench to test basic functionality of radio equipment. The equipment, shown above, was good to VHF, but had limited functionality in the UHF region.  In this post, we'll expand the bench's capability up to UHF in order to test 70cm ham gear and higher-end GMRS radios.

The UHF testing issues with the test bench above were in the SWR meter and dummy load. The SWR meter was only good to VHF, and the dummy load, a Heathkit Cantenna, tops out at 400 MHz. (We need a top end of about 470 MHz.)  Those two items need to be upgraded.

Here are two UHF-rated dummy loads and a VHF/UHF power-SWR meter.  Two of the three are amateur radio test gear, and would enable you to upgrade your test bench to UHF for a reasonable amount of money.

This is an old Radio Shack 60 watt VHF/UHF SWR/power meter. Now discontinued, but you find them at hamfests, or can buy an equivalent like a Diamond Antenna SX-27P, or Workman Model 104.

A QRP dummy load once sold by radio shack.  Another discontinued item, but equivalents are available.  The Diamond DL30A is the closest one to this.  The DL30A is actually rated 15 watts continuous, and 100 watts peak (for 2 seconds).  If you're going to be testing mobile radios on a regular basis, you'll probably want a heavier dummy load.

This is a professional dry dummy load rated for 100 watts continuous/2.5 KW peak, at frequencies up to 3 GHz.  It's also $200, but it'll be the last dummy load you'll need to buy, provided you don't abuse it.

A lot of gently used test equipment shows up at hamfests.  If you are on a budget, that would be your best bet.

1 comment:

  1. A lot of cheap test equipment ends up on Ebay.Picked up a HP8566B for under a thousand and an IFR 1200S for not much more.