Wednesday, March 31, 2010

Hendricks QRP radio - an easy intro to kit building

The holy grail of ham radio is to build your own equipment - receiver, transmitter, antenna - the works. So when my grandson needed a radio project for Cub Scouts I persuaded him that building a shortwave receiver was exactly what he needed to impress his follow scouts, and get me on the road to creating a home-built rig.

I searched the web and compared prices, features, and ease of building and selected the Scout Regenerative receiver from Hendricks QRP Kits. The kit features two bands (3.5 mHz to 10 mHz) powered by a 9-volt battery or optional 12-volt external power source.

The kit includes a double-sided silk-screened printed circuit board and all components, and very clear step-by-step instructions, including tests to insure everything is working as you complete the kit. The instructions recommend identifying all of the parts before starting, but this was fast and easy thanks again to the color photos included by Hendricks. Only basic tools are needed for construction - a 30 watt soldering iron, 60/40 rosin core solder, and a multi-meter. The printed circuit board is double-sided, so soldering is straightforward. As with any electronic kit construction, paying close attention to putting the right part in the right plus being careful about polarity for electrolytic capacitors and diodes is critical. Removing soldered parts is a hassle, so I was lucky that everything went in correctly the first time.

Hendricks provides convenient construction check points to test voltage and current through the circuit. My measurements were close but not exactly on the mark as indicated in the manual.

Perhaps the hardest part of construction was winding the coils. It requires at least three hands to hold the wire tight, insert it through the holes in the PVC pipe, and tie it off so it doesn't unravel. When winding coils, neatness counts. Too many - or too few - turns in the coil push the tuning out of tolerance, so count carefully.

With the last component soldered in place, I did a quick review of the plans, snapped in the 9-volt battery, attached a long wire antenna, and plugged in a pair of earphones. WoW! China Radio International, Radio Havanna, Radio Tirana - I could hear them all. True, the regeneration control takes some getting used to, sort of like letting out the clutch while stepping on the gas in a manual transmission, but once you get used to it it becomes second nature.

All in all, Hendricks has done a nice job of creating a sensitive regen shortwave receiver for $40. And yes, my grandson's Scout buddies were impressed!

- 73
- Steve KB3IHX

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