Heathkit HW-7… lunchtime project

Recently I’ve just bought a Heathkit HW-7 QRP CW transceiver off eBay.

Why you may ask when you have access to advanced SDR transceiver prototypes and other high end radio equipment?

Well sometimes it’s good to go back to basics and remember what radio was about when I started working in it.

The HW-7 was produced as a kit from 1972 to 1975. It was VFO controlled with a crystal transmit option CW transceiver covering the 40, 20 and 15m amateur bands. The RF output was around 1.5W but it’s main feature was the current consumption on receive at only 35 mA. Modern transceivers with synthesized frequency control, displays, DSP all eat power. The Yaesu FT-817 and FT-818 replacement take 400 mA on receive which is about the same as the this ancient HW-7 takes on transmit. Back in 1972 you could power a HW-7 with a pair of 6V lantern batteries for a week.

The listing on eBay stated that the seller had bought it as a project and never got around to looking at it. I’m sure that won’t happen here! It would be a nice project to bring it up to 21st century standards while still keeping the same low power consumption.

It looks in very clean unmodified condition but the rear phono plug and jack sockets show signs of rust so at some point in it’s long history it’s been stored somewhere damp. The only problem I can see is that the leads on one of the PA transistors have broken off, probably caused by a rough trip through the postal system shaking the large heatsink plate bolted to the transistor.

So for the first test with a temporary 12V cable soldered onto the back of the white Molex connector, an antenna connected via an adaptor and a Plantronics medium impedance headset plugged in the headphone jack.

Switch on and good, there is noise from the head phones, I can tune the preselector and get some broadcast stations breaking through (the HW-7 was legendary for that!) but I can’t tune any stations in with the VFO. There is no output on transmit but the sidetone is deafening (and I’m already deaf so it must be loud!).

With a suitable crystal in the crystal socket I can get 0.1W on 40m and 0.5W on 20m so it looks like the VFO is faulty.

What’s the old saying… amplifiers oscillate and oscillators don’t. This is going to be fun…

One thought on “Heathkit HW-7… lunchtime project

  1. Hello Chris, I’m VE2VEI and a friend gave me a HW7 few days ago with same Output problem as yours, I corrected in few minutes, with new direct solder connection on a PA Output. Mine give me 2.5w on 15 and 20m. but only .5w on 40m with tuning plate with minimum capacitance.I will take a look on the adjustable 40m coil to be sure it was well place on the board. Maybe it was install in a bad way. Or I will try to change the capacitor, next to 40 tuning coil, to reduce capacity on this one. Best 73 Email adress on Qrz.com


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