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Michael Bryce WBBVGE 2225 Mayflower NW Massif ton OH 44646

The Last of the HW-9!

I was checking my electronic mail from CompuServe one night and there it was, a note saying Heathkit will be dropping the HW-9, The good do die you ng. I have no idea how many H W-9s have been soldh but they were a very popular QRP radio. After logging off CompuServe, I got somewhat misty-eyed and brought down my little green HW-8. Ah, yesf This is QRP if ever there was.

After finding the power cord and a suitable length of coax with an RCA plug on the end, it was QRP time on 40 meters. But something was wrong. For the fife of me, I could not make a single contact with anyone. Off went the cables, and the HW 8 took a trip to the repair bench.

With Heath geart I always like to go through and check out the alignment. Any trouble areas will easily pop out, in my case, several trouble areas came right up to the surface.

The first problem was with the VFO. it was way off frequency. Heath has a strange way of calibrating the HW-8 that is both time-consuming and hit or miss. Heath wants you to zero beat the output of the VFO to a receiver tuned to 7.0 MHz or 7,250 MHz. You end up moving two VFOs—the HW-8 VFO and the receiver's VFO. This is a real pooper! There's a better way to do it.

Tuning the HW-8

You'll need a frequency counter and some patience The VFO generates frequencies from 8.645 MHz to 8.895 MHz A good place to tap the VFO is on the emitter of 03, the emitter follower, of the VFO, From here you'll be able to see the exact frequency the VFO is running at. Then it's time to play cat and mouse. The VFO must be adjusted to operate properly. Follow the instructions in the manual.

Basically, you move the VFO to one end of the band, adjust trim mer capacitor C302B (the screw adjust on the main VFO capacitor), and move the VFO to the upper end and adjust L9. You keep going back and forth until the zero on the dial and the 250 mark fafl exactly on 7 000 MHz and 7.250 MHz, with the band switch in the 7 0 MHz positiont of course. With a frequency counter connected to Q3, the values

Low Power Operation will be 8.645 MHz and 8.895 MHz.

It's easier said than done. No matter how 1 tried, 1 could not get the VFO to track 100 percent. The slug in L9 would not turn smoothly enough. It snapped back and forth. I ended up with the high end of the band out of alignment just a tad.

My reasoning is that most of the activity for the HW-8 is on the CW bands, and that that is where the VFO should be most accurate. It works for me.

When working on the HW-8's VFO, be sure to allow ample time, so the VFO can warm up to operating temperature. Use a stable power supply, not dead batteries. After I got the VFO back in line, the second problem came up to bite me: no VFO transmit offset.

When the HW-8 goes to transmit, diode D11 effectively adds capacitor CSS to the VFO, which causes a downward shift to the VFO frequency. This should produce a fixed offset of 750 Hz during transmit In my HW-8, C55 did in fact get switched into the VFO, Only

Photo A. The green QRP box, the HW-8, is a solid performer even on today's band.

Photo C. Terminal strip hofding the S-meter parts. The grain-of-wheat bulb is barely noticeable behind the meter s face.

Photo B. The 2 watt audio amplifier assembled on perfboard.

Photo B. The 2 watt audio amplifier assembled on perfboard.

trouble was, the offset was 3 kHz, not the desired 750 Hz. Useful, but hardly interchangeable. The offender was C55 It changed value The fix was simple: Replace C55 with a good capacitor. But i went one step further, 1 tried adding a small value trimmer capacitor in place of C55.

Experiment, Experiment

My thinking was simple: adjust the trimmer capaciior to the offset I wanted. But it didn't work! The trimmer changed the alignment of the VFO. The trimmer was not stable enough to use on the air. All in all, a pooper and a half. Heath's value of 6 pF is a good value to stay with, I ended up using 5 pF and having a 730 Hz offset. Capacitor C55 is kind of hard to get at. 1 removed the old one and soldered the new one on the trace side of the PC board. Bent down on the board, the capacitor fits quite nicely

To see how much offset you have during transmit, connect your counter up to the emitter of transistor Q5. Here you'll see the exact operating frequency of the HW-8. During transmit. C55 shifts the transmitter down. You'll see this shift at this test point. As a thought, here would be a good place to add a buffer/amplifier for a digital readout, replacing the analog dial in the HW-8. t can see it now. An LCD display instead of the plastic dial used now.

When 1 brought out the HW-8,1 had to dig up the 2000 ohm headphones required. I found them in a dark corner of the basement. After 15 minutes of use, I remembered why they were in a dark corner of the basement With this thought, how about some modifications for the HW-8?

The most common mod for the HW-8 is the addition of a small grain-of-wheat bulb behind the meter. It makes a super H,on" indicator. Use a small terminal strip to hold the bulb in place. Tap + 12 volts from the power switch and use the chassis for negative return. Simple, but really first class.

Building an S-Meter for the HW-8

This modification is simple and easy to build. With easy to come by parts we can have an S-meter for the HW-8. Granted it's not the best S-meter in the world, but it's an S-meter nonetheless. The circuit consists of nothing more

Photo C. Terminal strip hofding the S-meter parts. The grain-of-wheat bulb is barely noticeable behind the meter s face.

Figure 1 An S-meter for the HW-8.

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