Just wanted to share what I ended up doing for my latest QDX build. This is the first of 3 I intend eventually to operate remotely and probably into a Hardrock 50, so reliability is key. I'm loving the QDX only connecting to the computer with a single USB, no audio controls/cables, and directly operating in WJST-X. A few less things to go wrong, especially operating remote.?
Stats:
Post Mar 2023 Rev 5 (T37-17 LPF Toroids)
9V w/ WTST. 1.10 FW installed.
TN0110 finals instead of BS170, special heat sink added.
1N4148 Diode across L14?
Alternative USB Port (per Jeff Moore's note.)?
I measured a few of my toroids with capacitors and NanoVNA. Was getting higher #s than spec'd, more? than 20% higher. So ignored that initially, and built as manual suggested for the LPFs.? After seeing lower output on 15 vs 17, and 10 vs 12, removed some turns. This pushed things in the right direction, and tells me maybe my measurements actually weren't far off. I could go farther, but I'm happy enough with the output to stop here, especially if I mostly will use this unit at 8V and feeding a Hardrock 50.
Ended up with:
?
| ? |
LPFs |
Turns Suggested |
Turns Used |
| ? |
L2 |
21 |
20 |
| ? |
L6 |
21 |
21 |
| ? |
L3 |
12 |
11 |
| ? |
L8 |
12 |
12 |
| ? |
L4 |
13 |
12 |
| ? |
L10 |
14 |
13 |
Your results may vary, of course. Just my experience with this batch of toroids.
Power stats on 9V:? 168ma in receive. TX was 980 to 1100 ma, depending on band.?
Final power outputs, (lowest peak to peak value seen after 5+ seconds, into a QRP-Labs Dummy Load and a 200 mhz scope):
20M: 4.4w?
17m: 4.6w
15m: 3.8w
12m: 4.0w
10m: 3.9w
The heatsink: Wakefield LTN20069, $1.50 from Mouser. I drilled and tapped it for the 3mm screw a bit off center. It's 16mm square, and the original washer is 12mm. Needed to make sure it didn't hit the transformer. The TN0110s are reversed, so the flat part of the TO-92 case is against the heatsink. So went from 101 cubic mm of steel to over 1000 cubic mm of aluminum. It fits in the case with clearance.?
USB port; It does feel like a better fit than the supplied one, a bit more secure. This was another Mouser purchase for $1.20.?
?
Next up: Need to build a QRP-Guys SWR and Power meter kit, as well as their EFHW kit with tuner for 40-15m. Then I'll be trying to build a MidBand 40/30/20/15 QDX, and maybe 17M will work if I'm lucky.? The Midband, if it works, will be my POTA/Travel rig that I'd use with EFHW.?
?
-Nate? ?
N8BTR
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