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Kit Building

QCX-mini: a feature-packed, high performance, single-band 5W CW transceiver kit, with WSPR beacon and built-in alignment/test equipment. Available for 160, 80, 60, 40, 30, 20 or 17m bands. It has rotary encoder synthesised tuning, VFO A/B/Split, Iambic keyer, CW decoder, and more...
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The QCX-Mini is CW only. Voice (SSB) is more involved but I'm sure people make kits for that as well. CW requires much less power to reach the same distance as voice, which is why it's popular for DIYers.

The one I built uses crystals, so you get the frequency of the crystal. Technically it has a little bit of an offset so you get two frequencies about 500 Hz apart. If you look closely at my pics, you'll see two of these. One is for the TX circuit and the other is for the RX circuit. I'm using 7.040 MHz.

1687029973547.png
 
Well I'm bitten. I just ordered the 4SQRP (4 State QRP) Hi-Per-Mite CW audio amplifier/filter. Considering the parts list it was a bit spendy, but I knew I'd never do it if I had to get the parts myself. It's a 200 Hz bandpass filter centered at 700 Hz. You have some choices as far as gain and center frequency that I'll have to consider. I'll probably do the first planning on running to headphones, and if I like it, maybe I'll build up another to power a speaker.

I read a little about their circuit design and a lot went into it. I can't really comment on it, but they considered

The real question is, do I fit it in another Altoids tin to make a matched set? May have to start buying Altoids again. Back in the day I used to go through them all the time; where'd all those tins go?

$28 shipped.

Four State QRP Group

Four States QRP Group
www.4sqrp.com
 
ToddDubya said:
I almost went this way, but opted for lower tech for my first. What's surprising is that is almost the same price as the kit I bought. I think the QCX Mini is on the list for another band.
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The quality is excellent and they provide documentation on the design and operation of the circuits.

Here is another kit build I did, the FA-VA5 vector antenna analyzer. I used it to setup my last set of base antennas and with my Buddi pole.

FA-VA5 Antenna Analyzer Kit

www.sdr-kits.net www.sdr-kits.net

IMG_7699.jpeg
 
Yeah, the QCX Mini looks really nice. And I always forget that in German we're Funk Amateurs. That's a neat little project too.
 
My little audio amp/filter came today and I got it all soldered up. I'll give it a once over tomorrow and give it a try. Or tonight, but probably tomorrow. There weren't a ton of parts, but it did take some time to build. Then an extra half hour looking for the headphone extension cable I knew I had but wasn't where I thought it would be.
 
I couldn't wait, I powered it up, no smoke, so I installed the ICs, still no smoke, so I plugged in headphones and it made noise, so I plugged it into my radio and tuned in some CW signals. I should have used a worse radio to really test it out, but signals definitely dropped off within a few hundred Hz. It claims a 200Hz bandwidth... maybe. But I'm also not 100% sure I wasn't benefitting from the radio's already good filtering. Tomorrow I'll try a worse radio.

One thing I have to look into some more is there's some significant hiss, even with the volume all the way down (or not plugged into anything at all).
 
After some more shenanigannery I got the filter/amp tested tonight. Using the FT-818, I compared the built in speaker with the filtered audio in an external speaker and it's night and day. The stock audio was good enough to copy, but it would be exhausting with all the noise. The filtered audio was nice and clean. I couldn't find two stations close enough together to test the bandwidth/ability to isolate just the desired signal, but it has to be an improvement over the wide bandpass on the FT-818.

I tried it with the kit radio and it definitely removed adjacent signals, but nobody was on the correct frequency to really test that.

I looked into the hiss situation and what people recommend is what this already has, so maybe it's just something to live with. Certain headphones are definitely worse, so it might just be a matter of finding the least offensive ones.
 
Well bummer. I guess I never used the amp/filter into headphones because it is painfully loud. I just fussed around with it for a bit and can't get it to be anything but deafening. It's intended to power headphones, and the volume out of my QRP kit rig is fine, but holy moly the side tone just about blasted me out of my chair.

I just tried it with my FT-857 and it's the same.

I checked everything and it looks fine. Gonna email the guy and see if he has any suggestions. If I can't fix it, I guess I can use a little speaker but that pretty much defeats the purpose of what I'm trying to do.
 
ToddDubya said:
Well bummer. I guess I never used the amp/filter into headphones because it is painfully loud. I just fussed around with it for a bit and can't get it to be anything but deafening. It's intended to power headphones, and the volume out of my QRP kit rig is fine, but holy moly the side tone just about blasted me out of my chair.

I just tried it with my FT-857 and it's the same.

I checked everything and it looks fine. Gonna email the guy and see if he has any suggestions. If I can't fix it, I guess I can use a little speaker but that pretty much defeats the purpose of what I'm trying to do.
Click to expand...
Did you try putting a high value resistor in series with the amp output?
 
Uzi2 said:
Did you try putting a high value resistor in series with the amp output?
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That was one thought. It probably wouldn't take much. I'm hoping the guy will get back to me and tell me there's a known fix.

The other problem I found today is that to use a straight key with the RockMite rig, you ground the "other" pin, i.e. the ring, on powerup. I always read that as "hold the key down on powerup to configure as a straight key", but that just disables the straight key altogether. So either I need a dedicated key that only uses the tip/sleeve connections, an adapter that grounds the ring, or I have to just use paddles with it.
 
ToddDubya said:
That was one thought. It probably wouldn't take much. I'm hoping the guy will get back to me and tell me there's a known fix.

The other problem I found today is that to use a straight key with the RockMite rig, you ground the "other" pin, i.e. the ring, on powerup. I always read that as "hold the key down on powerup to configure as a straight key", but that just disables the straight key altogether. So either I need a dedicated key that only uses the tip/sleeve connections, an adapter that grounds the ring, or I have to just use paddles with it.
Click to expand...
If you have a small 10k or 50k pot, try clip leading it into the circuit.
 
I just heard back from the guy. He said if all the resistors check out, which they do, to add 100 ohm resistor to the output. Great minds think alike.
 
ToddDubya said:
ToddDubya said:
Well bummer. I guess I never used the amp/filter into headphones because it is painfully loud. I just fussed around with it for a bit and can't get it to be anything but deafening. It's intended to power headphones, and the volume out of my QRP kit rig is fine, but holy moly the side tone just about blasted me out of my chair.

I just tried it with my FT-857 and it's the same.

I checked everything and it looks fine. Gonna email the guy and see if he has any suggestions. If I can't fix it, I guess I can use a little speaker but that pretty much defeats the purpose of what I'm trying to do.
Click to expand...
Click to expand...


from the 4s-qrp site;
1692490695627.png

Got to find out where that user selection is ^^.

UJay
 
ToddDubya said:
I just heard back from the guy. He said if all the resistors check out, which they do, to add 100 ohm resistor to the output. Great minds think alike.
Click to expand...
Well, try the 100 ohm resistor, you can always increase it or put a variable in to adjust the output.
 
I'll have to fool around with it a little. 100 ohms might not be enough, 220 is okay. It's hard to tell with only the side tone and trying to finagle all of these dangly wires and stuff to something I can get a radio on.

All I have is a 50k pot and that's way too big. It'll be too sensitive. Back to Amazon for pots. 1k is probably close enough.
 
I was talking to my Elmer/friend about the QMX tonight and I think I need one. It does digital modes, via a USB interface (built-in sound card) as well as CW on 5 bands. I don't care much about the digital modes, but it could be cool. But 5 bands of CW is intriguing.

It also says it "receives" SSB, and there are rumors it'll be firmware upgradeable to transmit on SSB as well. That could be cool. Hmm, what's that unpopulated spot on the front panel control board?

1706844306736.png

It comes in two flavors: 80, 60, 40, 30 and 20m --- or --- 20, 17, 15, 12, 11 and 10m. I don't get the 11m, but okay. I think the 10-20 version would fit nicely in my QRP stable. There'd be some overlap, but I could live with it.
 
I've been trying to come up with a good solution to get my Mountain Topper on 80m. I don't like that there's a band on it I can't easily use. I opted for the 4SQRP (4 state QRP) tuner kit. It's not specifically for 80m, but covers 80m. I expect I'll probably just cut a dipole for the low end of the band and use the tuner to tame the SWR in the rest of the band.

Some manual tuners have what I assume is a variable capacitor. Some have two knobs, I assume one is a cap and one is an inductor. This is a T-match, so two variable caps in series, with an inductor to ground between them. The real beauty is it has LED circuits to indicate the relative power out/reflected power.

You can either connect to an antenna via BNC or use banana jacks (not visible in the pic) for a random wire, which may be an easier option depending on trees and stuff.

1708319579858.png

1708319667554.png

Four State QRP Group

Four States QRP Group
www.4sqrp.com
 
Oh baby, my kit got here a day early. I inventoried the parts and everything is there, ready to go. Hopefully I can stay awake after work to build it. I was up wicked late last night so my post work nap might be crucial today.

I'm impressed with the parts quality. Obviously I could have put the kit together myself for less, but I would have cheaped out on the parts and I like supporting the guys who put in the work to develop these kits. They do a nice job, this is my third kit from them.
 
Considering the parts count, it was a tougher build than I expected. It uses leaded through hole parts, but surface mount pads so you need a lot of hands. And I soldered the big toroid on first so it was in the way of everything. The directions say not to, but I knew better ;). It was interesting to do, and I had fun.

The whole thing is made of circuit board, and it has a hella ground plane so when it came to the BNCs I had to bust out the 100w soldering gun and really put the heat to it. My regular iron wasn't touching it, even at 800 degrees.

Once assembled, the first thing I did was test it out at 3x the max rated power. Whoops. I caught that before I blew anything up. Then I got it all assembled, tune up a few bands, made a few contacts, and it's good to go. I even got to test the repeatability of the settings, and it's good.

I need to buy/make a short jumper to connect to the radio. I know if I don't have something dedicated, I'll get out in the field and not have it.

1708719741669.jpeg
 

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