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A QRP antenna tuner for QCX Mini #qcx #antennatuner
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Hi All,
I've added an article to my blog on building a small QRP antenna tuner for the QCX mini. Also works with other QRP transceivers of course. Here's the link: http://blog.aha.nl: building a QRP antenna tuner If you're looking for an antenna tuner that's fairly easy to build and just works this may be the thing for you. Regards, Marc - PA1DMG
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QRP Guys offers some excellent antenna tuner and tuner/antenna combinations for only slightly more than those from China and the instructions are excellent. I know. I built their Digital Power/SWR Meter w/Dummy Load.
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https://qrpguys.com/qrpguys-power-swr-dummy-load You can download their assembly manuals to preview the steps involved. They seem to be restocking parts, but what they sell is well worth the wait. —Mike Perry, WA4MP
On May 6, 2022, at 5:40 pm, PA1DMG via groups.io <info@...> wrote:
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ken WA2MZE
YUCK, a TEE network.
Yes they work in that they do transform
the antenna impedance to match the transmitter. However the Tee
network acts as a high pass filter and provides NO harmonic
reduction. It also can exhibit several points of adjustment where
it appears to present a good match, however it also absorbs most
of the power. If the two capacitors are identical, one way to
adjust the unit is to set one at full capacitance, and the other
at minimum. Then rotate BOTH at the same time in opposite
directions, in the same amount. This causes the two capacitors to
act as a single differential capacitor, and if you find a good swr
null, it will be one with the least power loss.
However there are better networks. The
common L network is simple, has low loss, and performs as a low
pass filter to reduce harmonics. It also uses fewer parts.
There is also the Z match. This uses a coupling link to a wide
range tuner with a series capacitor coupling to the transmitter.
The Z match requires a fixed coil with a one or two taps and a
coupling link, one dual variable cap, and one single variable
cap. Broadcast type capacitors will handle up to about 100 watts,
and the miniature transistor radio type variables with plastic
dialectric sheets will handle about 20 watts (good for most QRP
rigs).
On 5/6/22 18:40, PA1DMG via groups.io
wrote:
Hi All,
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On Sat, May 7, 2022 at 12:08 AM, ken WA2MZE wrote:
So what ? The rig LPF has already sorted out the harmonics. And beside, ANY tuning network has a Q factor, meaning that anything outside of it's matching frequency is attenuated anyway, usually by at least 10db in the real world.
Any mistuned network will lose power L, T or Pi etc if you incorrectly use values that create a match, but have a lower Q factor (odd ball L and C values). Your assumption that it can only occur in a T network is bollocks.
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You’re right about the Z match being wide-range. The price is at the high end, but I’m happy with my EMTECH ZM-2. After doing a lot of reading up on portable antennas, I opted for non-random over a half-wave end fed, in part because they can be shorter than the 65-foot length of a half-wave on forty. I’ve had good luck with lengths as short as 29 feet on forty. That is a good length to string up to a tree.
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The tuning of the ZM-2 was a bit touchy until I got Nelson Antennas’s 9:1 UNUN on eBay. The combination has been a dream to tune. I display the SWR on a NanoVNA, use the left knob to move the dip onto the band and then the right knob to refine the tuning. Without the NanoVNA you can tune first by peaking the noise in the receiver and then tweaking to get a SWR-indicating LED to go out. Here’s the lengths for non-resonant antennas. https://www.hamuniverse.com/randomwireantennalengths.html The QRP Guys Multi Z Tuner is also a Z match. It costs less but lacks the pretty box of the ZM-2. —Mike Perry, WA4MP
On May 6, 2022, at 6:06 pm, ken WA2MZE <wa2mze@...> wrote:
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Steve in Okinawa
Nice mods! I've also modded one - yellow core, fewer turns, extra capacitors switched in, and a 3-watt resistor in the tune bridge. Carol Milazzo's blog is also very useful. I use mine with a random wire and 9:1 unun, easy to tune on 40 through 15 without leaving my seat! JS6TMW
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Hi Mike, yes i've seen the qrpguys products as well. However, I didn't know them at the time I ordered the Chinese kit.
They're probably a lot better, but this one now works well enough to try out for a while. Regards, Marc - PA1DMG
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I built a Z match tuner from a circuit which is almost the same as the Emtech.
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