Far more significant to me are the very recent firmware updates that corrected two major shortcomings with the radio:
Strict DC input voltage limitations and
Common failure of the final BS170's during high SWR at full power.
These two issues prevented the QMX (and QMX+) from being a serious consideration for outdoor ops who don't use resonant antennas and don't want to take along a buck converter, LiPo battery or place "dropping diodes" in series with the DC source.
Those are a lot of things to contend with if you want to just set up and be on the air with minimal fuss.
They are no real issue at all though, if you don't mind taking the time to accommodate the radio rather than have the radio accommodate you.
Sometimes I like to savor the steps necessary to put a station on the air and don't mind taking extra time (and steps) to enjoy the process.
But for a roadtrip like the one I have planned, I want a minimal to-do list and a quick set up time - and I'm happy to say that the QMX/QMX+ now support this.
This morning's was my first activation with the 15-40m QMX. Hans built this one for me and expedited it to me a few months ago as I was trying to get permission to operate in Vietnam and Thailand. Thailand said 'Yes" but Vietnam said "No, don't even bring a radio here". So I had to leave the radio at home since VN was our first stop.
Now, with a different type of trip on the horizon, the little QMX again has become the front runner of the 4 radios I'm considering.
I made contacts this morning on all 5 bands, using the same antenna (5m/17-ft) whip, a ZM-2 tuner and my motorcycle's battery.
I didn't shorten the whip for the higher bands; I lazily let the tuner take care of that because I wanted to use the QMX's TUNE feature, tuning the ZM2 as I watched the result on the QMX. I verified the tuning solution with a proper antenna analyzer; the two agreed on all bands, every time and the radio never shut down due to high SWR while tuning.
It still boggles my mind that this radio is the same size as a deck of cards!
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Hi John,
ReplyDeleteIn your last post you mentioned adding a coil to the whip for 40m.
If you measure your counterpoise wire at 1/4 wave for each band and keep it up off of the ground, and adjust the whip, you won't need a tuner, and it's quite repeatable once you get the hang of it. I keep 28 ga wire on a winder and unwind a 1/4 wave for each band and leave the rest on the winder. 28ga is so light that the slightest tree branches, bushes, or sometimes even tree bark is enough to keep it off of the ground.
I used to rely on the AH-705 with my IC-705 but once I got the hang of the NanoVNA (I see a RigExpert in your photo) my Icom gear stays home and my QRP Labs gear goes everywhere.
A NanoVNA would be smaller than the ZM-2.
Brian
KB9WFS
Hi Brian, I *usually* do activations where I can take the time to make those adjustments manually but for an upcoming road trip, I'm trying to find a way that focuses on speed, simplicity and less stuff - even when changing bands. The ability to use a single antenna as-is, even through band changes, requires me to use a tuner.
DeleteI'm willing to sacrifice efficiency for speed sometimes...
But for best efficiency, as you mention, above ground radials are the way to go. ON4UN's lowband DXing book agrees and says that 4 elevated radials are equivalent to 120 radials on the ground.
73,
John
I get excellent swrs with just a few short radials resting on the ground. This provided sufficient capacitance coupling to make an effective counterpoise. Think about how a car magmount works...
ReplyDeleteCongrats on the activation!
ReplyDeleteI nearly always use a resonant antenna (these days a trapped one for 20/30/40) with my QMX, with excellent results. On occasions when I have been unable to find appropriate trees, I have occasionally used a 17m whip: super-convenient. Sometimes my homebrew coils weren't enough, even with the ZM-2, but elevated radials made it work well.
With my QMX I use a TalentCell battery that is the same size as the QMX (super compact!) and puts out 12v. No longer so relevant with the updated firmware but still a great size and still plenty of power for all-day pota roves.
My pota-cycle is a KLR 650: the QRP (underpowered and cheap) of highway-capable motorcycles. :-) I'm looking forward to more hospitable weather!
73 de Todd W2TEF
Hi Todd,
DeleteI have a small manual tuner on the way that is the same size as the QMX. Hopefully it will work as well as the ZM-2. Confession time: I started out on 40m this morning and forgot to telescope the whip. The ZM-2 was able to give a good match on 40m even with the whip's retracted height of about 21 inches! Of course no one answered my CQ and then I glanced over and saw the results of my senior moment...
I had a KLR650 abut 15 years ago - it was too tall for me but I see they have a shorter version now. Regardless, I'm really liking the QRPp 300cc Honda - more than I thought I would.
73,
John