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Author Topic: (TR)USDR: tuner or resonant antenna?  (Read 227 times)

KD2HPQ

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(TR)USDR: tuner or resonant antenna?
« on: March 07, 2023, 07:08:29 AM »

I finally hooked up this tiny radio and completed a phone QSO with a station about 600 miles away on my first try, very first call. The antenna I used was "resonant" on 20m, with an SWR of about 1.2:1 as measured on my IC-7300. I do not know if I can duplicate that performance at a park, so here's the question:

Resonant antenna or tuner? I ask because I have never been able to duplicate the exact performance of my home-optimized end fed antennas at parks. I'd hate to get an acceptable but high-ish SWR in my yard, then see it's 8.7:1 at the park.

I have not been able to find any information on the "best" antenna or tuner to use with this radio. I've never owned an automatic tuner but I assume they work with any radio or antenna. However, I don't see anything in the (TR)USDR notes that mentions a tuner.

Some have suggested a vertical antenna, and I'm open to that idea as well. However, the suggestion was to use one of the KC8VWM designs. Upon investigation these look bulkier, heavier, and more difficult to set up than a wire in a tree.

Suggestions?
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AC7CW

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #1 on: March 07, 2023, 07:38:45 AM »

The simplest, most dependable, resonant antenna is a center fed dipole. I guess they can be deployed as slopers, never tried that but in a park that would mean only one end had to be elevated. Quarter wave verticals are dependent on the ground and typically radials are used. They are adjusted for resonance by altering the length of the vertical a little at a time. I'd choose one of those types of antennas or try both and see what happens.
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Novice 1958, 20WPM Extra now... (and get off my lawn)

K6SDW

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #2 on: March 07, 2023, 07:53:01 AM »

Yes, watch the ARRL/QST new technical editor, KE0OG, YouTube videos on all these subjects. You could also get a copy of the ARRL Antenna Handbook....great night-time read...LOL. Of course, there's plenty of antenna "experts" out there as well, I'm not one of them....HI HI

Dave's motto regarding antennas: "Everything affects everything"

Welcome aboard.....GL/73
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W1VT

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #3 on: March 07, 2023, 07:54:32 AM »

If you can get wires in the trees at 30ft or higher I have had great success with center fed half wave dipoles fed with RG-58 coax.
For long trips out of state I'd bring two simple stations, one for 40 and another for 20M.  If needed I could join the feedlines with a barrel for a long feedline and just use one station.
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VE3WMB

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #4 on: March 07, 2023, 08:11:38 AM »

One thing to consider with the (tr)uSDX and in fact any radio that uses Mosfets as PA transistors, is that these FETS are pretty durable but can be unforgiving when presented with a complex antenna impedance, sometimes  letting out their smoke during the antenna tuning process.

When using a non-resonant antenna the safest solution is to use a manual QRP tuner that has a resistive bridge circuit built-in that ensures that the PA sees a stable 50 ohms during the tuner adjustment process. Tuners like this one from QRP Labs have this feature : https://qrpguys.com/multi-tuner


 An alternative, is to reduce the supply voltage to the rig during antenna tuning. The (tr)uSDX can be powered via the USB port for QRPp operation and might still supply enough output power for an autotuner like the Elecraft T1 to do its thing. When I had my KD1JV MTR-3B I often just used a 9v battery as a power source during antenna tuning and switched to a 12V LiIon pack for operating.

If you want to use an autotuner then you can always insert one of these between the rig and tuner to protect the rig while the ATU does its thing: https://qrpguys.com/tuning-indicator . You just need to remember to switch it into "TUNE" during tuning and back to "OPERATE" after the antenna tuning process is complete. 

Cheers

Michael VE3WMB

P.S. With a compact rig like the (tr)uSDX it is convenient to be able to use just a piece of wire thrown over a tree branch as an antenna and worked against a few radial wires on the ground. With a small antenna tuner this gives you a truly pocket-sized station that can be used multi-band.  FWIW, a 27 to 28 foot wire works pretty well on 40m and up and is easy to match.


 
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KD2HPQ

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #5 on: March 07, 2023, 08:14:53 AM »

If you can get wires in the trees at 30ft or higher I have had great success with center fed half wave dipoles fed with RG-58 coax.
For long trips out of state I'd bring two simple stations, one for 40 and another for 20M.  If needed I could join the feedlines with a barrel for a long feedline and just use one station.
It's often hard enough to get ONE 30 ft attachment point, much less the 3 required for a dipole. A dipole is totally out of the question.

The choice is between an end fed resonant (or at least low SWR) on several bands, or something similar plus a tuner. I don't even know if a tuner works with this radio. I'd assume an auto tuner would, but there's nothing in the documentation.

Looking for specific recommendations here :)
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KD2HPQ

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #6 on: March 07, 2023, 08:18:59 AM »

One thing to consider with the (tr)uSDX and in fact any radio that uses Mosfets as PA transistors, is that these FETS are pretty durable but can be unforgiving when presented with a complex antenna impedance, sometimes  letting out their smoke during the antenna tuning process.

When using a non-resonant antenna the safest solution is to use a manual QRP tuner that has a resistive bridge circuit built-in that ensures that the PA sees a stable 50 ohms during the tuner adjustment process. Tuners like this one from QRP Labs have this feature : https://qrpguys.com/multi-tuner

How about tuning the wire UNPLUGGED from the radio, then plugging in the radio?? The radio doesn't need to participate, no?
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KD2HPQ

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #7 on: March 07, 2023, 08:41:48 AM »

One thing to consider with the (tr)uSDX and in fact any radio that uses Mosfets as PA transistors, is that these FETS are pretty durable but can be unforgiving when presented with a complex antenna impedance, sometimes  letting out their smoke during the antenna tuning process.

When using a non-resonant antenna the safest solution is to use a manual QRP tuner that has a resistive bridge circuit built-in that ensures that the PA sees a stable 50 ohms during the tuner adjustment process. Tuners like this one from QRP Labs have this feature : https://qrpguys.com/multi-tuner

How about tuning the wire UNPLUGGED from the radio, then plugging in the radio?? The radio doesn't need to participate, no?
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WB6BYU

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #8 on: March 07, 2023, 09:39:20 AM »

Quote from: KD2HPQ

It's often hard enough to get ONE 30 ft attachment point, much less the 3 required for a dipole. A dipole is totally out of the question...



There is no reason that a tuner wouldn't work with that
radio.  The radio just sees an impedance at the antenna
connector - it doesn't really care what all is connected beyond
that point.

But adjusting an antenna tuner at full power can present
unfavorable impedances to the radio.  Common solutions
are either to reduce power during tuning, or to use a
resistive SWR bridge that will act like a dummy load and
present a suitably low SWR while the tuner is being
adjusted.  (You then have to switch it out of the circuit
so your transmitter power makes it to the antenna.)


Meanwhile, I'd encourage you to reconsider the use
of a dipole or inverted vee.   You don't need 3 high
points - just one is sufficient. 

I've used a portable dipole kit (and no antenna
tuner, sometimes not even an SWR meter) from a lot
of different locations, from the Australian outback to
ocean cliffs to mountain tops in Alaska, beaches in
Hawaii, islands in Maine, campgrounds, wilderness
areas, parking lots, and pastures in Nova Scotia. 

Usually I just toss a rope over a tree branch, hoist
the center of the dipole, tie off the ropes on the
ends of the wires to rocks, bushes, tufts of grass, or
whatever is available, plug the coax into the rig, and
operate.

Sometimes it takes a bit of creativity:  I have propped
the center of the antenna up on my walking stick if
there is no other support, or hung it between two rock
outcrops (in one case with a 300' dropoff between them),
or two piles of road gravel, or used a handy fence post, or
run the antenna wire along a hedge.  (Running the dipole
along a barbed wire fence, however, didn't work very well.) 
I can string it up as a sloper or vertical dipole (useful for
seaside operation) or an inverted vee, or even a horizontal
dipole strung between two trees.

Perhaps the most important point is that I don't always
know in advance how I am going to set it up, but I'll
figure out how to do that when I find a location.

For backpacking I only carry 25' of feedline, using RG-174.
Yes, I lose 1/4 of my power on 10m in that length, but
the ability to get the antenna up in the air makes up for
the cable loss.  In practice my antennas may only be
up around 15' or so, depending on the available supports.
That's still enough to make contacts.

The dipole kit has wires cut for each of the pre-WARC HF
bands, 80m through 10m.  I can add whatever set of
elements I want each time I set it up.  Sometimes when
time is limited (like a lunch stop while backpacking) I
only put up one band, while if I'm staying a while I might
set it up for all 5 bands.  That allows me to switch bands
without making any changes to the antenna, which can
be very convenient in the middle of a storm.

That's not to say that the dipole is always the best portable
antenna, but, having used the present dipole kit for ~40
years, that's what I would choose if I could only take one
antenna.  Its small, light, cheap, efficient, versatile, and
usually doesn't require a tuner (depending on how sensitive
your radio is to SWR).  I pre-cut the wires years ago in a
local park, and now just string them up and use them.
These days I have larger kits using RG-58 for Field Day,
emergency service, and other uses when the small size
and light weight isn't as important as it is for backpacking.


Here is my backpack dipole kit.
And large versions of it.

Here are some videos of setting it up.  (I'm moving relatively slowly in
these for the benefit of the videographer.  This
summer I'll try to to it in a 1 minute video.)

KD2HPQ

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #9 on: March 07, 2023, 09:59:41 AM »

Quote from: KD2HPQ

It's often hard enough to get ONE 30 ft attachment point, much less the 3 required for a dipole. A dipole is totally out of the question...



There is no reason that a tuner wouldn't work with that
radio.  The radio just sees an impedance at the antenna
connector - it doesn't really care what all is connected beyond
that point.

But adjusting an antenna tuner at full power can present
unfavorable impedances to the radio.  Common solutions
are either to reduce power during tuning, or to use a
resistive SWR bridge that will act like a dummy load and
present a suitably low SWR while the tuner is being
adjusted.  (You then have to switch it out of the circuit
so your transmitter power makes it to the antenna.)


Meanwhile, I'd encourage you to reconsider the use
of a dipole or inverted vee.   You don't need 3 high
points - just one is sufficient. 

Thank you for the detailed response. I'm sure your design works splendidly. But, my friend, I have nightmares about taking a big pot of spaghetti like the one in your photo, and unraveling the strands for the various bands. I'm old and easily frustrated. Untangling a single wire that I have mis-wound is about as much as I can take before throwing everything back into my trunk and going home.

Operating portable is all about simplicity, versatility, and ease of use. I will sacrifice an S unit for a 5-minute setup (with my current equipment, an IC705, EF, tuner), vs. 40 minutes of swearing and cursing Marconi and all his descendants.

So I repeat my original question: What's a good tuner to use with the (TR)uSDR and an end fed wire? Will any manual tuner do, if I disconnect the radio before tuning? Can you recommend a QRP tuner?

Thanks!
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N8NK

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #10 on: March 07, 2023, 10:50:44 AM »

In my humble opinion, you just can't do better than a simple end fed wire and Multi-Tap UNUN. It's the perfect solution. You will most likely find that you don't need a tuner at all. I rarely do, and operate my end feds on multiple bands, usually with a match that does not require further tuning.
I have a playlist for all my end fed and Multi-Tap UNUN work. It's at:
https://www.youtube.com/watch?v=lTb3sFydpPQ&list=PL3CPduOS04Ncrid9dWw-p5fWFQkvMLKIi
And here's a sample... '80 EFHW & Multi tap UNUN part 1 of 3 Intro & Demo' at https://youtu.be/lTb3sFydpPQ
Chuck, on youtube as
N8NK QRP
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KD2HPQ

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #11 on: March 07, 2023, 11:45:26 AM »

In my humble opinion, you just can't do better than a simple end fed wire and Multi-Tap UNUN. It's the perfect solution. You will most likely find that you don't need a tuner at all. I rarely do, and operate my end feds on multiple bands, usually with a match that does not require further tuning.
I have a playlist for all my end fed and Multi-Tap UNUN work. It's at:
https://www.youtube.com/watch?v=lTb3sFydpPQ&list=PL3CPduOS04Ncrid9dWw-p5fWFQkvMLKIi
And here's a sample... '80 EFHW & Multi tap UNUN part 1 of 3 Intro & Demo' at https://youtu.be/lTb3sFydpPQ
Chuck, on youtube as
N8NK QRP

I really really like this but it's too complex and messy for the greater outdoors. Too complicated. I'd consider this for my main 100w station but it's just too much for portable.

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WA3SKN

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #12 on: March 07, 2023, 03:08:40 PM »

Get or make an antenna tuner.  Turn off the internal tuner and use this with your antenna.  For QRP it does not have to be big or bulky.  Switch to twin lead/ladder line feed when you can.

-Mike.
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N8TGQ

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #13 on: March 07, 2023, 03:45:50 PM »

I'd like to put a vote in for the end-fed half-wave antenna. I have one cut for 40 meters (about 65') that also works well on 20, 15 and 10 meters. I use the SOTA tuner from QRPGuys. It gives you the 49:1 matcher, a basic SWR indicator, and a capacitor for touching up the SWR on the different bands. I tied marker knots in the 65' wire to mark the resonant point for 30 and 17 meters, and just wind the wire out to the right length for those bands.

I have been using this for 10 years now. I've put it in trees, used a 16' fishing rod and just laid it over some bushes sometimes. I have worked Costa Rica, Europe and Great Brittain on 20m with the antenna at the 40m length and 3 watts. Sometimes I use a short counterpoise, but very seldom. For ease of use and most bands, it's hard to beat.

If you're gonna order one of these kits, please get it directly from QRPGuys. The counterfeit stuff on Amazon and ebay are junk with no quality control or warranty. Buy American and keep our homegrown radio companies alive!
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WB6BYU

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Re: (TR)USDR: tuner or resonant antenna?
« Reply #14 on: March 08, 2023, 07:06:43 AM »

Quote from: KD2HPQ

...So I repeat my original question: What's a good tuner to use with the (TR)uSDR and an end fed wire? Will any manual tuner do, if I disconnect the radio before tuning? Can you recommend a QRP tuner?




VK3YE has several suggestions
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