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Author Topic: milliwatt QRP activity?  (Read 1385 times)

N6YWU

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milliwatt QRP activity?
« on: December 07, 2020, 09:53:12 AM »

Who here is experimenting with milliwatt QRP?

I've been transmitting milliwatt and sub-milliwatt WSPR signals from my Hermes Lite 2 SDR by generating low IQ signal levels with customized SDR code.  I then measure the Vpp of the Tx output into a dummy load with my oscilloscope to confirm the output wattage.

The WSPR format seems to not have an encoding for Tx levels below 0 dBm, so I have to annotate test signals below 1 mW in my Tx log.  So far, I regularly get multiple spots at 0 dBm.  But have limited success at -6 dBm and lower, getting only a few spots very occasionally, mostly from contest stations with monster antenna farms.  But I'm not only running mW QRP, but only using a simple wire (vertical) antenna.

The standard FT8 frequencies seem to be filled with more and more stations operating QRO and saturating the bandwidth.  Is there any organized separate FT8 wateringhole and day for experimenting with milliwatt QRP FT8?  Or enough interest to propose one?  For example, for CW, there's the NAQCC mW sprint on 12/16.
« Last Edit: December 07, 2020, 09:55:13 AM by N6YWU »
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N8NK

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Re: milliwatt QRP activity?
« Reply #1 on: December 07, 2020, 10:35:36 AM »

Hi there..
Although I'm not into WSPR, I'm a life-long QRPer, who's never used a 'gain' antenna: only wire antennas and simple junk verticals. I'm into CW... and if anyone wants to read about my best QRP contact, using 2mw, and working a South American ham and getting an honest 579, I've posted the story on YouTube. Just search for 'A QRP Story' and you'll find it. It really IS amazing what one can do with QRPp and CW!
Chuck
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WB0FDJ

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Re: milliwatt QRP activity?
« Reply #2 on: December 07, 2020, 01:46:47 PM »

I'll be interested to see what response you get here. I've never run power that low but when JT9 made it's debut I made some contacts running 500 mW without problems and then wondered, later, how low could I have gone.

I do a fair amount of WSPR and honestly mostly see decodes in the 2-5 watt range. One night after I had just put up my 6BTV I ran 1 watt on 80 meters. Considering I have a 100 foot run of RG8X and an antenna efficiency of what, 10% (?) I was "just curious" to see who would hear me. I was decoded by a DK0 in Antarctica. So this intrigues me.....

WB0FDJ Doc
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N6YWU

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Re: milliwatt QRP activity?
« Reply #3 on: December 07, 2020, 05:43:48 PM »

My WSPR distance record at 1 Watt (30 dBm) is a couple spots from DP0GVN on an Antarctic ice shelf (at IB59ui).  I almost never transmit above 1 Watt.  My 10 mW (10 dBm) WSPR transmission often get dozens of spots.  On 2 mW, my WSPR often get spotted by AI6VN/KH6, which is over 1000 miles per milliwatt.

But I'm still trying to get my WSPR (or FT8) signal spotted by a "normal" station while transmitting at under 1 mW.  Maybe by hiking up to some POTA/SOTA locale where my one of my wire antennas might have a bit more reach?
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W9IQ

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Re: milliwatt QRP activity?
« Reply #4 on: December 07, 2020, 06:10:44 PM »

Very nice reports. Congratulations!

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

WB0FDJ

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Re: milliwatt QRP activity?
« Reply #5 on: December 09, 2020, 11:10:20 AM »

I stand corrected. It was DP0GVN that decoded my WSPR signal on 80. I spent some time finding their research station on the web. I would love to be locked in their radio room some night with one of Rockmites....

Please update your experiences here on the forum. You have kindled my interest in milliwatt activity. Thank you

WB0FDJ Doc 73/72
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KU3X

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Re: milliwatt QRP activity?
« Reply #6 on: December 10, 2020, 12:05:09 PM »

I work 500 mw cw for a few months. I think I am up to 35 countries.
I don't work any hf digital modes, just cw.
I want to get back to QRPp and try to work 100 countries.
Barry
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WB6YRW

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Re: milliwatt QRP activity?
« Reply #7 on: May 20, 2021, 01:16:34 AM »

I received my ZachTek desktop WSPR (midplus 1.8 to 14 mhz) 2 days ago and found this thread.

I am running 350 milliwatts and broadcasting on all midplus bands, non stop.

This WSPR transmitter is fed into a 522 foot skyloop.

Earlier today I made contact from San Jose, CA to Tasmania, 7946 miles or 12,788 kilometers.

I am using the WSPR to perform a lot of antenna skyloop experiments.  I detailed the skyloop build from inception and now running WSPR experiments in the Antenna, Towers, and More section / Debugging a 160meter skyloop.  I was really surprised with Tasmania today.
« Last Edit: May 20, 2021, 01:21:28 AM by WB6YRW »
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K4KRW

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Re: milliwatt QRP activity?
« Reply #8 on: May 20, 2021, 11:35:24 AM »

The NAQCC group has a 2 hour CW milliwatt sprint in June and December.  The next one is on June 16th at 00:30.  (so the evening of June 15th in the US).  It is a lot of fun.  There are usually plenty of signals.  December had 80 participants who submitted a log.

http://naqcc.info

Richard - K4KRW
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N8NK

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Re: milliwatt QRP activity?
« Reply #9 on: May 20, 2021, 08:28:28 PM »

Altho the WSPR technology is amazing, and the various digital modes a lot of fun for hams because we love to screw around, and we're darn good at it. Lots of cool modes to pla with these days.
But the cycle is starting to perk to life in fits and spits.. little ones at first.. we are in for some MOST EXCELLENT DX using milliwatts and CW and SSB!
Please don't forget good ol' CW and phone when running QRPp!
May I humbly ask that you watch my story of working southern Argentina using 2.5mw? I'm not going to tell you what my signal level was there. You'll have to watch my story!  :)
Please watch 'a QRP Story'. By me. lol.
https://www.youtube.com/watch?v=ja6e_uISvZ8&t=1s
Be well all...
Chuck
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VK3YE

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Re: milliwatt QRP activity?
« Reply #10 on: May 21, 2021, 02:48:07 PM »

Who here is experimenting with milliwatt QRP?


Some of my experiments with milliwatts, including videos, are here:

https://vk3ye.com/qrp/milliwatt.htm
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Peter VK3YE/AK3YE    Youtube videos at VK3YE

Author of 'Minimum QRP', 'Hand-carried QRP Antennas', 'Ham Radio Get Started' and other popular books on ham radio.
All available in paperback or $US 5 ebook. Learn more at vk3ye.com or 'VK3YE Radio Books' on Facebook.

WB6YRW

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Re: milliwatt QRP activity?
« Reply #11 on: May 22, 2021, 10:27:57 AM »

Who here is experimenting with milliwatt QRP?


Some of my experiments with milliwatts, including videos, are here:

https://vk3ye.com/qrp/milliwatt.htm

Hi Peter,

I went to your website...you had a WSPR radio video with an output power reduction box attached.  Did you build or buy it?  Also, what measuring device did you use to confirm your output after using the power reduction box?

Have you come across amps  (commercial or kits or diy) that can boost the WSPR from 300 milliwatts up to 800 or 900 milliwatts?

thanks.

-stu
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KM1H

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Re: milliwatt QRP activity?
« Reply #12 on: May 22, 2021, 06:04:06 PM »

160M DXCC with 5W CW took over 30 years and 19 DXCC with 100 mW on CW.

No computer run modes planned or wanted.
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VK3YE

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Re: milliwatt QRP activity?
« Reply #13 on: May 28, 2021, 07:17:48 PM »


I went to your website...you had a WSPR radio video with an output power reduction box attached.  Did you build or buy it?  Also, what measuring device did you use to confirm your output after using the power reduction box?

Stu - I've used RF attenuators that are either a kit (no longer sold) or made from scratch. Every amateur handbook eg ARRL will have a circuit of an RF attenuator made with resistors and switches. Have maybe 3, 6 or 7 dB per section. Values can be calculated online for the amount of attenuation you want. It's also fairly easy to build QRP power meters or you could use an RF probe across a dummy load to measure the voltage and calculate the power from that.

Personally I wouldn't bother with boosting WSPR from 300mW to 800mW. But you could easily add something like a BD139 transistor (good up to about 10 MHz) to boost power up to about that level or a bit more. Or an IRF510 FET can give 5w or more. There are many circuits for amplifiers using these transistors.
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Peter VK3YE/AK3YE    Youtube videos at VK3YE

Author of 'Minimum QRP', 'Hand-carried QRP Antennas', 'Ham Radio Get Started' and other popular books on ham radio.
All available in paperback or $US 5 ebook. Learn more at vk3ye.com or 'VK3YE Radio Books' on Facebook.

N6YWU

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Re: milliwatt QRP activity?
« Reply #14 on: May 29, 2021, 10:46:20 AM »

To generate what I think are valid milliWatt and sub-milliWatt QRPp signals, I use a direct-sampling SDR (a Hermes Lite 2), and synthesize a sub-1-bit dithered IQ carrier (for CW, FT8 or WSPR FSK).  A low-pass filter on the Tx output removes most of the HF/VHF dither noise.  I then use an oscilloscope to measure the RF signal's peak-to-peak voltage across a 50 Ohm dummy load, and calibrate my digital IQ amplitude.  610 (+-10) mV peak-to-peak should correspond to transmitting at 0 dBm or slightly less.

I find that more convenient than using attenuators, as I can try different power levels in software, even when operating remote.

I would try more QRS CW, but nobody I've tried a scheduled a QSO with has so far heard my QRPp signal.  However my WSPR Tx at the same dBm sometimes gets spotted in multiple States.  So I'll stick mostly with trying the digital modes until maybe we have more luck with the sunspot cycle.
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