Topics

What are you QRP guys using to measure power?

N3IZN@...
 

I have a CB power meter that sort of works on 10 meters. On the 10 watt scale show .25 watts on stock U3 on 28 Mhz. On 40 meters not so good. Shows 2.5 watts.

While on the subject. What about you MF guys, what are you using to measure power?

"Facility 406 DM09" <facility_406@...>
 

Boonton 428D MicroWatt Meter, DoD traceable.

Kurt

"Facility 406 DM09" <facility_406@...>
 

I found a 42BD is that the same?

Yes, sorry, pulled it out into the light, 42BD.

Kurt

John Molnar <wa3etd@...>
 

Rough process - if you have a decent scope, take p-p RF voltage, multiply that value by 0.707, square the result and divide by 50...RMS watts...assuming your antenna system is pure resistive 50 ohms!!  Get ya in the ballpark - probably as close as CB meter!

John WG2XKA


On Tue, Dec 31, 2013 at 6:52 PM, <N3IZN@...> wrote:
 

I have a CB power meter that sort of works on 10 meters. On the 10 watt scale show .25 watts on stock U3 on 28 Mhz. On 40 meters not so good. Shows 2.5 watts.

While on the subject. What about you MF guys, what are you using to measure power?


groups@...
 

Hi All,


Very similar to John's method I use an oscilloscope with my U2 terminated in a 50-ohm load. My 'scope will display the amplitude in rms volts which helps with the maths.


73,


Peter


G4DJB

wolfpcgn@...
 

Hi John,


I am using a Perseus SDR with an additional 50dB attenuator.

Yesterday I made the first measurement on 10m: 50mW Output (with 3 FETs).

Today I startet the first transmissions: more than 3000km (abt.1600 miles) with this power into an ICOM AH8000 (Discone, should work from 100MHz!)


Wolfgang (DF1KZ)



ke7hr@...
 

When I do not use a digital oscilloscope and a 50 ohm load, a simple RF probe which works with a multimeter and a 50 ohm load does the trick.


N5ESE probe is simple to make and gives pretty good accuracy down to about 30 mW.  Look at:

http://www.n5ese.com/rfprobe1.htm

http://www.n5ese.com/rfprobe2.htm


I built a spreadsheet to give me a look up table instead of having to punch numbers into the calculator.


The difference that you are seeing between 10 meters and 40 meters may be real.  The transmitter is much more efficient at lower frequencies and the RF output goes up.


Paul KE7HR

Brian Pease <bpease2@...>
 

You meant peak voltage (not peak-peak). The equation is then correct.
My digital scope gives RMS voltage directly, which I measure across a 50 Ohm dummy load. This works at MF and HF for QRP or higher power.
Also at MF I usually use an old HP-400FL AC Voltmeter to measure across the load. This will measure micro-power levels up to 10MHz. These are available at Hamfests for a few dollars.

ke7hr@...
 

QRP Kits is putting out a kit for the RF probe.

 

http://www.qrpkits.com/rfprobe.html

 

Paul KE7HR

airdry@...
 

I use this digital wattmeter ... a fine kit ..google k5bcq/Kits  .. David VE3KCL

ccoles326@...
 

Hello,
I'm using the radio-kits power meter kit. It's flippin' great!
--

It's a really useful kit. Great fun to build.

Find them here: https://www.radio-kits.co.uk/

#wattmeter

Best regards,
Chris
M0XFL

Eng. Fabio Barroso <fbbrito@...>
 

Hello, 

I am using my power meter model RS-102. It is beautiful and accurate with a green backlight.

73, PT7CA



Em sex, 29 de mai de 2020 às 17:56, <ccoles326@...> escreveu:

Hello,
I'm using the radio-kits power meter kit. It's flippin' great!
--

It's a really useful kit. Great fun to build.

Find them here: https://www.radio-kits.co.uk/

#wattmeter

Best regards,
Chris
M0XFL

--
Fábio Barroso Brito
Engenheiro de Telecomunicações
CREA 061787033-0 

ajparent1/KB1GMX
 

I use...

QPSA, a Steve Webber design for over 10 years ago also SWR/frquency counter/aux
audio amp.

DL5NG terminated diode mount (up to 10mw or so, with calibration table.

A dummy load based on caddock resistors (25W) and diode for the
10mw to  20W range HF and calibrated.

Bird Model 43 throughline watteter. Large number of slugs for it.
Loads:  Bird Dummy load (100W), Heath cantenna for higher power.
A lower power 100W pint-enna  (high power (caddoc) resistor in Pint can.

RIgol DSA815T or HP8568B SA with 30DB 50W power attenuator (narda 7768-30)
Also a Bird 50W model similar.

All in cal.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting

Mike Besemer - WM4B
 

Looks like it’s NLA.

 

Mike

WM4B

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of ccoles326@...
Sent: Friday, May 29, 2020 4:56 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] What are you QRP guys using to measure power?

 

Hello,
I'm using the radio-kits power meter kit. It's flippin' great!
--

It's a really useful kit. Great fun to build.

Find them here: https://www.radio-kits.co.uk/

#wattmeter

Best regards,
Chris
M0XFL

Mike Besemer - WM4B
 

I think we need a QRP-Labs meter – 0 to 5 watts!

 

Mike

WM4B

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of ajparent1/KB1GMX
Sent: Friday, May 29, 2020 5:39 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] What are you QRP guys using to measure power?

 

I use...

QPSA, a Steve Webber design for over 10 years ago also SWR/frquency counter/aux
audio amp.

DL5NG terminated diode mount (up to 10mw or so, with calibration table.

A dummy load based on caddock resistors (25W) and diode for the
10mw to  20W range HF and calibrated.

Bird Model 43 throughline watteter. Large number of slugs for it.
Loads:  Bird Dummy load (100W), Heath cantenna for higher power.
A lower power 100W pint-enna  (high power (caddoc) resistor in Pint can.

RIgol DSA815T or HP8568B SA with 30DB 50W power attenuator (narda 7768-30)
Also a Bird 50W model similar.

All in cal.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting

fred.g3srf@...
 

For low power, I use a Marconi TF1152/A. 1960's vintage it uses a thermocouple so the calibration can be checked at DC and it's good to VHF and low UHF. Two ranges of 10 Watts and 25 Watts. No good for SSB, only CW, AM and FM.

Al Clark
 

I use the QRPoMeter by NM0S David Cripe.  https://www.ebay.com/itm/QRPoMeter-Digital-15W-QRP-Wattmeter-Dummy-Load-VSWR-Meter-Kit/254596727364?hash=item3b4725c244:g:fgAAAOSwlY1ZMMdT
Handles up to 15 watts, won't let your rig see a high SWR, and is accurate.  Easy to build and calibrate.

--
Al W4KY

Mike Besemer - WM4B
 

Interesting.  Mine is off at least 50% compared to measuring with a scope.  Build has been validated; something is afoot at the Circle K.

 

Mike

WM4B

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Al Clark
Sent: Friday, May 29, 2020 6:17 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] What are you QRP guys using to measure power?

 

I use the QRPoMeter by NM0S David Cripe.  https://www.ebay.com/itm/QRPoMeter-Digital-15W-QRP-Wattmeter-Dummy-Load-VSWR-Meter-Kit/254596727364?hash=item3b4725c244:g:fgAAAOSwlY1ZMMdT
Handles up to 15 watts, won't let your rig see a high SWR, and is accurate.  Easy to build and calibrate.

--
Al W4KY

Daniel Conklin
 

I'm using the QRP guys 12w dummy load hooked to a resistive voltmeter. V squared divided by 100=watts 
--
73, Dan - W2DLC

George Korper
 

Me too. The QRPoMeter ( I have two) is accurate, fun to build and worth every penny. 


On Fri, May 29, 2020 at 6:17 PM Al Clark <hotdogx@...> wrote:
I use the QRPoMeter by NM0S David Cripe.  https://www.ebay.com/itm/QRPoMeter-Digital-15W-QRP-Wattmeter-Dummy-Load-VSWR-Meter-Kit/254596727364?hash=item3b4725c244:g:fgAAAOSwlY1ZMMdT
Handles up to 15 watts, won't let your rig see a high SWR, and is accurate.  Easy to build and calibrate.

--
Al W4KY