Milliwatting with the 6500...What is the Transverter line power output on my 6500?

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The other day, just for fun, I ran an interesting experiment with my friend about a mile away...

I connected my 80 meter offset fed dipole to the transverter output of my 6500 and was audible at a solid S5-6 on 10 meters SSB at a distance of 0.8 miles.
When I turned the power control down to "10," I was still audible just at the noise level, about S1-2. Both he and I were very impressed.

My question... Has anyone measured the power output from the transverter jack at various power level settings? I am curious as to whether this would be an interesting way to do "extreme milliwatting?"

I am aware that the standard of 0 dBm means one milliwatt, but what are some actual measurements? And has anyone tracked them with reduced drive level settings?

Has anyone else run a dumb experiment like this? I would like to hear some more of your experiences...
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Ken - NM9P, Elmer

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Posted 6 years ago

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Steve - N5AC, VP Engineering / CTO

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It is calibrated in dBm so you should be able to run the control up and down and read the output power.
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Doug Hall

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For anyone who is interested I measured the transverter output on my 6300 today. I used a Rigol spectrum analyzer with a 20 dB attenuator on the input. My measurements agree (within the limits of my equipment) with the Flex specifications. (50 ohm impedance assumed.)


If you want to calculate the transverter output level (in dBm) for a given SmartSDR power setting (1-100) you can use the following formula:

dBm = ((26.5/99) * (SmartSDR Power Setting - 1)) - 11.5

and if you want power in mW:

mW = 10 ^ (dBm / 10)

73,
Doug K4DSP
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Ken - NM9P, Elmer

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I need to load this into a spreadsheet so I can calculate it in mW vs. power setting.
Thanks for the measurements.

Ken - NM9P
(Edited)
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Ken - NM9P, Elmer

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I made a spreadsheet to calculate both dBm and Power in milliWatts based upon transverter output power setting.

Here are a few data points:  These are rounded approximations because the actual settings don't land evenly on precise numbers.

Power     Power
Setting    Out (mW)
    1  =  0.071 mW
    7  =  0.1 mW   (0.102 mW)
  33  =  0.5 mW   (0.509 mW)
  44  =  1.0 mW   (1.002 mW)
81/82 = 10 mW  (actually halfway between 81 & 82 = 10 mW)
  88  =  15 mW    (15.093 mW)
  99  =  30 mW    (29.73 mW)
100  =  31.62 mW

I hope this helps

Ken - NM9P
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Andrew Russell

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G'day Steve, \
Just to be sure, that means that the slider follows a log function for power/voltage if calibrated in dBm.\
I have recently smoked a mosfet in a 137kHz amp with too much drive.\
100mw or 20dBm at 100.
Andrew
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Eric - KE5DTO, Official Rep

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Official Response
When transmitting on the XVTR port below 80MHz, the RF Power slider is set to put out -11.5 to +15 dBm (-11.5 at setting 1, +15 at setting 100). Above 80MHz, this range is -11.5 to +8dBm.
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Craig Gagner

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Is this true of the 6300 as well as the 6500?

Craig - kg7ncf

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Eric - KE5DTO, Official Rep

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Yes.  Those models don't do the part above 80MHz, but the lower frequencies should have the same power output setup and controls.
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Ken - NM9P, Elmer

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OK...I majored in Math & Physics before I went on for my MDiv, but haven't done these calculations in a long time....
Someone check me here...

Starting with 0 dBm (1 milliWatt)

mW = 10^(dBm/10)

+15 dBm yields 10^(15dBm/10) = 31.623 milliWatts

+8 dBm yields 10^(8 dBm/10) = 6.31 milliWatts

-11.5 dBm yields 10^(-11.5 dBm/10) = .0708 milliWatts

This sounds about right to me.
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Steve - N5AC, VP Engineering / CTO

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Correct, Ken. We tend to forget everyone doesn't do dBm and mW all day long ;-)
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Ken - NM9P, Elmer

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No problem. It gave me a chance to look some long-forgotten formulas and brush up on my logarithms!

But I was impressed that I was audible at .0708 mW at a distance of .8 miles. and solid copy at somewhere around 5 mW! I was using my 80 meter OCF Dipole at 18 ft. and he was using a rotatable multi-band dipole at 50 ft.

I may try some serious QRPp with this this winter after the summer/autumn thunderstorm static dies off.

This is such a neat rig for both QRP and QRO, why do I need to keep my 1500? (Because I like it, that's why!)
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DrTeeth

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" It gave me a chance to look some long-forgotten formulas and brush up on my logarithms! " Logarithms...that brings back school memories. Talking of school maths, I used Pythagoras once to calculate the surface area of my home's roof without leaving the ground. My insurance company wanted to know  the ratio of flat roof area to sloping.

Sri fer OT post...I'll get my coat.
(Edited)
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Mark Erbaugh

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I just tried some mW operation with WSPR.  By my calculations from above a RF power setting of 3 results in an output of 1 mW. I set up WSPR and transmitted with 1 mw to a vertical antenna on 30m. According to the WSPR website, my signal was hear at least twice in NH (from OH).  By my calculations a setting of 62 is 20mW. That was heard by several stations.

Then I tried CW. I noticed a relay clicking on every element. The RX and TX antennas were both set to XVTR. Is this normal?  I'm using a WinKey USB and keying by CW and MOX with the WinKey. This is what I use for normal operation on ANT1 for both RX and TX and I don't hear the relay clicking.

Also,  when I transmit WSPR using DIG-U, the indicator button in Orange, but when I tried CW, the indicator button is Red (just in case, I did have a dummy load connected to my ANT1 output).
(Edited)
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Mark Erbaugh

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Steve,

Things are a bit strange here.  This is a 6300 and 1.4 software/firmware.  When the XVTR is enabled and I transmit in USB, the LED is indeed orange. When I transmit in CW, the LED is definitely RED and the relay is clicking like it is switching antennas. The antenna selection definitely has XVTR set for both Rx and Tx. Even though both antennas are XVTR, the QSK indicator is not lit.

I monitored the current and even though the LED is RED not ORANGE, I don't see a current increase like I do if not in XVTR mode.

Also, sometimes by switching to CW with XVTR, my sidetone goes away. The only way I've been able to restore it is a reset.  Speaking of a reset, the manual says to hold down the power button until the LED flashes PURPLE, but if I hold the power button down, the LED flashes WHITE.

After the reset, things appear normal until I setup a XVTR and switch to that. I get the same behavior.

73,
Mark
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Steve - N5AC, VP Engineering / CTO

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The relay is required when switching between RX/TX on XVTR.  It switches the antenna port between the exciter and the SCU receiver.  So anytime you use a " transverter common" setup, you will hear a really click.

OK it's possible that the LED logic has an issue in the CW mode for XVTR.

So you are saying that you lose the sidetone in CW on transverter on occasion?  Does toggling the sidetone on/off help restore it?  I've not seen this before.

I've entered an issue on the documentation LED color
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Mark Erbaugh

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No, toggling the sidetone on and off didn't restore it.
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Tim - W4TME, Customer Experience Manager

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I have added the side tone issue to the bug tracker for additional investigation. 
(Edited)
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Bill W2PKY

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32 mW on 20M or 15M Jt65 was spotted all over conteniental US using an Inverted "L". Made bunch of contacts in a QRP contest. 1 Watt was spotted all over Europe. On a clear channel doesn't take much.
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Mike - VE3CKO, Elmer

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I didn't major in Math & Physics so I used good old google, "dBm to milliwatts" 
http://www.rapidtables.com/convert/power/dBm_to_mW.htm

this is one of many online calculators that seem to fit Ken's calculations
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pa0bie

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I am using this "minidbcalc" already for years:

http://mini-db-calculator.software.informer.com/

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EA4GLI - 8P9EH - Salvador

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This makes for some interesting propagation and antenna experiments.

I just plugged the XVRT port to the log periodic antenna which I had to lower to about 9 ft because we have strong winds right now.

I started WSPR and launched my first TX sequence, and right way I was heard, with 0.032w in Germany as well as the US.