From: paulradge
To: softrock40@yahoogroups.com
Sent: Saturday, April 07, 2007 12:57 AM
Subject: [softrock40] RXTX please check my voltages
Hi all,
i borrowed a cro off a mate and took these measurements running
the m0kgk IQ generator both tones at 1khz with manual 12v on ptt ,,,,
audio input from pc = 0.3Vpp,,,,,,,,(R3/R9=4.9k),,,is this too low should i
increase volume output level on the pc ???
T1 output = 0.4Vpp
T2 output,,,,ie hot side(not the center tap) R26 = 1.2Vpp
R27 =
1.2Vpp
T3 output = 12Vpp
ANT out = 12Vpp
in the shack on my ft817 i'm rx'ving the oscilator and a single tx carrier
so i think my issue with T1 is fixed,,,i'm measuring gain through Q2 & Q3/Q4
so i think all is well there
i still can't measure any output on 3 different power meters but in
theory the cro is saying 12Vpp on the ant output so can i use P=Vsquared on
R ???
12 X 0.707 = 8.4 rms
8.4 x 8.4 = 70.56 / 50 ohms = 1.4watts or have i got something wrong?????
and any comments on the 0.3Vpp off the soundcard please ,,,?
almost there,
Paul
Hi Paul,
Your RF output calculation should be the (Vp-p / 2 )*0.707 to give RMS RF volts output.
Then square the RMS volts and divide by 50 to get the power output which in your case will be 0.36 watts.
The 0.36 watts output is about right for your soundcard line-out voltage to the board.
73,
Tony KB9YIG
From: lbeugnet
To: softrock40@yahoogroups.com
Sent: Friday, May 25, 2007 9:33 AM
Subject: [softrock40] rf power level
Hi Tony & all
My SRv6.1 80/40 is finally working...
One specific question regarding the output level:
- my sound card (sb live 16) delivers 2.6 v PP on each channel at most,
- the rf level mesured on a 50 ohms dummy load is 14.4 v pp ( = about
0.4 Watt)
Is this output level value correct with such an input level, or is there
an issue in the amplifier chain ?
If not, I guess I have to change the amplifier gain of U1 & U2, by
modifying the feedback resistors R4 & R10 ? Do you agree ? Or any other
idea ?
Thanks for your advise!
73 Laurent F6GOX Paris
Hi Laurent,
Extra 4.99k resistors were provided in the RXTXv6.1 kit to increase the TX audio gain. Resistors R3 and R9 may be reduced to 4.99k to increase the gain.
73,
Tony KB9YIG
To:
From: "Tony Parks"
Subject: Re: [softrock40] Re: rf power level
Hi Mike,
With the Delta 44 soundcard you can go to its M Audio Delta Control Panel and increase the Outputs range to +4 dBu. This will give you more output to drive the RXTXv6.1 board. Also make sure you have added the 0.1 uF capacitor from the gate of Q6 to ground. Without this capacitor the RF output will be low.
73,
Tony KB9YIG