From: John
To: softrock40@yahoogroups.com
Sent: Thursday, March 22, 2007 3:24 PM
Subject: [softrock40] 40m/80m RxTx v6.1 no rx

Hi,
I'm building an RxTx 6.1 40/80 meter kit and in initial testing I get
829 Ohms from ground to the IC supply leads. The radio draws approx. 37
milliamps on 12v. And I'm getting 4.9v to all the IC supply leads, but
when I connect it to my Laptop line in running Rocky I do not see any
change in the waterfall or spectrum displays. I tried the radio on 2
desktop PC's at work still nothing.
I tested the cable end to the board with my multimeter and it looks
good from the connector tip to tip, ring to ring and shield to ground.
I connected my old Teck 495 O scope to the output and I don't see any I
or Q signals. Putting the scope on the 4x and 8x jumper pins shows the
crystal oscillating. I've gone over the board with my magnifier and
touched up any questionable solder joints but I still have the same
results.
Any ideas where should I look or try next?

Thanks
John KE7JXM
Hi John,

Your supply current is about right for the 40m kit. Check to make sure pins 1 and 7 of U8 are at about 2.5 volts DC. Also check the signal path from the antenna to the primary of T4 and make sure each inductor lead, (L3, L4, L5 and L6), and the primary of T4 are soldered to their pads properly. Also make sure pins 1 and 15 of U7 are less than 0.5 volts and that the gate of Q6 is at about 12 volts DC.

If the above items are all good then it may be T4 is not wired correctly to its pads which can reduce the sensitivity of the receiver by a factor of 100.

73,
Tony KB9YIIG




From: Ray Benton
To: softrock40@yahoogroups.com
Sent: Thursday, April 05, 2007 8:56 AM
Subject: [softrock40] RXTX with 4mhz crystal Dead Oscillator

Hi All,
I have a RXTX in which the local oscillator works fine until I use
the 16mhz xtal. The signal from the output of Q10 is not as strong as
when I use a 28mhz xtal. Thus Q11 is not turned on. Checking with an
rf probe shows .7v with the 28 mhz xtal and only .2v with the 16mhz
xtal at the base of Q11.
I have tried two 16 mhz xtals .. both with the same result.

What can I do to correct this situation? Thanks to all. Ray W7RJC
Hi Ray,

The capacitors in the oscillator circuit may need to be changed for the lower frequency crystal.
I usually use C48=220pF and C49=100pf for crystals in that frequency range.

73,
Tony KB9YIG




To:
From: "Tony Parks"
Subject: Re: [softrock40] SoftRock40 Lite ... a bit deaf

Hi Tom,

The SoftRock Lite RX should have a sensitivity of about -110 dBm if working properly. If you have a calibrated source this is easy to checked. Listening tests require a 50 ohm antenna connected between the ANT IN-RTN plated through holes at the edge of the board near the crystal. (The antenna return connection is isolated from the circuit ground by the transformer T1.)

Other problems on the circuit board that can result in low sensitivity include bad solder joints at L1 and T1. Also if the secondary windings of T1 are not connected properly there can be a 40 dB sensitivity loss. Please see the builder's note for information on proper connection of T1. Another quick check to to make sure the op-amp U5 is not saturated by checking the voltage on pins 1 and 7 referenced to circuit ground. These two voltages should be about 2.5 VDC.

73,
Tony KB9YIG

To:
From: "Tony Parks"
Subject: Re: [softrock40] Re: Dead clock

Hi Peter,

The oscillator circuit for 30m in the 40m/30m version of the RXTXv6.1 should have C49 omitted. R56 should be 22.1k and the other components as indicated on the schematic. In some cases the activity of the 40.5 MHz crystal has been a bit low and R56 may need to be reduced to 15k to get proper clocking on 30m.

Please post what you find concerning the 30m operation.

Thanks and 73,
Tony KB9YIG