**EMRFD Message Archive 424**

MessageDateFromSubject424 2007-02-01 18:48:36 Mike Scott 3 dB splitter I wish to split the outputs of the UVFO to drive two I-Q receivers

(both R2Pro).

I am making a diversity receiver driven from two antennas.

The 3-dB hybrid splitter circuit in EMRFD that I see starts at 25 ohms

and drives two 50 ohm outputs at minus 3 dB.

With the UVFO I think I have single I and Q outputs at 50 ohms.

Help me get from single I and Q channels at 50 ohms (7 dBm) to two I

and Q channels at 50 ohms.

..Mike AE6WA425 2007-02-02 07:29:03 Bill Noyce Re: 3 dB splitter Look at figure 9.38 -- the RF port has a splitter that is essentially

a pair of 70-ohm 1/4 wave transmission lines built from lumped

components. The two input 70-ohm capacitors are in parallel,

so the equations show a single 35-ohm capacitor instead.

To get 7 dBm at each output port, you'll need 10 dBm input...

-- Bill, AB1AV

On 2/1/07, Mike Scott <mike@paxsen.com> wrote:

>

>

>

>

>

>

> I wish to split the outputs of the UVFO to drive two I-Q receivers

> (both R2Pro).

> I am making a diversity receiver driven from two antennas.

> The 3-dB hybrid splitter circuit in EMRFD that I see starts at 25 ohms

> and drives two 50 ohm outputs at minus 3 dB.

> With the UVFO I think I have single I and Q outputs at 50 ohms.

> Help me get from single I and Q channels at 50 ohms (7 dBm) to two I

> and Q channels at 50 ohms.

>

> ..Mike AE6WA

>

>440 2007-02-05 11:54:20 topossibilities Re: 3 dB splitter [I wish to split the outputs of the UVFO to drive two I-Q receivers

(both R2Pro).]

I built 75M SSB transceiver using R2 DC receiver and T2 transmitter

boards and had great success building a VFO and processing it's output

signal through a 'Johnson walking ring counter' to generate the two

pairs of needed quadrature signals (one for the Rx, one for the Tx).

Johnson counters are synchronous divide by 4 counters and provide very

accurate I/Q (90 degrees out of phase) square waves outputs for

driving diode ring mixers. They are very simple to build (e.g. a dual

D flip flop and a couple of resistors and capacitors). Using 74ACTxx

series D flip flops with a 100 ohm resistor in the output, the output

level was 7dBm into a 50 ohm load.

Although the oscillator runs at 4X the operating frequency, with care

15-28MHz oscillators can be made quite stable (any drift is also

divided by 4). For the higher operating bands, a heterodyning

oscillator is required.

I have the artwork and schedmatic (has VFO and two ring counters) and

would be happy to scan and email them.

Ed, W1AAZ

http://mysite.verizon.net/topossibilities/477 2007-02-14 18:34:51 Mike Scott Re: 3 dB splitter Bill (AB1AV),

You pointed me toward a Wilkinson splitter a couple of weeks ago,

thanks. I had to learn a few things before I could write this email.

Now I have built and tested a UVFO system which has 7dBm I&Q outputs

driving a board which has a 6 dB feedback amplifier (my first design)

to two 3 dB (power) pi resistor attenuator networks. These drive two

Wilkins