Red Wave Radio

by **Bill Mea** » Thu, 22 May 2003 16:48:52

I'm using an NE602 as a balanced modulator in my 20 meter QRP DSB
transceiver.
Sort of the same design used in the Wee-Willy rig. VXO into pin 6
(unbalanced). Audio (from an LM386 serving as mic amp) into pin 8
(also unbalanced).

I'm getting disappointing levles of carrier suppression. I don't have
the gear to measure it accurately, but I'm getting more carrier than I
got when I used diode modulators on earlier rigs. I estimate that the
carrier is about 10 db below voice peaks. I should be doing better.

Any thoughts on how to improve carrier suppression with the NE-602?
I've tried reducing the signal level at pin 6. This seems to help,
but not enough.

Would it help if I used a balance (two pin) input for the VXO input?

73 Bill CU2JL N2CQR
http://planeta.clix.pt/n2cqr

by **John R. Stroh** » Thu, 22 May 2003 19:22:31

Quote:> I'm using an NE602 as a balanced modulator in my 20 meter QRP DSB
> transceiver.
> Sort of the same design used in the Wee-Willy rig. VXO into pin 6
> (unbalanced). Audio (from an LM386 serving as mic amp) into pin 8
> (also unbalanced).

Check your pinouts against the datasheet.

Pin 8 is supposed to be Vcc, typically between 4.5 and 8 volts. Pins 1 and
2 are the main input, and pin 6 is the LO input (base of the oscillator
transistor).

by **LA3Z** » Fri, 23 May 2003 02:03:03

Check the Elecraft web site (www.elecraft.com) and look for the schematic
for the KSB2 SSB option. It uses the 602 also, and has a pot to fine tune
the carrier suppression to a better performance than the 602 does on its
own.

73 Sverre, LA3ZA
www.qsl.net/la3za

Quote:> I'm using an NE602 as a balanced modulator in my 20 meter QRP DSB
> transceiver.
> I'm getting disappointing levles of carrier suppression.

by **J M Noedi** » Fri, 23 May 2003 16:11:32

Quote:>I'm using an NE602 as a balanced modulator in my 20 meter QRP DSB
>transceiver.
>Sort of the same design used in the Wee-Willy rig. VXO into pin 6
>(unbalanced). Audio (from an LM386 serving as mic amp) into pin 8
>(also unbalanced).

>I'm getting disappointing levles of carrier suppression. I don't have
>the gear to measure it accurately, but I'm getting more carrier than I
>got when I used diode modulators on earlier rigs. I estimate that the
>carrier is about 10 db below voice peaks. I should be doing better.

>Any thoughts on how to improve carrier suppression with the NE-602?
>I've tried reducing the signal level at pin 6. This seems to help,
>but not enough.

>Would it help if I used a balance (two pin) input for the VXO input?

>73 Bill CU2JL N2CQR
>http://planeta.clix.pt/n2cqr

What sort of balancing arrangement do you use? I increased the S042P
balance - as mixer - by over 40dB using the usual balancing potmeter

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by **Bill Mea** » Fri, 23 May 2003 16:47:20

Quote:> Check the Elecraft web site (www.elecraft.com) and look for the schematic
> for the KSB2 SSB option. It uses the 602 also, and has a pot to fine tune
> the carrier suppression to a better performance than the 602 does on its
> own.

Svere: Great idea! I went to the K2 site this morning and got the circuit.
I will give it a try and let you know the results. Thanks very much. 73 Bill
http://planeta.clix.pt/n2cqr

Red Wave Radio

NE602 Balanced Modulator Problem

NE602 Balanced Modulator Problem

NE602 Balanced Modulator Problem

NE602 Balanced Modulator Problem

NE602 Balanced Modulator Problem

NE602 Balanced Modulator Problem