EMRFD Message Archive 9706

Message Date From Subject
9706 2014-02-10 12:36:51 Jim Miller Diode ring mixer question
I'm fiddling with a design for a transverter for the RSN 630M band. It's my first attempt at such a thing. It will convert 472-479Khz up by 10Mhz.

For receiving the path from the antenna will pass through a multiple pole BPF then into a Minicircuits SRA-8 double balanced mixer.

It looks like for transmitting I can just drive this part of the design in reverse since the IF and RF ports are taken from the same point on the diode mixer. The loss of the "dc" response of the IF port is not an issue in this design. So the 10.47x Mhz would be driven back into the mixer port that it would be output from on receive and the resulting downmixed output would come from the other port.

Do I have this right? I looked through EMRFD on mixers and didn't find this "symmetry" discussed.

Doing it this way may result in some minor simplification of the design.


Jim ab3cv
9707 2014-02-10 15:48:50 Ephemeral Re: Diode ring mixer question
I have been considering a similar problem myself, albeit at a higher frequency. Yes, a diode bridge mixer
will work in either direction. However, you do need to carefully consider signal levels and port matching.
What modulation modes are you considering using? If you are only emitting a single frequency at once then
transmit intermodulation distortion is not of great concern, as your filters can take out the spurious signals.
Receive distortion is nearly always important as adjacent strong signals combine and block
the one you wish to receive.
When receiving your signal levels are unknown and unpredictable and port matching is important. The reason
diode mixers are attractive is that for an off the shelf component they have quire a high IP3. However they
are not entirely convenient to use. When transmitting your signal level is fixed and distortion might not matter.
So you could use a very simple arrangement around a humble NE602.
Whether is is worth sharing the mixer between the transmit and receive signal chains depends on whether
the effort required to share it is less than the effort required to duplicate it.

9708 2014-02-10 16:01:27 Ephemeral Re: Diode ring mixer question
I notice you selected a Minicircuits SRA-8, presumably because it has a very low minimum RF
frequency. Generally mixers are specified on the assumption that the RF frequency is quite a
bit higher than the IF. In your case the reverse applies. With a diode bridge mixer you can
generally swap the RF and IF ports, so the RF has the response down to DC and the IF response
is limited by the transformer. This is commonly done for the first mixer on spectrum analysers,
that accept input down to DC and convert to a high IF. So you could use most of the ordinary
mixers: JMS1, ADE1, TUF1, etc and no need to order anything exotic.

9709 2014-02-10 18:41:00 Jim Miller Re: Diode ring mixer question
I haven't completely decided on the SRA-8. It had been used in a converter I saw on a website. An SBL-3 would work as well.

Your point about the TX mixer not being as critical is a good one. I expect on the 630 band to be using mostly CW, with perhaps some JT9 or Domino if it becomes popular. For now I'm staying away from modes that require a linear amp such as PSK31 but may relent if it becomes popular on that band.

I probably won't share the mixer and filter after all. Building the two strips separately makes it easier to do substitutions later on.


jim ab3cv

9710 2014-02-11 08:32:45 Eduardo Alonso NE602 - end of production in DIP8
Hello friends,

I read in the NXP website that the NE602 in DIP8 production will be
discontinued next month (march of 2014).


Thereafter only the SMD version will be available.

These are sad news, because there are lots of amateur KITS using this mixer.
In fact, this month we published a new very simple superhetereodyne TRX
using two of them in bidirectional configuration and two relays.


I have no clear which alternatives we have. I saw that YD1JJJ from
Indonesia uses
TOSHIBA TA7320P in SIP9 package, but I do not know who sells this component
in Europe (it do not appears in digikey,farnell,mouser,radioshack catalogs)

Comments wellcome,

9711 2014-02-11 08:40:38 John Levreault Re: NE602 - end of production in DIP8
There are many socket adapters available. For example:

You will need to solder the SM part to the board, which, if you haven't tried, is easier than you can imagine.

de John NB1I

9712 2014-02-11 08:41:04 Jim Strohm Re: NE602 - end of production in DIP8
Time for a lifetime buy in the DIP package, folks.


9713 2014-02-11 09:57:03 Leon Heller Re: NE602 - end of production in DIP8
9714 2014-02-11 10:01:22 Leon Heller Re: NE602 - end of production in DIP8
9715 2014-02-11 10:43:28 Ed Manuel Re: NE602 - end of production in DIP8
While it's not a long term solution, Mouser still has a about 1800 DIP SA602's in stock at the moment.  Stocking up for the long haul will be pricey at $2.25 each in hundred quantities. 

Ed, N5EM

9723 2014-02-12 06:33:39 Ashhar Farhan Re: NE602 - end of production in DIP8
just use an ADE-1 instead?

- farhan