9706	2014-02-10 12:36:51	Jim Miller	Diode ring mixer question
Message	Date	From	Subject
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. Thanks 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. Adrian
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. Adrian
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. Thanks 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). http://www.nxp.com/products/rf/fm_if_system_ics/SA602AN.html#showall http://www.nxp.com/products/rf/fm_if_system_ics/SA612AN.html#showall 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. http://ea3ghs.qrp.cat/peregrino.html 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, Eduardo EA3GHS
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. 73 Jim N6OTQ
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