Chinese crystals and inductorless mixers = poor results?

[them...@btinternet.com]

Greetings all.

Just getting some bits together to carve an experimental up-converter from out of a virgin copper board. Have ordered a couple of crystals (100 and 125 MHz) and also an NE602 mixer IC.

I was wondering if anyone might care to comment on my choice of source of crystals and the mixer (as opposed to a diode ring double balanced mixer).

I also have a technical point concerning the crystals but that can wait.

Regards and 73 to all.

[Simon Kennedy]

Hi,

I built something similar, using a 64MHz crystal salvaged from an old ADSL router. It worked well, when it worked, but I did have a small coil as an inductor and getting the correct amount of inductance was challenging.

Regards

Simon.

--
You received this message because you are subscribed to the Google Groups "Gqrx SDR" group.
To unsubscribe from this group and stop receiving emails from it, send an email to gqrx+unsubscribe@googlegroups.com.
To post to this group, send email to gq...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/gqrx/8c339960-a965-42c8-ae3a-25000c7e4cfe%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Tom Campbell]

============================================

Hi Simon, thanks for the input.

I too considered using a crystal from an old router: a 64 MHz rock from an "O2 Wireless box II" which is actually a Thomson product.

I am currently investigating the ferrite inductors they used to isolate the DSL phone connector

Your idea interests me: when you say "small inductor" where in the circuit was it used? In the oscillator section?

Regards and 73.

Tom

[Simon Kennedy]

Hi Tom,

I got the idea from the website of YO2LDK: link

If you scroll down the page ignoring the awful graphics and Flash components you get to an entry entitled "Up -Converter NE602, pentru SDR dongle RTL2832 - FunCube", below this there is a circuit diagram to click on which is self-explanatory. I left out the BFR91 pre-amp section. 

You have piqued my interest again because I am sure that this little circuit gave better up-convert performance than my NooElec up-converter. I'll add  rebuilding it to the list of projects.

73 Simon.

[juan]

saludos soy nuevo en esto quien me dice unos tutiriales para poder  aprender a usar esta herramienta

[Tom Campbell]

Hi Simon, apologies for delay in responding to you, I have had some 'technical difficulties' with BT Broadband, but all is well now.

Yes I have seen the circuit to which you refer. It uses a crystal - not a crystal osc pack,  which I suspect would give a cleaner output to the mixer.

I have now got 100MHz and 125 MHz crystal osc packs, and a 64MHz crystal. Don't know if its a side-tone or fundamental frequency - not that it matters. I intend to begin experiments some time this week.

Its been many years since I played with rf circuits - got diverted into computers in the mid 70's. So I was right gob-smacked when I went to order some small value silvered mica capacitors (I always used them
in rf frequency sensitive circuits): 12pf ...... £1:20p, postage extra. How much money must I have thrown-given away over the years?

So I have ordered ceramic disc caps instead. Needing them that day, I called into Maplin, having seen they stock all the values I required, and asked the young lad at the counter to get me the caps on my list:
values and Maplin codes provided. He looked on his terminal and told me they only stock one component of each value (3pf, 1pf, 12pf, ....), I said but I need at least two of each part, the reply I got was that they
could order them from head office, and it would take two days or so.

I of course went straight on Ebay, and ordered lots of values in packs of ten each.

So, when my caps arrive, I'll stick a chip onto some plain copper, and try out the circuit.

Cheers and 73 to you.

[Tom Campbell]

Hola Juan

Es posible que encuentres alguna información para ayudarte en YouTube.

La mejor de las suertes.