Tuesday, January 05, 2010

S9 signal generator

....I just knew it was to easy (on the online pdf) to be true....
When you finish soldering and go for a test then it's when the s!"#!" hits the fan...

I was looking for a test generator to start testing MDS on my new hf-radio (somewere on this blog). I could just get my cristal tester and place some attenuators, but no, I had to look for a specific schematic.... guess what, Elecraft make's a nice little kit, the XG2, (http://www.elecraft.com/manual/E740084%20XG2%20Manual%20Rev%20E.pdf).... I am sure them works... not my homebrew copy... I didn't had the reference regulator in the schematic so I replaced for a 1.5 Volt's battery removing the left part of the schematic (the 3v battery). I had heard that is not easy to make low voltage oscillators, mine didn't worked has in the original Elecraft schematic so I made some small changes. It could had been the type of crystals or any other thing but in fact I could just make the circuit start oscillating at around 2.8V
My schematic:

Anyhow the main output gives around S9+5 on my Yaesu FT-102 and around the same on the Kenwood TS-50.
I have some leakge from the attenuator so on 1uV setting I have around S5. Am now in the process off making a 34db (will probably make a 40db) attenuator with some blindage to try to get the S1 level. Will try an online attenuator tool: http://www.g4nsj.co.uk/attenuators.shtml
I didn't had the crystal frequencies specified on the schematic so I used for now 10Mhz and 4Mhz. At least with the 10Mhz I can test on the Yaesu, Kenwood and my new radio for comparation.

The box was from a previous PSK/RTTY interface, and no it's not a wine or wisky box, it's from a perfume. Cheap and easy.

Added a 40db attenuator (2 times 51 ohm and 2.5Kohm PI)and now have more or less S0 (can't measure level). Can't listen to it on the FT-102 without preamp (to FT-102 favor, there is a birdie at 10Mhz that overlaps). Can listen to this low level on the TS-50 (IPO in and out). On my homebrew radio.....well.....I can listen! Very, very faint but I have no preamp at the moment!

1 comment:

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