Re: [softrock40] 8.83MHz interfacing SR6.2 lite
- At 07:40 AM 5/28/2007, you wrote:
Just acquired a SR6.2Lite to be used at the 8.83MHz interface, after going through a number of articles in the file section of this group and the internet I still have some questions :-)
1. What would be the "best"* oscillator frequency ?
A) 8.83 * 4 = 35.320 MHz
B) (8.83 * 4 )/3 = 11.773 MHz
C) (8.83 * 8)/3 = 23.547 MHz
2. Assume the crystal oscillator operates with parallel resonance crystals, with Cload of approx 50pF. Is that a correct assumption ?
3. Assume the 40 mtrs input constellation will be ok for 8.83 MHz, or will it be degrading the overall sensitivity too much ?
* "best" is maybe too general...going to use it for weak signal operation on UHF/SHF including bandscope.
73's and thanks in advance.
I would go with option "B". When the softRock40 first came out I modified one to use with my Kenwood, the radio would pickup the LO that was in the IF pass band, 11,773MHz will be rejected out of hand.
The capacitance on the crystal depends on the model but most prefer from 18pF to 30pF, one reason the SoftRocks have the LO 1-4 KHz lower than the crystal rating is the massive capacitance across the crystal.
If you are connecting at the Pan-adapter connector in the back of the radio, be aware the signal levels at that point are rather high, you may want to consider lowering the gain of the op-amps after you get it working,, The signal has been amplified quite a bit by the time you get to that connector, and if you have the option pick the Pan-adapter output before the filters so you can see a bigger chunk of the band.
Go Kenwood, I love their radios, my TS-830 has a fantastic receiver, the only one that is close is the SDR-1000, I have several of their older models.