Hi Alan & LF,
The frequency calibration of my DDS VFO is so good (with a little hit & miss
twiddling)that it is zero beat with BBC Radio 4 on 198 Khz radio
transmission & the freq stability is every bit as good, during hours of
testing with 198 Khz as a reference I cannot detect any variation.
The problem as I have specified in my e-mails is the low output. Last night
I checked back to the DDS IC & there are no substantial losses in the signal
path, even the insertion loss of the LPF is negligable. Here are the actual
levels into 50 ohm load at the output of the DDS VFO.
137 & 274 Khz - 22mV
1.0 Mhz - 50mV
2.0 Mhz - 60mV
5.0 Mhz - 80mV
10.0 Mhz - 150mV
15.0 Mhz - 250mV
20.0 Mhz - 250mV
25.0 Mhz - 150mV
30.0 Mhz - 75mV
35.0 Mhz - 65mV
40.0 Mhz - 50mV
I am also sending this info to the organiser of the offer/project from the
G-QRP Club asking for his help, advice or a further contact point.
By the way, the DDS chip is a Analog Devices AD9850 w/ 120 MHz Clock
73
Gary - G4WGT
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Alan Melia
Sent: 03 February 2004 21:53
To: [email protected]
Subject: LF: Re: RE: Re: Re: G0MRF 300w Tx & DDS VFO
Yes Ok Gary, I guessed it was so. I just wondered whther you had a "tight"
filter. The signal out of the chip (do be carefull here) should be a logic
level ..i.e. 5v p-p I would have thought (??)
Cheers de Alan G3NYK
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