Re: LF: RE: G0MRF 300w Tx & DDS VFO

[G0MRF@aol.com]

In a message dated 2/5/04 9:45:06 PM GMT Standard Time, g4wgt@talkgas.net writes:

> Thanks for the very useful data Jim, I did in fact get a reply from the
> organiser of the kit/project &he has stated that several builders have
> experienced the same low output &have diagnosed a faulty modamp, I have
> doubly checked for the sort of error you suggest &that seems ok, also there
> is some gain thro' the ERA-1SM. Now that I have some figures to refer to I
> can have another look at the signal path etc. From memory I don't believe
> that I am getting anywere near 250mV p-p from the DDS IC before any
> amplification takes place.


There have been some problems with the ERA series of Mod-amps.  Even the older MAR series has encountered problems after a change from Silicon to a Silicon/Germanium production process.

Some of the Modamps have a white dot marking the input, others have a dot on the output lead. However, all have the input lead clipped at a 45 degree angle.

Correct operation can usually assessed by the voltage on the output lead.

Any short, even for a fraction of a second, on the input lead removes the bias from the FETs and destroys the device.

73

David