[minima] Re: KISS Mixer Musings
- From: "Tayloe, Dan (NSN - US/Tempe)" <dan.tayloe@xxxxxxx>
- To: "minima@xxxxxxxxxxxxx" <minima@xxxxxxxxxxxxx>
- Date: Fri, 28 Feb 2014 21:53:26 +0000
I have noticed in the past that the spectrum of a switching mixer tends to be a
bit rich in harmonic output. It seems like a good bandpass filter will be
needed for each band to clean up things, especially for the transmitter side.
It looks also like the 5 MHz output is 10 dB down from the 15 MHz input feed
through. Does tweaking the bias to give better 5 MHz output?
- Dan, N7VE
-----Original Message-----
From: minima-bounce@xxxxxxxxxxxxx [mailto:minima-bounce@xxxxxxxxxxxxx] On
Behalf Of ext Tayloe, Dan (NSN - US/Tempe)
Sent: Friday, February 28, 2014 2:26 PM
To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: KISS Mixer Musings
IF you have two separate bias pots, I guess you could hook up an input signal
and tweak both pots for the highest detected signal on the output. An AC
voltmeter would help with that. There is probably a PC program (audio spectrum
analyzer program?) that could take AC audio into the mike input and measure it
for you if you do not have an AC voltmeter.
- Dan, N7VE
-----Original Message-----
From: minima-bounce@xxxxxxxxxxxxx [mailto:minima-bounce@xxxxxxxxxxxxx] On
Behalf Of ext Tayloe, Dan (NSN - US/Tempe)
Sent: Friday, February 28, 2014 2:20 PM
To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: KISS Mixer Musings
You could bias the two JFETs with separate pots and adjust for similar drain
waveforms. I think you would want to adjust for highest pk-pk on each drain.
A lower voltage on one drain may mean that device did not turn fully off.
- Dan
-----Original Message-----
From: minima-bounce@xxxxxxxxxxxxx [mailto:minima-bounce@xxxxxxxxxxxxx] On
Behalf Of ext Joe Street
Sent: Friday, February 28, 2014 1:56 PM
To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: KISS Mixer Musings
Just thinking about this. I remember that the transconductance of JFETS
varies quite a bit so the fact that the signals are not symetrical might
be due to an imbalance in the device characteristics?
On 28/02/2014 3:29 PM, Mark G0MGX wrote:
> Hi Joe
>
> The 'scope was connected to the drains using a x10 probe - they were
> still connected to the transformers in circuit. The overall output at
> the IF port didn't change with the 'scope connected as the SA was
> monitoring throughout.
>
> Mark
>
>
> On 28/02/2014 19:24, Joe Street wrote:
>> When looking at the drain voltages with the scope did you give a load
>> resistance to the drains or was it just the scope input?
>>
>> On 28/02/2014 1:41 PM, Mark G0MGX wrote:
>>> Hi Team
>>>
>>> I've been threatening to have a fiddle with the KISS mixer for a
>>> while, and here are the results of my first bash:
>>>
>>> http://g0mgx.blogspot.co.uk/2014/02/kiss-mixer-musings.html
>>>
>>> I don't understand the 'scope signals on the drains of my FETs and I
>>> certainly don't understand the voltages I am reading on the sources
>>> (my sources are together and connected to the bias supply). The
>>> power end of the 4K7 to the FET bias adjusts from 0 to 5V as
>>> expected by I am reading -ve voltage on the sources themselves.
>>>
>>> Please take a look at the link and then any volunteers who can try
>>> and explain this to me most welcome!
>>>
>>> Mark
>>> G0MGX
>>>
>>
>
>
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