Currently playing with software to display spectrum. Looks nice.
https://youtu.be/9_QONciat_U
Frontend design 6m-4m-2m-70cm
Forum rules
This forum is run by the BATC (British Amateur Television Club), it is service made freely available to all interested parties, please do not abuse this privilege.
Thank you
This forum is run by the BATC (British Amateur Television Club), it is service made freely available to all interested parties, please do not abuse this privilege.
Thank you
Re: Frontend design 6m-4m-2m-70cm
Good progress. Designing the PCB is one step, stopping it oscillating is another, as I found out. Incidentally the prototype will be perfectly stable, only when you get someone else to make one will it oscillate. There is a lot to be said for a 4-layer board and avoiding gain where it is not strictly required. The front end does not need to have gain if it is to be followed by a PA or preceded by a preamplifier.
For mixers I used the ADE-1-24 which seems widely available, at least it was at design time.
You might want to extend the filter pads to make it easier to hand solder. Ditto inductors if you use the Coilcraft footprint.
It looks like there is a long track snaking through SMA ports. That might introduce some unwanted coupling?
Mike
For mixers I used the ADE-1-24 which seems widely available, at least it was at design time.
You might want to extend the filter pads to make it easier to hand solder. Ditto inductors if you use the Coilcraft footprint.
It looks like there is a long track snaking through SMA ports. That might introduce some unwanted coupling?
Mike
Re: Frontend design 6m-4m-2m-70cm
Hi Mike,
Well, I always use a stencil for soldering. About oscillating, The design is ported from another design I made for rather higher frequencies, and never had any oscillation. If you use original parts, the change of oscillation is almost 0. When using AliExpress MMIC's, it's almost 100%
Well, I always use a stencil for soldering. About oscillating, The design is ported from another design I made for rather higher frequencies, and never had any oscillation. If you use original parts, the change of oscillation is almost 0. When using AliExpress MMIC's, it's almost 100%
Re: Frontend design 6m-4m-2m-70cm
There is that. I try not to use the stencil as it makes it harder for others to replicate, but if you are going to make them yourself it does make sense. My solder paste has gone off it has been so long...
The problem with the devices like the PGA-103+ is they are not stable at low frequencies where the impedance is extremely high, but this is only noted in a later application note. Strangely it makes them a good choice for LF preamps, despite their 50MHz minimum spec. You just need to make sure they see the right input impedance at LF. Otherwise the impedance gets rather high towards DC, which is great for an electrically short active antenna. That's also probably why some earlier amateur designs suffered PGA-103 failures. I don't know about the devices you are using as I haven't used them. If both stable and available they are gold. I am using PGA-103s and Gali5s.
Ali-express devices are a gamble. There is no guarantee you get what you ordered or if it meets the spec. or actually contains anything inside at all. Sometimes they are bin parts out of spec, sometimes entirely different parts relabelled, sometimes genuine parts recovered from equipment, sometimes just the package with no die inside. Luckily, those mixers are fine, they can't oscillate and appear to be a genuine special run with I think IF and RF ports swapped, which matters in some applications, but not this one where I am using it bidirectionally anyway and don't need the IF to work down to DC.
Mike
The problem with the devices like the PGA-103+ is they are not stable at low frequencies where the impedance is extremely high, but this is only noted in a later application note. Strangely it makes them a good choice for LF preamps, despite their 50MHz minimum spec. You just need to make sure they see the right input impedance at LF. Otherwise the impedance gets rather high towards DC, which is great for an electrically short active antenna. That's also probably why some earlier amateur designs suffered PGA-103 failures. I don't know about the devices you are using as I haven't used them. If both stable and available they are gold. I am using PGA-103s and Gali5s.
Ali-express devices are a gamble. There is no guarantee you get what you ordered or if it meets the spec. or actually contains anything inside at all. Sometimes they are bin parts out of spec, sometimes entirely different parts relabelled, sometimes genuine parts recovered from equipment, sometimes just the package with no die inside. Luckily, those mixers are fine, they can't oscillate and appear to be a genuine special run with I think IF and RF ports swapped, which matters in some applications, but not this one where I am using it bidirectionally anyway and don't need the IF to work down to DC.
Mike