45 - IF Amplifiers

[@accountant1653]

Hi Nick. You radiate a lot of positive energy. After watching your videos, I always want to pick up a soldering iron.

[@M0NTVHomebrewing]

Thanks very much indeed. Don't fight the feeling!!! 73 Nick

[@jlog7395]

Hello Nick. I just wanted to say thank you for all the work you put into these videos. They are perfectly matched to us novice DIY’ers with the same RF design interests as you. Great content and videos - thank you. God bless.

[@M0NTVHomebrewing]

Thank you very much indeed! I'm glad you find them helpful. 73, Nick

[@tcarney57]

Nick--Many thanks for the shout-out! I didn't know you'd done this and I just happened to run across it. One thing I like about your PCB design is that it's not too compact . . . I think mine is too crammed together for some people. Coincidentally, I recent decided to do a "large-print" edition so those who suffer from FFS (fat-finger syndrome) have an easier time assembling them. I'm still waiting for the prototypes to come in from Shenzhen. In addition to spacing things out a bit, I made the pads for the gain-setting resistors without holes but big enough to use like Manhattan isolation pads (or like Chuck Adams' "muppet" pads). This will make it vastly easier to change the gain as desired. Getting those resistors out of the holes in the existing board is hard enough, but then clearing out the solder from those plated-through holes to install different resistors is a nightmare. The "large-print" edition with the surface pads should make it easy. --73, Todd K7TFC

[@M0NTVHomebrewing]

Hi Todd, you are very welcome! I think your boards are brilliant. Keep up the great work. 73, Nick

[@erichkeyes5578]

I will check out the previous video on scratch-building IF Amp. Thank you

[@M0NTVHomebrewing]

You are very welcome. 73 Nick

[@alanmacdonald65]

Another great video, and nice to see how the compression point is measured! So pleased that my student has become my teacher - long may it continue!

[@M0NTVHomebrewing]

Thanks so much my friend. I have much to be grateful to you for ... but I've still got a lot to learn! And let's not even mention the maths!!! See you soon for a catch up and some beer! 73, Nick

[@johnwest7993]

Thank you Nick.

[@M0NTVHomebrewing]

You are welcome John!

[@acestudioscouk-Ace-G0ACE]

Another great, informative video, thanks Nick! I was particularly interested in when amplifiers cease to be linear and why. You explain this very clearly. Best 73 G0ACE

[@M0NTVHomebrewing]

Thanks very much Ace. 73 Nick

[@andye2005]

Nicely done video Nick. Especially the compression point. Re the Gerbers: It is possible to edit Gerbers, but it's a bit of a faff and only done if you have to. Having the full circuits, netlist and layout files etc makes life much easier. The biggest problem is that the source files may not be readable by all systems, but eagle is (or was before they messed about with the license) one of the more common formats, so should be readable by other layout programs. Your layout looks really good for a first attempt so well done on that. Two things for the rev 1.01. Pop a hole in each coax pads so that you can insert a terminal pin. It's surprising how easy even big pads can lift if you rework the connections a few times. (In the current design you can drill the pad and solder the pin to both sides.) Rework the power connections so that they are in the same place and same polarity regardless of which way around the boards are positioned. Helps keep wiring tidy. A design nicety only Andy

[@M0NTVHomebrewing]

Hi Andy. Good to hear from you. Thank you so much not only for watching but for your very helpful comments on the PCB. That is really useful and good advice that I'm sure I will return to. It was an interesting experience designing the PCB but I think it'll probably be a bit like when I finish a homebrew radio: I immediately start thinking what I'll change about the next one! Thanks again. 73 Nick

[@andye2005]

Yes you can always do better if you tweak this and that... I generally go through about three revisions before I'm happy enough to send things off to the PCB house. With the TIA design while looking at your layout I thought, "I wonder how small that would go using SMT" ... maybe one day I'll find out 🙂

[@DAVIDGREGORYKERR]

There is a place called Osh Parc where there is a PCB production plant and must likely will let you create boards onto the area that would normally be waste material.

[@M0NTVHomebrewing]

Sounds great.

[@trevorwoods3367]

I'm only at the eight minute mark, but I just wanted to say what a beautiful looking little board. Then with the components, such a neat job.

[@M0NTVHomebrewing]

Cheers Trevor. That's very kind. 73 Nick

[@drstrangelove09]

such a nice board!

[@M0NTVHomebrewing]

Thanks very much! 73 Nick

[@gradje74]

Hi Nick, great video again. Are you going to use the same set of amplifiers between the BPF and first mixer? 73, Gerard

[@M0NTVHomebrewing]

Thanks Gerard. Yes, indeed! I've put two 20 dB TIAs in there: one works as the post mixer amp on TX and the other as the RF preamp on RX. Once I've built the mic amp I'll show the whole lot working together. Thanks again. 73 Nick

[@DAVIDGREGORYKERR]

Is that module from the Zero IF transceiver.

[@M0NTVHomebrewing]

Hi David, I've used it before in my 'Optimiser' Rig and now in my 15m/10m creation. Wes & Bob originally designed it to go into Farhan's BitX transceiver to replace the existing one transistor design. I've linked to their paper in the description. 73 Nick

[@gh-ur2lx]

Can the distortion be seen on an oscilloscope when you reach the compression point? I would like a spectrum analyser but it’s beyond my budget

[@M0NTVHomebrewing]

Hi there! There are different ways you can do this. The main things you need are (1) a way to alter the input signal by 1 dB increments and (2) a way of recording the output signal. The first can be achieved with a signal generator (either sweeping or on a spot frequency) + a stepped attenuator. Then you can put in some arbitrary signal level and a high level of attenuation (e.g. 30 dB). Then you progressively reduce the attenuation 1 dB at a time and so increase the signal level 1 dB at a time. When it comes to (2) measuring the output you can use: i) a TinySA ii) an SDR (e.g. SDRPlay RSP 1) + free Spectrum Analyser software iii) you could use your oscilloscope but you'd have to convert your Peak-to-Peak voltage readings into dBm. Check here: 3roam.com/dbm-to-vpp-calculator/ Hope this helps! 73, Nick

[@gh-ur2lx]

@@M0NTVHomebrewing Thanks for this. I was also inspired by your crystal filter design but put off by not having much in the way of test gear. You offer some good solutions there, Perhaps a VXO controlled direct conversion receiver plus PC based audio spectrum analyser would enable me to see the pass band?

[@M0NTVHomebrewing]

For filters you really need to be able to see it in the frequency domain. A cheap NanoVNA will do the job very well.

Be careful with that spectrum analyzer! I would recommend to put an external DC block on the input to the SA. Even if it is internally protected for DC it is a good practice and habit to get to always have a DC block (and possibly a pad as well) to protect the sensitive (and very expensive to repair) input stage of the SA.

[@M0NTVHomebrewing]

Thanks Orjan. That's a good call. I also usually use an external 20 dB attenuator on the RF input port - just to be safe. I'll check out the DC block. Thanks again. 73 Nick

[@luzookiipcbway]

Hello. We found you doing electroncis so much fun, and were wondering if any prototype services may help? Would love to supply and reach any YT collab together! Is there anyway we could get you connected? (PCBWay luz)

[@M0NTVHomebrewing]

Thanks. I'll bear that in mind.

[@luzookiipcbway]

you can find my contact info under this account if you are interested now