Homebrew rig features

[brandon7861]

If you had your heart set on homebrewing the most insane rig you've ever owned, what features would you want it have?

I am looking for any and all crazy ideas. Simple suggestions like "audio compression" are great, but if you also know of a neat way to implement it, I would love to hear those ideas too.

One of the reasons I wanted those BU2630F PLL chips I mentioned in the other thread (which I decided to order) was so I could start with a single 5.12MHz OCXO and have that feed the reference on multiple PLL chips so each LO would be nearly as stable as the OCXO and could be changed on the fly for testing different filters and other experiments. All I would need to do is change a VCO coil and tank component here and there and send some new serial data, no crystal swapping. I know, thats a job for those Si5351 modules, sure, but I can't wrap my head around it's datasheet, so I'm going with what I know (3 wire serial input, no code BS).

 

[brandon7861]

I think another neat feature would be to make each stage modular, like an actual block diagram, where each main function was contained it its own shielded unit. Those blocks could be quickly removed, tested out of the radio, and easily swapped with something else. Say i wanted to go from a single balanced mixer to a double balanced mixer. And then from there, maybe swap that out with a mixer having diplexed IF ports just to see the difference.

I would want the thing to be a perpetual learning platform, not just a daily driver.

How about using one of those heavy toroid transformers out of a high power sound system as a 48v power supply and some mosfet finals? Got an old denon here with bad relays (excuse) that has a beast of a transformer.

 

[Onelasttime]

The easiest way to implement audio compression is to start with a ready made solution. Audio IC's have included EQ, Noise Gate, Compression, filtering since the what the late 1970's early 1980's? Think about compact cassette players with all the Dolby and other filtering, compression, EQ functions built in. You even find delay, echo, reverb as functions.

You can purchase mic preamp/eq setups with all of that built in for $149 if you do not want to roll your own. You can purchase compact audio compression unites designed for 2 way radio that you install internally like the SP1-A. You have various seperate boxes that convert the audio to rf clip, compress and then convert back to audio like the old MFJ-LSP-520 I think it has 1 IC, 1 crystal and the rest is mostly capacitors high end styroflex cap's. The SSM2166 IC was the darling child for audio manipulation as an in all in chip in many ways.

Instead of building your own DSP and installing it off the shelf soultions exist. Your homebrew radio would quickly take up the same amount of space as a Henry or COllins amplifier.

So the real trick is to get China to build us a radio at a low price point that absolutely crushes the market forcing more traditional companies to stop fleecing our wallets for all that we are worth.

So you want to get as much into the radio as possible since most of these systems can be designed into one fairly compact board if done from day one. So you get them to build you an all mode HF+6 with continious tuning with antenna tuner, DSP, compression, noise gate, digital modes, water fall, PC interface, EQ, eSSB, NPC, 100 watts output etc.....It has to be done at a price point that allows you sell it at a profit for $249. Now comes the problem to do that you would need a huge ecconomy of scale.

Adding seperate boxes is what most of us have done forever. A lot of people in the past have done the home brew thing often having it temp. becoming a side business for some. A lot of these guys designed one thing say a DSP or an active notch filter, or an audio compressor and that is it.

I think if I had the skills and knowledge or wanted to truly learn these things I would first build various well worked out black boxes and such using old designs and modern parts. Once I had mastered those designs and concepts then I would design my own circuits and master those. Only after I had done that would I start trying to combine them into one box. Then after that a single board.

You do not wake up one day and decide to build a rocket and think your going to do it all on your own day 1. You do not wake up with no training and decide to enter a marathon the next day.

Finding really good vintage books on various electronic circuit theory might be a good place to start.

All of this is just my opinion and I am not the best at electronics I am a clumsy hack.

I would first find out the best examples in the last 75 years that has already been done in civilian, broadcast, and military radio technology and audio technology. Then figure out a better way to implement those ideas and loock at what is available on the market because I am sure all of the IC's needed already exist tot he point that it would be pointless to do any serious design work at that level. It is more about chosing the right parts and surrounding those parts with complementary parts and code.

Also is it the adenture and the discovery or is it the ourcome that you want to chase after. Depending on which one you want the most your path will change radicaly!

Good Luck and God Bless!

 

[brandon7861]

I appreciate the schematic and all the advice! The goal is learning and personal enjoyment, nothing for production or sales.

One of the goals I had was to make it out of readily available parts and keep the IC count to a bare minimum. Having everything integrated into a chip would sure make things easy, but I am hoping to use big old jellybean parts that are readily salvaged as much as I can. I know I will need a few low noise parts for the first transistors in the mic and RF chain, maybe a few good diodes too, but the rest I want to be so common that any scrap piece of electronics could be a donor. I know the PLL, if I use one, will be an IC chip, but the rest will probably be discrete components, including the audio stuff. I hesitate to add echo, but if I do, I will likely go with a generic bucket brigade IC to learn how that works instead of a pre-bought echo board.

The gain control and compression I also want to do with discrete parts as I have come across multiple methods of gain control and want to explore them in detail and learn their individual pros and cons. I will take a look at the schematic you shared as well. I like the point it makes about too much makes it sound unnatural, something I would have learned the hard way.

I figured on detailing in a notebook each step and each change and why, so when I die and this thing gets handed down to the next person, they will know why every part and parameter was chosen and how to use something else in its place. I think the record of the changes I make will be far more interesting as the years go by, who knows.

I honestly hate the idea of using microcontrollers, but most PLL chips nowadays are serial input. I could do a parallel to serial converter to clock it in, but I may just go analog with a VFO and a way to calibrate the dial. The BU2630's I ordered were a scam that I was able to avoid at the last minute, so back to the drawing board there. Had it not been for cancelling the order for a shipping address revision and raising the part quantity at the last minute, they would have had my money. They fumbled with the courier details and I started digging. Glad I did. I may not even use a PLL now.

Side note on ordering obsolete and hard to find parts from unknown companies. If a company sends you a paypal account based on an email using @163.com, just know that @163.com is a free email service based in china and no reputable company should be using that. Do your homework, see if others have successfully ordered from them, see if their domain info is redacted for privacy, check their socials to see if they have more than a shell company would have posted, ask them who they are affiliated with parts-wise and contact them, etc.

As for size, I fully expected it to turn out the size of my FL-2100B tube amp, and that's ok. I wouldn't care if it evolved into an entire rack system honestly. It's all about the journey and being able to say "this thing is completely homebrew" when I am shooting skip, even if the last screw goes in the cover when I turn 90. It's a hobby, not a job.

Thanks again!