HFU HF Underground

Technical Topics => Equipment => Topic started by: ButchKidd on September 09, 2019, 1903 UTC

Title: Test Equipment for First Time Build
Post by: ButchKidd on September 09, 2019, 1903 UTC
TLDR: What hobby-level test equipment would you recommend for a first build project, a 100mW medium wave AM transmitter?

Up until now, Iíve just been a user of radios, but never understood at a fundamental level how the parts worked together.  Iíve built crystal receiver kits and arduino-powered robots with the kids, but always following someone elseís instructions.  At present, my troubleshooting ability is mostly limited to making sure I followed directions or a schematic correctly and checking for bad connections/solder joints.  I look at RF circuits with a DC short, and it blows my mind that it works.  But, Iím working on correcting that.

I figure thereís only so much I can learn from reading forum posts and watching YouTube videos.  I want to build something, if not from scratch, then at least with an understanding of why the designer chose the components he did.  My plan is to build several iterations, starting with something super-simple, like using an op-amp to generate a carrier, and modulate it directly with a line-level audio source.  Then Iíd like to improve the design step-by-step to get better quality audio, low-pass filtering, and a usable range with a matched antenna.

Aside from the actual components and tools to assemble them, what am I going to need for this journey?  Iíve got a breadboard, soldering station, multi-meter, etc. as well as the ďend userĒ stuff like a dummy load and SWR meter, but I donít expect to need those until much later.  Iíve been thinking of getting an old analog oscilloscope on eBay or Craigslist since they seem to be available around $50 if youíre patient.  I guess at some point Iíll need to prototype a PCB or order it from China.  Can some of you more experienced guys tell me if thereís something important that Iím missing here?

I realize Iím probably not really giving enough information to get a good answer, but Iíd at least like to get some ideas on what to start thinking about from those who have done it before.
Title: Re: Test Equipment for First Time Build
Post by: RST111 on September 10, 2019, 0528 UTC
Thanks for asking this Butch! I'm interested in the answers as well.  I've been wanting to mess around with the same stuff and am kind of lost as to where to start equipment wise.

Title: Re: Test Equipment for First Time Build
Post by: ChrisSmolinski on September 10, 2019, 1117 UTC
Aside from the actual components and tools to assemble them, what am I going to need for this journey?  Iíve got a breadboard, soldering station, multi-meter, etc. as well as the ďend userĒ stuff like a dummy load and SWR meter, but I donít expect to need those until much later.  Iíve been thinking of getting an old analog oscilloscope on eBay or Craigslist since they seem to be available around $50 if youíre patient. 

A scope will be invaluable. I'd consider it to really be mandatory, unless you enjoy pulling your hair out.
Title: Re: Test Equipment for First Time Build
Post by: redhat on September 10, 2019, 1726 UTC
A scope is mandatory, I'll second that.  Garden variety scope probes are good to about 100W or so.  I've burned out several probes over the years at the 500W level, even though the signal voltage fell within the rating of the probes.

I would also highly recommend a good soldering iron and quality solder.  My main station is a Hakko FX888D and I run Kester 63/37 mild flux solder.  This is the equipment I do rework with as well to pay the bills.  For small one off's I'll spin my own boards in the kitchen using a photo etch process using pre-sensitized boards.

+-RH
Title: Re: Test Equipment for First Time Build
Post by: Josh on September 10, 2019, 1737 UTC
A scope is nice but most radio issues can be resolved with a lowly dmm and brains. For beginners, a dmm is about all they can handle, plus mebbe a freq counter. Scopes will help in the more advanced radio adventures, however.

Great news! China is building some scopes that display voltage and freq all in one tidy package, for a sum.
For ensample;
https://www.amazon.com/Rigol-DS1102E-Oscilloscope-Channels-Sampling/dp/B0039N9ZBA/ref=sr_1_6?gclid=EAIaIQobChMInd6PruXG5AIVmNlkCh00VAr2EAAYASAAEgIxSfD_BwE&hvadid=176299913216&hvdev=c&hvlocphy=1024403&hvnetw=s&hvpos=1t1&hvqmt=b&hvrand=4678028386373471961&hvtargid=kwd-79622566892&hydadcr=29354_10014455&keywords=rigol+ds1054z+digital+oscilloscope&qid=1568136959&s=gateway&sr=8-6
Title: Re: Test Equipment for First Time Build
Post by: ChrisSmolinski on September 10, 2019, 1900 UTC
I've had a Rigol DS1052E for several years now. It's sitting about 3 ft from me right now, in fact. Great value for the money.
Title: Re: Test Equipment for First Time Build
Post by: redhat on September 10, 2019, 1937 UTC
I picked up a MSO2202A last year.  It replaced an old 60 MHz dual channel Tek whose trace had become so dim it was almost impossible to make out.  I do prefer a conventional scope for a lot of things (looking at things in XY mode) but it's hard to beat the portability and price v. feature set.

+-RH
Title: Re: Test Equipment for First Time Build
Post by: Stretchyman on September 11, 2019, 0633 UTC
A good question and being a hobby for over 40 years and a part time business for 10 I hope I'm well placed to answer your question!

A scope is ESSENTIAL, simple as. You can't see radio without one, there's no excuse either as the ones from CH are super cheap.

Get a SIGLENT, RIGOL are similar (same in fact)

The old TEK scopes, they're nice sure, I've had plenty but they're so old now, sure if you can find a good one cheap, get one.

Soldering iron, most are crap and I'm afraid there's only one to get. METCAL.

Get one SH from wherever. At the best part of £800 new you know your buying something that's the best.
I've seen them SH for <£100 so figure $100.
You will not regret this purchase and your soldering skills will improve immediately.
You can solder 0402 and then a PL259 connector outside on a windy day with the same bit!

PCB wise use OSHPARK they're in the US so use them, I'd forget CH for PCB's unless you're making 1000's

Ohh... 2 port VNA's are <£40 now, you may not know what they are but trust me, look up what they can do, you'll be buying one for sure.

Let me know if you want a PCB for an A.M. TX, will save you a lot of time and will transmit somewhat more than 100mW should you prefer.

Str.
Title: Re: Test Equipment for First Time Build
Post by: ButchKidd on September 12, 2019, 1257 UTC
First off, thanks for all the great responses!  This community has been one of the most courtious and inclusive I've ever been a part of.

I'm starting to see the benefits of a DSO, and if I can't find a good analog scope for a song, I'll probably end up buying a Siglent or Rigol.

Thanks for the advice on a better soldering station and specific kinds of solder.  I've currently got a Weller WESD51 which has served me well, though I realize it's not something I'd make my living with.

The Nano VNAs are impressive for the price, even if you only use it as an antenna analyzer, which is about all I know how to do on a VNA right now.

Should I be worried about a function generator or spectrum analyzer?  I'm trying not to get overwhelmed learning about every piece of gear until I know I have a use for it.
Title: Re: Test Equipment for First Time Build
Post by: Josh on September 12, 2019, 1444 UTC
Some of the Chinese scopes can be privateered into a higher model class.

https://www.youtube.com/watch?v=Mtt-g5putLY
Title: Re: Test Equipment for First Time Build
Post by: ButchKidd on September 12, 2019, 1707 UTC
From what I’ve read on EEVBlog and reviews on Amazon, the Hantek scopes seem to be coming from the factory “pre-hacked” now.  I’m sure they only guarantee performance for what each model is rated for.  One theory is that they have a tiered Q/A system with the best performing units becoming 200mhz and the worse ones becoming 50-75mhz models.  They all seem to have 200mhz firmware now, but I’m not sure how accurate they are.
Title: Re: Test Equipment for First Time Build
Post by: redhat on September 13, 2019, 0601 UTC
In the beginning, I wouldn't bother with a spectrum analyzer.  They are easily damaged (done it) and for most of the stuff your interested in will be overkill.  An SDR with sufficient padding will serve you needs fine for now.  A VNA is great for filter tuning and antenna design, I don't leave for a show without one now.

For the beginner, a Weller or Hakko basic station is all you'll need.  The Hakko is probably better for SMD work with the right tips.  I've had Metcal irons in the past and used them professionally as well.  Used, they don't seem to hold up well.  The tips are also very expensive, and second hands ones are of dubious quality.  Hakkos are cheap, and amazon has all the tip choices your likely to need.

A function generator is worth having.  I have the DG1022 from Righol.  It produces beautiful AM waveforms for calibration, which is actually how I calibrate modulation monitors now.  I also use it in the field as my carrier source on the HF transmitter until I get a DDS one built.

+-RH
Title: Re: Test Equipment for First Time Build
Post by: Stretchyman on September 13, 2019, 1208 UTC
Function gen just use ur phone with a sg gen app, fine for audio and as suggested use an SDR for a spec ani. Do keep a look out for cheap second hand kit tho'.

Str.
Title: Re: Test Equipment for First Time Build
Post by: Exo on September 13, 2019, 1849 UTC
A calibrated radio receiver.
Title: Re: Test Equipment for First Time Build
Post by: ThElectriCat on September 25, 2019, 0406 UTC
In the beginning, I wouldn't bother with a spectrum analyzer. 
+-RH
I, begrudgingly, Agree
I lusted after one of those for a long time, I finally got one (an HP8594E) aaand...
I don't really use it anywhere below a few hundred MHz. I use my scope and frequency counter every day.

my recommended top three (after the usual electrinic stuff such as a multimeter, power supply etc) are;
1. oscilloscope (my preference is analog, but any good scope is good and some digital features are really nice)
2. frequency counter (a cheapie is probably sufficient)
3. signal source. (slightly less important for building transmitters, but good luck building or even fixing a receiver without one. of course a cheap analog one is fine if used with the frequency counter. )

hope this helps _