nixiefreqq wrote: ↑Thu Mar 06, 2025 12:27 pm
25 CPS wrote: ↑Thu Mar 06, 2025 3:20 am
mnementh wrote: ↑Sun Feb 16, 2025 11:29 pm
Chinesium TE has its place on a working workbench or on a tinkerer's sidebench. No judgement from this tinkerdwagon.
mnem
whatever it takes.
The Fnirsi order came in the day before I was due to travel on vacation and I was tied up with getting ready to leave that I reluctantly set these down on the bench and left them for later. I arrived back home late Monday night and been catching up on stuff since then so the signal generator and tweezers are both still in the shrink wrap, unfortunately. I don't return to work until next week so that'll give me some quality test equipment time over the next few days, thankfully. I'll do another post later with some pictures of test equipment action taken before and during the trip.
agree 100% with mnem. my tiny sa ultra goes up on the mountain with the roving station all the time, and comes in handy to make sure everything is working. when on the bench diddling with vhf/uhf/microwave transverters..... why risk the unobtainium first mixer or attenuator in a classic hp SA? these little Chinese boxes might be a couple of dB off, but can be replaced for pocket change. (for absolute measurements you triple check the set up and only then connect the hp8569b).
I'm also in agreement. I've long held the view that TinySA and NanoVNA are good training equipment for students to learn on before touching A-list equipment because if one of those gets damaged or destroyed by accident, the replacement cost is low vs. repair or replacement of something expensive. I think every one of us that's older and learned and started buying our own equipment all had the same trepidation when we got our first spectrum analyzer: excitement combined with the fear of accidentally blowing it up.
Mobile use, especially mobile use in environments that are rough are another good case for inexpensive gear like this. I was actually kicking myself for not bringing the TinySA with me while I was on vacation. The result of that is I'm tossing around the idea of getting a TinySA Ultra and leaving the regular TinySA in the truck permanently. I've also got a story about "expensive" and "broken" from that vacation too but that's going to be part of a separate post showing test equipment in action.
Anyways, why I wanted the TinySA while I was away:
My truck came with a Chinese two way radio installed in it when I bought it and since it's there, I might as well make use of it. What I've done in the past is program it for whatever railway museum is hosting this annual conference and offered to let whoever is dispatching do it from my truck if they want. I think I posted pictures of preparing that back in 2023 when I dragged the HP 8656B signal generator out into the driveway and set it up to simulate that museum's radio system. I missed 2024 but this year but could attend this year so I got the technical specifications for the museum in question which has two channels instead of one like the previous museum. We've also been having a real winter here unlike the last two years and there was no way to safely set up a signal generator on a table next to the driveway with all the snow surrounding it. What I settled for instead was firing up both signal generators on my bench which are located next to the driveway and parked the truck so that the radio's antenna was roughly in line with them:
Different music applied to the external modulation inputs on the HP 8665B and 8657A in order to identify source. I guess I could've done 400 Hz on one and 1000 Hz on the other but would rather have program audio. A bit higher of a signal level at +4 dBm on both to push it out into the driveway.
Verifying they're working using the SDR and laptop upstairs in the living room. This is where the first hint of problems emerged but I didn't realize it yet. I confirmed the two carriers were on and did some experimentation enabling and disabling each one because it looks like the two signal generators with antennas on them with live RF appear to have been creating intermodulation products that were visible with the software defined radio. Interestingly, the SDR was able to demodulate them. Yes, it was a fast,cheap, and nasty setup so with no filters or combiner to prevent RF backfeed, this could very well be a problem and was. This turned into a bit of a rabbit hole between the IM components and some other behaviour I couldn't explain and it got late so I never did get into the truck to set up the radio before I had to pack it in for the night. I also didn't get a chance the next morning before leaving home either.
What I did end up doing was propping up my laptop with the manual in the morning while my friend was in the shower and doing the setup on the two way radio out front of his house before we set out to the museum having the event and that's when I discovered a stuck live carrier with no modulation on it that you can see up on the top half of the radio's display. My friend told me there's been problems with one of the local businesses' radio system so we thought it might be that and were curious to see how far across Pennsylvania we'd have to drive before it falls off. Except it didn't.
The signal level never changed either, ruling out driving by an emitter located somewhere between my friend's place and the museum we were going to. The possibility of an RF source at the same frequency as one of the railway museum's channels being on board my truck started to sink in - and this is when I really wished I had the TinySA with me to sweep around and see what was causing giving off the unwanted RF, which also explained some of the oddities I saw on the SDR while testing at home with the two signal generators, especially when doing one at a time.
The radio still worked though. I was able to both receive the museum and transmit successfully over top of whatever was generating the interference. The interference was actually the
lesser problem at the museum. The bigger issue was the proliferation of cheap Chinese Baofang / Quangsheng radios that so many people had - but nobody was paying attention to. Every radio test I called in to the dispatcher was ignored by the dispatcher (
BIG problem if the dispatcher is ignoring his radio) and everyone else who had one until someone who had one wanted to ask me about something else. It doesn't matter if it's a Baofeng or a Motorola, a radio in the hands of a knucklehead is still a radio in the hands of a knucklehead.
Needless to say, this happening two days after "broken" and "expensive" took place left me with a very dim view of your ordinary, average railway museum volunteer.
. Anyway, they're repacked and checked out as complete, with propane burners. I'm usually leaving the spirit option at home, because if I'm going to get soot on them, I might as well cook over a wood fire. 
