This weekend marks the annual
Orlando Hamcation, marking 37 straight years we've been going This time I wasn't looking for anything in particular and found it. That is, I found nothing work buying. A battery vendor I know and trust was selling over-rated 18650 batteries like I talked about
last fall, so I passed on those and noted a decline in trust levels. Other than a couple of LED incandescent bulbs, which were about half the price of the big box home improvement stores, I found nothing worth picking up.
A table of
old, vintage radios in one of the tailgate areas. It's 100% certain some of those models of radios were on sale back in 1982 when we went to our first Orlando hamfest. Heck, it's possible one or more of the radios on that table or others around the hamfest were on sale at Orlando back in 1982. See those big black boxes in the left front? Those are Collins Radios, a favorite among collectors, and the second one from the left says "75A-2 Receiver". According to
this site, the model was introduced in 1950 so one could have been sold many times.
Table full of laptops and netbooks in one of the three buildings they use.
I honestly have to say it was an almost completely uninteresting hamfest, and that's a bit sad to say. I rush to add that my interests in radio tend toward the unconventional, so it's not really surprising that I'd find the same old 40 or 50 (or 69) year old radios not particularly interesting.
We ran into friends and catching up with several whom we see yearly or less was what the hamfest was mostly about.
FWIW, I think Collins is what a radio should look like. Yeah, I'm approaching old-fart-dom.
ReplyDeleteI don't mean to bad mouth them. I have two Collins radios: an R-390A mil-surplus receiver and a KWM-2 HF transceiver. At one time, I had a complete S-1 and S-3 station, so I've thinned the herd a bit.
DeleteThe January Hamfest out here seemed to have a lot more people than last year. Nothing I wanted to buy, but a few interesting items. All the old tube stuff was either dirty or really beat-up, and they were asking "eBay Prices" for it.
ReplyDeleteThe next one I'm going to is at the end of April, and is put on by the Bolder ARC. I didn't go last year, and my neighbor said I missed a good one.
The crowd seemed bigger than last year, and I've noticed the trend of getting bigger on Fridays for the few years I've been doing it. Same with Dayton in the last couple of years.
DeleteI also noticed what seemed to be high prices for most things. Maybe to give room to cut prices by Saturday afternoon or Sunday?
Would anyone be interested if the SM2000 or Whitebox projects were resurrected and completed? Imagine a VHF portable the size of a cellular bag phone. Completely SDR so you can tinker with modulations. Add a Raspberry Pi so you can tinker with fancy Internetty things like BATMAN mesh routing.
ReplyDeleteSM2000 Part1 – Open VHF Digital Voice Radio
https://www.rowetel.com/?p=4694
SM2000 – Part 8 – Gippstech 2016 Presentation
https://www.rowetel.com/?p=5273
I suppose you're asking me and I really don't have any input that matters. I was never involved with FreeDV. I've never heard of the SM2000 or his VHF design, and it seems the only advantage over the widely available $30 VHF radios is that it's open source and modifiable.
DeleteThe architecture seems oriented to using a simple (8 bit?) ADC built into the STM32F4 controller. That's the biggest design trade in a new receiver in terms of parts count and parts cost, total cost and performance, impacting every piece of the receiver, so I'll just leave it there.
Thank you for giving me your take on it. I find it exciting because I'm not interested in analog voice, instead I'd like to tinker with Internet-complexity data transmission over a few miles' radius. Sticking a modem on an existing HT seems like an inelegant way to do that.
DeleteWell, he kinda lost me at "don't get me started about data over FM links" then doing exactly that. With the exception of his data handling, it's not even a late 1970s design. Dual conversion to 10.7 for a crystal and then down to (was it 32?) kHz isn't necessary. I worked on a 2m radio in the 70s that single converted to 21.4 MHz. The filters are just as good.
DeleteBack to that 8 bit converter and what it implies. You'll never get better than a 48 dB SNR (well, you get "a couple" more dB). An ADC gets 6 dB per bit SNR, so 8 bits at 6 dB per is 48 dB. If that was a 12 bit A/D, that goes up to 72 dB. Suddenly, you don't need that crystal filter. Everything the filter does for you can be done in DSP.
That changes the design radically. Now you don't need that second conversion, you can convert the entire 2m band down to something like 20 to 24 MHz, digitize 20-24 and do all your channelizing in the DSP. Instead of using a PLL to tune the desired channel, you can do that in the digital domain with a Numerically Controlled Oscillator.
No doubt the software gets bigger and more challenging, but I'm fairly sure some of what's needed is already open sourced.
He doesn't even need the second conversion for what he's doing now if he undersamples the 10.7 IF, but it probably still needs a faster, better ADC. ADC performance does go down as you undersample higher frequencies, so it means a converter that's maybe $25 instead of "free" because it's in the microcontroller. I'm sure there will more costs associated with something or other.
I forgot to say, and this is always true, feel free to email me directly with these sorts of questions. I'm SiGraybeard at gmail with the usual substitutions.
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