At least, the rack is accessible and more in order.
To be done:
Power
Antennas
Internet for linking the 70cm analog repeater.
The Sepura in the box is an SRG3900 #TETRA radio programmed to our 70cm TMO base station, which is connected to the #tetrapack network.
The idea is to offer better indoor coverage with the TMO-DMO gateway.
The Nokia RD58 based analog 70cm repeater is planed to return to service as an experimental internet linked club repeater on R.Net2.
What uses would there be for 7638MHz and 7554MHz DRO oscillators?
Not phase locked, so not super stable, don't multiply immediately to any interesting bands either, so not that usable as a marker either.
And these have a negative supply voltage.
Btw, Nokia used to sell these things with their Actionet branded MTP1327 network.
IIRC Altai2 is one user of it's derivates, with Nokia RD72 terminals. I guess the units meant for the Chinese market could be used on the old Altai frequencies as well.
Here is it's schematic.
Pretty ingenious having that 70pF cap in series with the DUT to make the impedance measurement to work for inductive DUT's as well.
The noise source seems quite traditional amplified Zener noise source.
@recursive
Yep. No DRO oscillators anymore.
RDA and NXP made single chip wonders that do everything except the first low noise pHEMT amp's job.
9.7 - 10.6GHz VCO + PLL + mixer + IF amplifier + pHEMT bias voltage generation and horisontal / vertical polarization switching.
The only things left are the regulator and clock crystal.
@ftg Yeah, I took one apart around 2015, and it was basically this. I was amazed at the single chip solution, I didn't realize we'd been at the point of integrating that much at those frequencies.
Apparently it is possible to directly receive 2.4GHz FM video on this analog CRT TV.
2.4GHz TX on 2466MHz
TV on somewhere ch42 - ch44 UHF.
Mixing with 5th LO harmonic and slope detecting the video?
Hello lazy web, a friend of mine fudged the NVRAM battery replacement in his Tektronix TDS644B.
One of those Dallas jobbies where you get to really tear into them to pry out the existing batteries.
So now the calibration is gone and the instrument is unhappy.
So what next? Finding some random calibration file and use that and hope for the best?
Maybe some of you know more.
Sure, there is an Allwinner R16, but it is BGA and outside of a single USB (based on the common mode balun and balanced traces) no real easy to use interfaces to the world.
Sure there is also eMMC, DRAM and it's AXP223 PMIC.
But who designs SBC's around salvaged and reballed SoC's?
Shiny silvered brass from 1975.
A 2GHz local oscillator from some old 4GHz link transmitter.
Not a single circuit board in this unit. #GHz#surplus#junk#hamradio
@ftg RF Gain Align, oof. Hope it's not the mixer. Good luck with the repair! I have an E4406 VSA Transmitter Tester which seems similar, but for higher input powers and different use cases.
@philpem
The difference was only -20dB on 500MHz, instead of the -55ddB on 3.5MHz, so that points towards something being open.
The mixer seems to work, just that something in front of it severely attenuates the signal.