The local club came to me to add TX PL Mod to the local VHF repeater. It's a well aged REP 200 that had one tone board installed for RX. They specifically requested that the TX board only transmit during reception of the RX PL tone. This is to allow you to setup a RX PL so that you only hear voice traffic. I reviewed the new tone board and the REP-200 schematic and whipped up something that worked. I mounted the new Tone Board close to the existing one. I used a transistor on the new board to control the existing REP-200. Before giving it back to put into service, a slight alignment was done and thorough testing, including burn in. Its been on the mountain working now for at least 2 months with no issues.
DANGER DISCLAIMER! High Voltage devices are dangerous. So first and foremost don't mess with one if you don't know what you are doing and even then it may not pan out. You've been warned.
I happened across a HV Supply and just couldn't resist. It was indicated that he had no idea if the HV supply worked and I knew prior that the HV module in these supplies really are not serviceable according to manufacture (Good Advice). The Tek TDS Scope that was to be traded for this device I was in my way and this was a great way to get ride of it. I in no way shape or form ever planned on using it. So, I pulled the trigger and swapped the Tek Scope for the HV Supply with the justification it would be less room taken in the lab. Really I just wanted it. The packages traversed the US and it took about a week for the traded items to arrive. The HV Supply arrived well packed and I begin to ponder what my procedure was going to be to ensure my safety during testing, how to test, and what the plan for it working as expected or not.
#1 Safety This particular device is rated at 10KV. It's perfectly capable of "reaching out" to "git" you. Rumor is it turns you to goo. I don't plan on finding out.
#2 I needed to keep #1 in mind for any testing or risk getting instantly cremated into a pile of ash or goo on the lab floor (Not really, but death is a possibility so care will be taken).
#3 Do I dare dive into the non-serviceable regions of the supply? I likely will but once that teardown occurs the device won't be placed back into service, again abiding by #1.
The supply itself is a Acopian P010HP6 Supply. It appears it is still sold and serviced by the manufacture. The face has analog meters for current and voltage and really nice vernier controls for both. A large ON/OFF switch is also supplied. At the rear there is a HV output connector which looks like a GES HS-10 connector. There are connections as well for remotely controlling the unit and prior to turn-up, I'll use the Acopian guide to verify it is in local mode.
Before I had planned to do the actual teardown/test I started thinking about how I might use this and here were some of the ideas that came to me while driving back and forth to work.
1. Mouse Trap - As novel as this sounds, I remembered I have a cat who would be very angry and hold a grudge if I took this duty away from her.
2. Flame Thrower - HV can certainly be used to ignite fuel. Not very practical or safe.
3. Plasma Speaker - I remember seeing this on the inter web somewhere. Nah
4. Rail Gun - Nah
Although they all sound like lots of fun I haven't come up with anything really practical yet for this supply if it works. But I'm sure it will come in handy for something.
Here is a video of the teardown and end result.
The Wouxun's either wear the flash chip out or its a bad batch of parts. Either way, eventually all of them I've owned and everyone I know either throws it in the trash or repairs it. Below is a video of how to do the repair and its an easy fix. The replacement part is a 24C64 found just about everywhere for under $1. Please repair these when possible and if you are unable or unwilling, hand it over to a new ham or send to an old one to be repaired.
I recommend using a hot air station but it is possible to carefully cut leads with cutters for parts replacement.
I have several Symmetricom time references but needed something compact for my newest bench area. I fumbled upon a Nortel card (GPSTM) that is basically a Trimble Thunderbolt. It has a few minor differences and it utilizes the same software for configuration. Most importantly it has a 10mhz out (SMB Connectors) which I used with a Symmetricom Distribution Amp to sync all my equipment on the bench (Signal Gen, HP 8935 Spectrum Analyzer, HP Frequency Counter) with a stable reference source. Other than the 48V(24-48VDC) DC power supply its very straightforward to get one of these up and running as a repurposed piece of gear (GPS DO) that works very well, is small and compact, and won't break the bank. I completed this project for well under $200. A photo of the DC connection is below and a video as well.
I did a quick teardown of an old handspring visor. Very simple design powered off 2 AAA batteries.
Short video of replacing the TFTA Connector. I used hot air and solder wick to remove the old part without any damage to the TFTA board.
On the first combostar I constructed the CAT4240 was easy to find. Now its a very hard part to source. Luckily the CAT4237 is almost a direct replacement.
I built my first combostar/picastar back in 2012. I've made several modifications over the past three years including adding a STM32 based embedded board to do FreeDV. Many of the parts were difficult to get and even more so now. I learned so much from its construction and the wealth of information from the homebrew group that I'd really like to see an update or maybe something entirely new. The DSP used is very old in the design, the TFT controller parts are dated some aren't made anymore. Here is the short list of reasons to update or come up with a new design for a homebrew HF rig.
- There are better parts for the GUI out. Integrated graphics STM32F4 would be a great upgrade. Maybe multiple screens and small OLEDs have come way down in price for adding addtional controls at low cost and ease of use.
- The DSP could be replaced with a STM32 series ARM keeping it all on the same platform.
- There are already improvements to the H Mode Mixer and maybe a direct conversion would possible now with some of the low cost TI frontends and low power/cost FPGA.
- Codec2 is widely availible and there is no reason not to include not only this digital mode but a hardware platform that may run future digital modes.
- Modularization of the GUI, RF sections etc. I really like the idea of mounting the radio somewhere and the GUI/MIC elsewhere. I would also like to see VHF/UHF modules that utilize all the work done on digital modes/GUI keeping the idea of a remote/even distributed GUI Head.
I've added another GPSDO to my bench. This is a Nortel unit. Its fairly straightforward as its a Thunderbolt device. Requires 48VDC power.
Well I have had a few of these on the air for a few weeks. Phase noise is an issue . To be expected with the single chip transceiver. It's limited to about 3 watts output before spurs become an issue depending on frequency but I've been able to experiment with protocols.