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Wednesday 27 June 2012

GY560 Frequency counter

Ever one to have to take a screwdriver to something cheap to see how they have done it I have done it again this time to a GY560 frequency counter. The factory is kicking these out at 1000+ units a month apparently.

The specs say:

- Frequency step : 200K (digital radio signal), 1K, 100Hz.
- Testing distance : UHF : 8m, VHF : 5m.
- Testing range : 50 MHz ~ 2.4 GHz
- Antenna : pulling out antenna
- Battery : 9V 6F22
- Auto power off time : 1 mins. (except for the digital signal gear)
- Operation : the only one button with all functions.

And I can confirm with playing it really does work 50MHz to 2.4HGz.

It sort of scans constantly (once turned on) until there is a strong signal, locks on and shows the frequency and the signal strength. It auto shuts down after about 60 secs if nothing happens.

The uPC inside is an AVR Atmega8, they tried to hide that by a sticker but yu can still 'just' read the codes. Some of the smd IC are pretty standard and I found a 74HC00, 74HC393 both seem to be performing a divide/count function maybe? an LM358. Some are a little rarer MB506 High frequency pre-scalr, uPC 1667G which I have no idea what it is maybe a pre-amp of some sort maybe?

There is a A 7805 regulator, 4 discrete diodes, an inductor, electrolytic and a resistor, there is a nice little compact 2x8 LCD too, a 4MHz crystal, small trimmer capacitor and a handful of C and R SMD of course.

I managed to keep it working at 8V (I connected a variable supply to it.).

I'd say it operates more like a VHF/UHF field strength meter than a frequency counter, did pick up signals from my WiFi, 6m, 4m, 2m and 70cm. Also a car remote 433MHz and remote door bell 434MHz.

This was the household telephone.

The case comes off, 4 screws, the PCB is hld in place with 4 motherboard riser type hex stand offs that the other 4 screws attach to, the switch is a tiny push to make, and there is a PP3 battery connector and a tiny little whip antenna.

For £7.20 and £5.50 Post bargain really.

I found this schematic which seems to match up with my probing about.

I'll put up some more images of the guts hanging out :-)

The guts of the Yaege FC1, that Paul (see comments) asked about, note the 3.7V 1000mAH battery, you use a mini B USB cable to recharge it!Don't do that from the laptop !!!

The specification manual from mine.

 Again both of these are really field strength meters not frequency counters.

You 'could' add a tunable front end band pass filter.

Thursday 7 June 2012

NT7S Jason Milldrum Open Beacon QRSS Hell & DFCW

Yes there are C missing as this is the 30m version.

Picked up one of these at FDIM 2012 and put it together last night, took maybe 90 mins and I wasn't precious about it. The underside I have to clean the excess flux off yet.

Bit too big for an Altoid tin.

Top image is of the power and USB/uPC stage only... I had already stuffed all the resistors. The lower I soldered in the xtal and didn't bother with a socket. I always seem to wind the damned toroids back to front when lining up with a set of PCB holes. T1 he doesn't say how you should do it but I use a hint given to me a few years back and use a small hand drill and pre twist the bifilar winding in it, about 10 turns per inch, open the second image to see it clearer... T1 is the black toroid by the white BNC.

Blurb is:

"OpenBeacon is an open source crystal-controlled QRPp beacon transmitter which can output a variety of slow-speed modes, including QRSS, DFCW, and Sequential Multi-tone Hellschreiber. It is configured via USB port, so there are no jumpers to set and you can easily adjust all of the operating parameters via command line. Once configuration is complete, OpenBeacon may be removed from the PC and operate stand-alone.

OpenBeacon is considered a MEPT (manned experimental propagation transmitter), which means that you should never leave the control of it unattended.

  • Frequency: crystal controlled
    • Available bands: 30 meters
  • Modes: CW, QRSS, DFCW, Sequential Multi-tone Hellschreiber, Glyphcode, WSPR (experimental)
  • Power output: 300 mW nominal (at +13.7 VDC power supply)
  • Spectral purity: greatest harmonic <-45 dBc
  • Power supply: +5 VDC to +14 VDC
  • Current consumption: 50 mA at +5 VDC, 120 mA at +13.7 VDC
  • Control via USB on Windows, OS X, and Linux

From the project website is here and you can buy one online here

Once built I put the signal on scope etc and I measured about 310mW out when connected to a 7AH 12V SLA so for a QRSS beacon it is seriously QRO. I'll test it over the weekend and I think connected to the SLA with a solar trickle charger connected it would last for days/permanent.

I tested mine with Linux (CentOS, Mint and Ubuntu) and Windows 7 and no problems with any of them and to chnage the message/mode just means a few commands are all that is needed. I applaud the use of a standard USB B port not one of those mini B ports that seem to be the rage right now.

Not really sure the ISCP headers were needed but I guess if you want to reprogram the firmware you can. I think I'd have somehow added a power switch option to the PC so you can leave it plugged in.

Tuesday 5 June 2012

6C4 valves

At FDIM 2012 / Dayton HamVention I picked up a dozen 6C4 triode valves.
A conversation with a few including Hans Summers G0UPL who has been most helpful and the suggestion is a superhet receiver, for 80 and 20m. The front end band-pass filter determines 20m or 80m, all you need is to switch that front end filter, to select which band. No problem, 2 bands :-)

One possible line-up to aim for might be built from these modules, each could practically be built and tested on its own:

1. Switched Bandpass filters for 20m and 80m. I have some interesting variable capacitors that will make these a little special.
2. RF amplifier (V1), typical triode RF Amp.
3. Dual-triode mixer - Google "Pullen mixer" (V2, V3) plus oscillator input from:
4. Franklin VFO at 5.0-5.5MHz (V4, V5) W2LYH QST, October 1961. Hans recent low drift VFO using dual valves is inspirational. I have an old Mecanno worm drive that I will investigate.
5. 9MHz tuned circuit - perhaps something like a T50-6 and a trimmer capacitor. A secondary winding to match impedance to the crystal filter
6. 9MHz G-QRP club CW filter (I have the SSB one too)
7. Two IF amplifier stages (V6, V7)
8. "Infinite impedance detector" as per G3VA book (V8) + oscillator input from:
9. BFO, single valve crystal oscillator - There are multiple options Pierce, Colpitts usually work nicely too (V9)
10. AF amplifier (V10)

I will also try to make a TX.

Deluxe Tenna Dipper

I knew I would run into Doug Hendricks at FDIM2012/Dayton and I had asked him to put aside a couple of kits for me that he thought would be interesting. I have built several of Doug's kits in the past and I am a fan of Steve Weber KD1JV designs. After a few conversations he came up to the G-QRP booth the following day and with the Deluxe Tenna dipper, Battery monitor and the SOTA tuner.

Back home whilst waiting for lunch I put the Deluxe Tenna Dipper together.

I'll replace the photos with my own soon.

The blurb says:

"The Deluxe Tenna Dipper provides a simple means of determining the 50 ohm resonant frequency of an HF antenna or ATU (Antenna Tuning Unit). The small size and battery operation makes the unit ideal for use in the field. It's perfect for antenna experimenters that don't want to tie a bunch of money up in the higher priced analyzers. It's even priced lower than most swr bridges, and this tells you "where" you are resonant, not just that it's matched, or not matched, like a simple swr bridge."

Well it went together quickly and worked first time. I have not put the decals on the front yet I want to paint mine bright yellow first. And I have a feeling I might look at some sort of laminate cover to go over it to help keep it dry as I'll use /P and it is not always dry in UK. Only thing I had to add were a couple pieces of tape and some twisted pair (from CAT5 cable) for the antenna connection.

A quick check with the bicycle ATX-100 and sure enough it finds the resonant tuning for each band in seconds.

More shack test equipment

Well just taking a bit of time away from a project am working on some test kit I was given by brother of a G-QRP member when I visited the RSGB AGM A B4A Signal Generator. Was not supposed to be operational and it didn't turn on initially.

I lashed up a mains fed to it as did not have the appropriate plug. Fitted shrink wrap over the exposed plugs, I'll repair that later. The main transformer had an open secondary, it was a simple 230V:250V with a centre tap output, and I had been keeping one with 6.3V windings for a valve project but this looked suitable and right size so swapped it out. The old one I'll rewind the secondary and reuse.

I simply love the mains input choke.

PL1 was duff so replaced with a screw in 6V MES bicycle bulb.

Checked connectivity on the circuits. Insides (photos to follow) very clean.
Initially with the 6X5GT  removed turned it on and checked the heaters were all fine. Then put the 6X5GT back in and with the other valves removed tested the HT (301V) and other valve socket pins for the appropriate voltages. Seemed to loose the HT some where so thought maybe this was similar to the HRO problem so a quick once over with the home brew ESR meter and some of the bypass Dublier caps were proven to be open circuit. So rummage in the Dayton ham-fest brown bag of goodies and replaced three 350V paper tube 0.01uF and turned it on again. All seemed fine so turned off plugged in the three valves and turned on again waiting until heaters been on for a bit and then twiddled with the controls... The calibration is slightly off but I'll fix that. Nice rim dial control, must have slipped a bit.

Circuit and manual from a Google search...

Fed the signal into a oscilloscope and seems like nice clean output, across the various scales.... I now have a nice signal generator for the bench. I like the attenuation options dropping down to 1uV from 100mV

I do not have the RF/AF output leads so I might swap these (apologies all purists out there) for BNC or N type chassis connectors. And I have a spare digital frequency counter so might add that too after adding a pre-scaler as the generator will go from 100KHz to 80MHz.

Looks like this one (will put better photos up):

Monday 4 June 2012

UK Valve and Socket Supplier

Ever fed up with ever increasing ebay prices and those horrid shipping costs or waiting for the next rally and then never finding the valve I wanted I searched for a UK online alternative.This is the best option I have so far... and it is a trader that seems to have moved most of their stuff OFF ebay!
TubeZone Ltd Amplifier Valves and Sockets