I am in Athens and with few guys we plan to start developing rigs for squats and other communities across Greece. Now, we are learning by doing, so I ask you folks here: what equipment should we put on the initial list? There is some funding available and we want to use it wisely, so your advice will be highly appreciated.
As far as we already learned, the list would be:

• Soldering station (hot air and standard) with accessories (3rd hand, magnifying glass and others, as specified here: https://www.allaboutcircuits.com/projec ... omponents/)
• Hand tools assortment: cutters, pliers, tweezers, hemostats, scalpels.
• A set of drill bits (for coil winding).
• Multimeter
• SWR meter
• Power meter
• RF Oscilloscope / spectrum analyser

Thanks to a friendly makerlab we will have access to laser cutter, cnc etching for PCB and come metalworking tools for making cases.

Now, please recommend what should we add to the list and possibly what are the best (low-budget) options to get the stuff. We are quite happy to build whatever can be sensibly built, and buy, beg or borrow the rest.

Hi,
You need some power supply that gives out 5-12-15V 1-10Amps also something on 24-28V 10Apms as well as 48V 10-25Apms. It may also be good to have a power supply that produces positive and negative voltages with some amps and power limitation. Even a dummyload that can handle high power.

The dummy load is crucial. You really don't want to be radiating crap before you have a transmitter aligned and working correctly!

Albert H wrote: ↑Sun Dec 31, 2017 1:09 am The dummy load is crucial. You really don't want to be radiating crap before you have a transmitter aligned and working correctly!

Something like that?

http://www.derbywirelessclub.org.uk/dummy_load.pdf

3M amateur wrote: ↑Sat Dec 30, 2017 6:55 pm Hi,
You need some power supply that gives out 5-12-15V 1-10Amps also something on 24-28V 10Apms as well as 48V 10-25Apms. It may also be good to have a power supply that produces positive and negative voltages with some amps and power limitation. Even a dummyload that can handle high power.

Would you care to recommend some designs / schematics?

PPirx wrote: ↑Sun Dec 31, 2017 2:51 am

Albert H wrote: ↑Sun Dec 31, 2017 1:09 am The dummy load is crucial. You really don't want to be radiating crap before you have a transmitter aligned and working correctly!

Something like that?

http://www.derbywirelessclub.org.uk/dummy_load.pdf

That will do the job. My original load, which was good for about 50 Watts, was made quite like this, but used my metal bench-top for the heatsink! The important thing is that the load is completely non-inductive - so you can't use wirewound power resistors.

In my opinion, a spectrum analyser is essential for those wanting to make equipment that'll be used on air.

Also, consider how you're going to drive the spectrum analyser input because most will take a maximum input of 30dBm (1 watt) before damage occurs. You can do this several ways...

1. Use a "sniffer" such as the Bird model which can be adjusted for attenuation (this is just a basic directional coupler).

2. Use a directional coupler to take a feed from the RF input line going to the dummy load.

3. Use a coaxial attenuator rather than just a dummy load.

Spectrum analysers can be found on Ebay for between £200 and £500 pounds. Personally I would avoid buying new cheap models (Chinese "atten" or the handheld "RF Explorer" for example) but instead go for a proper old but used unit such as those made by HP/ Anritsu/ Advantest etc.

I've just had a look on Ebay and there's not a lot there right now (probably because it's around Christmas), but have a search for;

HP8590-8594 series, HP8568, HP141, HP8560 series. And the other brands I mentioned.

Just bear in mind that in addition to the analyser iteself, you'll need to anticipate the cost of 40-60dB attenuation before the input as well.

A frequency counter is also a good idea.

Guys, thank you for your feedback. I am no party animal, so I used New Year time to put together a beta version of the list, linked here for your amusement

https://cryptpad.fr/pad/#/1/view/rhPXB9 ... cyDr9TWUc/

Of course, all comments advices and _donation_pledges_ will be highly appreciated.

@Analyser, I totally agree that we need spectrum analyzer, but I really doubt our kidneys can be sold for enough money to get one of those you recommend. So perhaps we start from something shitty, but cheap...

http://pira.cz/counter.htm
you can try by this this how we could encourage you good luck .
an sdr as a relative cheap spectrum analyser for the moment is enough .
btw what kind of rigs fm transmitter will you try to develop can you give ideas or what you are want to clone ?

If you can't afford an analyser, you can use an Absorption Wavemeter as a basic tester looking for harmonics and instability. I still keep one that I built about 45 years ago on my bench for quick alignment of frequency multipliers and (when switched to GDO mode) I use it to check the approximate resonant frequency of tuned circuits and aerials. My Wavemeter / GDO also has a PIC-based frequency counter (that was added about 20 years ago) built-in, using a small calculator LED display. It makes the whole device surprisingly useful, since in GDO mode it shows the oscillator frequency and in Wavemeter mode it displays the frequency of the signal that the wavemeter is "seeing".

radium98 wrote: ↑Mon Jan 01, 2018 6:20 pm http://pira.cz/counter.htm
you can try by this this how we could encourage you good luck .
an sdr as a relative cheap spectrum analyser for the moment is enough .
btw what kind of rigs fm transmitter will you try to develop can you give ideas or what you are want to clone ?

1. Thanks for the link, I put it in the pad.
2. We start very humbly, from getting kits (mostly from http://electronics-diy.com) and learning by doing. When we are confident that we can build fully working units out of kits, we will start talking with wise people and learn how to create our own circuits. We are especially interested in Internet-controlled retransmission, as it fits our work on community data networks. The most interesting topic on the table is a Raspi shield with RF amplifier and bandpass filter.

Albert H wrote: ↑Mon Jan 01, 2018 7:00 pm If you can't afford an analyser, you can use an Absorption Wavemeter as a basic tester looking for harmonics and instability. I still keep one that I built about 45 years ago on my bench for quick alignment of frequency multipliers and (when switched to GDO mode) I use it to check the approximate resonant frequency of tuned circuits and aerials. My Wavemeter / GDO also has a PIC-based frequency counter (that was added about 20 years ago) built-in, using a small calculator LED display. It makes the whole device surprisingly useful, since in GDO mode it shows the oscillator frequency and in Wavemeter mode it displays the frequency of the signal that the wavemeter is "seeing".

Does it have brass fittings?
I did a quick read in Wikipedia and I like the idea. It also resonates (pun intended) with my inclination for low-tech solutions, based on the knowledge present in human mind, rather than embedded in the tool itself (says almost life-long user of internet and linux).

Do we have any DIY documentation to build the device, or shall we reverse-engineer yours?

Albert H wrote: ↑Mon Jan 01, 2018 7:00 pm My Wavemeter / GDO also has a PIC-based frequency counter (that was added about 20 years ago) built-in, using a small calculator LED display. It makes the whole device surprisingly useful, since in GDO mode it shows the oscillator frequency and in Wavemeter mode it displays the frequency of the signal that the wavemeter is "seeing".

So we are using GDO and Wavemeter modes to search for the signal with 5-10% accuracy (as Wikipedia says) and then the counter gives us exact frequency? Did I understand it correctly? If so, sounds great for me.

The wavemeter / Gate Dip Oscillator was a circuit published in Radcom many years ago. Originally it used a 40673 dual-gate FET, but I destroyed too many of those with static, so later it was changed to the more robust BF981.

This is pretty much the circuit I used, with a range of plug-in coils to cover various frequencies. The coils were wrapped around plastic TV Aerial plugs.

Yes! So instead of old fashioned phones to pick up the AM signal, we have auxiliary output to the counter. Brilliant evolutionary approach. I am putting it on the list of equipment to be made! Thanks!

Just noticed - there should be a label on R2 (50k pot): "Sensitivity".

My gdo 3 years ago never complited

Complete it!

It's one of those pieces of gear that you never thought that you'd need, but wonder how you managed without it when you have it on your bench!

Thank you will do .please share the bd 1