Do it yourself Spectrum Analyser

[saturation]

Thanks for the comments tinhead, your insights are always valuable.  What do you think of that Chinese SA?  Its about $2400 given conversion of yuan to dollars.

ehm, no idea what you guys talking about, Anritsu (and that's on the pictures) is not chinese manufacturer.
Beside this, Anritsu is producing since years much better SA than HP did or Agilent is doing.

The page we're referring to is this one: http://www.qsl.net/bg6khc/test_on_filters.htm

Yeah, this is for sure chinese SA (and here is bg6khc SA http://item.taobao.com/item.htm?id=13003940513 )

ok, i thought http://www.qsl.net/bg6khc/my_version2.htm

[tekfan]

This also might be an interesting spectrum analyzer project:

http://lea.hamradio.si/~s53mv/spectana/lcd.html

(navigate with the VCO, SA... buttons on top)

I know a lot of the local ham radio guys built his frequency counter and are very pleased.

[gregariz]

Years ago there were a number of kits doing the rounds in the magazines that used an old TV tuner as the Specan receiver section and a CRO for the readout. Just a quick seach shows this one - pretty cheap no cro but serial port instead.

http://www.mtmscientific.com/spectrum.html

If you want a good piece of gear - theres no shortage of 859x/856x HP/Agilent gear on the used market. I recently had to pick up a spare unit and picked up a 8594E for about 3.5k from one of the test rental places. That seemed like pretty good value to me for that instrument, warranted for a year, Cal'ed and NIST traceable.

[Neganur]

...
I bought a complete set of PCBs and aluminium boxes for about $130 from eBay
....

I did buy that PCB set as well and can not recommend it. Rather try to get a group buy going for those ExpressPCB panels or invest the time it takes to redraw the boards with software that exports gerber files (and send them to china). My reason is: even though the aluminium enclosures are excellent and allow for a nice modular design, the shielding is poor. The lack of fencing will punish you with a higher noise floor and a lot of spur.

Scotty & Sam spent a lot of time redesigning and verifying the boards.

[joelby]

Ah, good to know! Are you using his revised version, or an older set?

It's a shame that the 'official' site doesn't have a complete set of designs in gerber form that you can send off as a single panel or something (I find the site a bit baffling since details are scattered all over the place) - hence the attraction of buying a complete set.

I've just had another look at my boards and you're correct that the Chinese boards lack a mask-free perimeter fence area, or even clearance at the edges to remove the mask and add one in case you wanted to do that and still use the boxes. Maybe you could line the aluminium boxes with some sort of shielding material?

[Neganur]

The website links a BOM of about $300-400.  Is this still ~ right? Availability and obsolescence not an issue?  Add PCB and housings  total parts cost ~ $540.

It depends where you buy parts. I had the feeling that those in the US pay a lot less for parts, especially if they have access to surplus stores. (used coaxial SPDT switches etc., you need a few in case you want automatic band switching, or maybe a step attenuator)

The biggest part of my expenses were all the connectors, the Mini-Circuits VCOs and ICs like the 16-bit ADC and logarithmic amplifier. Also, I was really surprised how difficult it was to buy 1 inch (28 mm) copper tube in Helsinki. The local builder's store asked more than 50 EUR for a 3 m piece and I only needed 40 cm.

Next, if you don't have access to quality tools (drill press, fine saw, tube cutter) you may learn new swear words, at least I did On the positive side, the mechanical work is a lot of fun and you learn a lot.

I did not sum it up yet but I'm pretty sure I spent more than $400. You can save a lot by omitting connectors (or buy very cheap Chinese SMA connectors - I think they're OK for DC-3 GHz).

[Neganur]

Ah, good to know! Are you using his revised version, or an older set?

It's a shame that the 'official' site doesn't have a complete set of designs in gerber form that you can send off as a single panel or something (I find the site a bit baffling since details are scattered all over the place) - hence the attraction of buying a complete set.

I've just had another look at my boards and you're correct that the Chinese boards lack a mask-free perimeter fence area, or even clearance at the edges to remove the mask and add one in case you wanted to do that and still use the boxes. Maybe you could line the aluminium boxes with some sort of shielding material?

I was lucky to buy a spare panel from someone and it seemed to be the latest revision. If it wasn't for the high shipping cost (to Europe) I would simply order a panel from ExpressPCB. Minimum quantity is two panels though, a group buy of 10 panels would be ideal. Those are the basic boards for a complete vector network analyser, but there are additions like active reflection bridges, a DUT forward/reverse switch, special amplifiers and filters. Not sure why but those I asked (in Europe) would rather buy parts on their own than join a group buy.

The website holds incredibly much information and it takes several days of intensive reading to grasp what you need to look for. The great thing is, it doesn't take much to just get started. Even with a totally crappy IF-filter and a half-tuned cavity you have something that works well enough. You can tune filters with just the Control Board, the Log Detector, the ADC module, master oscillator and a DDS module and learn a lot about radio engineering in the process. It is a very laborious project. Keeping the website up to date must be a pain as well.

Regarding the aluminium boxes - I'm sure you can improve them to leak less but it's difficult with the way those lids are attached with screws. The problem inside them remains for a few boards that require fences like the DDS or the IF-filters (line of sight radiation). I decided it's not worth the risk compared to the amount of work invested and got myself a panel of those 'official' PCBs.