Affordable Avionics Portable Ramp Tester

It looks pretty comprehensive.

I can’t find the pricing – how much?

I am looking for a used IFR-4000 but there is nothing out there below this

$900 is a very good price if it emits the LOC and GS at the same time i.e. has two completely separate modulators and RF transmitters. The Sandel EHSIs, and I suspect most “EFIS” products, block the GS unless a valid LOC is present.

Most of the cheap testers emit only one at a time.

The “big UK Part 145 installer / aircraft dealer” who threw in my TAS605 had a NAV-401 and it did just one at a time, and was so shagged it barely worked. They had to bang it to get a signal out

OTOH the guy who checks my avionics has an old IFR4000.

You can build a very simple transmitter using a laptop running a $60 piece of java code, driving the ext modulation input of a sig gen like a Marconi 2024 (£1000 used). I have that right here at work and it works great. Not exactly portable however…

My A&P friend whose nephew used to work for a FAA repair station is coming to the hangar with a yellow box tomorrow. $75 and a flight for lunch will get my transponder checked and sticker in maintenance logbook. We did the same thing to check my Nav radio a few months ago. There are several ways to obtain yellow boxes

The A&P uses the repair station’s box on a Saturday, charges me $75, and gives $25 to the repair station for issuing the transponder check sticker I need to fly VFR legally in my area. I think he probably has a key to their shop…

I agree that its nice to have tools. I was able to straighten out my Nav radio using only the VOT signal on the field, then we checked it with the repair stations other yellow box afterward and found that my method worked well enough. It would have been nice to have tools from the start, particularly if there was no VOT available!

I can borrow the services of the IFR4000 guy for about 20-40 quid. The service is so valuable that I pay him in multiples of £20 and it is still very very cheap.

In GA, it’s all about “contacts”, preferably contacts in low places

The AV-10 looks good for that price.

Yes, the VOR and ILS signals are trivial to generate. They repeat (about every 30ms for a VOR, IIRC) and you just need to precompute enough samples, for a 16 bit DAC, to fill this 30ms timeslot, and then you repeat it. I think everybody does it that way. With a fast DSP you could generate them in real time using trig (integer trig if you are clever, floating point trig if you are lazy) but there is no point because you need to generate only a few thousand values for the table. You re-compute the table every time the user changes the radial. In fact you could easily factory-generate and store all possible values in 1 deg increments! In the 1980s and 1990s, Marconi (that part later taken over by IFR) patented various cunning ways to do this without needing a 16-bit DAC but nowadays these things are trivial. In fact I designed a product in 1991 which had a CD player DAC costing £5.

However, if I could get an IFR4000 for $4k or less, clean, full spec, I would buy it immediately. For stuff like this having your own box is priceless.

high precision crystal oscillator that is compensated to 1.0 part per million over 0 to 50 deg C

I have no idea why you stress the reference oscillator specification, as I cannot see right now what signal needs anywhere near that precision.

OTOH it better had to be this precise, as relatively cheep TCXO (~1$ in relatively small quantities) are spec’ed like this (over a wider temperature range). The LOC signal generator I had with me in Mali Losinj had a reference TCXO with approximately that spec, and yes, every timing aspect of the signal was derived from this clock.