Now, for testing a receiver (part), some kind of signal generator is needed. It is always nice to have the generators calibrated, but for amateur use less can do it.
Excluding using the transceiver, there are a few options for very simple and low cost test generators:
1) Low cost Chinese PCB modules. I found:
a) 0 - 5MHz function generator. It is using a DDS, meaning that the stability is essentially as good as a normal crystal oscillator, no calibrated output level, though, just a potentiometer.
b) 0 - 55MHz signal generator with a DDS, same limitations as above, but no level regulation at all.
c) 35 - 4400MHz generator, with same limitations as the one above.
This will create a usable signal for use up from close to DC up to 4400MHz. Using a harmonic of the 35 - 4400MHz it is quite possible to generate a signal usable for testing if a 10GHz receiver is functional at all. These modules can probably be purchased for less than $100 on Ebay. Not bad for a simple setup. I do have such a set of modules, but I decided to go up one step. Yes, somewhat more expensive, but easier to use.
There is one more option for a low cost signal generator: The NanoVNA.
This VNA comes in 4 different frequency ranges: 50kHz - 900MHz, 50kHz - 1000MHz, 50kHz - 1500MHz and the NanoVNA version 2 (SAA 2) with 50kHz - 3000MHz. The output of those are not all too clean, but they will all provide a signal that is sufficient to test the rough function of a receiver, or as a test oscillator for a transmitter.
2) My signal generators:
a) FY6800 DDS signal generator/unction generator up to 25MHz. output not calibrated in dBm or microvolts, but it can deliver up to 25V, as far as I recall. could be used as a test exciter for a transmitter, too. This one covers the low bands very nicely, and I can use attenuators for testing receivers.
b) 500kHz - 470MHz generator. This one has a sufficiently calibrated output level, and delivers up to -73dBm, the equivalent of an S9 signal in a receiver. A bit low, but fine for testing that a receiver is not defective or completely out of alignment. I could add some amplification to increase the level, and I will do that if I find the need.
c) TPI 1002A generator. This is built by a Texas radio amateur who runs the company RF-consultant ( www.rf-consultant.com ), and covers 35 - 4400MHz with a calibrated output level from very low up to over 10dBm. The generator is controlled via a USB cable needs a computer running Windows, at least XP. I ran a quick test of the generator at 2400MHz, using a (long ago) calibrated power meter, and the levels were nicely corresponding, and therefore good enough for my use. The generator can be programmed to optimize the output for low spurious output or low (sideband) noise output. very useful for many measurements on these high bands.
d) a small box with a Chinese built ADF 5355 generator capable of generating signal up to 13600MHz, yes 13.6GHz. The unit can be used independently, but I think that it can be controlled via the USB port, too.
Why not use surplus (professional) test equipment? I have had some of this, but space (or cost for newer, smaller equipment) does not allow for this in my case. Yes I do have a bit of this kind of equipment, but no longer for (RF) signal generators.
Why did I not try to build this kind of test equipment? First, it would take me far too long, and I would need access to calibrated test equipment to get them working properly. Second, my priority is to build some (not too complex) transmitter and receiver equipment for all amateur bands from 136kHz to 10GHz, I have got the idea that I want to try to make a QSO on every amateur band available to me with home made or modified (surplus or not-designed for amateur radio) equipment. For now, I have only done this for the 3.5, 5.2 and 7MHz bands, so there is some work to do.
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