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Hi Robb All I really did with the Spice model was to generate a series of Id vs Vgs traces across several drain voltages. i.e. I just looked at the linearity of the Vgs vs Id at DC and it shows the usual poor linearity from a FET device with the response varying in a non linear manner from...

I've never really messed with IRF520N devices in SSB CBs but here's my take on it based on looking at the device datasheet and playing with a Spice model. The first place to look is at the curve traces for Vgs vs Id vs Vd and you can see that this device needs to be biased quite hard to give...

Interesting picture.... The only test gear there that I would rate as useful to me would be the big old HP8657? sig gen, the DVM and what looks like a decent dummy load. (all circled and total value would be about £800 used) I already have several sig gens and DVMs but I guess you...

In terms of 10m band radios the worst I've used is the Uniden 2830. I have one of the early versions here and the whole radio is a poor design. It looks nice and it covers the whole 10m band (plus CB if modded) but it is an awful radio. I know a lot of people like them but the receiver...

Yes, I can see the appeal of the rugged design :) But on the technical side, you will see that Bird don't spec it for temperature (because the diode detector is uncompensated and its accuracy is woefully poor over temperature on low to medium dial readings) Also they don't tell you that...

My advice would be to forget the Bird 43 and just buy a reasonably good quality ham power meter rated for the HF bands. This will be a lot cheaper for very little difference in performance on the 10/11m band. The Bird 43 is one of the most over rated pieces of test gear out there. I don't own...

Yes, some generators can generate the 1kHz quite accurately. However, I have a couple of old Marconi 2019/A generators here and they weren't accurate enough when generating a 1kHz AF tone and this caused issues. I had better results with external modulation or when using a Marconi 2024...

I tried out the Commtek SW a year or so ago ((V1.1?) and I still have it installed on this PC but it expired after a couple of weeks. It did work reasonably well but on all the PCs I tried it on it did seem a bit flakey in operation at times. Maybe the later version is better or maybe I...

I think the basic idea (for AM) is that you let the SINAD program generate the 1kHz modulation tone and feed this (from the soundcard) to the signal generator as external AM modulation. That way the modulation tone should always be on the same frequency as the notch filter in the DSP in the...

However, if you removed the preselector (obviously a bad thing to do) then the image noise at 42.8MHz away would also arrive at the mixer at the same amplified level as the noise in the wanted ham band. So the the noise performance of the receiver would degrade because the image noise would...

I assume you are referring to VHF/UHF designs if you are concerned about modelling noise figure accurately? Not sure if the following is of any relevance or use to you but here goes anyway... :) Situation 1 with a regular superhet design at VHF with an IF at maybe 21.4MHz. A typical...

For a quick example of how the generator operates you can look in the user manual for an example of how to set the generator to 25uV rms into a 50R load. In the image below you can see that my little emulator app agrees with the service manual for a level of 25uV. i.e. you need to select...

I knocked up a quick and dirty Windows App to show how I think your generator operates. I've uploaded it to youtube here: B&K Signal Generator Level Control - YouTube If the link above doesn't work then search for: B&K signal generator on youtube to find it under my username of...

I don't think you are quite correct here :) S9 is normally at -73dBm (50uV rms delivered into a 50R load) I think the correct setting for S9 would be at 66dB attenuation on the BK E200D as 50uV is 66dB below 100mV.

Yes, to clear up any confusion for anyone reading these last few posts, the dB scale on a typical RF signal generator attenuator is usually referenced to a power ratio so a 20dB change in level means a change by a factor of 10 (or 0.1) in voltage. (and not a voltage change factor of 100 as...

Typical RF sig gens behave as below: A 3dB change is a change of a factor of about 1.41 in voltage on a typical signal generator (not a change factor of 2) A 10dB change is a change of a factor of about 3.16 in voltage (not 10) A 20dB change is a change of a factor of 10 in voltage (not...

I don't have many PL259 connectors here but I found a few adaptors. eg BNC to UHF and a UHF-UHF barrel. If you look at the image below I first calibrated the VNA with the short and direct BNC to BNC adaptor (with the red blob of paint) and then I swapped it for the three UHF adaptors in...

Provided you buy a decent brand of connector I'd expect the loss on a basic straight connector to be so small at 27MHz (per connector) that you would have a tough time to measure it accurately even with modern test equipment. eg I'd expect the loss at 27MHz to be MUCH less than 0.1dB per...

I've got a much better idea.... Why don't you tell me if you still think my statement below about measuring noise is WRONG. This is what started the whole debate. Please bear in mind that I have modern physics on my side and also I can quote from HP to back up the above statement...

I know it won't go up 3dB. I'm not saying it will :) The carrier is a continuous wave signal rather than noise. You aren't proving anything relevant with your latest example? What you are overlooking is that in order to assess the noise performance of an amplifier stage you have to measure...